MAXIM MAX3277U/D

19-2207; Rev 1; 3/05
Low-Noise, Fibre Channel Transimpedance
Amplifiers
Features
The MAX3275/MAX3277 transimpedance amplifiers
provide a compact low-power solution for communication up to 2.125Gbps. They feature 300nA inputreferred noise at 2.1GHz bandwidth (BW) with 0.85pF
input capacitance. The parts also have 2mA P-P AC
input overload.
♦ Up to 2.125Gbps (NRZ) Data Rates
The MAX3277 is identical to the MAX3275, but with the
output polarities inverted for optimum packaging flexibility. 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 compensation 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 amplifiers provide a two-chip solution for dual-rate, fibre
channel receiver applications.
♦ 25mA Supply Current at +3.3V
♦ 7psP-P Deterministic Jitter for <100µAP-P
Input Current
♦ 300nARMS Input-Referred Noise at 2.1GHz
Bandwidth
♦ 2.3GHz Small-Signal Bandwidth
♦ 2.0mAP-P AC Overload
♦ Die Size: 24mil x 47mil
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX3275U/D
0°C to +85°C
Dice*
MAX3277U/D
0°C to +85°C
Dice*
*Dice are guaranteed to operate from 0°C to +85°C, but are tested only at TA = +25°C.
Applications
Dual-Rate Fibre Channel Optical Receivers
Gigabit Ethernet Optical Receivers
Typical Application Circuit
SMALL FORM FACTOR
OPTICAL RECEIVER
HOST SERVER
OR SWITCH
+3.3V
+3.3V
4.7kΩ
TO
10kΩ
400pF
600Ω
VCC
LOS LOS
MAX3275
OUT+
CFILTER
400pF
IN
MAX3274
0.1µF
0.1µF
OUT+
IN+
100Ω
TIA
OUT-
IN-
LIMITING
AMP
100Ω
OUT-
0.1µF
GND
0.1µF
TH SQUELCH
660Ω
DESERIALIZER
BWSEL
RATE SELECT
________________________________________________________________ Maxim Integrated Products
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.
1
MAX3275/MAX3277
General Description
MAX3275/MAX3277
Low-Noise, Fibre Channel Transimpedance
Amplifiers
ABSOLUTE MAXIMUM RATINGS
Power-Supply Voltage (VCC) .................................-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 (TJ) ....-55°C to +150°C
Storage Ambient Temperature Range (TSTG) ...-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
(VCC = +3.0V to +3.6V, TA = 0°C to +85°C. Typical values are at VCC = +3.3V, source capacitance (CIN) = 0.85pF, TA = +25°C,
unless otherwise noted.) (Notes 1, 2)
PARAMETER
Supply Current
Small-Signal Bandwidth
SYMBOL
ICC
BW
Low-Frequency Cutoff
CONDITIONS
MIN
TYP
-3dB, CIN = 0.6pF (Note 3)
2.0
-3dB, CIN = 0.85pF (Note 3)
1.7
2.3
2.7
Including output termination current
-3dB, input current = 40µA (Note 3)
MAX
UNITS
25
41
mA
2.7
3.3
65
Input Bias Voltage
Input-Referred Noise
IN
CIN = 0.6pF, BW = 0.8GHz (Notes 3, 4)
185
250
CIN = 0.6pF, BW = 1.6GHz (Notes 3, 4)
245
350
CIN = 0.6pF, BW = 2.1GHz (Notes 3, 4)
275
380
CIN = 0.85pF, BW = 0.8GHz (Notes 3, 4)
193
275
CIN = 0.85pF, BW = 1.6GHz (Notes 3, 4)
272
400
CIN = 0.85pF, BW = 2.1GHz (Notes 3, 4)
300
430
(Notes 3, 5)
2
DC Input Overload
(Note 5)
1
Output Resistance (OUT+, OUT-)
Deterministic Jitter
DJ
2
mA
P-P
690
Ω
Single-ended
42.5
Ω
50
57.5
1mAP-P < input < 2mAP-P (Notes 3, 6, 7)
15
40
100µAP-P < input ≤ 1mAP-P (Notes 3, 6, 7)
15
31
Differential output
2.8
Transimpedance Linear Range
0.95 < linearity < 1.05 (Note 8)
50
Data Output Swing
Input > 100µAP-P (Note 9)
220
Output Data-Transition Time
PSR
mAP-P
600
10µAP-P < input ≤ 100µAP-P (Notes 3, 6, 7)
Power-Supply Rejection
nARMS
510
Transimpedance
Output Return Loss
V
Ω
40
AC Input Overload
Filter Resistance
kHz
1.0
Input Resistance
GHz
7
16
3.3
3.8
psP-P
kΩ
µAP-P
300
500
mVP-P
Input > 200µAP-P, 20% to 80% rise/fall time
(Notes 3, 10)
90
140
ps
Freq ≤ 1GHz
15
1GHz < freq ≤ 2GHz
10
f < 1MHz (Note 11)
40
1MHz ≤ f < 10MHz (Note 11)
34
_______________________________________________________________________________________
dB
dB
Low-Noise, Fibre Channel Transimpedance
Amplifiers
(VCC = +3.0V to +3.6V, TA = 0°C to +85°C. Typical values are at VCC = +3.3V, source capacitance (CIN) = 0.85pF, TA = +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 30µAP-P input.
Note 9: Production tested with 1mAP-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(∆VOUT/∆VCC), where ∆VOUT is the differential output voltage and ∆VCC is the noise
on VCC.
Typical Operating Characteristics
(VCC = +3.3V, CIN = 0.85pF, TA = +25°C, unless otherwise noted.)
CIN = 0.6pF
220
210
CIN = 0.85pF
200
190
CIN = 0.6pF
180
20
40
60
80
AMBIENT TEMPERATURE (°C)
100
67
65
63
61
59
BW = 0.8GHz
150
0
69
170
160
BW = 1.6GHz
MAX3275 toc03
230
71
TRANSIMPEDANCE (dBΩ)
CIN = 0.85pF
CIN IS SOURCE CAPACITANCE
PRESENTED TO DIE, INCLUDING
PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
240
FREQUENCY RESPONSE
MAX3275 toc02
CIN IS SOURCE CAPACITANCE
PRESENTED TO DIE, INCLUDING
PIN DIODE, AND PARASITIC
INTERCONNECT CAPACITANCE
250
INPUT-REFERRED NOISE (nARMS)
350
340
330
320
310
300
290
280
270
260
250
240
230
220
210
200
INPUT-REFERRED NOISE
vs. TEMPERATURE
MAX3275 toc01
INPUT-REFERRED NOISE (nARMS)
INPUT-REFERRED NOISE
vs. TEMPERATURE
57
0
20
40
60
80
AMBIENT TEMPERATURE (°C)
100
100M
1G
10G
FREQUENCY (Hz)
_______________________________________________________________________________________
3
MAX3275/MAX3277
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics (continued)
(VCC = +3.3V, CIN = 0.85pF, TA = +25°C, unless otherwise noted.)
DETERMINISTIC JITTER
vs. INPUT AMPLITUDE
35
30
25
20
15
10
5
0
0.1
1
10
MAX3275 toc06
2.9
2.8
CIN = 0.6pF
2.7
2.6
2.5
2.4
2.3
CIN = 0.85pF
2.2
2.1
2.0
0
20
40
60
100
80
0
20
40
60
80
100
INPUT AMPLITUDE (mAP-P)
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
EYE DIAGRAM (INPUT = 10µAP-P)
EYE DIAGRAM (INPUT = 2mAP-P)
DIFFERENTIAL OUTPUT REFLECTION
COEFFICIENT
MAX3275 toc09
0
MAX3275 toc08
MAX3275 toc07
0.01
BANDWIDTH vs. TEMPERATURE
3.0
BANDWIDTH (GHz)
TRANSIMPEDANCE (dBΩ)
40
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
MAX3275 toc05
2.125Gbps
K28.5 INPUT
45
MAX3275 toc04
SMALL-SIGNAL TRANSIMPEDANCE
vs. TEMPERATURE
50
DETERMINISTIC JITTER (psP-P)
-5
S22 (dB)
-10
50mV/div
5mV/div
-15
-20
-25
-30
-35
INPUT: K28.5
INPUT: K28.5
-40
0
80ps/div
80ps/div
500M
1G
1.5G
2G
FREQUENCY (Hz)
DC TRANSFER FUNCTION
(FILTER = GND)
SUPPLY CURRENT vs. TEMPERATURE
45
150
OUTPUT VOLTAGE (mV)
40
35
30
25
20
15
MAX3275 toc11
200
MAX3275 toc10
50
SUPPLY CURRENT (mA)
MAX3275/MAX3277
Low-Noise, Fibre Channel Transimpedance
Amplifiers
100
50
0
-50
-100
10
-150
5
-200
0
0
20
40
60
80
AMBIENT TEMPERATURE (°C)
4
100
-200
-100
0
100
200
INPUT CURRENT (µA)
_______________________________________________________________________________________
2.5G
3G
Low-Noise, Fibre Channel Transimpedance
Amplifiers
MAX3275
BOND PAD
MAX3277
BOND PAD
NAME
1, 9
1, 9
VCC
Supply Voltage
2, 5
2, 5
GND
Circuit Ground
3
4
OUT-
Inverting Data Output. Current flowing into IN causes the voltage at OUT- to decrease.
4
3
OUT+
Noninverting Data Output. Current flowing into IN causes the voltage at OUT+ to
increase.
6
6
N.C.
7
7
FILTER
8
8
IN
FUNCTION
No Connection. Not internally connected.
Provides bias voltage for the photodiode through a 600Ω resistor to VCC. 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.
VCC
Rf
VOLTAGE
AMPLIFIER
IN
OUTPUT
BUFFER
50Ω
50Ω
OUT+
OUT-
TIA
VCC
VCC
DC CANCELLATION
600Ω
DISABLE
FILTER
GND
LOWPASS
FILTER
MAX3275
MAX3277
Figure 1. Functional Diagram
Detailed Description
The MAX3275/MAX3277 are transimpedance amplifiers
designed for up to 2.125Gbps fibre channel applications. 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 RF converts this current to a voltage. In parallel with the feedback are two back-to-back Schottky
diodes that clamp the output signal for large input currents as shown in Figure 2.
Voltage Amplifier Stage
The voltage amplifier stage provides gain and converts
the single-ended input to differential outputs.
_______________________________________________________________________________________
5
MAX3275/MAX3277
Pad Description
AMPLITUDE
AMPLITUDE
INPUT FROM PHOTODIODE
TIME
TIME
OUTPUT (SMALL SIGNALS)
INPUT (AFTER DC CANCELLATION)
OUTPUT (LARGE SIGNALS)
Figure 2. MAX3275/MAX3277 Limited Output
Output Buffer
The output buffer provides a reverse-terminated voltage
output. The buffer is designed to drive a 100Ω differential load between OUT+ and OUT-. The output current
is divided between internal 50Ω resistors and the external load resistor.
For optimum supply-noise rejection, the MAX3275/
MAX3277 should be terminated with a differential load.
If a single-ended output is required, the unused
output should be terminated in a similar manner. The
MAX3275/MAX3277 will not drive a DC-coupled, 50Ω
grounded load; however, it will drive a compatible 50Ω
CML input.
DC Cancellation Circuit
The direct-current (DC) cancellation circuit uses lowfrequency feedback to remove the DC component of
the input signal (Figure 3). This feature centers the
input signal within the transimpedance amplifier’s linear
range, thereby reducing pulse-width distortion caused
by large input signals. Pulse-width distortion in small
signals will not be corrected.
The DC cancellation circuit is internally compensated
and therefore does not require external capacitors. This
circuit minimizes pulse-width distortion for data
sequences that exhibit a 50% mark density and 8b/10b
coding. A mark density significantly different from 50%
will cause the MAX3275/MAX3277 to generate pulsewidth distortion.
DC cancellation current is drawn from the input and
creates noise. For low-level signals with little or no DC
component, the added noise is insignificant.
Applications Information
Figure 3. DC Cancellation Effect on Input
average optical power and extinction ratio. Figure 4 and
Table 1 show relations that are helpful for converting
optical power to input signal when designing with
the MAX3275/MAX3277. (Refer to Application note
HFAN–3.0.0 Accurately Estimating Optical Receiver
Sensitivity.)
Table 1. Optical Power Relations
PARAMETER
SYMBOL
Average Power
PAVG
RELATION
PAVG = (P0 + P1)/2
Extinction Ratio
re
re = P1/P0
Optical Power of a 1
P1
P1 = 2PAVG(re)/(re + 1)
Optical Power of a 0
P0
P0 = 2PAVG/(re + 1)
Signal Amplitude
PIN
PIN = P1 - P0
PIN = 2PAVG(re - 1)/(re + 1)
P1
OPTICAL POWER
MAX3275/MAX3277
Low-Noise, Fibre Channel Transimpedance
Amplifiers
PAVG
P0
TIME
Figure 4. Optical Power Relations
Optical Power Relations
Many of the MAX3275/MAX3277 specifications relate to
the input signal amplitude. When working with optical
receivers, the input is sometimes expressed in terms of
6
Optical Sensitivity Calculation
The input-referred RMS noise current (I N ) of the
MAX3275/MAX3277 generally determines the receiver
_______________________________________________________________________________________
Low-Noise, Fibre Channel Transimpedance
Amplifiers
 14.1IN (re +1) × 1000 
Sensitivity =10 log
 dBm
2ρ(re -1)


where ρ is the photodiode responsivity in A/W and IN is
RMS current in Amps.
Input Optical Overload
The overload is the largest input that the MAX3275/
MAX3277 accept while meeting specifications. The
optical overload can be estimated in terms of average
power with the following equation:
 (2E - 3) (re +1) × 1000 
Overload=10 log
 dBm
2ρ(re -1)


Optical Linear Range
The MAX3275/MAX3277 have high gain, which limits
the output when the input signal exceeds 50µAP-P. The
MAX3275/MAX3277 operate in a linear range (10% linearity) for inputs not exceeding:
 (50E - 6) (re +1) × 1000 
Linear Range=10 log
 dBm
2ρ(re -1)


Layout Considerations
Noise performance and bandwidth will be adversely
affected by capacitance at the IN pad. Minimize
capacitance on this pad and select a low-capacitance
photodiode. Assembling the MAX3275/MAX3277 in die
form using chip and wire technology provides the best
possible performance. Figure 5 shows a suggested layout for a TO header for the MAX3275/MAX3277.
Special care should be taken to ensure that ESD at IN
does not exceed 500V.
Photodiode Filter
Supply voltage noise at the cathode of the photodiode
produces a current I = CPD ∆V/∆t, which reduces the
receiver sensitivity (C PD is the photodiode capacitance). The filter resistor of the MAX3275/MAX3277,
combined with an external capacitor, can be used to
reduce this noise (see the Typical Application Circuit).
Current generated by supply noise voltage is divided
between CFILTER and CPD. The input noise current due
to supply noise is (assuming the filter capacitor is much
larger than the photodiode capacitance):
INOISE = (VNOISE)(CPD) / (RFILTER)(CFILTER)
If the amount of tolerable noise is known, the filter
capacitor can be easily selected:
CFILTER = (VNOISE)(CPD) / (RFILTER)(INOISE)
For example, with maximum noise voltage = 100mVP-P,
CPD = 0.85pF, RFILTER = 600Ω, and INOISE selected to
be 350nA:
CFILTER = (100mV)(0.85pF) / (600Ω)(350nA) = 400pF
Wire Bonding
For high-current density and reliable operation, the
MAX3275/MAX3277 use gold metalization. Connections
to the die should be made with gold wire only, using
ball-bonding techniques. Wedge bonding is not recommended. Die thickness is typically 15 mils (0.4mm).
Pad Coordinates
VCC
CFILTER
PHOTODIODE
CAP
OUT+
OUTPUT POLARITIES
REVERSED FOR MAX3277
OUT-
MAX3275
CASE IS GROUND
PAD#
COORDINATES (µm)
1
16, 39
2
16, 372
3
16, 806
4
358, 806
5
358, 341
6
358, 36
7
362, -116
8
250, -116
9
138, -116
Figure 5. Suggested Layout for TO-46 Header
_______________________________________________________________________________________
7
MAX3275/MAX3277
sensitivity. To obtain a system bit error rate (BER) of 1E12, the signal-to-noise ratio must always exceed 14.1.
The input sensitivity, expressed in average power, can
be estimated as:
Low-Noise, Fibre Channel Transimpedance
Amplifiers
MAX3275/MAX3277
Chip Topographies
OUT(PAD 3)
OUT+
(PAD 4)
GND
(PAD 2)
MAX3275
GND
(PAD 5)
0.047"
(1.2mm)
VCC
(PAD 1)
N.C.
(PAD 6)
INDEX
FILTER
(PAD 7)
VCC
(PAD 9)
IN
(PAD 8)
0.024"
(0.6mm)
8
_______________________________________________________________________________________
Low-Noise, Fibre Channel Transimpedance
Amplifiers
OUT+
(PAD 3)
OUT(PAD 4)
GND
(PAD 2)
MAX3277
GND
(PAD 5)
VCC
(PAD 1)
0.047"
(1.2mm)
N.C.
(PAD 6)
INDEX
FILTER
(PAD 7)
VCC
(PAD 9)
IN
(PAD 8)
0.024"
(0.6mm)
Chip Information
TRANSISTOR COUNT: 301
SUBSTRATE: ISOLATED
PROCESS: SiGe BIPOLAR
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9
© 2005 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.
MAX3275/MAX3277
Chip Topographies (continued)