MAX3760 [MAXIM]
622Mbps, Low-Noise Transimpedance Preamplifier for LAN and WAN Optical Receivers; 622Mbps，低噪声互阻前置放大器，用于LAN和WAN光接收器
| 型号： | MAX3760 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 622Mbps, Low-Noise Transimpedance Preamplifier for LAN and WAN Optical Receivers |
| 文件： | 总8页 (文件大小：126K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4765; Rev 0; 7/98
6 2 2 Mb p s , Lo w -No is e Tra n s im p e d a n c e
P re a m p lifie r fo r LAN a n d WAN Op t ic a l Re c e ive rs
MAX3760
Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
♦ 73nA RMS Input-Referred Noise
♦ 560MHz Bandwidth
The MAX3760 is a transimpedance preamplifier for
622Mbps ATM applications. It operates from a single
+ 5V s up p ly a nd typ ic a lly c ons ume s only 100mW
power. The preamplifier converts a small photodiode
current to a differential voltage. A DC cancellation cir-
cuit provides a true differential output swing over a
wide range of input current levels, thus reducing pulse-
width distortion.
♦ 1mA Peak Input Current
♦ 6.5kΩ Gain
♦ Operation from -40°C to +85°C
♦ 100mW Typical Power Consumption
♦ Single +5V Supply
6.5kΩ transimpedance gain and 560MHz bandwidth,
combined with low 73nA input-referred noise, provide
-31.5dBm typical sensitivity in 1300nm receivers. The
circuit accepts a 1mAp-p input current, resulting in a
typical optical overload of -3dBm. The device operates
over an extended temperature range of -40°C to +85°C.
The MAX3760 is internally compensated and requires
fe w e xte rna l c omp one nts . In d ie form it inc lud e s a
space-saving filter connection, which provides positive
Ord e rin g In fo rm a t io n
PART
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 SO
bias for the photodiode through a 1kΩ resistor to V
.
CC
MAX3760ESA
MAX3760E/D
These features, combined with the die aspect ratio and
dimensioning, allow the MAX3760 to assemble easily
into a TO-style header with a photodiode.
Dice*
*Dice are designed to operate over a -40°C to +100°C junction
te mp e ra ture (T ) ra ng e , b ut a re te s te d a nd g ua ra nte e d a t
The MAX3760 is designed to be used with either the
MAX3761 or the MAX3762 limiting-amplifier ICs. When
combined with a photodiode, the chipset forms a com-
plete 5V, 622Mbps receiver. The MAX3760 is available
in die form and in an 8-pin SO package.
j
T
A
= +25°C.
________________________Ap p lic a t io n s
622Mbps ATM LAN Optical Receivers
Typ ic a l Ap p lic a t io n Circ u it
+5V
622Mbps WAN Optical Receivers
0.01µF
V
CC
P in Co n fig u ra t io n
1k
(FILTER)
MAX3761
MAX3762
LIMITING
MAX3760
TOP VIEW
0.01µF
100pF
INREF
AMPLIFIER
OUT+
100Ω
(OPTIONAL)
1
2
3
4
8
7
6
5
COMP
OUT+
OUT-
GND
V
CC
IN
INREF
GND
IN
MAX3760
OUT-
0.01µF
GND
COMP*
SO
( ) INDICATE PINS AVAILABLE ONLY ON THE DIE.
*NOT CONNECTED
________________________________________________________________ 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.
6 2 2 Mb p s , Lo w -No is e Tra n s im p e d a n c e
P re a m p lifie r fo r LAN a n d WAN Op t ic a l Re c e ive rs
ABSOLUTE MAXIMUM RATINGS
V
CC
........................................................................-0.5V to +7.0V
Continuous Power Dissipation (T = +85°C)
A
Continuous Current
SO (derate 5.88mW/°C above +85°C)..........................383mW
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10sec) .............................+300°C
Operating Junction Temperature Range (die) .....-55°C to +150°C
Processing Temperature (die) .........................................+400°C
IN, FILTER..........................................................-5mA to +5mA
OUT+, OUT-...................................................-25mA to +25mA
Voltage at INREF ...................................................-0.5V to +0.5V
Voltage at COMP........................................-0.5V to (V + 0.5V)
CC
MAX3760
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 = +4.5V to +5.5V, COMP = GND, 100Ω load between OUT+ and OUT-, T = -40°C to +85°C, unless otherwise noted. Typical
CC
A
values are at V = +5.0V, T = +25°C.) (Note 1)
CC
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
0.8
20
MAX
0.95
30
UNITS
V
Input Bias Voltage
Supply Current
V
IN
Input = open
Input = open
I
CC
mA
kΩ
V
Small-Signal Transimpedance
Output Common-Mode Level
Differential Output Offset
z
Differential output, input <10µA
5.2
6.5
7.8
21
V
- 2.0
CC
V
OS
I
IN
= 500µA, COMP = open
-25
40
25
60
mV
Ω
Output Impedance (per side)
Z
50
OUT
Maximum Differential
Output Voltage
I
= 500µA, total peak-to-peak,
IN
V
550
950
mV
OUT(MAX)
differential signal
FILTER Resistance
R
800
20
1000
45
1200
Ω
FILTER
Power-Supply Rejection Ratio
PSRR
f < 1MHz, referred to output
dB
Note 1: Dice are tested at T = +25°C.
A
AC ELECTRICAL CHARACTERISTICS
(V
CC
= +4.5V to +5.5V, COMP = open, C = 0.75pF, outputs terminated differentially into 100Ω, 8-pin SO package in MAX3760
IN
EV kit, T = +25°C, unless otherwise noted. Typical values are at V = +5V.) (Notes 2, 3)
A
CC
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
565
50
MAX
UNITS
MHz
kHz
ps
Small-Signal Bandwidth
Low-Frequency Cutoff
Pulse-Width Distortion
RMS Noise Referred to Input
Data-Dependent Jitter
BW
455
20µA average input current
(Note 4)
PWD
75
200
i
n
C
= 0.75pF (Notes 3, 5)
IN
73
93.5
nA
DDJ
200
ps
Note 2: AC characteristics are guaranteed by design and characterization.
Note 3: C is the source capacitance presented to the die. Includes package parasitic, photo diode, and parasitic interconnect
IN
capacitance.
Note 4: Input is a 622Mbps 1-0 pattern, signal amplitude = 0 to 1mA, extinction ratio (r ) = 10.
e
Note 5: Measured with a 4-pole, 470MHz Bessel filter.
2
_______________________________________________________________________________________
6 2 2 Mb p s , Lo w -No is e Tra n s im p e d a n c e
P re a m p lifie r fo r LAN a n d WAN Op t ic a l Re c e ive rs
MAX3760
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(MAX3760 EV kit, V = +5.0V, COMP = open, T = +25°C, unless otherwise noted.)
CC
A
INPUT-REFERRED NOISE
vs. JUNCTION TEMPERATURE
SMALL-SIGNAL GAIN
vs. FREQUENCY
PULSE-WIDTH DISTORTION vs.
INPUT SIGNAL AMPLITUDE
110
100
90
80
200
150
C
IS SOURCE CAPACITANCE
IN
r = 10
e
78
PRESENTED TO DIE. INCLUDES PACKAGE
PARASITIC, PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
622Mbps,
ONE-ZERO PATTERN
76
74
C
IN
= 1.25pF
72
70
68
66
80
100
50
0
C
= 0.75pF
IN
70
C
IN
= 0.25pF
60
64
62
50
470MHz BANDWIDTH
40
60
-40
-5
30
65
100
10k 100k 1M 10M 100M 1G
FREQUENCY (Hz)
10G
0
200
400
600
800
1000
JUNCTION TEMPERATURE (°C)
INPUT SIGNAL AMPLITUDE (µAp-p)
TYPICAL BANDWIDTH
vs. JUNCTION TEMPERATURE
TRANSIMPEDANCE
vs. AMBIENT TEMPERATURE
INPUT-REFERRED RMS NOISE CURRENT
vs. DC INPUT CURRENT
540
450
400
350
300
250
200
150
100
50
7000
6500
C
IN
= 0.25pF
IN TO-56 HEADER
C
IN
= 0.75pF
470MHz BANDWIDTH
520
500
480
460
440
420
C
IN
= 0.75pF
C
IN
= 1.25pF
6000
5500
5000
C
IN
IS SOURCE CAPACITANCE
PRESENTED TO DIE. INCLUDES PACKAGE
PARASITIC, PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
0
-40
-5
30
65
100
-40 -20
0
20
40
60
80
100
1.00 2.15 4.64 10.0 21.5 46.4 100 215 464 1000
JUNCTION TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
DC INPUT CURRENT (µA)
DATA-DEPENDENT JITTER
vs. INPUT SIGNAL AMPLITUDE
OUTPUT COMMON-MODE VOLTAGE
vs. AMBIENT TEMPERATURE
TYPICAL EYEWIDTH vs. INPUT SIGNAL
1.6
1.5
1.4
1.3
1.2
1.1
1.0
800
600
-1.0
23
2
- 1 PRBS
REFERENCED TO V
CC
-1.2
-1.4
-1.6
-1.8
-2.0
-2.2
-2.4
-2.6
-2.8
-3.0
622Mbps
r = 10
e
T = +85°C
A
T = +25°C
A
400
200
0
T = -40°C
A
0
200
400
600
800
1000
10 20 50 100 150 200 250 300 400 500 600
-40 -20
0
20
40
60
80
100
INPUT SIGNAL AMPLITUDE (µAp-p)
INPUT SIGNAL (µA)
AMBIENT TEMPERATURE (°C)
_______________________________________________________________________________________
3
6 2 2 Mb p s , Lo w -No is e Tra n s im p e d a n c e
P re a m p lifie r fo r LAN a n d WAN Op t ic a l Re c e ive rs
Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(MAX3760 EV kit, V = +5.0V, COMP = open, T = +25°C, unless otherwise noted.)
CC
A
MAXIMUM OUTPUT SIGNAL AMPLITUDE
vs. AMBIENT TEMPERATURE
800
700
MAX3760
600
500
400
-40 -20
0
20
40
60
80
100
AMBIENT TEMPERATURE (°C)
EYE DIAGRAM
(INPUT = 1mA)
EYE DIAGRAM
(INPUT = 10µA)
500mV
50mV
23
2
- 1 PRBS
23
2
- 1 PRBS
10mV/
div
100mV/
div
-50mV
-500mV
200ps/div
200ps/div
P in De s c rip t io n
PIN
1
NAME
FUNCTION
V
CC
Supply-Voltage Input
Signal Input
2
IN
3
INREF
GND
OUT-
OUT+
Input Reference Connection. Connect to photodetector AC ground.
Ground
4, 5
6
Inverting Voltage Output. Current flowing into the input causes OUT- to decrease.
7
Noninverting Voltage Output. Current flowing into the input causes OUT+ to increase.
Compensation Capacitor Connection. Connection for optional external compensation capacitor for DC-
cancellation circuit. Add capacitance here to reduce the low-frequency cutoff of the DC cancellation circuit.
Connect COMP directly to GND to disable the DC cancellation circuit.
8
COMP
Filter Connection. Provides positive bias for photodiode through a 1kΩ resistor to V (see the Designing
Filters section). Available on the die only.
CC
—
FILTER
4
_______________________________________________________________________________________
6 2 2 Mb p s , Lo w -No is e Tra n s im p e d a n c e
P re a m p lifie r fo r LAN a n d WAN Op t ic a l Re c e ive rs
MAX3760
V
CC
D1
1k
R1
RF
MAX3760
(FILTER)
OUT-
V
CC
V
CC
Q2
TRANSIMPEDANCE
AMPLIFIER
IN
PARAPHASE
AMP
V
CC
Q1
INREF
Q3
R2
OUT+
R3
R4
DC
CANCELLATION
AMPLIFIER
Q4
GND
( ) INDICATE PINS AVAILABLE ON DIE ONLY.
GND
COMP
Figure 1. Functional Diagram
b e te rmina te d with hig he r outp ut imp e d a nc e s for
increased gain and output voltage swing. The MAX3760
will not drive a 50Ω load to ground. For best noise rejec-
tion, terminate the MAX3760 with differential loads.
De t a ile d De s c rip t io n
The MAX3760 is a transimpedance amplifier designed
for 622Mbps fiber optic applications. As shown in the
Functional Diagram (Figure 1), it comprises a transim-
pedance amplifier, a paraphase amplifier with emitter-
follower outputs, and a DC cancellation circuit.
DC Ca n c e lla t io n Circ u it
The DC cancellation circuit removes the input signal’s
DC component by employing low-frequency feedback.
This feature centers the input signal within the transim-
pedance amplifier’s dynamic range, thereby reducing
pulse-width distortion on large input signals.
Tra n s im p e d a n c e Am p lifie r
The signal current at the input flows into a high-gain
amplifier’s summing node. Shunt feedback through RF
c onve rts this c urre nt to a volta g e with 6.5kΩ g a in.
Diode D1 clamps the output voltage for large input cur-
rents. INREF is a direct connection to the input transis-
tor’s emitter, and must be connected directly to the
photodetector AC ground return for best performance.
The paraphase amplifier’s output is sensed through
resistors R3 and R4, then filtered, amplified, and fed
back to the base of transistor Q4. The transistor draws
the input signal’s DC component away from the trans-
impedance amplifier’s summing node.
P a ra p h a s e Am p lifie r
The paraphase amplifier converts single-ended signals to
differential signals 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, deliv-
ering a 100Ω differential output impedance. The output
emitter followers are designed to drive a 100Ω differential
load between OUT+ and OUT-. The MAX3760 can also
The MAX3760 DC cancellation loop is internally com-
pensated and does not require external capacitors in
most 622Mbps applications. Add external capacitance
at the COMP pin to reduce the DC cancellation circuit’s
frequency response and improve data-dependent jitter.
Connecting the COMP pin directly to GND disables the
circuit. The DC cancellation circuit can sink up to 1mA
at the input.
_______________________________________________________________________________________
5
6 2 2 Mb p s , Lo w -No is e Tra n s im p e d a n c e
P re a m p lifie r fo r LAN a n d WAN Op t ic a l Re c e ive rs
The MAX3760 minimizes pulse-width distortion for data
1mA
Overload = 10log
1000 dBm
sequences exhibiting a 50% duty cycle. A duty cycle
significantly different from 50% will cause the MAX3760
to generate pulse-width distortion.
2ρ
Linear Range
DC cancellation current is drawn from the input and
creates noise. This is not a problem for low-level signals
with little or no DC c omp one nt. Pre a mp lifie r nois e
increases for signals with significant DC component
(see Typical Operating Characteristics).
The MAX3760 has high gain, which limits the output
when the input signal exceeds 20µAp-p. It operates
with 90% linearity for inputs not exceeding the follow-
ing:
MAX3760
The MAX3760 operates with the photodetector cathode
20µA r + 1
(
)
e
connected to V , as shown in the Typical Application
10log
1000 dBm
CC
ρ r - 1
Circuit. Connecting the photodetector anode to GND
and the cathode to IN defeats the DC cancellation cir-
cuit and causes pulse-width distortion.
e
Table 1. Optical Power Relations
In p u t Re fe re n c e
INREF is the reference point for IN. Connect it as close
as possible to the photodetector diode’s AC ground. The
photodetector’s AC ground is usually the ground of the
photodetector’s filter capacitor. The total length from
INREF, through the filter capacitor and the diode, and
back to the input should be no more than 2cm.
PARAMETER SYMBOL
RELATION
Average
Power
P
AVE
P
= P0 + P1 / 2
(
)
AVE
Extinction
Ratio
r
e
r
= P1 / P0
e
re
AVE (re + 1)
Ap p lic a t io n s In fo rm a t io n
Optical Power
of a “1”
P1 = 2P
P1
P0
Op t ic a l P o w e r De fin it io n s
Many of the MAX3760’s specifications relate to the
input signal amplitude. When working with fiber optic
re c e ive rs, the optic a l input is usua lly e xpre sse d in
terms of average optical power and extinction ratio.
Use the relations given in Table 1 to convert optical
p owe r to inp ut s ig na l whe n d e s ig ning with the
MAX3760.
Optical Power
of a “0”
P0 = 2P
/ r + 1
(
)
AVE
e
r
- 1
Signal
Amplitude
(
)
e
P
IN
PIN = P1 - P0 = 2P
AVE (re + 1)
Note: Assuming a 50% average input duty cycle.
Ca lc u la t in g S e n s it ivit y,
Ove rlo a d , a n d Lin e a r Ra n g e
OPTICAL
POWER
Sensitivity Calculation
The MAX3760’s input-referred RMS noise current (i )
n
P1
generally dominates the receiver sensitivity. In a system
where the bit error rate (BER) is 1E - 10, the signal-to-
noise ratio must always exceed 12.7. The sensitivity,
expressed in average power, can be estimated as:
P
AVE
12.7i r + 1
(
)
n e
Sensitivity = 10log
1000 dBm
2ρ r - 1
(
)
e
Where ρ is the photodiode responsivity in A/W.
Input Overload
P0
The overload is the largest input that the MAX3760
TIME
accepts while meeting specifications. It is calculated
as:
Figure 2. Optical Power Definitions
6
_______________________________________________________________________________________
6 2 2 Mb p s , Lo w -No is e Tra n s im p e d a n c e
P re a m p lifie r fo r LAN a n d WAN Op t ic a l Re c e ive rs
MAX3760
supply-noise voltage is divided between C
and
P o w e r S u p p ly
The MAX3760 can operate from a power-supply volt-
FILTER
C
. The input noise current due to supply noise is
PHOTO
as follows (assuming the filter capacitor is much larger
than the photodiode capacitance):
age (V - GND) between 4.5V and 5.5V. GND can be
any stable voltage, including -5.0V, as found in many
systems using ECL interface levels.
CC
V
C
PHOTO
(
=
)(
)
)
NOISE
I
La yo u t Co n s id e ra t io n s
Us e g ood hig h-fre q ue nc y d e s ig n a nd la yout te c h-
niques. The use of a multilayer circuit board with sepa-
NOISE
R
C
)(
FILTER
(
FILTER
If the amount of tolerable noise is known, the filter
capacitor is easy to select, as follows:
rate ground and V
planes is recommended. Take
CC
care to bypass V and to connect the GND pin to the
CC
ground plane with the shortest possible traces.
V
C
PHOTO
(
>
)(
)
NOISE
De s ig n in g a Lo w -Ca p a c it a n c e In p u t
Noise performance and bandwidth will be adversely
affected by stray capacitance at IN. Make every effort
to minimize capacitance on this node. Select a low-
capacitance photodiode and use good high-frequency
design and layout techniques. The MAX3760 is opti-
mized for 0.75pF of capacitance on the input—approxi-
mately the capacitance of a low-cost photodetector
packaged in a header.
C
FILTER
R
I
FILTER NOISE
For example, with maximum noise voltage = 10mV
,
RMS
C
= 0.75pF, R
= 1kΩ, and I
selected
PHOTO
FILTER
NOISE
to be 30nA (half the MAX3760’s input noise):
10mV 0.75pF
(
)(
)
C
=
= 250pF
FILTER
1000 30E- 9
When using the MAX3760 in the SO package, note that
the package capacitance is about 0.3pF. The PC board
between the MAX3760 input and the photodetector will
add parasitic capacitance. Keep the input line short,
and remove power and ground planes beneath it.
TOP VIEW OF TO-56 HEADER
For the b e s t p os s ib le p e rforma nc e , a s s e mb le the
MAX3760 in die form using chip-and-wire technology,
or package the die in a TO header. These techniques
minimize parasitic capacitance, resulting in the lowest
noise.
V
CC
C
FILTER
De s ig n in g Filt e rs
The MAX3760’s noise performance is strongly affected
by the circuit’s bandwidth, which changes over temper-
ature and varies from lot to lot. Receiver sensitivity can
be improved by adding filters to limit this bandwidth.
Filter designs range from a one-pole filter using a single
capacitor to more complex filters using inductors. The
simple filter provides a moderate rolloff with minimal
components, while the complex filter provides a sharp-
e r rolloff a nd b e tte r tra ns ie nt re s p ons e . A s imp le
530MHz filter can be created by placing a 6pF capaci-
tor between the OUT+ and OUT- pins.
PHOTODIODE
OUT-
OUT+
Supply-voltage noise at the photodiode cathode pro-
d uc e s a c urre nt, I = C
∆V/∆t, whic h re d uc e s
PHOTO
receiver sensitivity (C
is the photodiode capaci-
PHOTO
tance.) The MAX3760’s FILTER resistor, combined with
an external capacitor, can be used to reduce this noise
(see Typical Application Circuit). Current generated by
CASE IS GROUND
Figure 3. Suggested Layout for TO-56 Header
_______________________________________________________________________________________
7
6 2 2 Mb p s , Lo w -No is e Tra n s im p e d a n c e
P re a m p lifie r fo r LAN a n d WAN Op t ic a l Re c e ive rs
Wire Bo n d in g
For high current density and reliable operation, the
___________________Ch ip To p o g ra p h y
MAX3760 uses gold metalization. Make connections to
the die with gold wire only, using ball-bonding tech-
niques. Wedge bonding is not recommended. Die-pad
size is 4 mils square, with 6 mil pitch. Die thickness is
15 mils.
INREF FILTER IN
V
GND
GND
CC
MAX3760
COMP
0.042"
(1.05mm)
OUT-
OUT+
0.030"
(0.75mm)
TRANSISTOR COUNT: 131
SUBSTRATE CONNECTED TO GND
P a c k a g e In fo rm a t io n
8
_______________________________________________________________________________________
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