SY88053ALMG Micrel Inc, SY88053ALMG Datasheet - Page 8

• Manufacturer Part Number: SY88053ALMG
• Description: IC POST AMP 3.3V MLF33Q-16L
• Manufacturer: Micrel Inc
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of SY88053ALMG

• Data Rate: 12.5Gbps
• Number Of Channels: 1
• Voltage - Supply: 3 V ~ 3.6 V
• Current - Supply: 50mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 16-MLF®, QFN
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-3705-5; SY88053ALMG

May 2010
Detailed Description
The SY88053AL is a high-sensitivity limiting post
amplifier that operates from a single +3.3V power supply
over temperatures from –40°C to +85°C. Signals with
data rates up to 12.5Gbps, and as small as 15mV
be amplified. Figure 1 shows the allowed input voltage
swing. The SY88053AL generates a LOS output signal
that can be fed back to /EN for output stability in the
absence of a signal at the input. LOS
sensitivity of the input amplitude detection. In the
situations where the noise in not evenly distributed
between the high and the low levels of the signal, such
in links using EDFA amplifiers, the offset of the signal
can be adjusted, using VTHN and VTHP pins to
optimize the performance of the link.
Input Amplifier/Buffer
Figure 2 shows a simplified schematic of the input
stage. The high-sensitivity of the input amplifier allows
signals as small as 15mV
amplified. The input amplifier allows input signals as
large as 1800mV
typically 38dB differential voltage gain. Since it is a
limiting amplifier, the SY88053AL outputs typically
700mV
are greater than 10mV
Output Buffer
The SY88053AL’s CML output buffer is designed to
drive 50Ω lines and is internally terminated with 50Ω to
VCC. Figure 3 shows a schematic of the output stage.
Loss-of-Signal
The SY88053AL generates a chatter-free loss-of-signal
(LOS) open-collector TTL output as shown in Figure 4.
LOS is used to determine that the input amplitude is too
small to be considered as a valid input. LOS asserts
high if the input amplitude falls below the threshold set
by LOSLVL and de-asserts low otherwise. LOS can be
fed back to the enable (/EN) input to maintain output
stability under a loss of signal condition. /EN de-asserts
pp
voltage-limited waveforms for input signals that
pp
. Input signals are amplified with a
pp
.
pp
to be detected and
LVL
sets the
pp
, can
low the true output signal without removing the input
signals. Typically, 3dB LOS hysteresis is provided to
prevent chattering.
Loss-of-Signal-Level Set
A programmable LOS level set pin (LOS
threshold of the input amplitude detection. Connecting
an external resistor between V
voltage at LOS
VCC-1.3V. The external resistor creates a voltage
divider between V
5.
Hysteresis
The SY88053AL provides typically 3dB LOS electrical
hysteresis, which is defined as 20log (VIN
VIN
voltage out of the ROSA to optical power at its input is
linear, the optical hysteresis will be typically half of the
electrical hysteresis reported in the datasheet, but in
practice the ratio between electrical and optical
hysteresis is found to be within the range 1.5-1.8. Thus
3dB electrical hysteresis will correspond to an optical
hysteresis within the range 1.7dB - 2dB.
Signal Crossing Adjustment
In order to optimize the BER of the optical link where the
noise is unevenly distributed between the high and the
low levels, the SY88053AL provides two pins for output
signal crossing control. The output crossing can be
adjusted by connecting pins VTHN and VTHREF
together while applying a DC voltage at VTHP pin. By
varying the DC signal at VTHP from 1V to 1.5V while the
input signal to the post amplifier is less than 60mVpp,
the crossing of the output signal will change from 20% to
80%. The output crossing is at 50% when VTHP =
1.25V. If the crossing control function is not needed,
VTHN and VTHP should be connected to ground.
8
LOS-De-Assert
). Since the relationship between the
LVL
CC
. This voltage ranges from V
[e-mail]
and VCC-1.3V, as shown in Figure
CC
and LOS
or [phone]
M9999-052610-A
LVL
LVL
) sets the
LOS-Assert
sets the
CC
to
/