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DS32KHZ
32.768kHz Temperature-Compensated Crystal Oscillator
www.maxim-ic.com
GENERAL DESCRIPTION
The DS32KHZ is a temperature-compensated crystal oscillator (TCXO) with an output frequency of 32.768kHz. This device addresses applications requiring better timekeeping accuracy and can be used to drive the X1 input of most Dallas Semiconductor real-time clocks (RTCs), chipsets, and other ICs containing RTCs. This device is available in commercial (DS32KHZ) and industrial (DS32KHZ-N) temperature versions.
FEATURES

Accurate to 4 Min/Yr (-40C to +85C) Accurate to 1 Min/Yr (0C to +40C) Battery Backup for Continuous Timekeeping VBAT Operating Voltage: 2.7V to 5.5V with VCC Grounded VCC Operating Voltage: 4.5V to 5.5V Operating Temperature Range: 0C to +70C (Commercial) -40C to +85C (Industrial) No Calibration Required Low-Power Consumption Surface Mountable Using BGA Package UL Recognized
APPLICATIONS
GPS Receivers Telematics Network Timing and Synchronization in Servers, Routers, Hubs, and Switches Automatic Power Meters
ORDERING INFORMATION
PART DS32KHZ/DIP DS32KHZ-N/DIP DS32KHZ/WBGA DS32KHZ-N/WBGA TEMP RANGE 0C to +70C -40C to +85C 0C to +70C -40C to +85C PIN-PACKAGE 14 DIP 14 DIP 36 BGA 36 BGA
PIN CONFIGURATIONS
TOP VIEW
N.C.
1 2 3
DS32KHZ
14 13 12 11 10 9 8
N.C. VCC 32KHZ OUT TPIN TPIN N.C. N.C.
GND VBAT N.C. N.C.
4 5 6 7
DIP BGA
Note: Some revisions of this device may incorporate deviations from published specifications known as errata. Multiple revisions of any device may be simultaneously available through various sales channels. For information about device errata, click here: www.maxim-ic.com/errata.
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REV: 041603
DS32KHZ
ABSOLUTE MAXIMUM RATINGS
Voltage Range on Any Pin Relative to Ground Operating Temperature Range Commercial Industrial Storage Temperature Range Soldering Temperature (BGA) Soldering Temperature, Leads (DIP) -3.0V to +7.0V 0C to +70C -40C to +85C -40C to +85C See IPC/JEDEC J-STD-020A (2x max) (Note 1) 260C for 10 seconds (Notes 1, 2)
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to the absolute maximum rating conditions for extended periods may affect device.
RECOMMENDED DC OPERATING CONDITIONS
(TA = -40C to +85C) PARAMETER Power-Supply Voltage Battery Voltage (Note 3) SYMBOL VCC VBAT CONDITIONS MIN 4.5 2.7 TYP 5.0 3.0 MAX 5.5 3.3, 5.5 UNITS V V
DC ELECTRICAL CHARACTERISTICS
(Over the operating range, unless otherwise specified.) PARAMETER Active Supply Current Active Battery Current High Output Voltage (VCC) Low Output Voltage Battery Switch Voltage High Output Voltage (VBAT) SYMBOL ICC IBAT VOH VOL VSW VOH IOH = -0.1mA 2.4 CONDITIONS (Notes 4, 5) VCC = 0V, VBAT = 3.3V (Notes 4, 5, 6, 7) IOH = -1.0mA IOL = 2.1mA VBAT 2.4 0.4 MIN TYP 150 1 MAX 180 4 UNITS A A V V V V
Note 1: Post-solder cleaning with water-washing techniques is acceptable, provided that ultrasonic vibration is not used. Such cleaning can damage the crystal. Note 2: Encapsulated DIP modules can be successfully processed through conventional wave-soldering techniques, as long as the temperature of the crystal contained inside does not exceed +150C. Note 3: VBAT must be no greater than 3.3V when the device is used in the dual-supply operating modes. Note 4: Typical values are at +25C and 5.0V VCC, 3.0 VBAT, unless otherwise indicated. Note 5: These parameters are measured under no load conditions. Note 6: This current is the active mode current sourced from the backup supply/battery. Note 7: Battery current increases to 450A (typ) for 122ms (typ) for every 64 seconds.
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DS32KHZ
AC TIMING CHARACTERISTICS
(Over the operating range, unless otherwise specified.) PARAMETER Output Frequency Frequency Stability vs. Temperature Duty Cycle Cycle Time High/Low Time Rise Time Fall Time Oscillator Startup Time Frequency Stability vs. Operating Voltage Crystal Aging SYMBOL fOUT f/fO tW/t tCYC tH/tL tR tF tOSC f/V f/fO (Note 8) (Note 8) (Note 8) (Note 8) (Note 8) VCC = 5.0V or VBAT = 3.0V, VCC = 0V (Notes 4, 9) (Notes 4, 10) 0C to +40C -40C to +85C or 0C to +70C -2.0 -7.5 45 50 30.518 15.06 200 60 1 2.5 1.0 CONDITIONS MIN TYP 32.768 +2.0 +7.5 55 ppm % s s ns ns s ppm/V ppm/yr MAX UNITS kHz
Note 8: These parameters are measured using a 15pF load. Note 9: Error is measured from the nominal supply voltage of whichever supply is powering the device. Note 10: After reflow.
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DS32KHZ
TYPICAL OPERATING CHARACTERISTICS
(VCC = 3.3V, TA = +25C, unless otherwise noted.)
IBAT vs. VBAT
DS32KHZ toc01
ICC vs. VCC
DS32KHZ toc02
IBAT vs. OUTPUT LOAD vs. VCC
DS32KHZ toc03
4.5 4.0 SUPPLY CURRENT (mA) 3.5 3.0 2.5 2.0 1.5 2.5 3.0 3.5 4.0 VBAT (V) 4.5 5.0
150 125 SUPPLY CURRENT (mA) 100 75 50 25
15.0 12.5 SUPPLY CURRENT (mA) 10.0 7.50 6.00 2.50 0 22pF 10pF 0pF 47pF
5.5
2.5
3.0
3.5
4.0 VCC (V)
4.5
5.0
5.5
2.5
3.0
3.5
4.0 VBAT
4.5
5.0
5.5
FREQUENCY ERROR vs. VBAT
7 6 ERROR (ppm) 5 4 3 2 1 0 -1 2.5 3.0 3.5 4.0 VBAT (V) 4.5 5.0 5.5
DS32KHZ toc04
FREQUENCY ERROR vs. VCC
DS32KHZ toc05
8
2.0 1.5 1.0 0.5 0 -0.5 -1.0 4.5 5.0 VCC (V)
ERROR (ppm)
5.5
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DS32KHZ
PIN DESCRIPTIONS
PIN BGA A4, A5, B4, B5 A7, A8, B7, B8, C7, C8, D7, D8 C2, C3, D2, D3 C4, C5, D4, D5 -- All remaining balls DIP 5 10, 11 13 12 1, 6-9, 14 4 NAME VBAT TPIN VCC 32KHZ OUT N.C. GND FUNCTION +3V Batttery Supply Test Pin (must be grounded) Primary Power Supply 32.768kHz Output No Connection Ground
Figure 1. Delta Time and Frequency vs. Temperature
0.00 -10.00 -20.00 -30.00 -40.00 -50.00 TYPICAL CRYSTAL UNCOMPENSATED -60.00 DS32KHZ OUTPUT -70.00 -80.00 -90.00 -100.00
DELTA TIME (MIN/YR)
FUNCTIONAL DESCRIPTION
The DS32KHZ requires four pins for operation: VCC, GND, VBAT, and 32KHZ OUT. (See Figure 3 for connection schemes.) Power is applied through VCC and GND, while VBAT is used to maintain the 32kHz output in the absence of power. The output is accurate to 7.5ppm (4 min/yr) from -40C to +85C and 2ppm (1 min/yr) from 0C to +40C. The DS32KHZ is packaged in a small 36-pin SMD using ball grid array (BGA) with dimensions 0.400" wide, 0.450" long, and 0.124" high. It also is available in a 14-pin DIP module. technology
The additional board space required is negligible in most applications and, therefore, the recommended land pattern layout should be implemented on all new designs and future board revisions to satisfy applications requiring better timekeeping accuracy.
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DS32KHZ
Figure 2. Block Diagram
OPERATION
The DS32KHZ module contains a crystal and an IC. While powered, the DS32KHZ peridocially measures the temperature and adjusts the crystal load to compensate. The DS32KHZ is designed to operate in two modes. In the dual-supply mode, a comparator circuit, powered by VCC, monitors the relationship between the VCC and VBAT input levels. When VCC drops below a certain level compared to VBAT, the device switches over to VBAT (Figure 3A). This mode uses VCC to conserve the battery connected to VBAT while VCC is applied. In the single-supply mode, VCC is grounded and the unit is powered by VBAT. Current consumption is less than that of VCC, because the comparator circuit is unpowered (Figure 3B). Figure 3A shows how the DS32KHZ should be connected when using two power supplies. VCC should be between 4.5V and 5.5V and VBAT should be between 2.7V and 3.3V. Figure 3B shows how the DS32KHZ can be used when only a single-supply system is available. VCC should be grounded and VBAT should then be held between 2.7V and 5.5V. The VBAT pin should be connected directly to a battery. Figure 3C shows a single supply mode where VCC is held at +5V. See the frequency stability versus operating voltage for information about frequency error versus supply voltage.
Figure 3. Power-Supply Connections
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DS32KHZ Figure 4 illustrates how a standard 32.768kHz crystal and the DS32KHZ should be connected to address the interchangeable option. Using this connection scheme and the recommended layout provides a solution, which requires no hardware modifications. Only one device should be used at a time, and both layouts should be located very close together if the recommended layout is not used. The DS32KHZ ICC and IBAT currents are specified with no output loads. Many RTC oscillator circuits use a quartz crystal or resonator. Driving the oscillator circuit with the rail-to-rail output of the DS32KHZ can increase the ICC and IBAT currents significantly and increase the current consumption of the RTC as well. Figure 5 shows one circuit that can be used to reduce the current consumption of a DS32KHZ and an RTC. The values of R1 and C1 may vary depending on the RTC used. However, values of 1.0MW and 100pF are recommended as a starting point. R2 is used to shift the input waveform to the proper level. The recommended value for R2 is 33kW.
Figure 4. DS32KHZ Connections
THE STANDARD 32.768kHz CRYSTAL AND THE DS32KHZ SHOULD BE CONNECTED TO ADDRESS THE INTERCHANGEABLE OPTION.
Figure 5. DS32KHZ and RTC Connections
THIS SHOWS A CIRCUIT THAT CAN BE USED TO REDUCE THE CURRENT CONSUMPTION OF A DS32KHZ AND AN RTC.
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DS32KHZ
Figure 6. DS32KHZ Output Waveform
RELATED APPLICATION NOTES
Application Note 58: Crystal Considerations with Dallas Real-Time Clocks Application Note 701: Using the DS32KHZ with Dallas RTCs
PACKAGE INFORMATION
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package information, go to www.maxim-ic.com/DallasPackInfo.)
G
PKG
36-PIN BGA MIN 0.395 0.445 0.022 0.047 0.047 0.347 0.118 0.020 MAX 0.405 0.455 0.028 0.053 0.053 0.353 0.130 0.030
H D C
F A
E
DIM A IN B IN C IN D IN E IN F IN G IN H IN
B
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DS32KHZ
PACKAGE INFORMATION (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package information, go to www.maxim-ic.com/DallasPackInfo.)
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DS32KHZ
PACKAGE INFORMATION (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package information, go to www.maxim-ic.com/DallasPackInfo.)
Note: Pins 2, 3 are missing by design.
PKG DIM A IN B IN C IN D IN E IN F IN G IN H IN J IN K IN
14-PIN DIP MIN MAX 0.825 0.840 0.420 0.440 0.235 0.260 0.100 0.130 0.015 0.030 0.110 0.140 0.090 0.110 0.290 0.330 0.008 0.012 0.015 0.021
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