SY88903V_06 Datasheet, PDF (1/6 Pages) Micrel Semiconductor – 5V/3.3V 1.25Gbps HIGH-SPEED LIMITING POST AMPLIFIER

Micrel, Inc.
5V/3.3V 1.25Gbps HIGH-SPEED
LIMITING POST AMPLIFIER
SY88903V
SY88903V
FEATURES
■ 3.3V and 5V power supply option
■ 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 laser diode driver and
controller
■ Available in a tiny 10-pin (3mm × 3mm) MSOP
APPLICATIONS
■ 1.25Gbps Gigabit Ethernet
■ 531Mbps and 1062Mbps Fibre Channel
■ 622Mbps SONET
■ Gigabit Interface Converter
BLOCK DIAGRAM
DESCRIPTION
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
V_CC
2.5kΩ
DIN
DIN
VREF
VCC
GND
Limiting
Amplifer
ECL
Buffer
Enable
Level
Detect
DOUT
DOUT
EN
Figure 1. LOS Output with Desired Rise Time
All support documentation can be found on Micrel’s web
site at www.micrel.com.
LOSLVL
LOS
M9999-091406
[e-mail] or [phone]
1
Rev.: E Amendment: /0
Issue Date: September 2006