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1.25Gbps HIGH-SPEED LIMITING POST AMPLIFIER
SY88903
FEATURES
s s s s s s s s s Up to 1.25Gbps operation Low noise Chatter-Free LOS Generation Open Collector TTL LOS Output TTL /EN Input Differential PECL inputs for data Single power supply Designed for use with SY88902 and SY88904 Available in a tiny 10-pin (3mm) MSOP
DESCRIPTION
The SY88903 limiting post amplifier with its high gain and wide bandwidth is ideal for use as a post amplifier in fiber-optic receivers with data rates up to 1.25Gbps. Signals as small as 5mVp-p can be amplified to drive devices with PECL inputs. The SY88903 generates a chatter-free Loss of Signal (LOS) open collector TTL output. The SY88903 incorporates a programmble level detect function to identify when the input signal has been lost. This information can be fed back to the /EN input of the device to maintain stability under loss of signal conditions. Using LOSLVL pin the sensitivity of the level detect can be adjusted. The LOSLVL voltage can be set by connecting a resistor divider between VCC and VREF, Figure 3. Figure 4 shows the relationship between input level sensitivity and the voltage set on LOSLVL. Figure 5 shows the relationship between input level sensitivity and resistor divider ratio. The LOS output is a TTL open collector output that requires pull-up resistor for proper operation, Figure 1.
+5V
PIN CONFIGURATION
/EN 1 DIN 2 /DIN 3 VREF 4 LOSLVL 5 MSOP K10-1 10 VCC 9 DOUT 8 /DOUT 7 LOS 6 GND
SY88903
2k LOS
APPLICATIONS
s s s s 1.25Gbps Gigabit Ethernet 531Mbps and 1062Mbps Fibre Channel 622Mbps SONET Gigabit Interface Converter
Figure 1. LOS Output with Desired Rise Time
BLOCK DIAGRAM
DIN
Limiting Amplifier ECL Buffer
DOUT DOUT
Enable
DIN VREF VCC
Level Detect
EN
GND
LOSLVL
LOS
Rev.: G
Amendment: /1
1
Issue Date: July 2000
Micrel
SY88903
PIN NAMES
Pin DIN /DIN LOS LVL /EN LOS GND DOUT /DOUT VCC VREF Type Data Input Data Input Input TTL Input TTL Output (Open Collector) Ground PECL Output PECL Output Power Supply Output Function Data Input Inverting Data Input Loss of Signal Level Set Output Enable (active Low) Loss of Signal Indicator (active High) Ground Data Output Inverting Data Output Positive Power Supply Reference Voltage Output for LOS Level Set (see Fig. 3)
GENERAL DESCRIPTION
General The SY88903 is an integrated limiting amplifier intended for high-frequency fiber-optic applications. The circuit connects to typical transimpedance amplifiers found within a fiber-optics link. The linear signal output from a transimpedance amplifier can contain significant amounts of noise, and may vary in amplitude over time. The SY88903 limiting amplifier quantizes the signal and outputs a voltagelimited waveform. The TTL /EN pin allows the user to disable the output signal without removing the input signal.
ABSOLUTE MAXIMUM RATINGS(1)
Symbol VCC DIN, /DIN DOUT, /DOUT TA Tstore Rating Power Supply Voltage Input Voltage Output Voltage (with 50 load) Operating Temperature Range Storage Temperature Range Value 0 to +7.0 0 to VCC VCC -2.5, VCC +0.3 -40 to +85 -55 to +125 Unit V V V C C
NOTE: 1. Permanent device damage may occur if ABSOLUTE MAXIMUM RATINGS are exceeded. This is a stress rating only and functional operation is not implied at conditions other than those detailed in the operational sections of this data sheet. Exposure to ABSOLUTE MAXIMUM RATlNG conditions for extended periods may affect device reliability.
2
Micrel
SY88903
DC ELECTRICAL CHARACTERISTICS
VCC = +5V 10%, RLOAD = 50 to VCC-2V, TA = -40C to +85C
TA = -40C Symbol ICC IIL IIH VCMR Voffset LOSLVL VOL IOH VOH VOL VREF VIH VIL Parameter Power Supply Current(1) Min. -- -0.3 -- --
GND +2.0
TA = 0C Min. -- -0.3 -- -- Max. 35 -- 20(5) 100(6) 100 VCC 0.5 250
VCC-880
TA = +25C Min. -- -0.3 -- -- Typ. 21 -- -- -- -- -- -- -- --
VCC-955
TA = +85C Max. 35 -- 20(5) 100(6) 100 VCC 0.5 250
VCC-880
Max. 35 -- 20(5) 100(6) 100 VCC 0.5 250
VCC-880
Min. -- -0.3 -- --
Max. 35 -- 20(5) 100(6) 100 VCC 0.5 250
VCC-880 VCC-1620
Unit mA mA A V mV V V uA mV mV V V V
/EN Input LOW Current /EN Input HIGH Current Common Mode Range Differential Output Offset LOSLVL Level LOS Output Low Level(2) LOS Output Leakage(3) DOUT and /DOUT HIGH Output DOUT and /DOUT LOW Output Reference Supply(4) /EN Input HIGH Voltage /EN Input LOW Voltage
VCC -1.0 GND +2.0 VCC -1.0 GND +2.0 -- VREF -- --
VCC-1025
VCC -1.0 GND +2.0 VCC -1.0 -- VREF -- --
VCC-1025 VCC-1810
-- VREF -- --
VCC-1085 VCC-1830
-- VREF -- --
VCC-1025
VCC-1555 VCC-1810 VCC-1620 VCC-1810 VCC-1705 VCC-1620
VCC-2.625 VCC-2.325 VCC-2.625 VCC-2.325 VCC-2.625 VCC-2.475 VCC-2.325 VCC-2.625 VCC-2.325
2.0 --
-- 0.8
2.0 --
-- 0.8
2.0 --
-- --
-- 0.8
2.0 --
-- 0.8
NOTES: 1. No output load 2. IOL = + 2mA 3. VOH = 5.5V
4. IREF must be limited to be within -0.8mA (source) and 0.5mA (sink). 5. VIN = 2.7V 6. VIN = VCC
AC ELECTRICAL CHARACTERISTICS
VCC = +5V 10%, RLOAD = 50 to VCC - 2V, TA = -40C to +85C
TA = -40C Symbol PSRR VID tr, tf VOD tOFFL tOFFH tONL VSR HYS Parameter Power Rejection Ratio Supply(1) Min. -- 5 -- -- -- -- -- -- -- 5 2 Max. -- 1800 350 -- -- -- 0.5 0.5 0.5 50 8 TA = 0C Min. -- 5 -- -- -- -- -- -- -- 5 2 Max. -- 1800 350 -- -- -- 0.5 0.5 0.5 50 8 -- 5 -- -- -- -- -- -- -- 5 2 TA = +25C Min. Typ. 35 -- 200 trin,tfin 600 200 0.1 0.1 0.2 -- 4.6 Max. -- 1800 350 -- -- -- 0.5 0.5 0.5 50 8 TA = +85C Min. -- 5 -- -- -- -- -- -- -- 5 2 Max. -- Unit dB Conditions Input referred, 55MHz
Input Voltage Range Output Rise/Fall Time Differential Output Voltage Swing(2) LOS Release Time(3) Minimum Input LOS Release Time(4) Maximum Input LOS Assert Time(3) LOS Sensitivity Range LOS Hysteresis
1800 mVp-p 350 -- -- -- 0.5 0.5 0.5 50 8 ps mV mV s s s mVp-p dB VID > 100mVp-p VID < 100mVp-p VID = 15mVp-p VID = 5mVp-p
NOTES: 1. Input referred noise = RMS output noise/low frequency gain. 2. Input is 622MHz square wave.
3. Input is a 200MHz square wave, tr < 300ps, 8mVp-p. 4. Input is a 200MHz square wave, tr < 300ps, 1.8Vp-p.
3
Micrel
SY88903
APPLICATION INFORMATION
Output Termination The SY88903 outputs must be terminated with a 50 load to VCC - 2V (or Thevenin equivalent). Layout and PCB Design Since the SY88903 is a high-frequency component, performance can largely be determined by board layout and design. A common problem with high-gain amplifiers is feedback from the large swing outputs to the input via the power supply. The SY88903 ground pin should be connected to the circuit board ground. Use multiple PCB vias close to the part to connect to ground. Avoid long, inductive runs which can degrade performance.
NOTES: Resistor Divider = R2/ (R1 + R2) R1 + R2 5k
VCC
R1
0.1F
DIN+
LOSLVL
0.1F
DIN-
R2
50
50
VREF
VREF
0.1F
Figure 3. LOSLVL Circut
Figure 2. Differential Input Configuration
PRODUCT ORDERING CODE
Ordering Code SY88903KC Package Type K16-1 Operating Range Commercial
4
Micrel
SY88903
PERFORMANCE CURVE
100.00
90.00
80.00
Deassert
70.00
60.00
Level (mV)
50.00
Assert
40.00
30.00
20.00
10.00
0.00
2.53 2.65 2.77 2.90 3.02 3.14 3.27 3.39 3.52 3.64 3.76 3.89 4.01 4.13 4.26 4.38 4.51 4.63 4.75 4.88 5.00
LOSlvl (V)
Figure 4. LOS Assert and Deassert Levels vs LOSLVL
100.00
90.00
80.00
Deassert
70.00
60.00
Level (mV)
Assert
50.00
40.00
30.00
20.00
10.00
0.00
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00
Resistor Divider R2 / (R1 + R2)
Figure 5. LOS Assert and Deassert Levels vs Resistor Divider
5
SY88903
20k
82
82
VREF OUT DIN DIN
RSET
TX_DATA+
SY88902
EN
130
130
TX_DATA-
OUT
REXT
24
RSER
BLM21A102S
Laser Module
ENABLE/DISABLE
VCC
GND
VCC
APPLICATION EXAMPLE FOR 3-CHIP SET SOLUTION
GBIC Terminal
IBIAS
MD IBIAS SET
20k
The value of RSER depends on the Laser Diode.
SY88905
LOSOUT LOSIN
RX_LOS
IPIN SET
20k
VCC VCC EN
82 82
GND
VREF
VCC LOS DIN DOUT
RX_DATA+ RX_DATA-
130 130
130
LOSLVL
0.1F
VCC
VCC
GND
VREF
Micrel
0.1F
20k
130
DOUT
SY88903
DIN
82
82
6
IBIAS FB
1000pF
VCC
Photodiode Laserdiode
VCC
Micrel
SY88903
10 LEAD MSOP (K10-1)
Rev. 00
7
Micrel
SY88903
MICREL-SYNERGY
TEL
3250 SCOTT BOULEVARD SANTA CLARA CA 95054 USA
FAX
+ 1 (408) 980-9191
+ 1 (408) 914-7878
WEB
http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc. (c) 2000 Micrel Incorporated
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