19-0479; Rev 1; 7/97
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
________________General Description
The MAX3664 low-power transimpedance preamplifier
for 622Mbps SDH/SONET applications consumes only
85mW. Operating from a single +3.3V supply, it converts
a small photodiode current to a measurable differential
voltage. A DC cancellation circuit provides a true differ-
ential output swing over a wide range of input current
levels, thus reducing pulse-width distortion. The differen-
tial outputs are back-terminated with 60Ω per side.
The transimpedance gain is nominally 6kΩ. For input
signal levels beyond approximately 100µAp-p, the
amplifier will limit the output swing to 900mV. The
MAX3664’s low 55nA input noise provides a typical
sensitivity of -33.2dBm in 1300nm, 622Mbps receivers.
The MAX3664 is designed to be used in conjunction
with the MAX3675 clock recovery and data retiming IC
with limiting amplifier. Together, they form a complete
3.3V, 622Mbps SDH/SONET receiver.
In die form, the MAX3664 is designed to fit on a header
with a PIN diode. It includes a filter connection, which
provides positive bias for the photodiode through a 1kΩ
resistor to V
CC
. The device is also available in 8-pin SO
and µMAX packages.
KIT
ATION
EVALU
BLE
AVAILA
____________________________Features
o
Single +3.3V Supply Operation
o
55nA
RMS
Input-Referred Noise
o
6kΩ Gain
o
85mW Power
o
300µA Peak Input Current
o
200ps Max Pulse-Width Distortion
o
Differential Output Drives 100Ω Load
o
590MHz Bandwidth
MAX3664
_______________Ordering Information
PART
MAX3664E/D
MAX3664ESA
MAX3664EUA*
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
Dice
8 SO
8 µMAX
* Contact factory for package availability.
________________________Applications
SDH/SONET Receivers
PIN/Preamplifier Receivers
Regenerators for SDH/SONET
Pin Configuration appears at end of data sheet.
__________________________________________________Typical Application Circuit
V
CC
(+3.3V)
0.01µF
V
CC
(+3.3V)
1k
100pF
(FILT)
INREF2
INREF1
V
CC
OUT+
100Ω
LIMITING
AMP
47nF
DATA
AND
CLOCK
RECOVERY
DATA
47nF
MAX3664
IN
GND
OUT-
COMP
CLK
MAX3675
400pF
( ) ARE FOR MAX3664E/D (DICE) ONLY.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
MAX3664
ABSOLUTE MAXIMUM RATINGS
V
CC
........................................................................-0.5V to +5.5V
Continuous Current
IN, INREF1, INREF2, COMP, FILT....................................5mA
OUT+, OUT-...................................................................25mA
Continuous Power Dissipation (T
A
= +85°C)
SO (derate 5.88mW/°C above +85°C) ........................383mW
µMAX (derate 4.1mW/°C above +85°C) .....................268mW
Operating Junction Temperature (die) ..............-40°C to +150°C
Processing Temperature (die) .........................................+400°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.3V ±0.3V, COMP = GND, 100Ω load between OUT+ and OUT-, T
A
= -40°C to +85°C. Typical values are at T
A
= +25°C,
unless otherwise noted.) (Notes 1, 2)
PARAMETER
Input Bias Voltage
Gain Nonlinearity
Supply Current
Small-Signal Transimpedance
Output Common-Mode Level
Power-Supply Rejection Ratio
Differential Output Offset
Output Impedance (per side)
Maximum Output Voltage
Filter Resistor (die only)
PSRR
∆V
OUT
Z
OUT
V
OUT
(max)
R
FILT
I
IN
= 300µA
800
1000
f < 1MHz, referred to output
I
IN
= 200µA, C
COMP
= 400pF
40
20
±7
60
75
950
1200
I
CC
z
21
SYMBOL
V
IN
CONDITIONS
I
IN
= 0 to 300µA
I
IN
= 0 to 20µA
I
IN
= 0
Differential output
12
4.5
25
6
V
CC
- 1.3
MIN
TYP
0.8
MAX
0.95
±5
35
7.5
UNITS
V
%
mA
kΩ
V
dB
mV
Ω
mV
Ω
Note 1:
Dice are tested at T
j
= +27°C.
Note 2:
µMAX package tested at T
A
= +25°C to +85°C.
AC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.3V ±0.3V, C
COMP
= 400pF, C
IN
= 1.1pF, outputs terminated into 50Ω, 8-pin SO package in MAX3664 EV board,
T
A
= +25°C, unless otherwise noted.) (Notes 3, 4)
PARAMETER
Small-Signal Bandwidth
Low-Frequency Cutoff
Pulse-Width Distortion
(Note 5)
2µA to 100µA peak input current,
50% duty cycle, 1–0 pattern
PWD
100µA to 300µA peak input current,
50% duty cycle, 1–0 pattern
i
n
C
IN
= 0.3pF (Note 6), I
IN
= 0
C
IN
= 1.1pF (Note 6), I
IN
= 0
80
55
73
86
200
nA
6
SYMBOL
BW
-3dB
CONDITIONS
Relative to gain at 10MHz
MIN
TYP
590
150
100
ps
MAX
UNITS
MHz
kHz
RMS Noise Referred to Input
Note 3:
AC Characteristics are guaranteed by design.
Note 4:
C
IN
is the total capacitance at IN.
Note 5:
PWD = 2 x Pulse width - Period
|
|
2
Note 6:
DC to 470MHz, measured with 3-pole Bessel filter at output.
2
_______________________________________________________________________________________
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
__________________________________________Typical Operating Characteristics
(V
CC
= +3.3V, C
COMP
= 400pF, T
A
= +25°C, unless otherwise noted.)
MAX3664
INPUT-REFERRED NOISE
vs. TEMPERATURE
MAX3664-01
SMALL-SIGNAL GAIN
vs. FREQUENCY
MAX3664-02
PULSE-WIDTH DISTORTION
vs. TEMPERATURE
MAX3664 IN EV BOARD
150
MAX3664-03
100
90
80
70
NOISE (nA)
60
50
40
30
20
10
0
-40
-5
30
65
C
IN
IS SOURCE CAPACITANCE
PRESENTED TO DIE. INCLUDES PACKAGE
PARASITIC, PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
470MHz BANDWIDTH
C
IN
= 1.5pF
80
78
76
74
GAIN (dB)
72
70
68
66
64
62
60
COMP CONNECTED
THROUGH 400pF
TO GROUND
COMP CONNECTED
TO GROUND
MAX3664 IN EV BOARD
200
I
IN
= 300µA
PWD (ps)
100
C
IN
= 1.0pF
C
IN
= 0.5pF
50
I
IN
= 100µA
0
-50
10k
100k
1M
10M
100M
1G
10G
-40
-25
0
25
45
65
85
FREQUENCY (Hz)
AMBIENT TEMPERATURE (°C)
100
JUNCTION TEMPERATURE (°C)
INPUT-REFERRED RMS NOISE CURRENT
vs. DC INPUT CURRENT
MAX3664-04
SMALL-SIGNAL TRANSIMPEDANCE
vs. TEMPERATURE
MAX3664-05
BANDWIDTH vs. TEMPERATURE
C
IN
= 0.5pF
600
BANDWIDTH (MHz)
C
IN
= 1.0pF
550
C
IN
= 1.5pF
500
C
IN
IS SOURCE CAPACITANCE
PRESENTED TO DIE. INCLUDES PACKAGE
PARASITIC, PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
-40
-5
30
65
100
MAX3664-06
1000
C
STC
= 0.5pF
470MHz BANDWIDTH
RMS NOISE CURRENT (nA)
6400
V
CC
= 3.6V
6300
TRANSIMPEDANCE (Ω)
6200
6100
6000
5900
MEASUREMENT FREQUENCY = 20MHz
V
CC
= 3V
650
100
450
10
0.1
1
10
100
1000
DC INPUT CURRENT (µA)
5800
-40
-5
30
65
100
JUNCTION TEMPERATURE (°C)
400
JUNCTION TEMPERATURE (°C)
LOW-FREQUENCY CUTOFF
vs. AVERAGE INPUT CURRENT
MAX3664-07
DATA-DEPENDENT JITTER
vs. INPUT SIGNAL AMPLITUDE
EXTINCTION RATIO > 10
100
C
COMP
= 100pF
C
COMP
= 200pF
C
COMP
= 400pF
C
COMP
= 800pF
40
20
0
INPUT: 2
13
- 1 PRBS
CONTAINS 72 ZEROS
0
50
100
150
200
250
300
PEAK-TO-PEAK JITTER (ps)
MAX3664-08
OUTPUT COMMON-MODE VOLTAGE
(REFERENCED TO V
CC
) vs. TEMPERATURE
MAX3664-09
300
LOW-FREQUENCY CUTOFF (kHz)
250
200
150
100
50
0
0
20
40
60
80
C
COMP
= 200pF
C
COMP
= 400pF
C
COMP
= 1000pF
C
COMP
= 50pF
C
COMP
= 100pF
120
-1.15
-1.20
V
CC
= 3.0V
80
60
COMMON-MODE VOLTAGE (V)
-1.25
-1.30
V
CC
= 3.3V
-1.35
V
CC
= 3.6V
-1.40
-40
-20
0
20
40
60
80
100
PEAK-TO-PEAK AMPLITUDE (µA)
AMBIENT TEMPERATURE (°C)
100 120 140 160
AVERAGE INPUT CURRENT (µA)
_______________________________________________________________________________________
3
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
MAX3664
_____________________________Typical Operating Characteristics (continued)
(V
CC
= +3.3V, C
COMP
= 400pF, T
A
= +25°C, unless otherwise noted.)
OUTPUT AMPLITUDE
vs. TEMPERATURE
INPUT = 300µAp-p
700
AMPLITUDE (mV)
600
500
400
300
200
-40
-20
0
20
40
60
80
100
300ps/div
300ps/div
AMBIENT TEMPERATURE (°C)
INPUT: 2
13
- 1 PRBS
CONTAINS 72 ZEROS
V
CC
= 3.3V
V
CC
= 3.0V
10mV/
div
100mV/
div
V
CC
= 3.6V
MAX3664-10
EYE DIAGRAM
(INPUT = 10µAp-p)
MAX3664-11
EYE DIAGRAM
(INPUT = 300µAp-p)
MAX3664-12
800
INPUT: 2
13
- 1 PRBS
CONTAINS 72 ZEROS
_____________________Pin Description
V
CC
PIN
NAME
V
CC
IN
INREF1,
INREF2
GND
OUT+
FUNCTION
+3.3V Supply Voltage
D1
R
F
1k
(FILT)
1
2
3, 4
5
6
Signal Input
Input References 1 and 2. Connect to
photodetector AC ground.
Ground
Noninverting Voltage Output. Current
flowing into IN causes V
OUT+
to
increase.
Inverting Voltage Output. Current flow-
ing into IN causes V
OUT-
to decrease.
External Compensation Capacitor for
DC cancellation loop. Connect 400pF
or more from COMP to GND for nor-
mal operation. Connect COMP directly
to GND to disable the DC cancellation
loop.
Filter Connection. Provides positive
bias for photodiode through a 1kΩ
resistor to V
CC
. See
Step 3:
Designing Filters.
(This pad is acces-
sible on the die only.)
IN
INREF1
Q3
TRANSIMPEDANCE
AMP
R3
R4
Q4
INREF2
DC
CANCELLATION
AMP
R2
OUT-
Q1
PARAPHASE
AMP
6k
V
CC
V
CC
Q2
R1
OUT+
V
CC
7
OUT-
8
COMP
MAX3664
COMP
( ) ARE FOR MAX3664E/D (DIE) ONLY.
—
FILT*
* MAX3664E/D (die) only.
Figure 1. Functional Diagram
4
_______________________________________________________________________________________
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
________________Detailed Description
The MAX3664 is a transimpedance amplifier designed
for 622Mbps SDH/SONET applications. It comprises a
transimpedance amplifier, a paraphase amplifier with
emitter-follower outputs, and a DC cancellation loop.
Figure 1 is a functional diagram of the MAX3664.
component, this is not a problem. Preamplifier noise will
increase for signals with significant DC component.
MAX3664
___________Applications Information
The MAX3664 is a low-noise, wide-bandwidth transim-
pedance amplifier that is ideal for 622Mbps SDH/
SONET receivers. Its features allow easy design into a
fiber optic module, in four simple steps.
Transimpedance Amplifier
The signal current at IN flows into the summing node of
a high-gain amplifier. Shunt feedback through R
F
con-
verts this current to a voltage with a gain of 6kΩ. Diode
D1 clamps the output voltage for large input currents.
INREF1 is a direct connection to the emitter of the input
transistor, and must be connected directly to the pho-
todetector AC ground return for best performance.
Step 1: Selecting a Preamplifier for a 622Mbps
Receiver
Fiber optic systems place requirements on the band-
width, gain, and noise of the transimpedance preampli-
fier. The MAX3664 optimizes these characteristics for
SDH/SONET receiver applications that operate at
622Mbps.
In general, the bandwidth of a fiber optic preamplifier
should be 0.6 to 1 times the data rate. Therefore, in a
622Mbps system, the bandwidth should be between
375MHz and 622MHz. Lower bandwidth causes pat-
tern-dependent jitter and a lower signal-to-noise ratio,
while higher bandwidth increases thermal noise. The
MAX3664 typical bandwidth is 590MHz, making it ideal
for 622Mbps applications.
The preamplifier’s transimpedance must be high
enough to ensure that expected input signals generate
output levels exceeding the sensitivity of the limiting
amplifier (quantizer) in the following stage. The
MAX3675 clock recovery and limiting amplifier IC has
an input sensitivity of 3.6mVp-p, which means that
3.6mVp-p is the minimum signal amplitude required to
produce a fully limited output. Therefore, when used
with the MAX3664, which has a 6kΩ transimpedance,
the minimum detectable photodetector current is 600nA.
It is common to relate peak-to-peak input signals to
average optical power. The relationship between opti-
cal input power and output current for a photodetector
is called the responsivity (ρ), with units Amperes/Watt
(A/W). The photodetector peak-to-peak current is relat-
ed to the peak-to-peak optical power as follows:
Ip-p = (Pp-p)(ρ)
Based on the assumption that SDH/SONET signals
maintain a 50% duty cycle, the following equations
relate peak-to-peak optical power to average optical
power and extinction ratio (Figure 2):
Average Optical Power = P
AVE
= (P0 + P1) / 2
Extinction Ratio = r
e
= P1 / P0
Peak-to-Peak Signal Amplitude = Pp-p = P1 - P0
Therefore,
P
AVE
= Pp-p (1 / 2)[(r
e
+ 1) / (r
e
- 1)]
5
Paraphase Amplifier
The paraphase amplifier converts single-ended inputs to
differential outputs, and introduces a voltage gain of 2.
This signal drives a pair of internally biased emitter follow-
ers, Q2 and Q3, which form the output stage. Resistors
R1 and R2 provide back-termination at the output,
absorbing reflections between the MAX3664 and its load.
The output emitter followers are designed to drive a
100Ω differential load between OUT+ and OUT-. They
can also drive higher output impedances, resulting in
increased gain and output voltage swing.
DC Cancellation Loop
The DC cancellation loop removes the DC component
of the input signal by using low-frequency feedback.
This feature centers the signal within the MAX3664’s
dynamic range, reducing pulse-width distortion on
large input signals.
The output of the paraphase amplifier is sensed through
resistors R3 and R4 and then filtered, amplified, and fed
back to the base of transistor Q4. The transistor draws
the DC component of the input signal away from the
transimpedance amplifier’s summing node.
The COMP pin sets the DC cancellation loop’s
response. Connect 400pF or more between COMP and
GND for normal operation. Connect the pin directly to
GND to disable the loop. The DC cancellation loop can
sink up to 300µA of current at the input. When operated
with C
COMP
= 400pF, the loop takes approximately
20µs to stabilize.
The MAX3664 minimizes pulse-width distortion for data
sequences that exhibit a 50% duty cycle. A duty cycle
other than 50% causes the device to generate pulse-
width distortion.
DC cancellation current is drawn from the input and
adds noise. For low-level signals with little or no DC
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