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19-0479; Rev 1; 7/97
________________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 60
per side.
The transimpedance gain is nominally 6k
. 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 1k
resistor to V
CC
. The device is also available in 8-pin SO
and µMAX packages.
________________________Applications
SDH/SONET Receivers
PIN/Preamplifier Receivers
Regenerators for SDH/SONET
____________________________Features
o
Single +3.3V Supply Operation
o
55nA
RMS
Input-Referred Noise
o
6k
Gain
o
85mW Power
o
300µA Peak Input Current
o
200ps Max Pulse-Width Distortion
o
Differential Output Drives 100
Load
o
590MHz Bandwidth
MAX3664
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
________________________________________________________________
Maxim Integrated Products
1
MAX3664
MAX3675
LIMITING
AMP
100pF
INREF2
1k
V
CC
100
0.01
µ
F
47nF
V
CC
(+3.3V)
DATA
CLK
( ) ARE FOR MAX3664E/D (DICE) ONLY.
47nF
400pF
OUT+
OUT-
COMP
GND
V
CC
(+3.3V)
(FILT)
INREF1
IN
DATA
AND
CLOCK
RECOVERY
__________________________________________________Typical Application Circuit
PART
MAX3664E/D
MAX3664ESA
MAX3664EUA*
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
TEMP. RANGE
PIN-PACKAGE
Dice
8 SO
8 µMAX
EVALUATION KIT
AVAILABLE
_______________Ordering Information
Pin Configuration appears at end of data sheet.
* Contact factory for package availability.
MAX3664
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
DC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.3V ±0.3V, COMP = GND, 100
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)
AC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.3V ±0.3V, C
COMP
= 400pF, C
IN
= 1.1pF, outputs terminated into 50
, 8-pin SO package in MAX3664 EV board,
T
A
= +25°C, unless otherwise noted.) (Notes 3, 4)
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.
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.
Note 1:
Dice are tested at T
j
= +27°C.
Note 2:
µMAX package tested at T
A
= +25°C to +85°C.
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
I
IN
= 0
I
IN
= 0 to 20µA
I
IN
= 0 to 300µA
I
IN
= 300µA
Differential output
f < 1MHz, referred to output
I
IN
= 200µA, C
COMP
= 400pF
CONDITIONS
mA
12
25
35
I
CC
Supply Current
%
±5
V
0.8
0.95
V
IN
Input Bias Voltage
Gain Nonlinearity
mV
950
V
OUT
(max)
Maximum Output Voltage
40
60
75
Z
OUT
Output Impedance (per side)
k
4.5
6
7.5
z
21
Small-Signal Transimpedance
V
V
CC
- 1.3
Output Common-Mode Level
dB
20
PSRR
Power-Supply Rejection Ratio
mV
±7
V
OUT
Differential Output Offset
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
Relative to gain at 10MHz
C
IN
= 1.1pF (Note 6), I
IN
= 0
2µA to 100µA peak input current,
50% duty cycle, 10 pattern
100µA to 300µA peak input current,
50% duty cycle, 10 pattern
C
IN
= 0.3pF (Note 6), I
IN
= 0
CONDITIONS
kHz
150
MHz
590
BW
-3dB
Small-Signal Bandwidth
Low-Frequency Cutoff
nA
73
86
i
n
RMS Noise Referred to Input
6
100
ps
80
200
PWD
Pulse-Width Distortion
(Note 5)
55
UNITS
MIN
TYP
MAX
SYMBOL
PARAMETER
800
1000
1200
R
FILT
Filter Resistor (die only)
MAX3664
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
_______________________________________________________________________________________
3
100
0
-40
30
100
INPUT-REFERRED NOISE
vs. TEMPERATURE
30
20
40
10
70
90
80
60
MAX3664-01
JUNCTION TEMPERATURE (°C)
NOISE (nA)
-5
65
50
470MHz BANDWIDTH
C
IN
= 1.5pF
C
IN
= 0.5pF
C
IN
= 1.0pF
C
IN
IS SOURCE CAPACITANCE
PRESENTED TO DIE. INCLUDES PACKAGE
PARASITIC, PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
80
78
76
10k
100k
10M
10G
SMALL-SIGNAL GAIN
vs. FREQUENCY
62
60
72
70
74
68
MAX3664-02
FREQUENCY (Hz)
GAIN (dB)
1M
100M
64
66
1G
MAX3664 IN EV BOARD
COMP CONNECTED
TO GROUND
COMP CONNECTED
THROUGH 400pF
TO GROUND
200
-50
-40
25
45
85
PULSE-WIDTH DISTORTION
vs. TEMPERATURE
0
100
150
MAX3664-03
AMBIENT TEMPERATURE (°C)
PWD (ps)
-25
0
65
50
I
IN
= 100
µ
A
I
IN
= 300
µ
A
MAX3664 IN EV BOARD
1000
0.1
1
10
100
1000
INPUT-REFERRED RMS NOISE CURRENT
vs. DC INPUT CURRENT
MAX3664-04
DC INPUT CURRENT (
µ
A)
RMS NOISE CURRENT (nA)
10
100
C
STC
= 0.5pF
470MHz BANDWIDTH
300
0
0
80
100
120
160
LOW-FREQUENCY CUTOFF
vs. AVERAGE INPUT CURRENT
50
150
250
200
MAX3664-07
AVERAGE INPUT CURRENT (
µ
A)
LOW-FREQUENCY CUTOFF (kHz)
20
40
60
140
100
C
COMP
= 50pF
C
COMP
= 100pF
C
COMP
= 200pF
C
COMP
= 400pF
C
COMP
= 1000pF
6400
5800
-40
30
100
SMALL-SIGNAL TRANSIMPEDANCE
vs. TEMPERATURE
5900
6000
6200
6300
MAX3664-05
JUNCTION TEMPERATURE (°C)
TRANSIMPEDANCE (
)
-5
65
6100
V
CC
= 3V
MEASUREMENT FREQUENCY = 20MHz
V
CC
= 3.6V
650
400
-40
30
100
BANDWIDTH vs. TEMPERATURE
450
500
550
600
MAX3664-06
JUNCTION TEMPERATURE (°C)
BANDWIDTH (MHz)
-5
65
C
IN
= 0.5pF
C
IN
= 1.0pF
C
IN
= 1.5pF
C
IN
IS SOURCE CAPACITANCE
PRESENTED TO DIE. INCLUDES PACKAGE
PARASITIC, PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
120
0
0
150
200
300
DATA-DEPENDENT JITTER
vs. INPUT SIGNAL AMPLITUDE
20
60
100
80
MAX3664-08
PEAK-TO-PEAK AMPLITUDE (
µ
A)
PEAK-TO-PEAK JITTER (ps)
50
100
250
40
C
COMP
= 100pF
C
COMP
= 200pF
C
COMP
= 400pF
C
COMP
= 800pF
EXTINCTION RATIO > 10
INPUT: 2
13
- 1 PRBS
CONTAINS 72 ZEROS
__________________________________________Typical Operating Characteristics
(V
CC
= +3.3V, C
COMP
= 400pF, T
A
= +25°C, unless otherwise noted.)
-1.15
-1.40
-40
40
60
100
OUTPUT COMMON-MODE VOLTAGE
(REFERENCED TO V
CC
) vs. TEMPERATURE
-1.35
-1.30
-1.20
-1.25
MAX3664-09
AMBIENT TEMPERATURE (°C)
COMMON-MODE VOLTAGE (V)
-20
0
20
80
V
CC
= 3.0V
V
CC
= 3.3V
V
CC
= 3.6V
MAX3664
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
4
_______________________________________________________________________________________
_____________________________Typical Operating Characteristics (continued)
(V
CC
= +3.3V, C
COMP
= 400pF, T
A
= +25°C, unless otherwise noted.)
800
200
-40
40
60
100
OUTPUT AMPLITUDE
vs. TEMPERATURE
300
500
700
600
MAX3664-10
AMBIENT TEMPERATURE (°C)
AMPLITUDE (mV)
-20
0
20
80
400
INPUT = 300
µ
Ap-p
V
CC
= 3.6V
V
CC
= 3.3V
V
CC
= 3.0V
EYE DIAGRAM
(INPUT = 10
µ
Ap-p)
10mV/
div
MAX3664-11
300ps/div
INPUT: 2
13
- 1 PRBS
CONTAINS 72 ZEROS
EYE DIAGRAM
(INPUT = 300
µ
Ap-p)
100mV/
div
MAX3664-12
300ps/div
INPUT: 2
13
- 1 PRBS
CONTAINS 72 ZEROS
DC
CANCELLATION
AMP
PARAPHASE
AMP
V
CC
V
CC
V
CC
V
CC
D1
Q2
Q3
R3
R4
R2
R1
OUT+
(FILT)
OUT-
1k
6k
Q1
INREF2
INREF1
IN
Q4
TRANSIMPEDANCE
AMP
COMP
MAX3664
( ) ARE FOR MAX3664E/D (DIE) ONLY.
R
F
_____________________Pin Description
NAME
FUNCTION
1
V
CC
+3.3V Supply Voltage
2
IN
Signal Input
PIN
3, 4
INREF1,
INREF2
Input References 1 and 2. Connect to
photodetector AC ground.
5
GND
Ground
--
FILT*
Filter Connection. Provides positive
bias for photodiode through a 1k
resistor to V
CC
. See
Step 3:
Designing Filters. (This pad is acces-
sible on the die only.)
8
COMP
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.
7
OUT-
Inverting Voltage Output. Current flow-
ing into IN causes V
OUT-
to decrease.
6
OUT+
Noninverting Voltage Output. Current
flowing into IN causes V
OUT+
to
increase.
* MAX3664E/D (die) only.
Figure 1. Functional Diagram
________________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.
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 6k
. 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.
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
100
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
component, this is not a problem. Preamplifier noise will
increase for signals with significant DC component.
___________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.
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 6k
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 (
), 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)(
)
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)]
MAX3664
622Mbps, Ultra-Low-Power, 3.3V
Transimpedance Preamplifier for SDH/SONET
_______________________________________________________________________________________
5
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