sy84113bu Micrel Semiconductor, sy84113bu Datasheet - Page 6

• Manufacturer Part Number: sy84113bu
• Description: Low Power 2.5v 1.25gbps Limiting Post Amplifier With Ultra Wide Los Range
• Manufacturer: Micrel Semiconductor

January 2011
Functional Block Diagram
Detailed Description
The SY84113BU is a high-sensitivity limiting post
amplifier that operates from a single +2.5V power supply
over temperatures from –40°C to +85°C. Signals with
data rates up to 1.25Gbps, and as small as 5mVpp, can
be amplified. Figure 1 shows the allowed input voltage
swing. The SY84113BU 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. SY84113BU
offers ultra wide LOS detection range. This allows the
device to be used in multiple AC-coupled applications.
Input Amplifier/Buffer
Figure 2 shows a simplified schematic of the input
stage. The high-sensitivity of the input amplifier can
detect and amplify AC-coupled signals as small as
5mV
allow signals as large as 1800mV
amplified with a typically 38dB differential voltage gain
until they reach the limiting mode of the amplifier.
SY84113BU outputs in standard 400mV CML output
levels.
Output Buffer
The SY84113BU’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.
pp
to full CML output level. The input stage also can
pp
. Input signals are
LVL
sets the
Loss-of-Signal
The SY84113BU 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
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
VREF. The external resistor creates a voltage divider
between V
Hysteresis
The SY84113BU 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.
6
LOS-De-Assert
CC
and VREF, as shown in Figure 5.
). Since the relationship between the
LVL
. This voltage ranges from V
[e-mail]
CC
and LOS
or [phone]
M9999-011711-
LVL
LVL
) sets the
LOS-Assert
sets the
CC
to
A
/