1
SY88903V
Micrel, Inc.
M9999-041505
hbwhelp@micrel.com or (408) 955-1690
DESCRIPTION
s
3.3V and 5V power supply option
s
Up to 1.25Gbps operation
s
Low noise
s
Chatter-free LOS generation
s
Open collector TTL LOS output
s
TTL /EN Input
s
Differential PECL inputs for data
s
Single power supply
s
Designed for use with laser diode driver and
controller
s
Available in a tiny 10-pin (3mm
3mm) MSOP
The SY88903V 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 5mV
pp
can be amplified to drive devices with
PECL inputs. The SY88903V generates a chatter-free, Loss-
-of-Signal (LOS), open-collector TTL output.
The SY88903V 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
SY88903V limiting amplifier quantizes the signal and outputs
a voltage-limited waveform.
The /EN pin allows the user to disable the output signal
without removing the input signal.
The SY88903V incorporates a programmable 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 condition.
The sensitivity of the level detection can be adjusted using
LOS
LVL
. The LOS
LVL
voltage can be set by connecting a
resistor divider between V
CC
and V
REF
as shown in Figure
3. "Typical Characteristics" show the relationship between
input level sensitivity and the voltage set on LOS
LVL
.
The LOS output is a TTL open-collector output that
requires a pull-up resistor for proper operation, Figure 1.
SY88903V
LOS
2k
V
CC
Figure 1. LOS Output with Desired Rise Time
All support documentation can be found on Micrel's web
site at www.micrel.com.
FEATURES
APPLICATIONS
s
1.25Gbps Gigabit Ethernet
s
531Mbps and 1062Mbps Fibre Channel
s
622Mbps SONET
s
Gigabit Interface Converter
BLOCK DIAGRAM
Limiting
Amplifer
ECL
Buffer
D
IN
D
IN
V
REF
V
CC
GND
LOS
LVL
Enable
Level
Detect
D
OUT
D
OUT
EN
LOS
Rev.: B
Amendment: /0
Issue Date:
April 2005
5V/3.3V 1.25Gbps HIGH-SPEED
LIMITING POST AMPLIFIER
SY88903V
2
SY88903V
Micrel, Inc.
M9999-041505
hbwhelp@micrel.com or (408) 955-1690
Pin Number
Pin Name
Type
Pin Function
1
EN
TTL Input
Output Enable (Active Low).
2
DIN
Data Input
Data Input.
3
/DIN
Data Input
Inverting Data Input.
4
VREF
Output
Reference Voltage Output for LOS Level Set (see Figure 3).
5
LOSLVL
Input
LOS Limit Set.
6
GND
Ground
Ground
7
LOS
TTL Output
Loss-of-Signal Indicator (Active Low).
(Open Collector)
8
/DOUT
PECL Output
Inverting Data Output.
9
DOUT
PECL Output
Data Output.
10
VCC
Power Supply
Positive Power Supply.
PACKAGE/ORDERING INFORMATION
Ordering Information
(1)
Package
Operating
Package
Lead
Part Number
Type
Range
Marking
Finish
SY88903VKC
K10-1
Commercial
903V with Pb-free
Sn-Pb
bar-line indicator
SY88903VKCTR
(2)
K10-1
Commercial
903V with Pb-free
Sn-Pb
bar-line indicator
SY88903VKG
K10-1
Industrial
903V with Pb-free
NiPdAu
bar-line indicator
SY88903VKGTR
(2)
K10-1
Industrial
903V with Pb-free
NiPdAu
bar-line indicator
Notes:
1. Contact factory for die availability. Die is guaranteed at T
A
= 25
C, DC electricals only.
2. Tape and Reel.
PIN DESCRIPTION
LOSLVL
GND
6
5
1
/EN
DIN
/DIN
VREF
10 VCC
DOUT
/DOUT
LOS
9
8
7
2
3
4
10-Pin MSOP (K10-1)
3
SY88903V
Micrel, Inc.
M9999-041505
hbwhelp@micrel.com or (408) 955-1690
Absolute Maximum Ratings
(1)
Supply Voltage (V
CC
) ....................................... 0V to +7.0V
Input Voltage (D
IN
,
/D
IN
, /EN, LOS
LVL
) ............... 0V to V
CC
Output Voltage
(D
OUT
,
/D
OUT
) with 50
Load ... V
CC
2.5V to V
CC
+0.3V
(VREF) ............................................ V
CC
2.0V to V
CC
Lead Temperature (soldering, 10 sec.) ..................... 270
C
Storage Temperature (T
S
) ....................... 55
C to +125
C
Operating Ratings
(2)
Supply Voltage (V
IN
) ...................................... +xxV to +xxV
Ambient Temperature (T
A
) ......................... 40
C to +85
C
Package Thermal Resistance
MSOP
(
JA
) ......................................................... xx
C/W
V
CC
= +5V
10% or +3.3V
10%; R
LOAD
= 50
to V
CC
2V; T
A
= 40
C to +85
C; unless noted.
Symbol
Parameter
Condition
Min
Typ
Max
Units
I
CC
Power Supply Current
No output load
30
42
mA
I
IL
/EN Input LOW Current
V
IN
= 0.5V
0.3
mA
I
IH
/EN Input HIGH Current
V
IN
= 2.7V
20
A
V
IN
= VCC
100
V
CMR
Common Mode Range
GND +2.0
V
CC
V
V
offset
Differential Output Offset
100
mV
LOS
LVL
LOSLVL Level
V
REF
V
CC
V
V
OL
LOS Output Low Level
I
OL
= +2mA
0.5
V
I
OH
LOS Output Leakage
V
OH
= 5.5V
250
A
V
OH
DOUT and /DOUT
V
CC
1085 V
CC
955
V
CC
880
mV
HIGH Output
V
OL
DOUT and /DOUT
V
CC
1830 V
CC
1705 V
CC
1620
mV
LOW Output
V
REF
Reference Supply
V
CC
1.38 V
CC
1.32 V
CC
1.26
V
I
REF
VREF Output Current
0.8
0.5
mA
V
IH
/EN Input HIGH Voltage
2.0
V
V
IL
/EN Input LOW Voltage
0.8
V
Notes:
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 Ratings" conditions for
extended periods may affect device reliability.
2. The data sheet limits are not guaranteed if the device is operated beyond the operating ratings.
DC ELECTRICAL CHARACTERISTICS
4
SY88903V
Micrel, Inc.
M9999-041505
hbwhelp@micrel.com or (408) 955-1690
V
CC
= +5V
10% or +3.3V
10%; R
LOAD
= 50
to V
CC
2V; T
A
= 40
C to +85
C; unless noted.
Symbol
Parameter
Condition
Min
Typ
Max
Units
PSRR
Power Supply
(3)
Input referred, 55MHz
35
dB
Rejection Ratio
V
ID
Input Voltage Range
5
1800
mV
pp
t
r
, t
f
Output Rise/Fall Time
V
ID
> 100mV
pp
260
ps
V
ID
< 100mV
pp
trin,tfin
V
OD
Differential Output
V
ID
= 15mV
pp
600
mV
Voltage Swing
(4)
V
ID
= 5mV
pp
200
mV
t
OFFL
LOS Release Time
(5)
0.1
0.5
s
Minimum Input
t
OFFH
LOS Release Time
(6)
0.1
0.5
s
Maximum Input
t
ONL
LOS Assert Time
(5)
0.2
0.5
s
VSR
LOS Sensitivity Range
2
23
1 pattern
5
50
mV
pp
HYS
LOS Hysteresis
2
23
1 pattern
2
4.6
8
dB
Notes:
3. Input referred noise = RMS output noise/low frequency gain.
4. Input is a 622MHz square wave.
5. Input is a 200MHz square wave, t
r
< 300ps, 8mV
pp
.
6. Input is a 200MHz square wave, t
r
< 300ps, 1.8V
pp
.
AC ELECTRICAL CHARACTERISTICS
TYPICAL CHARACTERISTICS
0
10
20
30
40
50
60
70
80
90
100
0
-0.2 -0.4 -0.6 -0.8 -1.0 -1.2
INPUT LEVEL (mV
pp
)
LOSLVL V
CC
V
LOS Assert and De-assert
Levels vs LOS
LVL
3.3V
T
A
= 25
C
1.25Gbps
Pattern 2
7
-1
0
10
20
30
40
50
60
70
80
90
100
0
-0.2 -0.4 -0.6 -0.8 -1.0 -1.2
INPUT LEVEL (mV
pp
)
LOSLVL V
CC
V
LOS Assert and De-assert
Levels vs LOS
LVL
5.0V
T
A
= 25
C
1.25Gbps
Pattern 2
7
-1
5
SY88903V
Micrel, Inc.
M9999-041505
hbwhelp@micrel.com or (408) 955-1690
Output Termination
The SY88903V outputs must be terminated with a 50
load to V
CC
2V (or Thevenin equivalent).
Layout and PCB Design
Since the SY88903V 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.
DESIGN PROCEDURE
R1
R2
V
REF
LOS
LVL
V
CC
Figure 3. LOSLVL Circut
50
50
0.1
F
0.1
F
0.1
F
V
REF
D
IN
D
IN+
Figure 2. Differential Input Configuration
The SY88903V 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:
LOS
LVS
= V
CC
-1.32V +
R1 + R2
2.6k
R2
1.32V
R1 + R2
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