DESCRIPTION
■Up to 1.25Gbps operation
■25mA peak drive current
■Separate modulation control
■Separate output enable for laser safety
■Differential inputs for data
■75KΩ input pulldown resistor
■Single power supply
■Designed for use with SY88903 and SY88904
■Available in a tiny 10-pin (3mm) MSOP
The SY88902 is a high speed current switch for driving
a semiconductor laser diode in optical transmission
applications. The output current, or modulation current
IMOD, is DC current controlled by IRSET, current through
the resistor RSET. The output OUT is HIGH when output
enable is HIGH.
The device incorporates complementary open collector
outputs with a capability of driving peak current of 25mA.
The resistor REXT must be placed between /OUT and
VCC to dissipate the worst case power. RSER is
recommended to compensate for laser diode matching
issues.
The SY88902 utilizes the high performance bipolar
ASSET™ technology.
FEATURES
LASER DIODE
DRIVER WTIH
OUTPUT ENABLE
PIN CONFIGURATIONS
BLOCK DIAGRAM
SY88902
FINAL
■1.25Gbps Gigabit Ethernet
■531Mbps and 1062Mbps Fibre Channel
■622Mbps SONET
■Gigabit Interface Converter
APPLICATIONS
1/EN
D
IN
/D
IN
V
REF
R
SET
10 V
CC
OUT
/OUT
GND
GND
9
8
7
6
2
3
4
5
MSOP
K10-1
DIN
VCC
REXT
OUT OUT
RSER
to Laser Diode
DIN
Modulation Control
Internal Logic
BIAS
Control
EN
IMOD
VREF
40X
RSET
VEE
VCC
GND
RSET
1Rev.: C Amendment: /1
Issue Date: July 2000
2
SY88902
Micrel
Pin Function
VCC Most positive power supply input, +5V for PECL
operation.
GND Ground
DIN, /DIN These differential PECL 100K compatible inputs
receive NRZ data.
/EN This PECL 100K compatible input enables
Laser Driver. Modulation current goes to zero
when asserted HIGH.
OUT, /OUT Open collector outputs from the modulation
buffer drive these differential current outputs.
VREF Voltage reference for use with RSET.
RSET An external resistor sets up the source current
for modulation Imod.
D D /EN OUT (2) /OUT
LHLHL
HLLLH
XXHHL
NOTES:
1. L = LOW, H = HIGH, X = don't care
2. H = IOUT = OmA
PIN NAMES TRUTH TABLE(1)
Symbol Rating Value Unit
VCC Power Supply Voltage 0 to +7.0 V
VIInput Voltage 0 to VCC V
IOOutput Current 25 mA
TAOperating Temperature Range 0 to +85 °C
Tstore Storage Temperature Range –55 to +125 °C
Ptot Power Dissipation 250 mW
ABSOLUTE MAXIMUM RATINGS(1)
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.
Symbol Rating Value Unit
VCC Power Supply Voltage +4.5 to +5.5 V
REXT Resistor to Dissipate Power 10 to 50 Ω
RSER Laser Diode Serial Resistor 0 to 50 Ω
RSET Resistor to Adjust Current 1500 to 50,000 Ω
ΘJA Thermal Resistance of Package to Ambient(2) 206 °C/W
COUT Capacitance on OUT + /OUT 2.5 typical pf
OPERATIONING CONDITIONS(1)
NOTES:
1. The voltage drop across REXT and RSER plus Laser Diode should not be greater than 2V.
2. Still air without heatsink.
3
SY88902
Micrel
TA = 0°CTA = +25°CTA = +85°C
Symbol Parameter Min. Typ. Max. Min. Typ. Max. Min. Typ. Max. Unit
VIH Input HIGH Voltage
V
CC
-1165 —V
CC
-880 V
CC
-1165 —V
CC
-880 V
CC
-1165 —V
CC
-880
mV
(DIN, /DIN, /EN)
VIL Input LOW Voltage VCC-1810 —VCC-1475 VCC-1810 —VCC-1475 VCC-1810 —VCC-1475 mV
(DIN, /DIN, /EN)
VREF Reference Voltage —3.12 ——3.00 ——2.80 —V
IIL Input LOW Current(1) 0.5 —— 0.5 —— 0.5 ——uA
(DIN, /DIN, /EN)
IIH Input HIGH Current ——100 ——100 ——100 uA
(DIN, /DIN, /EN)
ICC Supply Current(2) —16 25 —16 25 —16 25 mA
IOL Output LOW Current ——500 ——500 ——500 uA
(/EN = HIGH)
IOUT Modulation Current 5 15 25 5 15 25 5 15 25 mA
IRSET Modulation Control 0.125 —0.625 0.125 —0.625 0.125 —0.625 mA
ARSET =IOUT/IRSET 30 38 44 30 38 44 30 38 44 —
NOTES:
1. VI = VIL(Min.)
2. IMOD = 25mA.
DC ELECTRICAL CHARACTERISTICS
GND = 0V; VCC = +5.0V ±10%; TA = 0˚C to + 85˚C
TA = 0°CTA = +25°CTA = +85°C
Symbol Parameter Min. Typ. Max. Min. Typ. Max. Min. Typ. Max. Unit Conditions
tpd D Propagation Delay ——1000 —500 1000 ——1000 ps IMOD = 10mA
DIN - OUT
tpd EN Propagation Delay ——1000 —450 1000 ——1000 ps IMOD = 10mA
/EN - OUT
trRise/Fall Time —200 ——200 ——200 —ps
tf(20% to 80%)
IOR Output Current Ringing(2) ——10 ——10 ——10 %
AC ELECTRICAL CHARACTERISTICS(1)
IMOD =10mA; GND = 0V; VCC = +5V ±10%; TA = 0˚C to + 85˚C
NOTES:
1. REXT = RSER = 50Ω ±1%, RSER connects to VCC directly without Laser Diode.
2. IOH = 5 to 25mA
4
SY88902
Micrel
APPLICATION EXAMPLE FOR 3-CHIP SET SOLUTION
OUT
V
CC
GND
SY88904
D
IN
D
IN
TX_FAULT
TX_DISABLE
LOS
OUT
GBIC Terminal
V
CC
OUT
TX_Out I
BIAS
EN
OC PECL
LOSEN
MD
D
OUT
D
OUT
D
IN
D
IN
V
CC
GND
SY88902
SY88903
V
CC
GND
V
CC
I
BIAS SET
I
BIAS SET
I
LIMIT SET
Laser
Module
PECL
R
EXT
R
SER
–RX_DAT
+RX_DAT
TX_DISABLE
TX_FAULT
–TX_DATA
+TX_DAT
V
REF
R
SET
R
WIN
V
REF
LOS
V
CC
V
REF
V
CC
I
BIAS FB
V
CC
DET
V
REF
2meg
0.1µf
I
PIN SET
V
REF
RX_LOS
I
LIMIT SET
V
CC
LOS
LVL
5
SY88902
Micrel
APPLICATION EXAMPLE FOR 3-CHIP SET SOLUTION
OUT
V
CC
V
EE
SY88905
D
IN
D
IN
LOSOUT
Gigabit EthernetTerminal
V
CC
OUT
I
BIAS
EN
LOSEN
MD
D
OUT
D
OUT
D
IN
D
IN
V
CC
V
EE
SY88902
SY88903
V
CC
V
CC
V
BIAS SET
I
BIAS SET
Laser
Module
PECL
R
EXT
R
SER
–RX_DAT
+RX_DAT
–TX_DATA
+TX_DAT
V
REF
R
SET
V
LVL
V
REF
LOS
IN
V
REF
I
BIAS FB
I
PIN SET
V
REF
RX_LOS
V
BB
V
CC
I
BIAS SET
V
PIN SET
GND
6
SY88902
Micrel
PERFORMANCE CURVES
PRODUCT ORDERING CODE
Ordering Package Operating
Code Type Range
SY88902KC K10-1 Commercial
SY88902KCTR K10-1 Commercial
10
20
25
30
I
O
(mA)
I
O
and R
SET
0.00.0
15
5
4.0K 6.0K 8.0K 10K
2.0K
R
SET
(ohm)
12K
7
SY88902
Micrel
10 LEAD MSOP (K10-1)
Rev. 00
8
SY88902
Micrel
MICREL-SYNERGY 3250 SCOTT BOULEVARD SANTA CLARA CA 95054 USA
TEL + 1 (408) 980-9191 FAX + 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.
© 2000 Micrel Incorporated