DESCRIPTION
s
Up to 1.25Gbps operation
s
25mA peak drive current
s
Separate modulation control
s
Separate output enable for laser safety
s
Differential inputs for data
s
75K
input pulldown resistor
s
Single power supply
s
Designed for use with SY88903 and SY88904
s
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
I
MOD
, is DC current controlled by I
RSET
, current through
the resistor R
SET
. 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 R
EXT
must be placed between /OUT and
V
CC
to dissipate the worst case power. R
SER
is
recommended to compensate for laser diode matching
issues.
The SY88902 utilizes the high performance bipolar
ASSETTM technology.
FEATURES
LASER DIODE
DRIVER WTIH
OUTPUT ENABLE
PIN CONFIGURATIONS
BLOCK DIAGRAM
SY88902
s
1.25Gbps Gigabit Ethernet
s
531Mbps and 1062Mbps Fibre Channel
s
622Mbps SONET
s
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
D
IN
V
CC
R
EXT
OUT
OUT
R
SER
to Laser Diode
D
IN
Modulation Control
Internal Logic
BIAS
Control
EN
I
MOD
V
REF
40X
R
SET
V
EE
V
CC
GND
R
SET
1
Rev.: C
Amendment: /1
Issue Date:
July 2000
2
SY88902
Micrel
Pin
Function
V
CC
Most positive power supply input, +5V for PECL
operation.
GND
Ground
D
IN
, /D
IN
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.
V
REF
Voltage reference for use with R
SET.
R
SET
An external resistor sets up the source current
for modulation I
mod
.
D
D
/EN
OUT
(2)
/OUT
L
H
L
H
L
H
L
L
L
H
X
X
H
H
L
NOTES:
1. L = LOW, H = HIGH, X = don't care
2. H = I
OUT
= OmA
PIN NAMES
TRUTH TABLE
(1)
Symbol
Rating
Value
Unit
V
CC
Power Supply Voltage
0 to +7.0
V
V
I
Input Voltage
0 to V
CC
V
I
O
Output Current
25
mA
T
A
Operating Temperature Range
0 to +85
C
T
store
Storage Temperature Range
55 to +125
C
P
tot
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
V
CC
Power Supply Voltage
+4.5 to +5.5
V
R
EXT
Resistor to Dissipate Power
10 to 50
R
SER
Laser Diode Serial Resistor
0 to 50
R
SET
Resistor to Adjust Current
1500 to 50,000
JA
Thermal Resistance of Package to Ambient
(2)
206
C/W
C
OUT
Capacitance on OUT + /OUT
2.5 typical
pf
OPERATIONING CONDITIONS
(1)
NOTES:
1. The voltage drop across R
EXT
and R
SER
plus Laser Diode should not be greater than 2V.
2. Still air without heatsink.
3
SY88902
Micrel
T
A
= 0
C
T
A
= +25
C
T
A
= +85
C
Symbol
Parameter
Min.
Typ.
Max.
Min.
Typ.
Max.
Min.
Typ.
Max.
Unit
V
IH
Input HIGH Voltage
V
CC
-1165
--
V
CC
-880
V
CC
-1165
--
V
CC
-880
V
CC
-1165
--
V
CC
-880
mV
(D
IN
, /D
IN
, /EN)
V
IL
Input LOW Voltage
V
CC
-1810
--
V
CC
-1475 V
CC
-1810
--
V
CC
-1475 V
CC
-1810
--
V
CC
-1475
mV
(D
IN
, /D
IN
, /EN)
V
REF
Reference Voltage
--
3.12
--
--
3.00
--
--
2.80
--
V
I
IL
Input LOW Current
(1)
0.5
--
--
0.5
--
--
0.5
--
--
uA
(D
IN
, /D
IN
, /EN)
I
IH
Input HIGH Current
--
--
100
--
--
100
--
--
100
uA
(D
IN
, /D
IN
, /EN)
I
CC
Supply Current
(2)
--
16
25
--
16
25
--
16
25
mA
I
OL
Output LOW Current
--
--
500
--
--
500
--
--
500
uA
(/EN = HIGH)
I
OUT
Modulation Current
5
15
25
5
15
25
5
15
25
mA
I
RSET
Modulation Control
0.125
--
0.625
0.125
--
0.625
0.125
--
0.625
mA
A
RSET
=I
OUT
/I
RSET
30
38
44
30
38
44
30
38
44
--
NOTES:
1. V
I
= V
IL
(Min.)
2. I
MOD
= 25mA.
DC ELECTRICAL CHARACTERISTICS
GND = 0V; V
CC
= +5.0V
10%; T
A
= 0
C
to + 85
C
T
A
= 0
C
T
A
= +25
C
T
A
= +85
C
Symbol
Parameter
Min.
Typ.
Max.
Min.
Typ.
Max.
Min.
Typ.
Max.
Unit
Conditions
t
pd
D
Propagation Delay
--
--
1000
--
500
1000
--
--
1000
ps
I
MOD
= 10mA
D
IN
- OUT
t
pd
EN
Propagation Delay
--
--
1000
--
450
1000
--
--
1000
ps
I
MOD
= 10mA
/EN - OUT
t
r
Rise/Fall Time
--
200
--
--
200
--
--
200
--
ps
t
f
(20% to 80%)
I
OR
Output Current Ringing
(2)
--
--
10
--
--
10
--
--
10
%
AC ELECTRICAL CHARACTERISTICS
(1)
I
MOD
=10mA; GND = 0V; V
CC
= +5V
10%; T
A
= 0
C
to + 85
C
NOTES:
1. R
EXT
= R
SER
= 50
1%, R
SER
connects to V
CC
directly without Laser Diode.
2. I
OH
= 5 to 25mA
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