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1.25Gbps HIGH-SPEED
LIMITING POST AMPLIFIER
SY88903
FEATURES
■ 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
PIN CONFIGURATION
LOS
1/EN
D
IN
2
/D
IN
V
REF
LVL
MSOP
3
K10-1
4
5
10 V
9
8
7
6
CC
D
OUT
/D
OUT
LOS
GND
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
APPLICATIONS
■ 1.25Gbps Gigabit Ethernet
■ 531Mbps and 1062Mbps Fibre Channel
■ 622Mbps SONET
■ Gigabit Interface Converter
BLOCK DIAGRAM
D
IN
Limiting
Amplifier
D
IN
V
REF
V
CC
GND
ECL
Buffer
Level
Detect
SY88903
Figure 1. LOS Output with Desired Rise Time
Enable
D
D
EN
LOS
OUT
OUT
2k
LOS
LVL
LOS
1
Rev.: G Amendment: /1
Issue Date: July 2000
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PIN NAMES GENERAL DESCRIPTION
SY88903
Pin Type Function
DIN Data Input Data Input
/DIN Data Input Inverting Data Input
LOS LVL Input Loss of Signal Level Set
/EN TTL Input Output Enable (active Low)
LOS TTL Output Loss of Signal Indicator
(Open Collector) (active High)
GND Ground Ground
DOUT PECL Output Data Output
/DOUT PECL Output Inverting Data Output
VCC Power Supply Positive Power Supply
REF Output Reference Voltage Output
V
for LOS Level Set (see Fig. 3)
ABSOLUTE MAXIMUM RATINGS
(1)
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.
Symbol Rating Value Unit
VCC Power Supply Voltage 0 to +7.0 V
DIN, /DIN Input Voltage 0 to VCC V
DOUT, /DOUT Output Voltage (with 50Ω load) VCC –2.5, VCC +0.3 V
TA Operating Temperature Range –40 to +85 °C
T
store Storage Temperature Range –55 to +125 °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.
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SY88903
DC ELECTRICAL CHARACTERISTICS
VCC = +5V ±10%, RLOAD = 50Ω to VCC-2V, TA = –40°C to +85°C
TA = –40°CTA = 0°CTA = +25°CTA = +85°C
Symbol Parameter Min. Max. Min. Max. Min. Typ. Max. Min. Max. Unit
(4)
(1)
— 35 — 35 — 21 35 — 35 mA
–0.3 — –0.3 — –0.3 — — –0.3 — mA
—20
— 100
GND +2.0 VCC -1.0 GND +2.0 VCC -1.0 GND +2.0 —VCC -1.0 GND +2.0 VCC -1.0
(3)
— 250 — 250 — — 250 — 250 uA
VCC-1085 VCC-880 VCC-1025 VCC-880 VCC-1025 VCC-955 VCC-880 VCC-1025 VCC-880
VCC-1830 VCC–1555 VCC-1810 VCC–1620 VCC-1810 VCC–1705 VCC–1620 VCC-1810 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
(5)
(6)
—20
— 100
(5)
(6)
——20
— — 100
(5)
(6)
—20
— 100
2.0 — 2.0 — 2.0 — — 2.0 — V
— 0.8 — 0.8 — — 0.8 — 0.8 V
4. IREF must be limited to be within -0.8mA (source) and 0.5mA (sink).
5. VIN = 2.7V
6. VIN = VCC
(5)
(6)
ICC
IIL
I
IH
Power Supply Current
/EN Input LOW Current
/EN Input HIGH Current
VCMR Common Mode Range
Voffset Differential Output Offset — ±100 — ±100 — — ±100 — ±100 mV
LOSLVL LOSLVL Level VREF VCC VREF VCC VREF —VCC VREF VCC V
OL LOS Output Low — 0.5 — 0.5 — — 0.5 — 0.5 V
V
Level
(2)
IOH LOS Output Leakage
OH DOUT and /DOUT
V
HIGH Output
OL DOUT and /DOUT
V
LOW Output
VREF Reference Supply
VIH
IL
V
NOTES:
1. No output load
2. IOL = + 2mA
3. VOH = 5.5V
/EN Input HIGH Voltage
/EN Input LOW Voltage
µA
V
mV
mV
V
AC ELECTRICAL CHARACTERISTICS
VCC = +5V ±10%, RLOAD = 50Ω to VCC - 2V, TA = –40°C to +85°C
TA = –40°CTA = 0°CTA = +25°CTA = +85°C
Symbol Parameter Min. Max. Min. Max. Min. Typ. Max. Min. Max. Unit Conditions
PSRR Power Supply
(1)
Rejection Ratio 55MHz
VID Input Voltage Range 5 1800 5 1800 5 — 1800 5 1800 mVp-p
r, tf Output Rise/Fall Time — 350 — 350 — 200 350 — 350 ps VID > 100mVp-p
t
V
OD Differential Output — — — — — 600 — — — mV VID = 15mVp-p
Voltage Swing
OFFL LOS Release Time
t
(2)
(3)
Minimum Input
OFFH LOS Release Time
t
(4)
Maximum Input
tONL LOS Assert Time
(3)
VSR LOS Sensitivity Range 5 50 5 50 5 — 50 5 50 mVp-p
HYS LOS Hysteresis 2 8 2 8 2 4.6 8 2 8 dB
NOTES:
1. Input referred noise = RMS output noise/low frequency gain.
2. Input is 622MHz square wave.
— — — — — 35 — — — dB Input referred,
—————trin,tfin ——— VID < 100mVp-p
—————200———mVVID = 5mVp-p
— 0.5 — 0.5 — 0.1 0.5 — 0.5 µs
— 0.5 — 0.5 — 0.1 0.5 — 0.5 µs
— 0.5 — 0.5 — 0.2 0.5 — 0.5 µs
3. Input is a 200MHz square wave, tr < 300ps, 8mVp-p.
4. Input is a 200MHz square wave, tr < 300ps, 1.8Vp-p.
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APPLICATION INFORMATION
SY88903
Output Termination
The SY88903 outputs must be terminated with a 50Ω
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.
IN
+
0.1µF
0.1µF
50Ω
0.1µF
D
DIN–
50Ω
V
REF
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 ≥ 5kΩ
V
CC
R1
LOS
LVL
R2
V
REF
Figure 3. LOSLVL Circut
Figure 2. Differential Input Configuration
PRODUCT ORDERING CODE
Ordering Package Operating
Code Type Range
SY88903KC K16-1 Commercial
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)
PERFORMANCE CURVE
100.00
90.00
80.00
70.00
60.00
50.00
Level (mV)
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
LOSlvl (V)
3.89
4.01
4.13
4.26
4.38
4.51
4.63
4.75
4.88
SY88903
Deassert
Assert
5.00
100.00
90.00
80.00
70.00
60.00
50.00
40.00
Level (mV)
30.00
20.00
10.00
0.00
Figure 4. LOS Assert and Deassert Levels vs LOSLVL
0.00
0.05
0.15
0.10
0.20
0.25
0.30
0.40
0.35
0.45
0.50
0.55
0.65
0.60
0.70
0.75
0.80
Resistor Divider R2 / (R1 + R2
0.85
0.90
0.95
Deassert
Assert
1.00
Figure 5. LOS Assert and Deassert Levels vs Resistor Divider
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D
IN
D
IN
GBIC Terminal
EN
RX_DATA–
RX_DATA+
TX_DATA–
TX_DATA+
RX_LOS
ENABLE/DISABLE
130Ω
V
CC
GND
130Ω
82Ω
82Ω
V
CC
EN
V
CC
GND
V
CC
GND
D
OUT
D
OUT
130Ω
130Ω
82Ω
82Ω
V
CC
OUT
OUT
D
IN
24Ω
V
CC
R
EXT
R
SER
Laserdiode
Photodiode
V
REF
MD
I
BIAS
LOS
OUT
LOS
IN
D
IN
LOS
LVL
I
BIAS SET
SY88905
20kΩ
20kΩ
1000pF
BLM21A102S
Laser
Module
I
BIAS FB
I
PIN SET
LOS
V
REF
SY88903
0.1µF
20kΩ
0.1µF
130Ω
130Ω
82Ω
82Ω
V
CC
20kΩ
SY88902
V
REF
R
SET
The value of RSER
depends on the Laser Diode.
V
CC
V
CC
APPLICATION EXAMPLE FOR 3-CHIP SET SOLUTION
SY88903
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10 LEAD MSOP (K10-1)
SY88903
Rev. 00
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SY88903
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
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