Maxim MAX3963D 155mbps preamplifier for fddi and atm lan fiber optic receiver Datasheet

19-1215; Rev 1; 4/98
155Mbps Preamplifier for FDDI
and ATM LAN Fiber Optic Receivers
____________________________Features
♦ 21nA Total RMS Noise
♦ 22kΩ Differential Transimpedance
♦ 180MHz Bandwidth
♦ 60mW Typical Power Consumption
♦ 60µA Peak Input Current
♦ Low, 85ps Pulse-Width Distortion
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX3963CSA
0°C to +70°C
8 SO
MAX3963C/D
0°C to +70°C*
Dice
*Dice are designed to operate over a 0°C to +100°C junction
temperature (Tj) range, but are tested and guaranteed at TA =
+25°C.
__________________Pin Configuration
TOP VIEW
N.C. 1
IN 2
________________________Applications
MAX3963
8
VCC
7
OUT-
FDDI
N.C. 3
6
OUT+
155Mbps ATM
BYP 4
5
GND
SO
__________________________________________________Typical Application Circuit
VCC
0.01µF
VCC
1k
0.056µF
(FILTER)
OUT+
100pF
PHOTODIODE
MAX3964
IN
OUT-
MAX3963
( ) ARE FOR MAX3963C/D ONLY.
GND
BYP
0.056µF
LIMITING AMPLIFIER
CBYP
100pF
(OPTIONAL)
________________________________________________________________ Maxim Integrated Products
1
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MAX3963
_______________General Description
The MAX3963 is a low-noise transimpedance preamplifier for FDDI and 155Mbps ATM optical receivers. The
MAX3963’s dynamic range is optimized for use in multimode LED-based applications.
The preamplifier converts a small photodiode current to
a differential voltage, with typical transimpedance of
22kΩ. Input-referred noise of only 21nA allows detection of signals as small as 267nA, while pulse-width distortion is only 85ps with a 60µA input signal. In a
1300nm multimode receiver, with responsivity of
0.7A/W, the MAX3963’s dynamic range spans from
-36dBm to -13.7dBm. The circuit operates from a single
+5V supply, and typically consumes only 60mW power.
The MAX3963 die includes a filter connection, which
provides positive bias for the photodiode through a 1kΩ
resistor to VCC. This feature, combined with the small
die size, allows the MAX3963 to fit easily into a TO-style
package with a photodiode.
The differential outputs are back terminated with 60Ω
per side, allowing the easy use of filters to improve sensitivity.
The MAX3963 is designed to be used with the
MAX3964 limiting amplifier IC. It is available in an 8-pin
SO package and as dice.
MAX3963
155Mbps Preamplifier for FDDI
and ATM LAN Fiber Optic Receivers
ABSOLUTE MAXIMUM RATINGS
VCC ........................................................................-0.5V to +7.0V
Continuous Current
IN.......................................................................................5mA
OUT+, OUT-....................................................................25mA
BYP .......................................................................................5mA
Continuous Power Dissipation (TA = +70°C)
SO (derate 5.88mW/°C above +70°C) .........................471mW
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
Operating Junction Temperature (die) ..............-55°C to +150°C
Processing Temperature (die) .........................................+400°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
(VCC = +4.5V to +5.5V, CBYP = 100pF, 1kΩ load between OUT+ and OUT-, TA = 0°C to +70°C. Typical values are at VCC = 5.0V,
TA = +25°C, unless otherwise noted.) (Note 1)
TYP
MAX
Input Bias Voltage
PARAMETER
SYMBOL
VIN
Input = 0µA to 60µA
CONDITIONS
MIN
1.6
1.8
V
Supply Current
ICC
Input = 0µA
12
20
mA
Small-Signal Transimpedance
z21
Differential output, input < 60µA
22
26.3
kΩ
17.5
Output Common-Mode Voltage
VCC - 2.85
Power-Supply Rejection Ratio
PSRR
Output Resistance (per side)
ROUT
Maximum Differential Output
Voltage
VOD
(MAX)
f < 1MHz, referred to output
V
35
45
UNITS
dB
60
IIN = 80µA
68
Ω
2.2
V
AC ELECTRICAL CHARACTERISTICS
(VCC = +4.5V to +5.5V, CBYP = 100pF, CIN = 1.15pF, TA = +25°C, unless otherwise noted.) (Notes 2, 3)
PARAMETER
Small-Signal Bandwidth
Pulse-Width Distortion
RMS Noise Referred to Input
SYMBOL
BW-3dB
PWD
in
CONDITIONS
MIN
TYP
MAX
UNITS
100
180
220
MHz
IIN = 60µAp-p (Note 4)
85
160
ps
(Note 5)
21
24.5
nA
(Note 6)
37
COUT = 5pF
nA
Dice are tested at TA = +25°C only.
AC characteristics are guaranteed by design.
CIN is the total capacitance at IN. COUT is the differential output capacitive load.
PWD = [(width of wider pulse) - (width of narrower pulse)] / 2. Input is a 155Mbps 1-0 pattern, with rise time approximately
2ns.
Note 5: Measured with a 117MHz, 3-pole Bessel filter.
Note 6: Measured with COUT = 5pF, TA = +25°C.
Note 1:
Note 2:
Note 3:
Note 4:
2
_______________________________________________________________________________________
155Mbps Preamplifier for FDDI
and ATM LAN Fiber Optic Receivers
(VCC = 5.0V, CBYP = 100pF, CIN = 1.3pF, TA = +25°C, unless otherwise noted.)
SMALL-SIGNAL TRANSIMPEDANCE
vs. TEMPERATURE
SUPPLY CURRENT
vs. TEMPERATURE
1.8
22
21
VCC = 5.5V
13
12
VCC = 5V
11
20
10
20
30
40
50
60
70
1.2
1.0
0
10
20
30
40
50
60
0
70
10
20
30
40
50
60
TEMPERATURE (°C)
PULSE-WIDTH DISTORTION
vs. TEMPERATURE
PULSE-WIDTH DISTORTION
vs. INPUT CURRENT
DIFFERENTIAL OUTPUT VOLTAGE
vs. INPUT CURRENT
60
40
200
150
100
50
20
0
0
40
50
60
FREQUENCY RESPONSE
BANDWIDTH vs. TEMPERATURE
MAX3963-07
CIN = 1pF
200
-4
-5
-6
-7
BANDWIDTH (MHz)
CIN = 11pF
-50
CIN = 0.5pF
CIN = 1pF
180
CIN = 1.5pF
160
140
100
100M
FREQUENCY (Hz)
*RELATIVE TO TRANSIMPEDANCE AT DC
50
100
150
26
24
CIN = 1.5pF
22
CIN = 1pF
20
CIN = 0.5pF
18
16
14
12
-8
-9
0
INPUT-REFERRED RMS NOISE
120
10M
-100
INPUT CURRENT (µA)
220
-1
-3
-150
INPUT CURRENT (µAp-p)
1
-2
-1
10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
0
0
-2
0
70
1
MAX3963-09
30
INPUT-REFERRED NOISE* (nARMS)
20
MAX3963-08
10
MAX3963-06
MAX3963-05
250
70
2
DIFFERENTIAL OUTPUT VOLTAGE (V)
80
300
PULSE-WIDTH DISTORTION (ps)
MAX3963-04
100
1M
1.4
TEMPERATURE (°C)
IIN = 6OµAp-p
0
1.6
TEMPERATURE (°C)
120
PULSE-WIDTH DISTORTION (ps)
VCC = 4.5V
10
0
TRANSIMPEDANCE* (dB)
INPUT BIAS VOLTAGE (V)
SUPPLY CURRENT (mA)
TRANSIMPEDANCE (kΩ)
14
23
MAX3963-03
2.0
MAX3963-02
15
MAX3963-01
24
INPUT BIAS VOLTAGE (VIN)
vs. TEMPERATURE
10
0
10
20
30
40
50
TEMPERATURE (°C)
60
70
0
10
20
30
40
50
60
70
TEMPERATURE (°C)
*MEASURED WITH 4-POLE, 117MHz BESSEL FILTER
_______________________________________________________________________________________
3
MAX3963
__________________________________________Typical Operating Characteristics
MAX3963
155Mbps Preamplifier for FDDI
and ATM LAN Fiber Optic Receivers
______________________________________________________________Pin Description
PIN
NAME
FUNCTION
1, 3
N.C.
2
IN
4
BYP
Connection for optional noise-reducing capacitor
5
GND
Signal Ground
6
OUT+
Noninverting Voltage Output. Current flowing into IN causes VOUT+ to increase.
7
OUT-
Inverting Voltage Output. Current flowing into IN causes VOUT- to decrease.
8
VCC
Supply Voltage
—
FILTER*
No Connect. No internal connection to the die.
Signal Input
Connection for 1kΩ filter resistor. This pad is accessible on the die only.
*MAX3963C/D (die) only.
VCC
1k
(FILTER)
VCC
MAX3963
Q1
R1
RF
OUT+
IN
BYP
VCC
TRANSIMPEDANCE
AMPLIFIER
PARAPHASE
AMPLIFIER
Q2
REFERENCE
R2
OUT-
( ) ARE FOR MAX3963C/D ONLY.
Figure 1. Functional Diagram
4
_______________________________________________________________________________________
155Mbps Preamplifier for FDDI
and ATM LAN Fiber Optic Receivers
__________Applications Information
Optical-Power Relations
The signal current at the input flows into the summing
node of a high-gain amplifier. Shunt feedback through
RF converts this current to a voltage with a 10kΩ gain.
Many of the MAX3963 specifications relate to the input
signal amplitude. When working with fiber optic
receivers, the input is usually expressed in terms of
average optical power and extinction ratio. The relations
shown in Table 1 are helpful for converting optical
power to input signal when designing with the
MAX3963. These relations are true if the average data
duty cycle is 50%.
Paraphase Amplifier
Calculating Sensitivity and Overload
The paraphase amplifier converts single-ended signals
to differential signals and introduces a 2x voltage gain.
This signal drives a pair of internally biased emitter followers, Q1 and Q2, which form the output stage.
Resistors R1 and R2 provide back termination at the
output, providing a 120Ω differential output impedance.
The output emitter followers are designed to drive a 1kΩ
differential load between OUT+ and OUT-. Higher output impedances can also be driven, resulting in slightly
increased gain and output voltage swing. The MAX3963
will not drive a 50Ω grounded load. The MAX3963 outputs may be AC coupled to a limiting amplifier.
Sensitivity Calculation
The MAX3963’s input-referred RMS noise current (in)
generally dominates receiver sensitivity. In a system
where the bit error rate is 1E-10, the signal-to-noise ratio
must always exceed 12.7. The sensitivity, expressed in
average power, can be estimated as shown in the following equation:
Transimpedance Amplifier
 12.7 in (re + 1)

Sensitivity = 10log 
x 1000 dBm
2
ρ
(r
1)
e


where ρ is the photodiode responsivity in A/W.
Input Overload
The overload is the largest input that the MAX3963
accepts while meeting specifications. A larger input
causes increased pulse-width distortion.
 60µA

Overload = 10log 
x 1000 dBm
 2ρ

Table 1. Optical-Power Relations*
SYMBOL
RELATION
P1
Average
Power
PAVE
Extinction
Ratio
re
re = P1 / P0
Optical Power
of a “1”
P1
P1 = 2PAVE (re) / (re + 1)
Optical Power
of a “0”
P0
P0 = 2PAVE / (re + 1)
Signal
Amplitude
PINPUT
PAVE = (P0 + P1) / 2
PINPUT = P1 - P0 =
2PAVE (re - 1) / (re + 1)
*Assuming 50% average data duty cycle
OPTICAL POWER
PARAMETER
PAVE
P0
TIME
Figure 2. Optical-Power Definitions
_______________________________________________________________________________________
5
MAX3963
_______________Detailed Description
The MAX3963 transimpedance amplifier is designed for
155Mbps fiber optic applications. Figure 1 is a functional diagram of the MAX3963, which comprises a transimpedance amplifier and a paraphase amplifier with
emitter-follower outputs.
MAX3963
155Mbps Preamplifier for FDDI
and ATM LAN Fiber Optic Receivers
Output Filter
Wire Bonding
The MAX3963’s noise can be reduced by filtering the
output signal. For digital communications systems, a
linear-phase filter with -3dB lowpass response of (0.7 x
data rate) is recommended.
A single-pole filter implemented with a capacitor across
the outputs also reduces noise, and consumes less
board space than a linear-phase filter. The following
equation represents the filter frequency:
For high current density and reliable operation, the
MAX3963 uses gold metalization. Make connections to
the die with gold wire only, using ball-bonding techniques. Wedge bonding is not recommended. Die-pad
size is 4mils square, with 6mil pitch. Die thickness is
15mils.
f -3dB =
___________________Chip Topography
1
2π ROUT COUT
OUT-
OUT+
GND
where ROUT is the MAX3963 differential output resistance (typically 120Ω), and COUT is the differential output load capacitance. For 155Mbps receivers, an 11pF
capacitor is recommended.
Layout Considerations
Use good high-frequency design and layout techniques. The use of a multilayer circuit board with separate ground and VCC planes is recommended. Bypass
VCC and connect the GND pin to the ground plane with
traces kept as short as possible. Ensure that commonmode output capacitance is less than 2pF per output.
0.031"
(0.79mm)
Low-Capacitance Input
Design Considerations
Noise performance and bandwidth are adversely
affected by stray capacitance on the input node. Every
effort must be made to minimize capacitance on this
pin. Select a low-capacitance photodiode, and use
good high-frequency design and layout techniques.
The MAX3963 is optimized for 1.0pF of capacitance on
the input, approximately the capacitance of a photodetector diode packaged in a header.
When using the SO package version of the MAX3963,
the package capacitance is about 0.3pF. This means
that great care must be used to reduce input capacitance. The PC board between the MAX3963 input and
the photodiode can add parasitic capacitance. Keep
the input line short, and remove power and ground
planes beneath it.
Assembling the MAX3963 in die form provides the best
possible performance. Parasitic capacitance can be
reduced to a minimum, resulting in the lowest noise and
the best bandwidth.
VCC
IN
FILTER
BYP
0.031"
(0.79mm)
TRANSISTOR COUNT: 116
SUBSTRATE CONNECTED TO GND
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1998 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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