SY88903_07 Datasheet, PDF (1/7 Pages) Micrel Semiconductor – 1.25Gbps HIGH-SPEED LIMITING POST AMPLIFIER

Micrel, Inc.
1.25Gbps HIGH-SPEED
LIMITING POST AMPLIFIER
Not recommended for new designs
SY88903
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
APPLICATIONS
■ 1.25Gbps Gigabit Ethernet
■ 531Mbps and 1062Mbps Fibre Channel
■ 622Mbps SONET
■ Gigabit Interface Converter
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
SY88903
LOS
2k
BLOCK DIAGRAM
DIN
DIN
VREF
VCC
GND
LOSLVL
Limiting
Amplifier
M9999-061907
[e-mail] or [phone]
Figure 1. LOS Output with Desired Rise Time
ECL
Buffer
Level
Detect
Enable
DOUT
DOUT
EN
LOS
Rev.: I
Amendment: /0
1
Issue Date: June 2007