19-2207; Rev 1; 3/05
Low-Noise, Fibre Channel Transimpedance
Amplifiers
General Description
The MAX3275/MAX3277 transimpedance amplifiers
provide a compact low-power solution for communica-
tion up to 2.125Gbps. They feature 300nA input-
referred noise at 2.1GHz bandwidth (BW) with 0.85pF
input capacitance. The parts also have 2mA
P-P
AC
input overload.
The MAX3277 is identical to the MAX3275, but with the
output polarities inverted for optimum packaging flexi-
bility. Both parts operate from a single 3.3V supply and
consume only 83mW. The MAX3275/MAX3277 are
compact 24mil x 47mil die and require no external com-
pensation capacitor. A space-saving filter connection is
provided for positive bias to the photodiode through an
on-chip 600Ω resistor to V
CC
. These features allow
easy assembly into a TO-46 or TO-56 header with a
photodiode.
The MAX3275/MAX3277 and MAX3274 limiting ampli-
fiers provide a two-chip solution for dual-rate, fibre
channel receiver applications.
o
Up to 2.125Gbps (NRZ) Data Rates
o
7ps
P-P
Deterministic Jitter for <100µA
P-P
Input Current
o
300nA
RMS
Input-Referred Noise at 2.1GHz
Bandwidth
o
25mA Supply Current at +3.3V
o
2.3GHz Small-Signal Bandwidth
o
2.0mA
P-P
AC Overload
o
Die Size: 24mil x 47mil
Features
MAX3275/MAX3277
Ordering Information
PART
MAX3275U/D
MAX3277U/D
TEMP RANGE
0°C to +85°C
0°C to +85°C
PIN-PACKAGE
Dice*
Dice*
Applications
Dual-Rate Fibre Channel Optical Receivers
Gigabit Ethernet Optical Receivers
*Dice
are guaranteed to operate from 0°C to +85°C, but are test-
ed only at T
A
= +25°C.
Typical Application Circuit
SMALL FORM FACTOR
OPTICAL RECEIVER
+3.3V
+3.3V
4.7kΩ
TO
10kΩ
HOST SERVER
OR SWITCH
400pF
600Ω
C
FILTER
400pF
IN
V
CC
MAX3275
OUT+
TIA
OUT-
0.1µF
GND
660Ω
TH SQUELCH
IN-
0.1µF
IN+
100Ω
MAX3274
LOS LOS
0.1µF
OUT+
LIMITING
AMP
OUT-
0.1µF
BWSEL
RATE SELECT
DESERIALIZER
100Ω
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Low-Noise, Fibre Channel Transimpedance
Amplifiers
MAX3275/MAX3277
ABSOLUTE MAXIMUM RATINGS
Power-Supply Voltage (V
CC
) .................................-0.5V to +4.0V
Continuous CML Output Current
(OUT+, OUT-) ...............................................-25mA to +25mA
Continuous Input Current (IN)...............................-4mA to +4mA
Continuous Input Current (FILTER).......................-8mA to +8mA
Operating Junction Temperature Range (T
J
) ....-55°C to +150°C
Storage Ambient Temperature Range (T
STG
) ...-55°C to +150°C
Die Attach Temperature...................................................+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.
ELECTRICAL CHARACTERISTICS
(V
CC
= +3.0V to +3.6V, T
A
= 0°C to +85°C. Typical values are at V
CC
= +3.3V, source capacitance (C
IN
) = 0.85pF, T
A
= +25°C,
unless otherwise noted.) (Notes 1, 2)
PARAMETER
Supply Current
Small-Signal Bandwidth
Low-Frequency Cutoff
Input Bias Voltage
Input Resistance
C
IN
= 0.6pF, BW = 0.8GHz (Notes 3, 4)
C
IN
= 0.6pF, BW = 1.6GHz (Notes 3, 4)
Input-Referred Noise
I
N
C
IN
= 0.6pF, BW = 2.1GHz (Notes 3, 4)
C
IN
= 0.85pF, BW = 0.8GHz (Notes 3, 4)
C
IN
= 0.85pF, BW = 1.6GHz (Notes 3, 4)
C
IN
= 0.85pF, BW = 2.1GHz (Notes 3, 4)
AC Input Overload
DC Input Overload
Filter Resistance
Output Resistance (OUT+, OUT-)
Deterministic Jitter
Transimpedance
Transimpedance Linear Range
Data Output Swing
Output Data-Transition Time
Output Return Loss
Power-Supply Rejection
PSR
DJ
(Notes 3, 5)
(Note 5)
P-P
SYMBOL
I
CC
BW
CONDITIONS
Including output termination current
-3dB, C
IN
= 0.6pF (Note 3)
-3dB, C
IN
= 0.85pF (Note 3)
-3dB, input current = 40µA (Note 3)
MIN
2.0
1.7
TYP
25
2.7
2.3
65
MAX
41
3.3
2.7
1.0
UNITS
mA
GHz
kHz
V
Ω
40
185
245
275
193
272
300
2
1
510
42.5
600
50
15
15
7
2.8
50
220
300
90
15
10
40
34
500
140
3.3
690
57.5
40
31
16
3.8
250
350
380
275
400
430
nA
RMS
mA
P-P
mA
Ω
Ω
ps
P-P
kΩ
µA
P-P
mV
P-P
ps
dB
dB
Single-ended
1mA
P-P
< input < 2mA
P-P
(Notes 3, 6, 7)
100µA
P-P
< input
≤
1mA
P-P
(Notes 3, 6, 7)
10µA
P-P
< input
≤
100µA
P-P
(Notes 3, 6, 7)
Differential output
0.95 < linearity < 1.05 (Note 8)
Input > 100µA
P-P
(Note 9)
Input > 200µA
P-P
, 20% to 80% rise/fall time
(Notes 3, 10)
Freq
≤
1GHz
1GHz < freq
≤
2GHz
f < 1MHz (Note 11)
1MHz
≤
f < 10MHz (Note 11)
2
_______________________________________________________________________________________
Low-Noise, Fibre Channel Transimpedance
Amplifiers
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +3.0V to +3.6V, T
A
= 0°C to +85°C. Typical values are at V
CC
= +3.3V, source capacitance (C
IN
) = 0.85pF, T
A
= +25°C,
unless otherwise noted.) (Notes 1, 2)
Note 1:
Die parameters are production tested at room temperature only, but are guaranteed by design and characterization from
0°C to +85°C.
Note 2:
Source capacitance represents the total capacitance at the IN pad during characterization of the noise and bandwidth
parameters.
Note 3:
Guaranteed by design and characterization.
Note 4:
Measured using an RF-power meter with no pattern applied at the input. The TIA output is bandwidth limited for
measurement using a 4th-order Bessel Thompson filter. The -3dB frequency of the filter matches the frequency (0.8GHz,
1.6GHz, or 2.1GHz) for the specified noise BW.
Note 5:
DC offset and deterministic jitter may exceed specification if AC or DC overload conditions are exceeded.
Note 6:
Using fibre channel K28.5± pattern. The input bandwidth is limited to 0.75
✕
(2.125Gbps) by a 4th-order Bessel Thompson
filter. Measured differentially across an AC-coupled 100Ω external load.
Note 7:
K28.5± pattern: (00111110101100000101).
Note 8:
Gain may vary ±5% relative to reference measured with 30µA
P-P
input.
Note 9:
Production tested with 1mA
P-P
input.
Note 10:
Using a K28.7 (0011111000) pattern. Measured differentially across an AC-coupled 100Ω external load.
Note 11:
Power-supply rejection PSR = -20log(∆V
OUT
/∆V
CC
), where
∆V
OUT
is the differential output voltage and
∆V
CC
is the noise
on V
CC
.
MAX3275/MAX3277
Typical Operating Characteristics
(V
CC
= +3.3V, C
IN
= 0.85pF, T
A
= +25°C, unless otherwise noted.)
INPUT-REFERRED NOISE
vs. TEMPERATURE
350
340
330
320
310
300
290
280
270
260
250
240
230
220
210
200
0
MAX3275 toc01
INPUT-REFERRED NOISE
vs. TEMPERATURE
MAX3275 toc02
FREQUENCY RESPONSE
71
TRANSIMPEDANCE (dBΩ)
69
67
65
63
61
59
MAX3275 toc03
250
240
INPUT-REFERRED NOISE (nA
RMS
)
230
220
210
200
190
180
170
160
150
BW = 0.8GHz
C
IN
= 0.85pF
C
IN
= 0.6pF
C
IN
IS SOURCE CAPACITANCE
PRESENTED TO DIE, INCLUDING
PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
INPUT-REFERRED NOISE (nA
RMS
)
C
IN
IS SOURCE CAPACITANCE
PRESENTED TO DIE, INCLUDING
PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
C
IN
= 0.85pF
C
IN
= 0.6pF
BW = 1.6GHz
20
40
60
80
100
57
0
20
40
60
80
100
100M
1G
FREQUENCY (Hz)
10G
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
_______________________________________________________________________________________
3
Low-Noise, Fibre Channel Transimpedance
Amplifiers
MAX3275/MAX3277
Typical Operating Characteristics (continued)
(
V
CC
= +3.3V, C
IN
= 0.85pF, T
A
= +25°C, unless otherwise noted.)
DETERMINISTIC JITTER
vs. INPUT AMPLITUDE
MAX3275 toc04
SMALL-SIGNAL TRANSIMPEDANCE
vs. TEMPERATURE
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
0
20
40
60
80
AMBIENT TEMPERATURE (°C)
MAX3275 toc05
BANDWIDTH vs. TEMPERATURE
2.9
2.8
BANDWIDTH (GHz)
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
100
0
20
40
60
80
100
AMBIENT TEMPERATURE (°C)
C
IN
= 0.85pF
C
IN
= 0.6pF
MAX3275 toc06
50
45
DETERMINISTIC JITTER (ps
P-P
)
40
35
30
25
20
15
10
5
0
0.01
0.1
1
2.125Gbps
K28.5 INPUT
3.0
10
INPUT AMPLITUDE (mA
P-P
)
TRANSIMPEDANCE (dBΩ)
EYE DIAGRAM (INPUT = 10µA
P-P
)
MAX3275 toc07
EYE DIAGRAM (INPUT = 2mA
P-P
)
MAX3275 toc08
DIFFERENTIAL OUTPUT REFLECTION
COEFFICIENT
-5
-10
S22 (dB)
-15
-20
-25
-30
-35
MAX3275 toc09
0
5mV/div
50mV/div
INPUT: K28.5
80ps/div
INPUT: K28.5
80ps/div
-40
0
500M
1G
1.5G
2G
2.5G
3G
FREQUENCY (Hz)
SUPPLY CURRENT vs. TEMPERATURE
45
40
SUPPLY CURRENT (mA)
35
30
25
20
15
10
5
0
0
20
40
60
80
100
AMBIENT TEMPERATURE (°C)
-150
-200
-200
MAX3275 toc10
DC TRANSFER FUNCTION
(FILTER = GND)
150
OUTPUT VOLTAGE (mV)
100
50
0
-50
-100
MAX3275 toc11
50
200
-100
0
100
200
INPUT CURRENT (µA)
4
_______________________________________________________________________________________
Low-Noise, Fibre Channel Transimpedance
Amplifiers
Pad Description
MAX3275
BOND PAD
1, 9
2, 5
3
4
6
MAX3277
BOND PAD
1, 9
2, 5
4
3
6
NAME
V
CC
GND
OUT-
OUT+
N.C.
Supply Voltage
Circuit Ground
Inverting Data Output. Current flowing into IN causes the voltage at OUT- to decrease.
Noninverting Data Output. Current flowing into IN causes the voltage at OUT+ to
increase.
No Connection. Not internally connected.
Provides bias voltage for the photodiode through a 600Ω resistor to V
CC
. When
grounded, this pin disables the DC cancellation amplifier to allow a DC path from IN to
OUT+ and OUT- for testing.
TIA Input. Signal current from photodiode flows into this pin.
FUNCTION
MAX3275/MAX3277
7
7
FILTER
8
8
IN
V
CC
R
f
VOLTAGE
AMPLIFIER
IN
TIA
OUTPUT
BUFFER
50Ω
50Ω
OUT+
OUT-
V
CC
V
CC
600Ω
FILTER
DISABLE
LOWPASS
FILTER
DC CANCELLATION
GND
MAX3275
MAX3277
Figure 1. Functional Diagram
Detailed Description
The MAX3275/MAX3277 are transimpedance amplifiers
designed for up to 2.125Gbps fibre channel applica-
tions. A functional diagram of the MAX3275/MAX3277 is
shown in Figure 1. The MAX3275/MAX3277 comprises a
transimpedance amplifier stage, a voltage amplifier
stage, an output buffer, and a direct-current feedback
cancellation circuit.
Transimpedance Amplifier Stage
The signal current at the input flows into the summing
node of a high-gain amplifier. Shunt feedback through
the resistor R
F
converts this current to a voltage. In par-
allel with the feedback are two back-to-back Schottky
diodes that clamp the output signal for large input cur-
rents as shown in Figure 2.
Voltage Amplifier Stage
The voltage amplifier stage provides gain and converts
the single-ended input to differential outputs.
_______________________________________________________________________________________
5
