Micrel AN-45 3.3v, 3.2 gbps limiting post amplifier with programmable decision threshold Datasheet

SY88353BL
3.3V, 3.2 Gbps Limiting Post Amplifier with
Programmable Decision Threshold
General Description
Features
The SY88353BL limiting post amplifier is designed for
use in fiber-optic receivers, and is specially optimized for
WDM applications where optical amplifiers such as
EDFAs and Raman amplifier are used. The device
connects to typical transimpedance amplifiers (TIAs).
The linear signal from TIAs can contain significant
amounts of noise that is unevenly distributed between
top and bottom rails due to the ASE noise generated by
the optical amplifiers, crosstalk, or non-linear effect in
the fiber. In order to optimize the BER in such noisy
conditions, the decision threshold between bit 1 and bit
0, needs to be moved to the rail that contains less noise.
The SY88353BL features a pin at which an external
voltage can be applied to move the crossing point up
and down, from 20% to 80%, for BER optimization
purposes.
The SY88353BL operates from a single +3.3V power
supply, over temperatures ranging from –40oC to +85oC.
Signals with data rates from 155Mbps up to 3.2Gbps,
and as small as10mVpp, can be amplified to drive
devices with CML or PECL inputs.
The SY88353L features a Loss-of-Signal (LOS) opencollector TTL output. A programmable Loss-of-Signal
level set pin (LOSLVL) sets the sensitivity of the input
amplitude detection. LOS asserts high if the input
amplitude falls below the threshold sets by LOSLVL and
de-asserts low otherwise. The enable bar input (/EN)
de-asserts the true output signal without removing the
input signal. The LOS output can be fed back to the /EN
input to maintain output stability under a loss-of-signal
condition. Typically, 3.3dB LOS hysteresis is provided to
prevent chattering.
All support documentation can be found on Micrel’s web
site at: www.micrel.com.
•
•
•
•
•
•
•
•
•
Single 3.3V power supply
Fast LOS release/assert
155Mbps to 3.2Gbps operation
Low-noise CML data outputs
Chatter-free Open-Collector TTL loss-of-signal (LOS)
output.
TTL /EN input
Programmable LOS level set (LOSLVL)
Programmable Decision Threshold
Available in a tiny 3mm x 3mm MLF™ package
Applications
•
•
•
•
WDM Systems
Gigabit Ethernet, 1X and 2X Fibre Channel
SONET/SDH: OC-3/12/24/48 – STM1/4/8/16
Low-gain TIA interface
Markets
• Datacom/telecom
• Optical transceiver
MLF and MicroLeadFrame are trademarks of Amkor Technology, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
April 2006
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Micrel, Inc.
SY88353BL
Typical Application Circuit
Programmable Decision Threshold
Fixed Decision Threshold
Ordering Information
Package
Type
Operating
Range
Package Marking
Lead Finish
SY88353BLMG
MLF-16
Industrial
SY88353BL with Pb-Free bar line indicator
NiPdAu Pb-Free
SY88353BLMGTR(1)
MLF16
Industrial
SY88353BL with Pb-Free bar line indicator
NiPdAu Pb-Free
Part Number
Notes:
1. Tape and Reel.
Pin Configuration
16-Pin MLF™ (MLF-16)
April 2006
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Micrel, Inc.
SY88353BL
Pin Description
Pin Number
Pin Name
Type
Pin Function
1
DIN
Data Input
True data input.
4
/DIN
Data Input
Complementary data input.
5
VTHN
DC Input
6
VTHREF
7
LOS
Open-collector TTL
output
Tie this pin to pin 6 (VTHREF) and apply a DC voltage on pin 16
(VTHP) for signal crossing adjustment. Connect to ground if no
crossing adjustment is needed.
1.25V Reference voltage (referenced to ground) for decision
threshold adjustment.
Loss-of-Signal: asserts high when the data input amplitude falls
below the threshold set by LOSLVL.
9
/DOUT
CML Output
Complementary data output.
12
DOUT
CML Output
True data output.
14
LOSLVL
Input
Loss-of-Signal Level Set. A resistor from this pin to VCC sets the
threshold for the data input amplitude at which LOS will be
asserted.
15
/EN
TTL Input: Default is
HIGH.
/Enable: This input enables the outputs when it is LOW. Note
that this input is internally connected to a 25kΩ pull-up resistor
and will default to a logic HIGH state if left open.
16
VTHP
DC Input
Apply a DC voltage from 0 to 2.4V to adjust the signal crossing
level when pin 5 (VTHN) is tied to pin 6 (VTHREF). 1.25V sets
the crossing close to 50%. Connect to ground if no crossing
adjustment is needed.
2, 3, 10, 11
GND
Ground
8, 13
VCC
Power Supply
April 2006
Device ground.
Positive power supply.
3
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Micrel, Inc.
SY88353BL
Absolute Maximum Ratings(1)
Operating Ratings(2)
Supply Voltage (VCC) ....................................... 0V to +4.0V
Input Voltage (DIN, /DIN) .......................................0 to VCC
Output Current (IOUT)
Continuous........................................................ ±25mA
/EN Voltage ............................................................0 to VCC
VREF Current .......................................... -800µA to +500µA
LOSLVL Voltage................................................. VREF to VCC
Lead Temperature (soldering, 20sec.) ................... +260°C
Storage Temperature (Ts) ....................... –65°C to +150°C
Supply Voltage (VCC)............................. +3.0V to +3.6V
Ambient Temperature (TA) ................... –40°C to +85°C
Junction Temperature (TJ) ................. –40°C to +120°C
Supply Voltage (VCC) ........................... +3.0V to +3.6V
Ambient Temperature (TA).................. –40°C to +85°C
Package Thermal Resistance(3)
MLF™
(θJA) Still-air ............................................... 60°C/W
(ψJB) ........................................................... 33°C/W
DC Electrical Characteristics
VCC = 3.0 to 3.6V; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C.
Symbol
Parameter
Condition
Min
Typ
ICC
Power Supply Current
No output load
LOSLVL
LOSLVL Voltage
VOH
DOUT, /DOUT HIGH Voltage
VCC-0.020 VCC-0.005
VOL
DOUT, /DOUT LOW Voltage
VCC-0.475 VCC-0.400 VCC-0.350
VOFFSET
Differential Output Offset
VTHREF
Decision Threshold Reference
Voltage
Z0
Single-Ended Output Impedance
40
50
60
Ω
ZI
Single-Ended Input Impedance
40
50
60
Ω
Min
Typ
Max
Units
20
%
45
VCC -1.3
Max
Units
62
mA
VCC
V
VCC
V
±80
1.25
V
mV
V
TTL DC Electrical Characteristics
VCC = 3.0 to 3.6V; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C.
Symbol
VIH
Parameter
Condition
Output signal Crossing Range
Lower Limit
VTHN connected to VTHREF and 02.4V applied to VTHP.
Output signal Crossing Range
Upper Limit
20 ≤ DIN ≤ 100(mVpp), see Figure on
page 6.
/EN Input HIGH Voltage
VIL
/EN Input LOW Voltage
IIH
/EN Input HIGH Current
80
%
2.0
V
0.8
V
VIN = 2.7V
20
µA
VIN = VCC
100
µA
IIL
/EN Input LOW Current
VIN = 0.5V
ICEX
LOS Output Leakage Current
VOUT = VCC
100
µA
VOL
LOS Output LOW Level
Sinking 2mA
0.5
V
April 2006
-0.3
4
mA
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SY88353BL
AC Electrical Characteristics
VCC = 3.0 to 3.6V; RLoad = 50Ω to VCC; TA = –40°C to +85°C, typical values at VCC = 3.3V, TA = 25°C.
Symbol
Parameter
Condition
tr, tf
Output Rise/Fall Time
(20% to 80%)
tJITTER
Deterministic
Random
Min
Typ
Max
Note 4
60
100
Note 5
15
psPP
Note 6
5
psRMS
20
ps
VID
Differential Input Voltage Swing
VOD
Differential Output Voltage
Swing
TOFF
LOS Release Time
Note 9
TON
LOS Assert Time
Note 9
LOSAL
Low LOS Assert Level
RLOSLVL = 15kΩ, Note 7
9
mVPP
LOSDL
Low LOS De-assert Level
RLOSLVL = 15kΩ, Note 7
13
mVPP
HYSL
Low LOS Hysteresis
RLOSLVL = 15kΩ, Note 8
3.2
dB
LOSAM
Medium LOS Assert Level
RLOSLVL = 5kΩ, Note 7
17
mVPP
LOSDM
Medium LOS De-assert Level
RLOSLVL = 5kΩ, Note 7
25
mVPP
HYSM
Medium LOS Hysteresis
RLOSLVL = 5kΩ, Note 8
3.3
dB
LOSAH
High LOS Assert Level
RLOSLVL = 100Ω, Note 7
47
mVPP
LOSDH
High LOS De-assert Level
RLOSLVL = 100Ω, Note 7
70
mVPP
HSYH
High LOS Hysteresis
RLOSLVL = 100Ω, Note 8
3.4
dB
B-3dB
3dB Bandwidth
2.0
GHz
AV(Diff)
Differential Voltage Gain
38
dB
S21
Single-Ended Small-Signal Gain
32
dB
Note 4
700
26
1800
Units
800
950
2
10
2
10
mVPP
mVPP
µs
µs
Notes:
1. 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 ratings conditions for
extended periods may affect device reliability.
2. The data sheet limits are not guaranteed if the device is operated beyond the operating ratings.
3. Package Thermal Resistance assumes exposed pad is soldered (or equivalent) to the devices most negative potential on the PCB. ψJB uses a 4layer and θJA in still-air number, unless otherwise stated.
4. Amplifier in limiting mode. Input is a 200MHz square wave.
5. Deterministic jitter measured using 2.5Gbps K28.5 pattern, VID = 10mVPP.
6. Random jitter measured using 2.5Gbps K28.7 pattern, VID = 10mVPP.
7. See “Typical Operating Characteristics” for a graph showing how to choose a particular RLOSLVL for a particular LOS assert and its associated deassert amplitude.
8. This specification defines electrical hysteresis as 20log (LOS De-Assert/LOS Assert). The ratio between optical hysteresis and electrical
hysteresis is found to vary between 1.5 and 2, depending upon the level of received optical power and ROSA characteristics. Based upon that
ratio, the optical hysteresis corresponding to the electrical hysteresis range 1dB-4.5 dB, shown in the AC characteristics table, will be 0.5dB-3dB
Optical Hysteresis.
9. In real world applications, the LOS Release/Assert time can be strongly influenced by the RC time constant of the AC-coupling cap and the 50Ω
input termination. To keep this time low, use a decoupling cap with the lowest value that is allowed by the data rate and the number of
consecutive identical bits in the application. Typical values are in the range of 0.001µF to 1.0µF.
April 2006
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Micrel, Inc.
SY88353BL
Typical Operating Characteristics
VCC = 3.3V, TA = 25°C, RL = 50Ω to VCC-2V, unless otherwise stated.
LOSLVL RESISTOR (kΩ)
April 2006
6
LOSLVL RESISTOR (kΩ)
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SY88353BL
Functional Characteristics
VCC = 3.3V, TA = 25°C, RL = 50Ω to VCC-2V, unless otherwise stated.
April 2006
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SY88353BL
Functional Block Diagram
Detailed Description
The SY88353L limiting post amplifier operates from a
single +3.3V power supply, over temperatures from
–40°C to +85°C. Signals with data rates from 155Mbps
up to 3.2Gbps, and as small as 10mVpp, can be
amplified. Figure 1 shows the allowed input voltage
swing. The SY88353L generates a LOS output that can
be feedback to /EN for output stability in the absence of
a signal at the input. LOSLVL sets the sensitivity of the
input amplitude detection. The amplifier features a
signal crossing adjustment for BER optimization in
optical links using optical amplifiers such in WDM
applications.
Input Amplifier/Buffer
Figure 2 shows a simplified schematic of the input
stage. The input amplifier allows signals as small as
10mVpp to be detected and amplified. The input amplifier
allows input signals as large as 1800mVpp. Input signals
are linearly amplified with a typical 38dB differential
voltage gain. Since it is a limiting amplifier, the
SY88353BL outputs typically 800mVpp voltage-limited
waveforms for input signals that are greater than
12mVpp. Applications requiring the SY88353L to operate
with high gain should have the upstream TIA placed as
close as possible to the SY88353BL’s input pins to
ensure the best performance of the device.
Output Buffer
The SY88353BL’s CML output buffer is designed to
drive 50Ω lines and is internally terminated with 50Ω to
VCC. Figure 3 shows a simplified schematic of the output
stage.
April 2006
Loss-of-Signal
The SY88353L generates a chatter-free loss-of-signal
(LOS) open-collector, TTL output, as shown in Figure 4.
LOS is used to determine if the input amplitude is too
small to be considered 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, 3.3dB LOS hysteresis is provided to
prevent chattering.
Loss-of-Signal-Level Set
A programmable LOS level set pin (LOSLVL) sets the
threshold of the input amplitude detection. Connecting
an external resistor between VCC and LOSLVL sets the
voltage at LOSLVL. This voltage ranges from VCC to VCC1.3V. The external resistor creates a voltage divider
between VCC and VCC-1.3V, as shown in Figure 5.
Hysteresis
The SY88353L typically provides 3.3dB LOS electrical
hysteresis, which is defined as 20log (VINLOS-De-assert/
VINLOS-Assert). Since the relationship between the voltage
out of the ROSA and optical power at its input is linear,
the optical hysteresis will be typically half of the
electrical hysteresis reported in the datasheet. In
practice, the ratio between electrical and optical
hysteresis is found to be within the range 1.5 to 1.8dB.
Thus, 3.3dB electrical hysteresis will correspond to an
optical hysteresis within the range 1.8 to 2.2dB.
8
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SY88353BL
Signal Crossing Adjustment
In order to optimize the decision threshold level and
hence, the BER of the optical link, the SY88353L
provides two pins for output signal crossing control. The
signal crossing can be adjusted by connecting VTHN
(pin 5) to VTHREF (pin 6), and applying a DC signal at
VTHP (pin 16). By varying the DC signal at VTHP from
– 0V to 2.5V – while the input signal to the post amplifier
is less than 100mVpp, the crossing of the output signal
will change from 20% to 80% reaching 50% when VTHP
= VTHREF = 1.25V. If the crossing control function is
not needed, VTHN and VTHP must be connected to
ground.
The zero crossing vs. VTHP plot, shown on page 6,
shows how the crossing of the output signal changes
with the voltage applied at VTHP (pin 16) while VTHN
(pin 5) is tied to VTHREF (pin 6) for different input signal
levels.
Figure 1. VIS and VID Definition
Figure 2. Input Structure
April 2006
Figure 3. Output Structure
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SY88353BL
Figure 4. LOS Output Structure
Figure 5. LOSLVL Setting Circuit
Note: Recommended value for RLOSLVL is 15kΩ or less.
Related Product and Support Documentation
Part Number
Function
Data Sheet Link
AN-45
Notes on Sensitivity and Hysteresis in Micrel
Post Amplifiers
http://www.micrel.com/product-info/app_hints+notes.shtml
April 2006
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SY88353BL
Package Information
16-Pin (3mm x 3mm) MLF™ (MLF-16)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for
its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a
product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for
surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant
injury to the user. A Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk
and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale.
© 2006 Micrel, Incorporated.
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