Micrel
3.3V/5V 1.25Gbps PECL LOW-POWER
LIMITING POST AMPLIFIER
w/TTL SIGNAL DETECT
DESCRIPTION
SY88933V
Final
SY88933V
FEATURES
Single 3.3V or 5V power supply
DC to 1.25Gbps operation
Low noise PECL data outputs
Chatter-free OC-TTL signal setect (SD) output with
internal 6.75k
Ω
pull-up resistor
s
TTL EN input
s
Programmable SD level set (SD
LVL
)
s
Available in a tiny 10-pin MSOP (3mm) package
s
s
s
s
APPLICATIONS
s
1.25Gbps Ethernet
s
1.55Mbps and 622Mbps SONET/SDH
s
High-gain line driver and line receiver
s
531Mbps and 1062Mbps Fibre Channel
s
Gigabit interface converter
The SY88933V low-power limiting post amplifier is
designed for use in fiber-optic receivers. The device connects
to typical transimpedance amplifiers (TIAs). The linear signal
output from TIAs can contain significant amounts of noise
and may vary in amplitude over time. The SY88933V
quantizes these signals and outputs PECL level waveforms.
The SY88933V operates from a single +3.3V or +5V
power supply, over temperatures ranging from –40°C to
+85°C. With its wide bandwidth and high gain, signals with
data rates up to 1.25Gbps and as small as 5mVp-p can be
amplified to drive devices with PECL inputs.
The SY88933V generates a TTL SD output. A
programmable signal-detect level set pin (SD
LVL
) sets the
sensitivity of the input amplitude detection. SD asserts high
if the input amplitude rises above the threshold set by SD
LVL
and deasserts low otherwise. EN deasserts the true output
signal without removing the input signal. Typically 4.6dB
SD hysteresis is provided to prevent chattering.
TYPICAL APPLICATIONS CIRCUIT
V
CC
SD
From
Transimpedance
Amp.
0.1µF
0.1µF
50Ω
D
IN
/D
IN
50Ω
EN
D
OUT
0.1µF
0.1µF
R
pd
SY88933V
SD
LVL
V
REF
/D
OUT
R
pd
To
CDR
GND
V
CC
100kΩ
0.1µF
GND
For 3.3V, R
pd
= 120Ω
For 5V, R
pd
= 220Ω
Rev.: A
Amendment: /0
1
Issue Date: May 1, 2003
Micrel
SY88933V
PACKAGE/ORDERING INFORMATION
Ordering Information
EN 1
DIN 2
/DIN 3
VREF 4
SDLVL 5
10 VCC
9 DOUT
8 /DOUT
7 SD
6 GND
Part Number
SY88933VKC
SY88933VKCTR
(Note 1)
SY88933VKI
SY88933VKITR
(Note 1)
Package
Type
K10-1
K10-1
K10-1
K10-1
Operating
Range
Commercial
Commercial
Industrial
Industrial
Package
Marking
933V
933V
933V
933V
10-Pin MSOP (K10-1)
Note 1.
Tape and Reel.
PIN DESCRIPTION
Pin Number
1
2
3
4
5
6
7
Pin Name
EN
DIN
/DIN
VREF
SDLVL
GND
SD
Input
Ground
Open-collector
TTL output w/
internal 6.75kΩ
pull-up resistor
PECL Output
PECL Output
Power Supply
Type
TTL Input:
Default is high.
Data Input
Data Input
Pin Function
Enable: Deasserts true data output when high.
True data input.
Complementary data input.
Reference voltage: capacitor here to V
CC
helps stabilize SD
LVL
.
Signal-Detect Level Set: a resistor from this pin to V
CC
sets the
threshold for the data input amplitude at which SD will be asserted.
Device ground.
Signal-Detect: asserts high when the data input amplitude rises above
the threshold set by SD
LVL
.
8
9
10
/DOUT
DOUT
VCC
Complementary data output.
True data output.
Positive power supply.
2
Micrel
SY88933V
Absolute Maximum Ratings
(Note 1)
Supply Voltage (V
CC
) ....................................... 0V to +7.0V
Input Voltage (D
IN
, /D
IN
) .........................................0 to V
CC
Output Current (I
OUT
)
Continuous ............................................................. 50mA
Surge .................................................................... 100mA
EN Voltage ............................................................. 0 to V
CC
V
REF
Current ......................................... –800µA to +500µA
SD
LVL
Voltage ................................................. V
REF
to V
CC
Storage Temperature (T
S
) ....................... –55°C to +125°C
Note 1.
Operating Ratings
(Note 2)
Supply Voltage (V
CC
) .............................. +3.0V to +3.6V or
............................................................ +4.5V to +5.5V
Ambient Temperature (T
A
),
Note 3 ............
–40°C to +85°C
Junction Temperature (T
J
),
Note 3 ..........
–40°C to +120°C
Package Thermal Resistance
MSOP
(θ
JA
) Still-Air .................................................. 113°C/W
Permanent device damage may occur if ABSOLUTE MAXIMUM RATINGS are exceeded. This is a stress rating only and functional operation is
not implied at conditions other than those detailed in the operational sections of this data sheet. Exposure to ABSOLUTE MAXIMUM RATlNG
conditions for extended periods may affect device reliability.
The data sheet limits are not guaranteed if the device is operated beyond the operating ratings.
Commercial devices are guaranteed from 0°C to +85°C ambient temperature.
Note 2.
Note 3.
DC ELECTRICAL CHARACTERISTICS
V
CC
= 3.0V to 3.6V or 4.5V to 5.5V; R
LOAD
= 50Ω to V
CC
–2V; T
A
= –40°C to +85°C; typical values at V
CC
= 3.3V, T
A
= 25°C.
Symbol
I
CC
SD
LVL
V
IH
V
IL
I
IH
I
IL
V
OH
V
OL
V
OH
V
OL
V
OFFSET
V
IHCMR
V
REF
Note 1.
Note 2.
Parameter
Power Supply Current
SD
LVL
Voltage
EN Input HIGH Voltage
EN Input LOW Voltage
EN Input HIGH Current
EN Input LOW Current
SD Output HIGH Level
SD Output LOW Level
PECL Output HIGH Voltage
PECL Output LOW Voltage
Differential Output Offset
Common Mode Range
Reference Voltage
Condition
No output load
Min
Typ
22
Max
42
V
CC
0.8
Units
mA
V
V
V
µA
µA
mA
V
V
V
REF
2.0
V
IN
= 2.7V
V
IN
= V
CC
V
IN
= 0.5V
V
CC
≥
3.3V
V
CC
< 3.3V
I
OL
= +2mA
50Ω to V
CC
–2V output load
50Ω to V
CC
–2V output load
Note 1
Note 2
–0.3
2.4
2.0
20
100
0.5
V
CC
–1.085 V
CC
–0.955 V
CC
–0.880
V
CC
–1.830 V
CC
–1.705 V
CC
–1.555
±100
GND +2.0
V
CC
–1.38
V
CC
–1.32
V
CC
V
CC
–1.26
V
V
V
mV
V
V
The V
IHCMR
range is referenced to the most positive side of the differential input signal.
The current provided into or from V
REF
must be limited to 800µA source and 500µA sink.
3
Micrel
SY88933V
AC ELECTRICAL CHARACTERISTICS
V
CC
= 3.0V to 3.6V or 4.5V to 5.5V; R
LOAD
= 50Ω to V
CC
–2V; T
A
= –40°C to +85°C; typical values at V
CC
= 3.3V, T
A
= 25°C.
Symbol
HYS
t
OFF
t
ON
V
ID
V
OD
V
SR
A
V(Diff)
B
–3dB
S
21
t
r
,t
f
Parameter
SD Hysteresis
SD Release Time
SD Assert Time
Differential Input Voltage Swing
Differential Output Voltage Swing
SD Sensitivity Range
Differential Voltage Gain
3dB Bandwidth
Single-Ended Small-Signal Gain
Differential Output Rise/Fall Time
(20% to 80%)
V
ID
> 100mVp-p and 50Ω to V
CC
– 2V load
1
26
32
260
V
ID
≥
18mVp-p
V
ID
= 5mVp-p
5
38
5
1500
400
50
Condition
electrical signal
Min
2
Typ
4.6
0.1
0.2
Max
8
0.5
0.5
1800
Units
dB
µs
µs
mVp-p
mVp-p
mVp-p
mVp-p
dB
GHz
dB
ps
TYPICAL OPERATING CHARACTERISTICS
120
100
V
ID
(mVp-p)
SD Assert and Deassert
Levels vs. SD
LVL
V
SUP
= 3.3V
T
A
= 25°C
1.25Gbps
Pattern 2
23
–1
140
120
100
V
ID
(mVp-p)
80
60
40
SD Assert and Deassert
Levels vs. R
SDLVL
V
SUP
= 3.3V
T
A
= 25°C
1.25Gbps
Pattern 2
23
–1
ASSERT
80
60
ASSERT
40
20
DEASSERT
20
1
1.2 1.4
1
0
DEASSERT
0
10000
10
1000
SD
LVL
(referenced to V
CC
) (V)
R
SDLVL
(Ω)
4
100000
100
0
0.2 0.4 0.6 0.8
Micrel
SY88933V
DETAILED DESCRIPTION
The SY88933V low-power limiting post amplifier operates
from a single +3.3V or +5V power supply, over temperatures
from –40°C to +85°C. Signals with data rates up to 1.25Gbps
and as small as 5mVp-p can be amplified. Figure 1 shows
the allowed input voltage swing. The SY88933V generates
an SD output. SD
LVL
sets the sensitivity of the input
amplitude detection.
Input Amplifier/Buffer
Figure 2 shows a simplified schematic of the SY88933V's
input stage. The high-sensitivity of the input amplifier allows
signals as small as 5mVp-p to be detected and amplified.
The input amplifier allows input signals as large as
1800mVp-p. Input signals are linearly amplified with a
typically 38dB differential voltage gain. Since it is a limiting
amplifier, the SY88933V outputs typically 1500mVp-p
voltage-limited waveforms for input signals that are greater
than 18mVp-p. Applications requiring the SY88933V to
operate with high-gain should have the upstream TIA placed
as close as possible to the SY88933V’s input pins to ensure
the best performance of the device.
Output Buffer
The SY88933V’s PECL output buffer is designed to drive
50Ω lines. The output buffer requires appropriate termination
for proper operation. An external 50Ω resistor to V
CC
–2V
for each output pin provides this. Figure 3 shows a simplified
schematic of the output stage and includes an appropriate
termination method.
Signal-Detect
The SY88933V generates a chatter-free SD open-collector
TTL output with internal 6.75kΩ pullup resistor as shown in
Figure 4. SD is used to determine that the input amplitude
is large enough to be considered a valid input. SD asserts
high if the input amplitude rises above the threshold set by
SD
LVL
and deasserts low otherwise. SD can be fed back to
the enable (EN) input to maintain output stability under a
loss of signal condition. EN deasserts the true output signal
without removing the input signals. Typically 4.6dB SD
hysteresis is provided to prevent chattering.
Signal-Detect Level Set
A programmable SD level set pin (SD
LVL
) sets the
threshold of the input amplitude detection. Connecting an
external resistor between V
CC
and SD
LVL
sets the voltage
at SD
LVL
. This voltages ranges from V
CC
to V
REF
. The
external resistor creates a voltage divider between V
CC
and
V
REF
as shown in Figure 5. If desired, an appropriate
external voltage may be applied rather than using a resistor.
The smaller the external resistor, implying a smaller voltage
difference from SD
LVL
to V
CC
, the smaller the SD sensitivity.
Hence, larger input amplitude is required to assert SD.
“Typical Operating Characteristics”
shows the relationship
between the input amplitude detection sensitivity and the
SD
LVL
voltage.
Hysteresis
The SY88933V provides typically 4.6dB SD electrical
hysteresis. By definition, a power ratio measured in dB is
10log(power ratio). Power is calculated as V
2IN
/R for an
electrical signal. Hence 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
hence the ratios change linearly. Therefore, the optical
hysteresis in dB is half the electrical hysteresis in dB given
in the datasheet. The SY88933V provides typically 2.3dB
SD optical hysteresis. As the SY88933V is an electrical
device, this datasheet refers to hysteresis in electrical terms.
With 6dB SD hysteresis, a voltage factor of two is required
to assert or deassert SD.
5
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