The SY88923 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 2.5Gbps. Signals
as small as 5mVp-p can be amplified to drive devices with
PECL inputs. The SY88923 generates a chatter-free Loss
of Signal (LOS) open collector TTL output.
The SY88923 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.
Using LOS
LVL
pin, the sensitivity of the level detection can
be adjusted. The LOS
LVL
voltage can be set by connecting
a resistor divider between V
CC
and V
REF
. Figure 3 and
Figure 4 show the relationship between input level sensitivity
and the voltage set on LOS
LVL
. Figure 5 shows the
relationship between input level sensitivity and resistor
divider ratio.
The LOS output is a TTL open collector output that
requires a pull-up resistor for proper operation, Figure 1.
+5.0V
SY88923
LOS
2.5k
Figure 1. LOS Output with Desired Rise Time
BLOCK DIAGRAM
D
IN
Limiting
Amplifer
ECL
Buffer
D
OUT
D
OUT
D
IN
V
REF
Enable
V
CC
GND
Level
Detect
EN
LOS
LVL
LOS
M9999-061907
hbwhelp@micrel.com or (408) 955-1690
Rev.: F
Amendment: /0
1
Issue Date: June 2007
Micrel, Inc.
SY88923
PACKAGE/ORDERING INFORMATION
Ordering Information
/EN 1
D
IN
2
/D
IN
3
V
REF
4
LOS
LVL
5
MSOP
K10-1
10 V
CC
9 D
OUT
8 /D
OUT
7 LOS
6 GND
Part Number
SY88923KC
SY88923KCTR
(1)
SY88923KG
SY88923KGTR
(1)
Note:
1.
Tape and Reel.
Package
Type
K10-1
K10-1
K10-1
K10-1
Operating
Range
Commercial
Commercial
Industrial
Industrial
Package
Marking
923
923
923 with
Pb-Free bar-line indicator
923 with
Pb-Free bar-line indicator
Lead
Finish
Sn-Pb
Sn-Pb
Pb-Free
NiPdAu
Pb-Free
NiPdAu
10-Pin MSOP (K10-1)
PIN NAMES
Pin
D
IN
/D
IN
LOS
LVL
/EN
LOS
GND
/D
OUT
D
OUT
V
CC
V
REF
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
LOS Limit Set
Output Enable (Active Low)
Loss of Signal Indicator
(Active High)
Ground
Inverting Data Output
Data Output
Positive Power Supply
Reference Voltage Output for
LOS Level Set (see Fig. 3)
GENERAL DESCRIPTION
General
The SY88923 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 SY88923
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.
ABSOLUTE MAXIMUM RATINGS
(1)
Symbol
V
CC
D
IN
, /D
IN
D
OUT
, /D
OUT
T
A
T
store
Rating
Power Supply Voltage
Input Voltage
Output Voltage (with 50Ω load)
Operating Temperature Range
Storage Temperature Range
Value
0 to +7.0
0 to V
CC
V
CC
–2.5, V
CC
+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.
M9999-061907
hbwhelp@micrel.com or (408) 955-1690
2
Micrel, Inc.
SY88923
DC ELECTRICAL CHARACTERISTICS
V
CC
= +5V
±10%,
R
LOAD
= 50Ω to V
CC
-2V, T
A
= –40°C to +85°C
T
A
= –40
°
C
Symbol
I
CC
I
IL
I
IH
V
CMR
V
offset
LOS
LVL
V
OL
I
OH
V
OH
V
OL
V
REF
V
IH
V
IL
Parameter
Power Supply Current
(1)
/EN Input LOW Current
/EN Input HIGH Current
Common Mode Range
Differential Output Offset
LOS
LVL
Level
(2)
LOS Output Low Level
(3)
LOS Output Leakage
(4)
D
OUT
and /D
OUT
HIGH Output
D
OUT
and /D
OUT
LOW Output
Reference Supply
(7)
/EN Input HIGH Voltage
/EN Input LOW Voltage
Min.
—
–0.3
(8)
—
—
Max.
35
—
20
(5)
100
(6)
T
A
= 0
°
C
Min.
—
–0.3
(8)
—
—
Max.
35
—
20
(5)
100
(6)
Min.
—
–0.3
(8)
—
—
T
A
= +25
°
C
Typ.
21
—
—
—
—
—
—
—
—
Max.
35
—
20
(5)
100
(6)
T
A
= +85
°
C
Min.
—
–0.3
(8)
—
—
Max.
35
—
20
(5)
100
(6)
Unit
mA
mA
µA
V
mV
V
V
uA
mV
mV
V
V
V
GND +2.0
V
CC
–1.0
GND +2.0
V
CC
–1.0
GND +2.0
V
CC
–1.0
GND +2.0
V
CC
–1.0
±100
V
CC
0.5
250
—
V
REF
—
—
±100
V
CC
0.5
250
V
CC
–880
—
V
REF
—
—
V
CC
–1085
±100
V
CC
0.5
250
—
V
REF
—
—
±100
V
CC
0.5
250
—
V
REF
—
—
V
CC
–880 V
CC
–1025 V
CC
–880 V
CC
–1025 V
CC
–955 V
CC
–880 V
CC
–1025
V
CC
–1830 V
CC
–1555 V
CC
–1810 V
CC
–1620 V
CC
–1810 V
CC
–1705 V
CC
–1620 V
CC
–1810 V
CC
–1620
V
CC
–2.625 V
CC
–2.325 V
CC
–2.625 V
CC
–2.325 V
CC
–2.625 V
CC
–2.475 V
CC
–2.325 V
CC
–2.625 V
CC
–2.325
2.0
—
—
0.8
2.0
—
5.
6.
7.
8.
—
0.8
2.0
—
—
—
—
0.8
2.0
—
—
0.8
Notes:
1. No output load.
2. 2
23
-1 pattern.
3. I
OL
= + 2mA.
4. V
OH
= 5.5V.
V
IN
= 2.7.
V
IN
=V
CC.
I
REF
must be limited within –0.8mA (source) and 0.4mA (sink).
V
IN
= 0.5V
.
AC ELECTRICAL CHARACTERISTICS
V
CC
= +5V
±10%,
R
LOAD
= 50Ω to V
CC
- 2V, T
A
= –40°C to +85°C
T
A
= –40
°
C
Symbol
PSRR
V
ID
t
r,
t
f
V
OD
t
OFFL
t
OFFH
t
ONL
V
SR
HYS
Parameter
Power Supply
(1)
Rejection Ratio
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
Min.
—
5
—
—
—
—
—
—
—
5
2
Max.
—
1800
175
—
—
—
0.5
0.5
0.5
50
8
T
A
= 0
°
C
Min.
—
5
—
—
—
—
—
—
—
5
2
Max.
—
1800
175
—
—
—
0.5
0.5
0.5
50
8
—
5
—
—
—
—
—
—
—
5
2
T
A
= +25
°
C
Min.
Typ.
35
—
—
t
rin
,t
fin
600
200
0.1
0.1
0.2
—
4.6
Max.
—
1800
175
—
—
—
0.5
0.5
0.5
50
8
T
A
= +85
°
C
Min.
—
5
—
—
—
—
—
—
—
5
2
Max.
—
Unit
dB
Conditions
Input referred,
55MHz
1800 mVp-p
175
—
—
—
0.5
0.5
0.5
50
8
ps
mV
mV
µs
µs
µs
mVp-p
dB
2
23
-1 pattern
V
ID
> 100mVp-p
V
ID
< 100mVp-p
V
ID
= 15mVp-p
V
ID
= 5mVp-p
Notes:
1. Input referred noise = RMS output noise/low frequency gain.
2. Input is a 622MHz square wave.
M9999-061907
hbwhelp@micrel.com or (408) 955-1690
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, Inc.
SY88923
DESIGN PROCEDURE
Output Termination
The SY88923 outputs must be terminated with a 50Ω
load to V
CC
– 2V (or thevenin equivalent).
Layout and PCB Design
Since the SY88923 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 power
supply.
The SY88923 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
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