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CS2000-OTP
Fractional-N Clock Synthesizer & Clock Multiplier
Features
Delta-Sigma Fractional-N Frequency Synthesis - Generates a Low Jitter 6 - 75 MHz Clock from an 8 - 75 MHz Reference Clock Clock Multiplier / Jitter Reduction - Generates a Low Jitter 6 - 75 MHz Clock from a Jittery or Intermittent 50 Hz to 30 MHz Clock Source Highly Accurate PLL Multiplication Factor - Maximum Error Less Than 1 PPM in HighResolution Mode One-Time Programmability - Configurable Hardware Control Pins - Configurable Auxiliary Output Flexible Sourcing of Reference Clock - External Oscillator or Clock Source - Supports Inexpensive Local Crystal Minimal Board Space Required - No External Analog Loop-filter Components
General Description
The CS2000-OTP is an extremely versatile system clocking device that utilizes a programmable phase lock loop. The CS2000-OTP is based on a hybrid analogdigital PLL architecture comprised of a unique combination of a Delta-Sigma Fractional-N Frequency Synthesizer and a Digital PLL. This architecture allows for both frequency synthesis/clock generation from a stable reference clock as well as generation of a low-jitter clock relative to an external noisy synchronization clock with frequencies as low as 50 Hz. The CS2000OTP has many configuration options which are set once prior to runtime. At runtime there are three hardware configuration pins available for mode and feature selection. The CS2000-OTP is available in a 10-pin MSOP package in Commercial (-10C to +70C) grade. Customer development kits are also available for custom device prototyping, small production programming, and device evaluation. Please see "Ordering Information" on page 30 for complete details.
3.3 V
Timing Reference Frequency Reference PLL Output Lock Indicator
Hardware Control
Hardware Configuration
Auxiliary Output
8 MHz to 75 MHz Low-Jitter Timing Reference
Fractional-N Frequency Synthesizer
6 to 75 MHz PLL Output
Output to Input Clock Ratio
N
50 Hz to 30 MHz Frequency Reference
Digital PLL & Fractional N Logic
Output to Input Clock Ratio
Preliminary Product Information
http://www.cirrus.com
This document contains information for a new product. Cirrus Logic reserves the right to modify this product without notice.
Copyright (c) Cirrus Logic, Inc. 2008 (All Rights Reserved)
JUN '08 DS758PP1
CS2000-OTP
TABLE OF CONTENTS
1. PIN DESCRIPTION ................................................................................................................................. 4 2. TYPICAL CONNECTION DIAGRAM ..................................................................................................... 5 3. CHARACTERISTICS AND SPECIFICATIONS ...................................................................................... 6 RECOMMENDED OPERATING CONDITIONS .................................................................................... 6 ABSOLUTE MAXIMUM RATINGS ........................................................................................................ 6 DC ELECTRICAL CHARACTERISTICS ................................................................................................ 6 AC ELECTRICAL CHARACTERISTICS ................................................................................................ 7 4. ARCHITECTURE OVERVIEW ............................................................................................................... 8 4.1 Delta-Sigma Fractional-N Frequency Synthesizer ........................................................................... 8 4.2 Hybrid Analog-Digital Phase Locked Loop ...................................................................................... 8 4.2.1 Fractional-N Source Selection for the Frequency Synthesizer ................................................ 9 5. APPLICATIONS ................................................................................................................................... 10 5.1 One Time Programmability ............................................................................................................ 10 5.2 Timing Reference Clock Input ........................................................................................................ 10 5.2.1 Internal Timing Reference Clock Divider ............................................................................... 10 5.2.2 Crystal Connections (XTI and XTO) ...................................................................................... 11 5.2.3 External Reference Clock (REF_CLK) .................................................................................. 11 5.3 Frequency Reference Clock Input, CLK_IN ................................................................................... 11 5.3.1 CLK_IN Skipping Mode ......................................................................................................... 11 5.3.2 Adjusting the Minimum Loop Bandwidth for CLK_IN ............................................................ 13 5.4 Output to Input Frequency Ratio Configuration ............................................................................. 14 5.4.1 User Defined Ratio (RUD), Frequency Synthesizer Mode .................................................... 14 5.4.2 User Defined Ratio (RUD), Hybrid PLL Mode ....................................................................... 14 5.4.3 Manual Ratio Modifier (R-Mod) ............................................................................................. 15 5.4.4 Automatic Ratio Modifier (Auto R-Mod) - Hybrid PLL Mode Only ......................................... 15 5.4.5 Effective Ratio (REFF) .......................................................................................................... 16 5.4.6 Fractional-N Source Selection ............................................................................................... 16 5.4.6.1 Manual Fractional-N Source Selection for the Frequency Synthesizer ..................... 17 5.4.6.2 Automatic Fractional-N Source Selection for the Frequency Synthesizer ................. 17 5.4.7 Ratio Configuration Summary ............................................................................................... 18 5.5 PLL Clock Output ........................................................................................................................... 19 5.6 Auxiliary Output .............................................................................................................................. 19 5.7 Mode Pin Functionality ................................................................................................................... 20 5.7.1 M1 and M0 Mode Pin Functionality ....................................................................................... 20 5.7.2 M2 Mode Pin Functionality .................................................................................................... 20 5.7.2.1 M2 Configured as Output Disable .............................................................................. 20 5.7.2.2 M2 Configured as R-Mod Enable .............................................................................. 20 5.7.2.3 M2 Configured as Auto Fractional-N Source Selection Disable ................................ 21 5.7.2.4 M2 Configured as Auto R-Mod Enable ...................................................................... 21 5.7.2.5 M2 Configured as Fractional-N Source Select .......................................................... 21 5.7.2.6 M2 Configured as AuxOutSrc Override ..................................................................... 21 5.8 Clock Output Stability Considerations ............................................................................................ 21 5.8.1 Output Switching ................................................................................................................... 21 5.8.2 PLL Unlock Conditions .......................................................................................................... 22 6. PARAMETER DESCRIPTIONS ........................................................................................................... 23 6.1 Modal Configuration Sets ............................................................................................................... 23 6.1.1 R-Mod Selection (RModSel[1:0]) ........................................................................................... 23 6.1.2 Auxiliary Output Source Selection (AuxOutSrc[1:0]) ............................................................. 24 6.1.3 Auto R-Modifier Enable (AutoRMod) ..................................................................................... 24 6.1.4 Lock Clock Ratio (LockClk[1:0]) ............................................................................................ 24 6.1.5 Fractional-N Source for Frequency Synthesizer (FracNSrc) ................................................. 24 6.2 Ratio 0 - 3 ...................................................................................................................................... 24 DS758PP1 2
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6.3 Global Configuration Parameters ................................................................................................... 25 6.3.1 Clock Skip Enable (ClkSkipEn) ............................................................................................. 25 6.3.2 AUX PLL Lock Output Configuration (AuxLockCfg) .............................................................. 25 6.3.3 Reference Clock Input Divider (RefClkDiv[1:0]) .................................................................... 25 6.3.4 Enable PLL Clock Output on Unlock (ClkOutUnl) ................................................................. 25 6.3.5 Low-Frequency Ratio Configuration (LFRatioCfg) ................................................................ 26 6.3.6 M2 Pin Configuration (M2Config[2:0]) ................................................................................... 26 6.3.7 Clock Input Bandwidth (ClkIn_BW[2:0]) ................................................................................ 26 7. CALCULATING THE USER DEFINED RATIO .................................................................................... 27 7.1 High Resolution 12.20 Format ....................................................................................................... 27 7.2 High Multiplication 20.12 Format ................................................................................................... 27 8. PROGRAMMING INFORMATION ........................................................................................................ 28 9. PACKAGE DIMENSIONS .................................................................................................................... 29 THERMAL CHARACTERISTICS ......................................................................................................... 29 10. ORDERING INFORMATION .............................................................................................................. 30 11. REVISION HISTORY .......................................................................................................................... 30
LIST OF FIGURES
Figure 1. Typical Connection Diagram ........................................................................................................ 5 Figure 2. Delta-Sigma Fractional-N Frequency Synthesizer ....................................................................... 8 Figure 3. Hybrid Analog-Digital PLL ............................................................................................................ 9 Figure 4. Fractional-N Source Selection Overview ..................................................................................... 9 Figure 5. Internal Timing Reference Clock Divider ................................................................................... 10 Figure 6. External Component Requirements for Crystal Circuit .............................................................. 11 Figure 7. CLK_IN removed for > 223 SysClk cycles ................................................................................. 12 Figure 8. CLK_IN removed for < 223 SysClk cycles but > tCS ................................................................. 12 Figure 9. CLK_IN removed for < tCS ........................................................................................................ 13 Figure 10. Low bandwidth and new clock domain .................................................................................... 13 Figure 11. High bandwidth with CLK_IN domain re-use ........................................................................... 14 Figure 12. Ratio Feature Summary ........................................................................................................... 18 Figure 13. PLL Clock Output Options ....................................................................................................... 19 Figure 14. Auxiliary Output Selection ........................................................................................................ 19 Figure 15. M2 Mapping Options ................................................................................................................ 20 Figure 16. Parameter Configuration Sets .................................................................................................. 23
LIST OF TABLES
Table 1. Modal and Global Configuration .................................................................................................. 10 Table 2. Ratio Modifier .............................................................................................................................. 15 Table 3. Automatic Ratio Modifier ............................................................................................................. 15 Table 4. Example Audio Oversampling Clock Generation from CLK_IN .................................................. 16 Table 5. Example 12.20 R-Values ............................................................................................................ 27 Table 6. Example 20.12 R-Values ............................................................................................................ 27
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CS2000-OTP 1. PIN DESCRIPTION
VD GND CLK_OUT AUX_OUT CLK_IN
1 2 3 4 5
10 9 8 7 6
M0 M1 M2 XTI/REF_CLK XTO
Pin Name
VD GND CLK_OUT AUX_OUT CLK_IN XTO XTI/REF_CLK M2 M1 M0
#
1 2 3 4 5 6 7 8 9
Pin Description
Digital Power (Input) - Positive power supply for the digital and analog sections. Ground (Input) - Ground reference. PLL Clock Output (Output) - PLL clock output. Auxiliary Output (Output) - This pin outputs a buffered version of one of the input or output clocks, or a status signal, depending on configuration. Frequency Reference Clock Input (Input) - Clock input for the Digital PLL frequency reference. Crystal Connections (XTI/XTO) / Timing Reference Clock Input (REF_CLK) (Input/Output) XTI/XTO are I/O pins for an external crystal which may be used to generate the low-jitter PLL input clock. REF_CLK is an input for an externally generated low-jitter reference clock. Mode Select (Input) - M2 is a configurable mode selection pin. Mode Select (Input) - M1 is a configurable mode selection pin.
10 Mode Select (Input) - M0 is a configurable mode selection pin.
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CS2000-OTP 2. TYPICAL CONNECTION DIAGRAM
0.1 F
1 F
+3.3 V
VD M2 System Microcontroller M1 M0
CS2000-OTP
CLK_OUT To circuitry which requires a low-jitter clock To other circuitry or Microcontroller
Frequency Reference
CLK_IN XTI/REF_CLK XTO GND
1 or 2
AUX_OUT
Low-Jitter Timing Reference
N.C. x or Crystal
2
1
REF_CLK XTO
XTI XTO
40 pF
40 pF
Figure 1. Typical Connection Diagram
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CS2000-OTP 3. CHARACTERISTICS AND SPECIFICATIONS RECOMMENDED OPERATING CONDITIONS
GND = 0 V; all voltages with respect to ground. (Note 1) Parameters
DC Power Supply Ambient Operating Temperature (Power Applied) Commercial Grade TAC -10 +70 C
Symbol
VD
Min
3.1
Typ
3.3
Max
3.5
Units
V
Notes: 1. Device functional operation is guaranteed within these limits. Functionality is not guaranteed or implied outside of these limits. Operation outside of these limits may adversely affect device reliability.
ABSOLUTE MAXIMUM RATINGS
GND = 0 V; all voltages with respect to ground. Parameters
DC Power Supply Input Current Digital Input Voltage (Note 1) Ambient Operating Temperature (Power Applied) Storage Temperature
Symbol
VD IIN VIN TA Tstg
Min
-0.3 -0.3 -55 -65
Max
6.0 10 VD + 0.4 125 150
Units
V mA V C C
WARNING: Operation at or beyond these limits may result in permanent damage to the device. Notes: 1. The maximum over/under voltage is limited by the input current except on the power supply pin.
DC ELECTRICAL CHARACTERISTICS
Test Conditions (unless otherwise specified): VD = 3.1 V to 3.5 V; TA = -10C to +70C (Commercial Grade). Parameters
Power Supply Current - Unloaded Power Dissipation - Unloaded Input Leakage Current Input Capacitance High-Level Input Voltage Low-Level Input Voltage High-Level Output Voltage (IOH = -1.2 mA) Low-Level Output Voltage (IOH = 1.2 mA) (Note 2) (Note 2)
Symbol
ID PD IIN IC VIH VIL VOH VOL
Min
70% 80% -
Typ
12 40 8 -
Max
18 60 10 30% 20%
Units
mA mW A pF VD VD VD VD
Notes: 2. To calculate the additional current consumption due to loading (per output pin), multiply clock output frequency by load capacitance and power supply voltage. For example, fCLK_OUT (49.152 MHz) * CL (15 pF) * VD (3.3 V) = 2.4 mA of additional current due to these loading conditions on CLK_OUT.
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CS2000-OTP AC ELECTRICAL CHARACTERISTICS
Test Conditions (unless otherwise specified): VD = 3.1 V to 3.5 V; TA = -10C to +70C (Commercial Grade); CL = 15 pF. Parameters
Crystal Frequency Reference Clock Input Frequency Reference Clock Input Duty Cycle Internal System Clock Frequency Clock Input Frequency (Auto R-Mod Disabled) Clock Input Frequency (Auto R-mod Enabled)
Symbol
fXTAL fREF_CLK DREF_CLK fSYS_CLK fCLK_IN fCLK_IN
Conditions
Fundamental Mode
Min
8 8 45 8 50 Hz
Typ
50 1.7 1.7 70 50 175 100 1 1 -
Max
50 75 55 18.75 30 59 138 256 80 75 52 3.0 3.0 150 200 3 2 0.5 112
Units
MHz MHz % MHz MHz kHz kHz kHz UI ns ms kHz MHz % ns ns ps rms ps rms ps rms UI ms ms ppm ppm
Auto R Modifier = 1 Auto R Modifier = 0.5 Auto R Modifier = 0.25 fCLK_IN < fSYS_CLK/96 fCLK_IN > fSYS_CLK/96 (Notes 4, 5) (Note 5) Measured at VD/2 20% to 80% of VD 80% to 20% of VD (Note 6) (Notes 6, 7) (Notes 6, 8)
4 72 168 2 10 20 50 Hz 6 48 0 0
Clock Input Pulse Width (Note 3) Clock Skipping Timeout Clock Skipping Input Frequency PLL Clock Output Frequency PLL Clock Output Duty Cycle Clock Output Rise Time Clock Output Fall Time Period Jitter Base Band Jitter (100 Hz to 40 kHz) Wide Band JItter (100 Hz Corner) PLL Lock Time - CLK_IN (Note 9) PLL Lock Time - REF_CLK Output Frequency Synthesis Resolution (Note 10)
pwCLK_IN tCS fCLK_SKIP fCLK_OUT tOD tOR tOF tJIT
tLC tLR ferr
fCLK_IN < 200 kHz fCLK_IN > 200 kHz fREF_CLK = 8 to 75 MHz High Resolution High Multiplication
Notes: 3. 1 UI (unit interval) corresponds to tSYS_CLK or 1/fSYS_CLK. 4. tCS represents the time from the removal of CLK_IN by which CLK_IN must be re-applied to ensure that PLL_OUT continues while the PLL re-acquires lock. This timeout is based on the internal VCO frequency, with the minimum timeout occurring at the maximum VCO frequency. Lower VCO frequencies will result in larger values of tCS. 5. Only valid in clock skipping mode; See "CLK_IN Skipping Mode" on page 11 for more information. 6. fCLK_OUT = 24.576 MHz; Sample size = 10,000 points; AuxOutSrc[1:0] = 11. 7. In accordance with AES-12id-2006 section 3.4.2. Measurements are Time Interval Error taken with 3rd order 100 Hz to 40 kHz bandpass filter. 8. In accordance with AES-12id-2006 section 3.4.1. Measurements are Time Interval Error taken with 3rd order 100 Hz Highpass filter. 9. 1 UI (unit interval) corresponds to tCLK_IN or 1/fCLK_IN. 10. The frequency accuracy of the PLL clock output is directly proportional to the frequency accuracy of the reference clock.
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CS2000-OTP 4. ARCHITECTURE OVERVIEW
4.1 Delta-Sigma Fractional-N Frequency Synthesizer
The core of the CS2000 is a Delta-Sigma Fractional-N Frequency Synthesizer which has very high-resolution for Input/Output clock ratios, low phase noise, very wide range of output frequencies and the ability to quickly tune to a new frequency. In very simplistic terms, the Fractional-N Frequency Synthesizer multiplies the Timing Reference Clock by the value of N to generate the PLL output clock. The desired output to input clock ratio is the value of N that is applied to the delta-sigma modulator (see Figure 2). The analog PLL based frequency synthesizer uses a low-jitter timing reference clock as a time and phase reference for the internal voltage controlled oscillator (VCO). The phase comparator compares the fractional-N divided clock with the original timing reference and generates a control signal. The control signal is filtered by the internal loop filter to generate the VCO's control voltage which sets its output frequency. The delta-sigma modulator modulates the loop integer divide ratio to get the desired fractional ratio between the reference clock and the VCO output (thus the duty cycle of the modulator sets the fractional value). This allows the design to be optimized for very fast lock times for a wide range of output frequencies without the need for external filter components. As with any Fractional-N Frequency Synthesizer the timing reference clock should be stable and jitter-free.
Timing Reference Clock
Phase Comparator
Internal Loop Filter
Voltage Controlled Oscillator
PLL Output
Fractional-N Divider
Delta-Sigma Modulator
N
Figure 2. Delta-Sigma Fractional-N Frequency Synthesizer
4.2
Hybrid Analog-Digital Phase Locked Loop
The addition of the Digital PLL and Fractional-N Logic (shown in Figure 3) to the Fractional-N Frequency Synthesizer creates the Hybrid Analog-Digital Phase Locked Loop with many advantages over classical analog PLL techniques. These advantages include the ability to operate over extremely wide frequency ranges without the need to change external loop filter components while maintaining impressive jitter reduction performance. In the Hybrid architecture, the Digital PLL calculates the ratio of the PLL output clock to the frequency reference and compares that to the desired ratio. The digital logic generates a value of N which is then applied to the Fractional-N frequency synthesizer to generate the desired PLL output frequency. Notice that the frequency and phase of the timing reference signal do not affect the output of the PLL since the digital control loop will correct for the PLL output. A major advantage of the Digital PLL is the ease with which the loop filter bandwidth can be altered. The PLL bandwidth is set to a wide-bandwidth mode to quickly achieve lock and then reduced for optimal jitter rejection.
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CS2000-OTP
Delta-Sigma Fractional-N Frequency Synthesizer
Timing Reference Clock
Phase Comparator
Internal Loop Filter
Voltage Controlled Oscillator
PLL Output
Fractional-N Divider
Delta-Sigma Modulator
Digital PLL and Fractional-N Logic
N
Digital Filter
Frequency Reference Clock
Frequency Comparator for Frac-N Generation
Output to Input Ratio for Hybrid mode
Figure 3. Hybrid Analog-Digital PLL
4.2.1
Fractional-N Source Selection for the Frequency Synthesizer
The fractional-N value for the frequency synthesizer can be sourced from either a static ratio or a dynamic ratio generated from the digital PLL (see Figure 4). This allows for the selection between operating in the static ratio based Frequency Synthesizer Mode as a simple frequency synthesizer (for frequency generation from the Timing Reference Clock) and in the dynamic ratio based Hybrid PLL Mode (for jitter reduction and clock multiplication). Selection between these two modes can either be made automatically based on the presence of the Frequency Reference Clock or manually through the mode select pins.
Timing Reference Clock
Fractional-N Frequency Synthesizer
PLL Output
N Output to Input Ratio for Synthesizer Mode
Frequency Reference Clock
Digital PLL & Fractional-N Logic
Output to Input ratio for Hybrid Mode
Figure 4. Fractional-N Source Selection Overview
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CS2000-OTP 5. APPLICATIONS
5.1 One Time Programmability
The one time programmable (OTP) circuitry in the CS2000-OTP allows for pre-configuration of the device prior to use in a system. There are two types of parameters that are used for device pre-configuration: modal and global. The modal parameters are features which, when grouped together, create a modal configuration set (see Figure 16 on page 23). Up to four modal configuration sets can be permanently stored and then dynamically selected using the M[1:0] mode select pins (see Table 1). The global parameters are the remaining configuration settings which do not change with the mode select pins. The modal and global parameters can be pre-set at the factory or user programmed using the customer development kit, CDK2000; Please see "Programming Information" on page 28 for more details. Parameter Type
Modal Global
M[1:0] pins = 00
Configuration Set 0 Ratio 0
M[1:0] pins = 01
Configuration Set 1 Ratio 1
M[1:0] pins = 10
Configuration Set 2 Ratio 2
M[1:0] pins = 11
Configuration Set 3 Ratio 3
Configuration settings set once for all modes.
Table 1. Modal and Global Configuration
5.2
Timing Reference Clock Input
The low jitter timing reference clock (RefClk) can be provided by either an external reference clock or an external crystal in conjunction with the internal oscillator. In order to maintain a stable and low-jitter PLL output the timing reference clock must also be stable and low-jitter; the quality of the timing reference clock directly affects the performance of the PLL and hence the quality of the PLL output.
5.2.1
Internal Timing Reference Clock Divider
The Internal Timing Reference Clock (SysClk) is limited to a lower maximum frequency than that allowed on the XTI/REF_CLK pin. The CS2000-OTP supports the wider external frequency range by offering an internal divider for RefClk. The RefClkDiv[1:0] global parameter should be configured such that SysClk, the divided RefClk, then falls within the valid range as indicated in Figure 5.
Timing Reference Clock Divider
Internal Timing Reference Clock 8 MHz < SysClk < 18.75 MHz
XTI/REF_CLK
Timing Reference Clock 8 MHz < RefClk <
50 MHz (XTI) 75 MHz (REF_CLK)
/1 /2 /4
RefClkDiv[1:0]
Fractional-N Frequency Synthesizer
PLL Output
N
Figure 5. Internal Timing Reference Clock Divider It should be noted that the maximum allowable input frequency of the XTI/REF_CLK pin is dependent upon its configuration as either a crystal connection or external clock input. See the "AC Electrical Characteristics" on page 7 for more details.
Referenced Control Parameter Definition RefClkDiv[1:0] ......................."Reference Clock Input Divider (RefClkDiv[1:0])" on page 25
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5.2.2 Crystal Connections (XTI and XTO)
An external crystal may be used to generate RefClk. To accomplish this, a 20 pF fundamental mode parallel resonant crystal must be connected between the XTI and XTO pins as shown in Figure 6. As shown, nothing other than the crystal and its load capacitors should be connected to XTI and XTO. Please refer to the "AC Electrical Characteristics" on page 7 for the allowed crystal frequency range.
XTI
XTO
40 pF
40 pF
Figure 6. External Component Requirements for Crystal Circuit
5.2.3
External Reference Clock (REF_CLK)
For operation with an externally generated REF_CLK signal, XTI/REF_CLK should be connected to the reference clock source and XTO should be left unconnected or terminated through a 47 k resistor to GND.
5.3
Frequency Reference Clock Input, CLK_IN
The frequency reference clock input (CLK_IN) is used in Hybrid PLL Mode by the Digital PLL and FractionalN Logic block to dynamically generate a fractional-N value for the Frequency Synthesizer (see "Hybrid Analog-Digital PLL" on page 9). The Digital PLL first compares the CLK_IN frequency to the PLL output. The Fractional-N logic block then translates the desired ratio based off of CLK_IN to one based off of the internal timing reference clock (SysClk). This allows the low-jitter timing reference clock to be used as the clock which the Frequency Synthesizer multiplies while maintaining synchronicity with the frequency reference clock through the Digital PLL. The allowable frequency range for CLK_IN is found in the "AC Electrical Characteristics" on page 7.
5.3.1
CLK_IN Skipping Mode
CLK_IN skipping mode allows the PLL to maintain lock even when the CLK_IN signal has missing pulses for up to 20 ms (tCS) at a time (see "AC Electrical Characteristics" on page 7 for specifications). CLK_IN skipping mode can only be used when the CLK_IN frequency is below 80 kHz. The ClkSkipEn global parameter enables this function. Regardless of the setting of the ClkSkipEn parameter the PLL output will continue for 223 SysClk cycles (466 ms to 1048 ms) after CLK_IN is removed (see Figure 7). This is true as long as CLK_IN does not glitch or have an effective change in period as the clock source is removed, otherwise the PLL will interpret this as a change in frequency causing clock skipping and the 223 SysClk cycle time-out to be bypassed and the PLL to immediately unlock. If the prior conditions are met while CLK_IN is removed and 223 SysClk cycles pass, the PLL will unlock and the PLL_OUT state will be determined by the ClkOutUnl parameter; See "PLL Clock Output" on page 19. If CLK_IN is re-applied after such time, the PLL will re-
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main unlocked for the specified time listed in the "AC Electrical Characteristics" on page 7 after which lock will be acquired and the PLL output will resume.
223 SysClk cycles
Lock Time
223 SysClk cycles
Lock Time
CLK_IN
ClkSkipEn=0 or 1 ClkOutUnl=0
CLK_IN
ClkSkipEn=0 or 1 ClkOutUnl=1
PLL_OUT UNLOCK
PLL_OUT UNLOCK
= invalid clocks
Figure 7. CLK_IN removed for > 223 SysClk cycles f CLK_IN is removed and then reapplied within 223 SysClk cycles but later than tCS, the ClkSkipEn parameter will have no effect and the PLL output will continue until CLK_IN is re-applied (see Figure 8). Once CLK_IN is re-applied, the PLL will go unlocked only for the time it takes to acquire lock; the PLL_OUT state will be determined by the ClkOutUnl parameter during this time.
tCS Lock Time
223 SysClk cycles
223 SysClk cycles
tCS Lock Time
CLK_IN
ClkSkipEn=0 or 1 ClkOutUnl=0
CLK_IN
ClkSkipEn=0 or 1 ClkOutUnl=1
PLL_OUT UNLOCK
PLL_OUT UNLOCK
= invalid clocks
Figure 8. CLK_IN removed for < 223 SysClk cycles but > tCS If CLK_IN is removed and then re-applied within tCS, the ClkSkipEn parameter determines whether PLL_OUT continues while the PLL re-acquires lock (see Figure 9). When ClkSkipEn is disabled and CLK_IN is removed the PLL output will continue until CLK_IN is re-applied at which point the PLL will go unlocked only for the time it takes to acquire lock; the PLL_OUT state will be determined by the ClkOutUnl parameter during this time. When ClkSkipEn is enabled and CLK_IN is removed the PLL output clock will
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remain continuous throughout the missing CLK_IN period including the time while the PLL re-acquires lock.
tCS tCS Lock Time
CLK_IN
ClkSkipEn=1 ClkOutUnl=0 or 1
CLK_IN
ClkSkipEn=0 ClkOutUnl=1
PLL_OUT UNLOCK
PLL_OUT UNLOCK
= invalid clocks
Lock Time
tCS
CLK_IN
ClkSkipEn=0 ClkOutUnl=0
PLL_OUT UNLOCK
Figure 9. CLK_IN removed for < tCS
Referenced Control Parameter Definition
ClkSkipEn.............................."Clock Skip Enable (ClkSkipEn)" on page 25 ClkOutUnl.............................."Enable PLL Clock Output on Unlock (ClkOutUnl)" on page 25
5.3.2
Adjusting the Minimum Loop Bandwidth for CLK_IN
The CS2000 allows the minimum loop bandwidth of the Digital PLL to be adjusted between 1 Hz and 128 Hz using the ClkIn_BW[2:0] global parameter. The minimum loop bandwidth of the Digital PLL directly affects the jitter transfer function; specifically, jitter frequencies below the loop bandwidth corner are passed from the PLL input directly to the PLL output without attenuation. In some applications it is desirable to have a very low minimum loop bandwidth to reject very low jitter frequencies, commonly referred to as wander. In others it may be preferable to remove only higher frequency jitter, allowing the input wander to pass through the PLL without attenuation. Typically, applications in which the PLL_OUT signal creates a new clock domain from which all other system clocks and associated data are derived will benefit from the maximum jitter and wander rejection of the lowest PLL bandwidth setting. See Figure 10.
CLK_IN
PLL BW = 1 Hz
or
PLL_OUT
Wander and Jitter > 1 Hz Rejected
Wander > 1 Hz
Jitter Subclocks generated from new clock domain.
MCLK
MCLK LRCK SCLK SDATA D0 D1
LRCK SCLK SDATA D0 D1
Figure 10. Low bandwidth and new clock domain Systems in which some clocks and data are derived from the PLL_OUT signal while other clocks and data are derived from the CLK_IN signal will often require phase alignment of all the clocks and data in the system. See Figure 11. If there is substantial wander on the CLK_IN signal in these applications, it may be necessary to increase the minimum loop bandwidth allowing this wander to pass through to the DS758PP1 13
CS2000-OTP
CLK_OUT signal in order to maintain phase alignment. For these applications, it is advised to experiment with the loop bandwidth settings and choose the lowest bandwidth setting that does not produce system timing errors due to wandering between the clocks and data synchronous to the CLK_IN domain and those synchronous to the PLL_OUT domain.
CLK_IN
PLL BW = 128 Hz
or
PLL_OUT
Jitter > 128 Hz Rejected Wander < 128 Hz Passed to Output
Wander < 128 Hz
Jitter
MCLK
MCLK LRCK SCLK SDATA D0 D1
Subclocks and data re-used from previous clock domain.
LRCK SCLK SDATA D0 D1
Figure 11. High bandwidth with CLK_IN domain re-use While acquiring lock, the digital loop bandwidth is automatically set to a large value. Once lock is achieved, the digital loop bandwidth will settle to the minimum value selected by the ClkIn_BW[2:0] parameter.
Referenced Control Parameter Definition ClkIn_BW[2:0] ......................."Clock Input Bandwidth (ClkIn_BW[2:0])" on page 26
5.4 5.4.1
Output to Input Frequency Ratio Configuration User Defined Ratio (RUD), Frequency Synthesizer Mode
The User Defined Ratio, RUD, is a 32-bit un-signed fixed-point number which determines the basis for the desired input to output clock ratio. Up to four different ratios, Ratio0-3, can be stored in the CS2000's one time programmable memory. Selection between the four ratios is achieved by the M[1:0] mode select pins. The 32-bit RUD is represented in a high-resolution 12.20 format where the 12 MSBs represent the integer binary portion while the remaining 20 LSBs represent the fractional binary portion. The maximum multiplication factor is approximately 4096 with a resolution of 0.954 PPM in this configuration. See "Calculating the User Defined Ratio" on page 27 for more information. The status of internal dividers, such as the internal timing reference clock divider, are automatically taken into account. Therefore RUD is simply the desired ratio of the output to input clock frequencies.
Referenced Control Parameter Definition Ratio 0-3................................"Ratio 0 - 3" on page 24 M[1:0] ...................................."M1 and M0 Mode Pin Functionality" on page 20
5.4.2
User Defined Ratio (RUD), Hybrid PLL Mode
The same four ratio locations, Ratio0-3, are used to store the User Defined Ratios for Hybrid PLL Mode. Selection of the User Defined Ratio for the dynamic ratio based Hybrid PLL Mode is made with the M[1:0] pins (unless auto fractional N source selection is enabled; see section 5.4.6 on page 16). In addition to the High-Resolution ratio format, a High-Multiplication format is also available. In the HighMultiplication format mode, the 32-bit fixed-point number for RUD is represented in a 20.12 format where the 20 MSBs represent the integer binary portion while the remaining 12 LSBs represent the fractional
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binary portion. In this configuration, the maximum multiplication factor is approximately 1,048,575 with a resolution of 244 PPM. The 20.12 format is enabled by the LFRatioCfg global parameter. The 20.12 ratio format is only available when the device is running in Hybrid PLL Mode. In Auto Fractional-N Source Selection Mode (see section 5.4.6.2 on page 17) when CLK_IN is not present the LFRatioCfg parameter is ignored and the ratio format is 12.20. It is recommended that the 12.20 High-Resolution format be utilized whenever the desired ratio is less than 4096 since the output frequency accuracy of the PLL is directly proportional to the accuracy of the timing reference clock and the resolution of the RUD.
Referenced Control Parameter Definition LockClk[1:0] .........................."Lock Clock Ratio (LockClk[1:0])" section on page 24 LFRatioCfg ............................"Low-Frequency Ratio Configuration (LFRatioCfg)" on page 26 FracNSrc ..............................."Fractional-N Source for Frequency Synthesizer (FracNSrc)" section on page 24
5.4.3
Manual Ratio Modifier (R-Mod)
The manual Ratio Modifier is used to internally multiply/divide the currently addressed RUD (Ratio0-3 stored in the register space remain unchanged). The available options for R-Mod are summarized in Table 2 on page 15. R-Mod is enabled via the M2 pin in conjunction with the appropriate setting of the M2Config[2:0] global parameter (see Section 5.7.2 on page 20). RModSel[1:0] 00 01 10 11 R Modifier 0.5 0.25 0.125 0.0625 Table 2. Ratio Modifier
Referenced Control Parameter Definition Ratio 0-3................................"Ratio 0 - 3" on page 24 RModSel[1:0] ........................"R-Mod Selection (RModSel[1:0])" section on page 23 M2Config[2:0]........................"M2 Pin Configuration (M2Config[2:0])" on page 26
5.4.4
Automatic Ratio Modifier (Auto R-Mod) - Hybrid PLL Mode Only
The Automatic R-Modifier uses the CLK_IN Frequency Range Detector to implement a frequency dependent multiply of the currently addressed RUD as shown in Table 3. The CLK_IN Frequency Range Detector determines the ratio between the frequency of the internal SysClk and the CLK_IN input signal. The result of the ratio measurement is the internal status signal called FsDetect[1:0]. Like with R-Mod, the Ratio0-3 parameters stored in the one time programmable memory remain unchanged. The Automatic Ratio Modifier is enabled either by the AutoRMod modal parameter or via the M2 pin in conjunction with the appropriate setting of the M2Config[2:0] global parameter (see Section 5.7.2 on page 20). FsDetect[1:0]
00 01 10
fSysClk / fCLK_IN
> 224 96 - 224 < 96
Auto R Modifier
1 0.5 0.25
Table 3. Automatic Ratio Modifier DS758PP1 15
CS2000-OTP
It is important to note that Auto R-Mod (if enabled) is applied in addition to any R-Mod already selected by the RModSel[1:0] modal parameter and is used to calculate the Effective Ratio (see Section 5.4.5 on page 16). Auto R-Mod can be used to generate the appropriate oversampling clock (MCLK) for audio A/D and D/A converters. For example, if the clock applied to CLK_IN is the audio sample rate, Fs (also known as the word, frame or Left/Right clock), and SysClk is 12.288 MHz (REF_CLK = 12.288 MHz with RefClkDiv[1:0] set to `10'), FsDetect[1:0] would then reflect the frequency range of the audio sample rate. An RUD of 512 generates the audio oversampling clocks as shown in Table 4. FsDetect[1:0]
00 01 10
Inferred Audio Sample Rate when SysClk = 12.288 MHz
< 54.8 kHz 54.8 kHz to 128 kHz > 128 kHz
Speed Mode (used for audio converters)
Single Speed Double Speed Quad Speed
Audio Oversampling Clock
512 x 256 x 128 x
Table 4. Example Audio Oversampling Clock Generation from CLK_IN
Referenced Control Parameter Definition Ratio 0-3................................"Ratio 0 - 3" on page 24 RModSel[1:0] ........................"R-Mod Selection (RModSel[1:0])" section on page 23 AutoRMod ............................."Auto R-Modifier Enable (AutoRMod)" on page 24 M2Config[2:0]........................"M2 Pin Configuration (M2Config[2:0])" on page 26
5.4.5
Effective Ratio (REFF)
The Effective Ratio (REFF) is an internal calculation comprised of RUD and the appropriate modifiers, as previously described. REFF is calculated as follows: Frequency Synthesizer (Static Ratio) Mode: REFF = RUD * R-Mod Hybrid PLL (Dynamic Ratio) Mode: REFF = RUD * R-Mod * Auto R-Mod To simplify operation the device handles some of the ratio calculation functions automatically (such as when the internal timing reference clock divider is set). For this reason, the Effective Ratio does not need to be altered to account for internal dividers. Ratio modifiers which would produce an overflow or truncation of REFF should not be used. In all cases, the maximum and minimum allowable values for REFF are dictated by the frequency limits for both the input and output clocks as shown in the "AC Electrical Characteristics" on page 7. Selection of the user defined ratio from the four stored ratios is made by using the M[1:0] pins unless auto clock switching is enabled in which case the LockClk[1:0] modal parameter also selects the ratio (see "Fractional-N Source Selection" on page 16).
Referenced Control Parameter Definition M[1:0] pins............................."M1 and M0 Mode Pin Functionality" on page 20 LockClk[1:0] .........................."Lock Clock Ratio (LockClk[1:0])" section on page 24
5.4.6
Fractional-N Source Selection
To select between the static ratio based Frequency Synthesizer Mode and the dynamic ratio based Hybrid PLL Mode, the source for the fractional-N value for the Frequency Synthesizer must be changed. The Fractional-N value can either be sourced directly from the Effective Ratio (static ratio) or from the output of the Digital PLL (dynamic ratio) (see Figure 12 on page 18). The setting of this function can be made manual or automatically depending on the presence of CLK_IN.
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5.4.6.1 Manual Fractional-N Source Selection for the Frequency Synthesizer
Manual selection of the fractional-N source for the frequency synthesizer can be done in one of two ways. The FracNSrc modal parameter can be set to the desired setting for each available configuration mode and then the Fractional N source is selected by the M1 and M0 pins. In order for this manual selection to work, the LockClk[1:0] modal parameter (even if unused) must be set to the same value as the modal ratio (Ratio 0 for Mode 0, Ratio 1 for Mode 1, etc.), see Section 5.4.6.2 on page 17. Alternatively, the M2 pin in conjunction with the M2Config[2:0] global parameter can be set to control the fractional N source directly and thus override the FracNSrc modal parameter (see Section 5.7.2.5 on page 21 for details).
Referenced Control Parameter Definition M[1:0] pins ............................ "M1 and M0 Mode Pin Functionality" on page 20 LockClk[1:0] .......................... "Lock Clock Ratio (LockClk[1:0])" section on page 24 FracNSrc............................... "Fractional-N Source for Frequency Synthesizer (FracNSrc)" section on page 24 M2Config[2:0] ....................... "M2 Pin Configuration (M2Config[2:0])" on page 26
5.4.6.2
Automatic Fractional-N Source Selection for the Frequency Synthesizer
Automatic source selection allows for the selection of the frequency synthesizer's fractional-N value to be made dependent on the presence of the CLK_IN signal. When CLK_IN is present the device will use the dynamic ratio generated from the Digital PLL and CLK_IN for Hybrid PLL Mode. When CLK_IN is not present, the device will use RefClk and the static ratio for Frequency Synthesizer Mode. After losing CLK_IN, the CS2000-OTP will wait for 223 SysClk cycles before switching to SysClk and re-acquiring lock, during which time the PLL is unlocked The modal ratio location (see Table 1 on page 10) should contain the desired CLK_OUT to RefClk ratio to be used when CLK_IN is not present. The User Defined Ratio pointed to by LockClk[1:0] should contain the desired CLK_OUT to CLK_IN ratio to be used when CLK_IN is present. Automatic source selection is enabled when the LockClk[1:0] modal parameter is set to a different User Defined Ratio from the modal ratio location. When automatic source selection is enabled, the FracNSrc modal parameter (used for manual clock selection) will be ignored. The automatic source selection feature can be disabled by setting the LockClk[1:0] modal parameter to the modal ratio location. The FracNSrc modal parameter must then be used to select the desired clock used for the PLL's frequency reference. The automatic source selection feature can also be disabled by using the M2 pin in conjunction with the M2Config[2:0] global parameter.
Referenced Control Parameter Definition M[1:0] pins ............................ "M1 and M0 Mode Pin Functionality" on page 20 LockClk[1:0] .......................... "Lock Clock Ratio (LockClk[1:0])" section on page 24 FracNSrc............................... "Fractional-N Source for Frequency Synthesizer (FracNSrc)" section on page 24 M2Config[2:0] ....................... "M2 Pin Configuration (M2Config[2:0])" on page 26
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5.4.7 Ratio Configuration Summary
The RUD is the user defined ratio for which up to four different values (Ratio0-3) can be stored in the one time programmable memory. The M[1:0] pins or LockClk[1:0] modal parameter then select the user defined ratio to be used (depending on if static or dynamic ratio mode is to be used). The resolution for the RUD is selectable for the dynamic ratio mode. R-Mods can be applied to both modes whereas Auto R-Mod is only available in dynamic mode. The user defined ratio, ratio modifier, and automatic ratio modifier make up the effective ratio REFF, the final calculation used to determine the output to input clock ratio. The effective ratio is then corrected for the internal dividers. The frequency synthesizer's fractional-N source selection is made between the static ratio (in frequency synthesizer mode) or the dynamic ratio generated from the digital PLL (in Hybrid PLL mode) by either the FracNSrc modal parameter for manual mode or the presence of CLK_IN in automatic mode. The conceptual diagram in Figure 12 summarizes the features involved in the calculation of the ratio values used to generate the fractional-N value which controls the Frequency Synthesizer. The subscript `4' indicates the modal parameters.
M2 pin force Manual or M[1:0] pins =? LockClk[1:0] Auto Selection (CLK_IN sense) Effective Ratio REFF M[1:0] pins User Defined Ratio RUD Ratio 0 Ratio 1 Ratio 2 Ratio 3 Ratio Format 12.20 only Ratio Modifier M2 pin RModSel[1:0]4 Manual Selection (FracNSrc4 or M2 pin) RefClkDiv[1:0] Static Ratio N Dynamic Ratio Timing Reference Clock (XTI/REF_CLK)
=
Divide
RefClkDiv[1:0]
SysClk
Frequency Synthesizer
PLL Output
R Correction
12.20 20.12
Ratio Modifier
Auto R-Mod
R Correction
Digital PLL & Fractional N Logic
LFRatioCfg LockClk[1:0]4 AutoRMod4 or M2 pin FsDet[1:0]
Frequency Reference Clock (CLK_IN)
Figure 12. Ratio Feature Summary
Referenced Control Parameter Definition Ratio 0-3................................"Ratio 0 - 3" on page 24 M[1:0] pins............................."M1 and M0 Mode Pin Functionality" on page 20 LockClk[1:0] .........................."Lock Clock Ratio (LockClk[1:0])" section on page 24 LFRatioCfg ............................"Low-Frequency Ratio Configuration (LFRatioCfg)" on page 26 RModSel[1:0] ........................"R-Mod Selection (RModSel[1:0])" section on page 23 AutoRMod ............................."Auto R-Modifier Enable (AutoRMod)" on page 24 RefClkDiv[1:0] ......................."Reference Clock Input Divider (RefClkDiv[1:0])" on page 25 FracNSrc ..............................."Fractional-N Source for Frequency Synthesizer (FracNSrc)" section on page 24
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5.5 PLL Clock Output
The PLL clock output pin (CLK_OUT) provides a buffered version of the output of the frequency synthesizer. The driver can be set to high-impedance with the M2 pin when the M2Config[1:0] global parameter is set to either 000 or 010. The output from the PLL automatically drives a static low condition while the PLL is unlocked (when the clock may be unreliable). This feature can be disabled by setting the ClkOutUnl global parameter, however the state CLK_OUT may then be unreliable during an unlock condition.
ClkOutUnl PLL Locked/Unlocked 0 0
2:1 Mux
1
0
M2 pin with M2Config[1:0] = 000, 010
2:1 Mux
1
PLL Clock Output PLLClkOut
PLL Clock Output Pin (CLK_OUT)
PLL Output
Figure 13. PLL Clock Output Options
Referenced Control Parameter Definition ClkOutUnl.............................."Enable PLL Clock Output on Unlock (ClkOutUnl)" on page 25 ClkOutDis .............................."M2 Configured as Output Disable" on page 20 M2Config[2:0]........................"M2 Pin Configuration (M2Config[2:0])" on page 26
5.6
Auxiliary Output
The auxiliary output pin (AUX_OUT) can be mapped, as shown in Figure 14, to one of four signals: reference clock (RefClk), input clock (CLK_IN), additional PLL clock output (CLK_OUT), or a PLL lock indicator (Lock). The mux is controlled via the AuxOutSrc[1:0] modal parameter. If AUX_OUT is set to Lock, the AuxLockCfg global parameter is then used to control the output driver type and polarity of the LOCK signal (see section 6.3.2 on page 25). If AUX_OUT is set to CLK_OUT, the phase of the PLL Clock Output signal on AUX_OUT may differ from the CLK_OUT pin. The driver for the pin can be set to high-impedance using the M2 pin when the M2Config[1:0] global parameter is set to either 001 or 010.
AuxOutSrc[1:0]
Timing Reference Clock (RefClk) M2 pin with M2Config[1:0] = 001, 010 Frequency Reference Clock (CLK_IN)
4:1 Mux
PLL Clock Output (PLLClkOut) AuxLockCfg PLL Lock/Unlock Indication (Lock)
Auxiliary Output Pin (AUX_OUT)
Figure 14. Auxiliary Output Selection
Referenced Control Parameter Definition AuxOutSrc[1:0]......................"Auxiliary Output Source Selection (AuxOutSrc[1:0])" on page 24 AuxOutDis ............................."M2 Configured as Output Disable" on page 20 AuxLockCfg..........................."AUX PLL Lock Output Configuration (AuxLockCfg)" section on page 25 M2Config[2:0]........................"M2 Pin Configuration (M2Config[2:0])" on page 26
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5.7 5.7.1 Mode Pin Functionality M1 and M0 Mode Pin Functionality
M[1:0] determine the functional mode of the device and select both the default User Defined Ratio and the set of modal parameters. The modal parameters are RModSel[1:0], AuxOutSrc[1:0], AutoRMod, LockClk[1:0], and FracNSrc. By modifying one or more of the modal parameters between the 4 sets, different functional configurations can be achieved. However, global parameters are fixed and the same value will be applied to each functional configuration. Figure 16 on page 23 provides a summary of all parameters used by the device.
5.7.2
M2 Mode Pin Functionality
M2 usage is mapped to one of the optional special functions via the M2Config[2:0] global parameter. Depending on what M2 is mapped to, it will either act as an output enable/disable pin or override certain modal parameters. Figure 15 summarizes the available options and the following sections will describe each option in more detail.
M2Config[2:0] global parameter
000 001 010 011 M2 pin 100 101 110 111
Disable CLK_OUT pin Disable AUX_OUT pin Disable CLK_OUT and AUX_OUT pins RModSel[1:0] Modal Parameter Enable Force Manual Fractional N Source Selection AutoRMod Modal Parameter Override FracNSrc Modal Parameter Override Force AuxOutSel[1:0] = 10 (PLL Clock Out)
Figure 15. M2 Mapping Options
5.7.2.1
M2 Configured as Output Disable
If M2Config[2:0] is set to either `000', `001', or `010', M2 becomes an output disable pin for one or both output pins. If M2 is driven `low', the corresponding output(s) will be enabled, if M2 is driven `high', the corresponding output(s) will be disabled.
5.7.2.2
M2 Configured as R-Mod Enable
If M2Config[2:0] is set to `011', M2 becomes the R-Mod enable pin. It should be noted that M2 is the only way to enable R-Mod. Even though the RModSel[1:0] modal parameter can be set arbitrarily for each configuration set, it will not take effect unless enabled via M2. If M2 is driven `low', R-Mod will be disabled, if M2 is driven `high' R-Mod will be enabled.
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5.7.2.3 M2 Configured as Auto Fractional-N Source Selection Disable
If M2Config[2:0] is set to `100', M2 becomes a disable pin for the auto fractional-N source selection functionality. If auto fractional-N source selection is enabled (see section 5.4.6 on page 16), driving M2 `high' will disable the auto fractional-N source selection and revert control over the fractional-N source to the FracNSrc modal parameter, regardless of the LockClk[1:0] modal parameter and the presence of a clock on CLK_IN. If auto fractional-N source selection is not enabled, toggling M2 will have no effect in this case.
5.7.2.4
M2 Configured as Auto R-Mod Enable
If M2Config[2:0] is set to `101', M2 becomes the Auto R-Mod enable pin and will override the AutoRMod modal parameter. If M2 is driven `low', Auto R-Mod will be disabled, if M2 is driven `high' Auto R-Mod will be enabled.
5.7.2.5
M2 Configured as Fractional-N Source Select
If M2Config[2:0] is set to `110', M2 becomes the Fractional-N Source Select pin and will override the FracNSrc modal parameter. It should be noted that overriding FracNSrc has no effect when auto clock switching is enabled (see section 5.4.6 on page 16). If M2 is driven `low', the fractionalN value will be the Static Ratio sourced directly from REFF for Frequency Synthesizer Mode. If M2 is driven `high' the fractional-N value will be the Dynamic Ratio sourced from the Digital PLL for Hybrid PLL Mode.
5.7.2.6
M2 Configured as AuxOutSrc Override
If M2Config[2:0] is set to `111', M2 when driven `high' will override the AuxOutSrc[1:0] modal parameter and force the AUX_OUT source to PLL Clock Output. When M2 is driven `low', AUX_OUT will function according to AuxOutSrc[1:0].
5.8 5.8.1
Clock Output Stability Considerations Output Switching
The CS2000-OTP is designed such that re-configuration of the clock routing functions do not result in a partial clock period on any of the active outputs (CLK_OUT and/or AUX_OUT). In particular, enabling or disabling an output, changing the auxiliary output source between REF_CLK and CLK_OUT, changing between Frequency Synthesizer and Hybrid PLL Mode, and the automatic disabling of the output(s) during unlock will not cause a runt or partial clock period. The following exceptions/limitations exist: * * Enabling/disabling AUX_OUT when AuxOutSrc = 11 (unlock indicator). Switching AuxOutSrc[1:0] to or from 01 (CLK_IN) and to or from 11 (unlock indicator) (Transitions between AuxOutSrc[1:0] = [00,10] will not produce a glitch).
When any of these exceptions occur, a partial clock period on the output may result.
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5.8.2 PLL Unlock Conditions
Certain changes to the clock inputs and mode pins can cause the PLL to lose lock which will affect the presence of a clock signal on CLK_OUT. The following outlines which conditions cause the PLL to go unlocked: * * * * Any change in the state of the M1 and M0 pins will cause the PLL to temporarily lose lock as the new setting takes affect. Changes made to the state of the M2 when the M2Config[2:0] global parameter is set to 011, 100, 101, or 110 can cause the PLL to temporarily lose lock as the new setting takes affect. Any discontinuities on the Timing Reference Clock, REF_CLK. Discontinuities on the Frequency Reference Clock, CLK_IN, except when the Clock Skipping feature is enabled and the requirements of Clock Skipping are satisfied (see "CLK_IN Skipping Mode" on page 11). Gradual changes in CLK_IN frequency greater than 30% from the starting frequency. Step changes in CLK_IN frequency.
* *
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CS2000-OTP 6. PARAMETER DESCRIPTIONS
As mentioned in Section 5.1 on page 10, there are two different kinds of parameter configuration sets, Modal and Global. These configuration sets, shown in Figure 16, can be programmed in the field using the CDK2000 or preprogrammed at the factory. Please see "Programming Information" on page 28 for more details.
M[1:0] pins
Modal Configuration Set #0 Ratio 0 RModSel[1:0] AuxOutSrc[1:0] AutoRmod LockClk[1:0] FracNSrc
00
Modal Configuration Set #1
Modal Configuration Set #2 Ratio 2 RModSel[1:0] AuxOutSrc[1:0] AutoRmod LockClk[1:0] FracNSrc
10
Modal Configuration Set #3 Ratio 3 RModSel[1:0] AuxOutSrc[1:0] AutoRmod LockClk[1:0] FracNSrc
11
Global Configuration Set ClkSkipEn AuxLockCfg RefClkDiv[1:0] ClkOutUnl LFRatioCfg M2Config[2:0] ClkIn_BW[2:0]
Figure 16. Parameter Configuration Sets
6.1
Modal Configuration Sets
There are four instances of each of these configuration parameters. Selection between the four stored sets is made using the M[1:0] pins.
6.1.1
R-Mod Selection (RModSel[1:0])
Selects the R-Mod value, which is used as a factor in determining the PLL's Fractional N.
RModSel[1:0] 00 01 10 11 Application: R-Mod Selection Right-shift R-value by 1 (/ 2). Right-shift R-value by 2 (/ 4). Right-shift R-value by 3 (/ 8). Right-shift R-value by 4 (/ 16). "Manual Ratio Modifier (R-Mod)" on page 15
Note: This parameter does not take affect unless M2 pin is high and the M2Config[2:0] global parameter is set to `011'.
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23
Ratio 1
RModSel[1:0]
AuxOutSrc[1:0]
AutoRmod
LockClk[1:0]
FracNSrc
01
CS2000-OTP
6.1.2 Auxiliary Output Source Selection (AuxOutSrc[1:0])
Selects the source of the AUX_OUT signal.
AuxOutSrc[1:0] 00 01 10 11 Application: Auxiliary Output Source RefClk. CLK_IN. CLK_OUT. PLL Lock Status Indicator. "Auxiliary Output" on page 19
Note: When set to 11, the AuxLockCfg global parameter sets the polarity and driver type ("AUX PLL Lock Output Configuration (AuxLockCfg)" on page 25).
6.1.3
Auto R-Modifier Enable (AutoRMod)
Controls the automatic ratio modifier function.
AutoRMod 0 1 Application: Automatic R-Mod State Disabled. Enabled. "Automatic Ratio Modifier (Auto R-Mod) - Hybrid PLL Mode Only" on page 15
6.1.4
Lock Clock Ratio (LockClk[1:0])
Selects one of the four stored User Defined Ratios for use in the dynamic ratio based Hybrid PLL Mode.
LockClk[1:0] 00 01 10 11 Application: CLK_IN Ratio Selection Ratio 0. Ratio 1. Ratio 2. Ratio 3. Section 5.4.2 on page 14
Note: The User Defined Ratio for the static ratio based Frequency Synthesizer mode is the ratio that corresponds with the currently chosen configuration set as shown in Figure 16 on page 23.
6.1.5
Fractional-N Source for Frequency Synthesizer (FracNSrc)
Selects static or dynamic ratio mode when auto clock switching is disabled.
FracNSrc 0 1 Application: Fractional-N Source Selection Static Ratio directly from REFF for Frequency Synthesizer Mode Dynamic Ratio from Digital PLL for Hybrid PLL Mode "Fractional-N Source Selection" on page 16
6.2
Ratio 0 - 3
The four 32-bit User Defined Ratios are stored in the CS2000's one time programmable memory. See "Output to Input Frequency Ratio Configuration" on page 14 and "Calculating the User Defined Ratio" on page 27 for more details.
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6.3 6.3.1 Global Configuration Parameters Clock Skip Enable (ClkSkipEn)
This parameter enables clock skipping mode for the PLL and allows the PLL to maintain lock even when the CLK_IN has missing pulses.
ClkSkipEn 0 1 Application: PLL Clock Skipping Mode Disabled. Enabled. "CLK_IN Skipping Mode" on page 11
Note:
fCLK_IN must be < 80 kHz to use this feature.
6.3.2
AUX PLL Lock Output Configuration (AuxLockCfg)
When the AUX_OUT pin is configured as a lock indicator (AuxOutSrc[1:0] modal parameter = `11'), this global parameter configures the AUX_OUT driver to either push-pull or open drain. It also determines the polarity of the lock signal. If AUX_OUT is configured as a clock output, the state of this parameter is disregarded.
AuxLockCfg 0 1 Application: AUX_OUT Driver Configuration Push-Pull, Active High (output `high' for unlocked condition, `low' for locked condition). Open Drain, Active Low (output `low' for unlocked condition, high-Z for locked condition). "Auxiliary Output" on page 19
Note: AUX_OUT is an unlock indicator, signalling an error condition when the PLL is unlocked. Therefore, the pin polarity is defined relative to the unlock condition.
6.3.3
Reference Clock Input Divider (RefClkDiv[1:0])
Selects the input divider for the timing reference clock.
RefClkDiv[1:0] 00 01 10 11 Application: Reference Clock Input Divider / 4. / 2. / 1. Reserved. "Internal Timing Reference Clock Divider" on page 10 REF_CLK Frequency Range 32 MHz to 75 MHz (50 MHz with XTI) 16 MHz to 37.5 MHz 8 MHz to 18.75 MHz
6.3.4
Enable PLL Clock Output on Unlock (ClkOutUnl)
Defines the state of the PLL output during the PLL unlock condition.
ClkOutUnl 0 1 Application: Clock Output Enable Status Clock outputs are driven `low' when PLL is unlocked. Clock outputs are always enabled (results in unpredictable output when PLL is unlocked). "PLL Clock Output" on page 19
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6.3.5 Low-Frequency Ratio Configuration (LFRatioCfg)
Determines how to interpret the currently indexed 32-bit User Defined Ratio when the dynamic ratio based Hybrid PLL Mode is selected (either manually or automatically, see section 5.4.6 on page 16).
LFRatioCfg 0 1 Application: Ratio Bit Encoding Interpretation when Input Clock Source is CLK_IN 20.12 - High Multiplier. 12.20 - High Accuracy. "User Defined Ratio (RUD), Frequency Synthesizer Mode" on page 14
Note: When the static ratio based Frequency Synthesizer Mode is selected (either manually or automatically), the currently indexed User Defined Ratio will always be interpreted as a 12.20 fixed point value, regardless of how this parameter is set.
6.3.6
M2 Pin Configuration (M2Config[2:0])
Controls which special function is mapped to the M2 pin.
M2Config[2:0] 000 001 010 011 100 101 110 111 Application: M2 pin function Disable CLK_OUT pin. Disable AUX_OUT pin. Disable CLK_OUT and AUX_OUT. RModSel[1:0] Modal Parameter Enable. Force Manual Fractional N Source Selection. AutoRMod Modal Parameter Override. FracNSrc Modal Parameter Override Force AuxOutSrc[1:0] = 10 (PLL Clock Out). "M2 Mode Pin Functionality" on page 20
6.3.7
Clock Input Bandwidth (ClkIn_BW[2:0])
Sets the minimum loop bandwidth when locked to CLK_IN.
ClkIn_BW[2:0] 000 001 010 011 100 101 110 111 Application: Minimum Loop Bandwidth 1 Hz 2 Hz 4 Hz 8 Hz 16 Hz 32 Hz 64 Hz 128 Hz "Adjusting the Minimum Loop Bandwidth for CLK_IN" on page 13
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CS2000-OTP 7. CALCULATING THE USER DEFINED RATIO
Note: The software for use with the evaluation kit has built in tools to aid in calculating and converting the User Defined Ratio. This section is for those who would like to know more about how the User Defined Ratio is calculated and stored.
Most calculators do not interpret the fixed point binary representation which the CS2000-OTP uses to define the output to input clock ratio (see Section 5.4.1 on page 14); However, with a simple conversion we can use these tools to generate a binary or hex value for Ratio0-3 to be stored in one time programmable memory. Please see "Programming Information" on page 28 for more details on programming.
7.1
High Resolution 12.20 Format
To calculate the User Defined Ratio (RUD) to store in the register(s), divide the desired output clock frequency by the given input clock (CLK_IN or RefClk). Then multiply the desired ratio by the scaling factor of 220 to get the scaled decimal representation; then use the decimal to binary/hex conversion function on a calculator and write to the register. A few examples have been provided in Table 5. Desired Output to Input Clock Ratio (output clock/input clock)
12.288 MHz/10 MHz=1.2288 11.2896 MHz/44.1 kHz=256
Scaled Decimal Representation = (output clock/input clock) * 220 1288490 268435456
Hex Representation of Binary RUD 00 13 A9 2A 10 00 00 00
Table 5. Example 12.20 R-Values
7.2
High Multiplication 20.12 Format
To calculate the User Defined Ratio (RUD) to store in the register(s), divide the desired output clock frequency by the given input clock (CLK_IN). Then multiply the desired ratio by the scaling factor of 212 to get the scaled decimal representation; then use the decimal to binary/hex conversion function on a calculator and write to the register. A few examples have been provided in Table 6. Desired Output to Input Clock Ratio (output clock/input clock)
12.288 MHz/60 Hz=204,800 11.2896 MHz/59.97 Hz =188254.127...
Scaled Decimal Representation = (output clock/input clock) * 212 838860800 771088904
Hex Representation of Binary RUD 32 00 00 00 2D F5 E2 08
Table 6. Example 20.12 R-Values
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CS2000-OTP 8. PROGRAMMING INFORMATION
Field programming of the CS2000-OTP is achieved using the hardware and software tools included with the CDK2000. The software tools can be downloaded from www.cirrus.com for evaluation prior to ordering a CDK. The CDK2000 is designed with built-in features to ease the process of programming small quantities of devices for prototype and small production builds. In addition to its field programming capabilities, the CDK2000 can also be used for the complete evaluation of programmed CS2000-OTP devices. The CS2000-OTP can also be factory programmed for large quantity orders. When ordering factory programmed devices, the CDK should first be used to program and evaluate the desired configuration. When evaluation is complete, the CS2000 Configuration Wizard is used to generate a file containing all device configuration information; this file is conveyed to Cirrus Logic as a complete specification for the factory programming configuration. Please contact your local Cirrus Logic sales representative for more information regarding factory programmed parts. See the CDK2000 datasheet, available at www.cirrus.com, for detailed information on the use of the CDK2000 programming and evaluation tools. Below is a form which represents the information required for programming a device (noted in gray). The "Parameter Descriptions" section beginning on page 23 describes the functions of each parameter. This form may be used either for personal notation for device configuration or it can be filled out and given to a Cirrus representative in conjunction with the programming file from the CDK2000 as an additional check. The User Defined Ratio may be filled out in decimal or it may be entered as hex as outlined in "Calculating the User Defined Ratio" on page 27. For all other parameters mark a `0' or `1' below the parameter name.
OTP Modal and Global Configuration Parameters Form Modal Configuration Set #0 Ratio 0 (dec) Ratio 0 (hex) __ __ : __ __ : __ __ : __ __ RModSel1 RModSel0 AuxOutSrc1 AuxOutSrc0 Modal Configuration Set #1 Ratio 0 (dec) Ratio 0 (hex) __ __ : __ __ : __ __ : __ __ RModSel1 RModSel0 AuxOutSrc1 AuxOutSrc0 Modal Configuration Set #2 Ratio 0 (dec) Ratio 0 (hex) __ __ : __ __ : __ __ : __ __ RModSel1 RModSel0 AuxOutSrc1 AuxOutSrc0 Modal Configuration Set #3 Ratio 0 (dec) Ratio 0 (hex) __ __ : __ __ : __ __ : __ __ RModSel1 RModSel0 AuxOutSrc1 AuxOutSrc0 Global Configuration Set ClkSkipEn AuxLockCfg RefClkDiv1 ClkIn_BW2 ClkIn_BW1 ClkIn_BW0
AutoRMod
LockClk1
LockClk0
FracNSrc
AutoRMod
LockClk1
LockClk0
FracNSrc
AutoRMod
LockClk1
LockClk0
FracNSrc
AutoRMod
LockClk1
LockClk0
FracNSrc
RefClkDiv0
ClkOutUnl
LFRatioCfg
M2Cfg2
M2Cfg1
M2Cfg0
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CS2000-OTP 9. PACKAGE DIMENSIONS 10L MSOP (3 mm BODY) PACKAGE DRAWING (Note 1)
N
D c E A2 A1 SEATING PLANE A
E11
L L1
e
b
END VIEW
123
SIDE VIEW
TOP VIEW
DIM
A A1 A2 b c D E E1 e L L1
MIN
-0 0.0295 0.0059 0.0031 ----0.0157 --
INCHES NOM
-----0.1181 BSC 0.1929 BSC 0.1181 BSC 0.0197 BSC 0.0236 0.0374 REF
MAX
0.0433 0.0059 0.0374 0.0118 0.0091 ----0.0315 --
MIN
-0 0.75 0.15 0.08 ----0.40 --
MILLIMETERS NOM
-----3.00 BSC 4.90 BSC 3.00 BSC 0.50 BSC 0.60 0.95 REF
NOTE MAX
1.10 0.15 0.95 0.30 0.23 ----0.80 --
4, 5 2 3
Notes: 1. Reference document: JEDEC MO-187 2. D does not include mold flash or protrusions which is 0.15 mm max. per side. 3. E1 does not include inter-lead flash or protrusions which is 0.15 mm max per side. 4. Dimension b does not include a total allowable dambar protrusion of 0.08 mm max. 5. Exceptions to JEDEC dimension.
THERMAL CHARACTERISTICS
Parameter
Junction to Ambient Thermal Impedance JEDEC 2-Layer JEDEC 4-Layer
Symbol
JA JA
Min
-
Typ
170 100
Max
-
Units
C/W C/W
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CS2000-OTP 10.ORDERING INFORMATION
The CS2000-OTP is ordered as an un-programmed device. The CS2000-OTP can also be factory programmed for large quantity orders. Please see "Programming Information" on page 28 for more details.
Product
CS2000-OTP CS2000-OTP CDK2000
Description
Clocking Device Clocking Device Evaluation Platform
Package
10L-MSOP 10L-MSOP -
Pb-Free Yes Yes Yes
Grade Commercial -
Temp Range Container
-10 to +70C -10 to +70C Rail Tape and Reel -
Order# CS2000P-CZZ CS2000P-CZZR CDK-2000-CLK
11.REVISION HISTORY
Release
A1 PP1 Initial Release Updated "AC Electrical Characteristics" on page 7
Changes
Contacting Cirrus Logic Support
For all product questions and inquiries, contact a Cirrus Logic Sales Representative. To find one nearest you, go to www.cirrus.com.
IMPORTANT NOTICE "Preliminary" product information describes products that are in production, but for which full characterization data is not yet available. Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, indemnification, and limitation of liability. No responsibility is assumed by Cirrus for the use of this information, including use of this information as the basis for manufacture or sale of any items, or for infringement of patents or other rights of third parties. This document is the property of Cirrus and by furnishing this information, Cirrus grants no license, express or implied under any patents, mask work rights, copyrights, trademarks, trade secrets or other intellectual property rights. Cirrus owns the copyrights associated with the information contained herein and gives consent for copies to be made of the information only for use within your organization with respect to Cirrus integrated circuits or other products of Cirrus. This consent does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale. CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE ("CRITICAL APPLICATIONS"). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED FOR USE IN PRODUCTS SURGICALLY IMPLANTED INTO THE BODY, AUTOMOTIVE SAFETY OR SECURITY DEVICES, LIFE SUPPORT PRODUCTS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF CIRRUS PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE FULLY AT THE CUSTOMER'S RISK AND CIRRUS DISCLAIMS AND MAKES NO WARRANTY, EXPRESS, STATUTORY OR IMPLIED, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR PARTICULAR PURPOSE, WITH REGARD TO ANY CIRRUS PRODUCT THAT IS USED IN SUCH A MANNER. IF THE CUSTOMER OR CUSTOMER'S CUSTOMER USES OR PERMITS THE USE OF CIRRUS PRODUCTS IN CRITICAL APPLICATIONS, CUSTOMER AGREES, BY SUCH USE, TO FULLY INDEMNIFY CIRRUS, ITS OFFICERS, DIRECTORS, EMPLOYEES, DISTRIBUTORS AND OTHER AGENTS FROM ANY AND ALL LIABILITY, INCLUDING ATTORNEYS' FEES AND COSTS, THAT MAY RESULT FROM OR ARISE IN CONNECTION WITH THESE USES. Cirrus Logic, Cirrus, and the Cirrus Logic logo designs are trademarks of Cirrus Logic, Inc. All other brand and product names in this document may be trademarks or service marks of their respective owners.
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DS758PP1

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