SY88289ALMG Micrel Inc, SY88289ALMG Datasheet - Page 6

• Manufacturer Part Number: SY88289ALMG
• Description: 3.3V 155-3200 Mbps CML Post Amp: OCP Pinout/I Temp, Green/1xLOSgain/20xTC/16 MLFr
• Manufacturer: Micrel Inc
• Type: Limiting Postamplifierr

Specifications of SY88289ALMG

• Applications: Optical Networks
• Mounting Type: Surface Mount
• Package / Case: 16-MLF®, QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-1600

February 2007
Micrel, Inc.
Functional Block Diagram
Detailed Description
The SY88289AL low-power limiting post amplifier
operates from a single +3.3V power supply, over
temperatures from –40
rates of up to 3.2Gbps and as small as 10mV
be amplified. Figure 1 shows the allowed input voltage
swing. The SY88289AL generates a LOS output.
LOS
detection.
Input Amplifier/Buffer
Figure 2 shows a simplified schematic of the
SY88289AL’s input stage. The high-sensitivity of the
input amplifier allows signals as small as 10mV
be detected and amplified. The input amplifier also
allows input signals as large as 1800mV
signals are linearly amplified with a typical 38dB
differential voltage gain. Since it is a limiting amplifier,
the SY88289AL outputs typically 800mV
limited waveforms for input signals that are greater
than 12mV
to operate with high gain should have the upstream
TIA placed as close as possible to the SY88289AL’s
input pins to ensure the best performance of the
device.
Output Buffer
The SY88289AL’s CML output buffer is designed to
drive 50Ω lines. The output buffer requires appropriate
termination for proper operation. An external 50
resistor to V
3 shows a simplified schematic of the output stage.
LVL
sets the sensitivity of the input amplitude
PP
CC
. Applications requiring the SY88289AL
for each output pin provides this. Figure
o
C to +85
o
C. Signals with data
PP
PP
voltage-
Ω
. Input
PP
PP
can
to
6
Loss-of-signal
The SY88289AL generates a chatter-free LOS open-
collector TTL output with an internal 4.75k
resistor as shown in Figure 4. LOS is used to
determine that the input amplitude is large enough to
be considered a valid input. LOS asserts high if the
input amplitude falls below the threshold sets by
LOS
back to the enable bar (/EN) input to maintain output
stability under a loss of signal condition. /EN de-
asserts the true output signal without removing the
input signals. Typically, 3.5dB LOS hysteresis is
provided to prevent chattering.
Loss-of-signal Level Set
A programmable LOS level-set (LOS
threshold of the input amplitude detection. Connecting
an external resistor between V
voltage at LOS
V
between V
Hysteresis
The SY88289AL provides typically 3.5dB LOS
electrical hysteresis. By definition, a power ratio
measured in dB is 10log (power ratio). Power is
calculated as V
the same ratio can be stated as 20log (voltage ratio).
While in linear mode, the electrical voltage input
changes linearly with the optical power and therefore,
the ratios change linearly. Thus, the optical hysteresis
in dB is half the electrical hysteresis in dB given in the
data sheet. Since the SY88289AL is an electrical
device, this data sheet refers to hysteresis in electrical
terms. With 3.5dB LOS hysteresis, a voltage factor of
1.5 is required to assert or de-assert LOS.
CC
. The external resistor creates a voltage divider
LVL
and de-asserts low otherwise. LOS can be fed
CC
and V
LVL
2
IN
[e-mail]
. This voltage ranges from V
/R for an electrical signal. Hence,
REF
as shown in Figure 5.
CC
and LOS
LVL
or [phone]
M9999-021207-B
) pin sets the
Ω pull
SY88289AL
LVL
sets the
REF
-up
to