Datasheet MAX3864D Datasheet (Maxim)

General Description

The MAX3864 is a transimpedance preamplifier for
applications in SDH/SONET systems operating up to

2.5Gbps. It features 490nA (typ) input-referred noise,

2.0GHz bandwidth, and 2mA input overload.

The MAX3864 operates from a single +3.0V to +5.5V
supply. It includes an integrated low-frequency com­pensation capacitor, as well as a filter connection that
provides positive bias through a 750Ω resistor to VCC.
These features save external components, simplifying
design and assembly into a TO-46 header with a photo­diode.

The MAX3864 has a typical optical dynamic range of

-24dBm to 0dBm using a PIN photodetector.

Applications

SDH/SONET Transmission Systems

PIN Preamplifier Receivers

APD Preamplifier Receivers

2.5Gbps ATM Receivers

Regenerators for SDH/SONET

Features

♦ 490nA (typ) Input-Referred Noise

♦ 2000MHz Bandwidth

♦ 2mA Input Overload
♦ 100Ω Differential Output Impedance

♦ 112mW Power Dissipation at +3.3V

♦ Integrated Filter Resistor

♦ CML Outputs

♦ Single +3.0V to +5.5V Supply Voltage

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

________________________________________________________________ Maxim Integrated Products 1

19-1790; Rev 0; 8/00

For free samples and the latest literature, visit www.maxim-ic.com or phone [phone].
For small orders, phone [phone].

OUT-

GNDFILTER

1

2

87GND

OUT+N.C.

IN

V

CC

SO

TOP VIEW

3

4

6

5

MAX3864

0.01µF

PHOTODIODE

750Ω

V

CC

V

CC

GND

FILTER

IN

0.1µF

OUT+

OUT-

0.1µF

C

FILTER

400pF

100Ω

MAX3864

LIMITING
AMPLIFIER

Typical Application Circuit

Pin Configuration

Ordering Information

PART TEMP. RANGE PIN-PACKAGE

MAX3864ESA

-40°C to +85°C

8 SO

MAX3864E/D

-40°C to +85°C

Dice*

* Dice are designed to operate with junction temperatures of -40°C
to +140°C but are tested and guaranteed only at T

A

= +25°C.

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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 1: Source capacitance represents the total capacitance at the IN pin during characterization of noise and bandwidth parame-

ters. Noise and bandwidth will be affected by the source capacitance. See the Typical Operating Characteristics for more
information.

Note 2: Input-referred noise is calculated as (RMS output noise) / (Gain at f = 10MHz). Noise density is (Input-Referred Noise) /

(Bandwidth)

1/2

. No external filters are used for the noise measurements.

Note 3: Deterministic jitter is defined as the arithmetic sum of pulse-width distortion and pattern dependent jitter measured with a

repeating 20-bit pattern of 00111110101100000101 (K28.5). See Typical Operating Characteristics.

Supply Voltage (V

CC

- GND).................................-0.5V to +6.0V

IN Current..............................................................-4mA to +4mA

FILTER Current......................................................-8mA to +8mA

Voltages at OUT+, OUT- .................(V

CC

- 1.5V) to (VCC+ 0.5V)

Continuous Power Dissipation (T

A

= +85°C)

8-Pin SO package (derate 6.7mW/°C above +85°C) ..436mW

Storage Temperature Range .............................-55°C to +150°C

Operating Junction Temperature ......................-55°C to +150°C

Processing Temperature (die) .........................................+400°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(VCC= +3.0V to +5.5V, 100Ω load between OUT+ and OUT-, 0.1µF coupling capacitors on OUT+ and OUT-, TA= -40°C to +85°C,
unless otherwise noted. Typical values are at +3.3V, source capacitance = 0.85pF, and T

A

= +25°C.) (Note 1)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Bias Voltage 0.66 0.83 0.99 V

Supply Current 34 63 mA
Transimpedance Differential, measured with 40µAp-p input 2100 2750 3400 Ω
Output Impedance Single ended (per side) 48 50 52 Ω

Maximum Differential Output Voltage

Input = 2mAp-p with 100Ω differential output
termination

220 380 575 mVp-p

Filter Resistor 600 750 930 Ω

AC Input Overload 2 mAp-p

DC Input Overload 1mA

Input-Referred RMS Noise 490 668 nA
Input-Referred Noise Density Bandwidth = 2.0GHz (Note 2) 11 pA/√(Hz)

Small-Signal Bandwidth 1525 2000 MHz
Low-Frequency Cutoff -3dB, input ≤ 20µADC 30 kHz

Transimpedance Linear Range

Gain at 40µAp-p is within 5% of the small­signal gain

40 µAp-p

3.13V < VCC < 5.5V (Note 3) 24 67

Deterministic Jitter

3.0V ≤ V

CC

≤ 3.13V (Note 3) 24 77

ps

Power-Supply Rejection Ratio (PSRR)

Output referred, f < 2MHz,
PSRR = -20log(∆V

OUT

/∆Vcc)

50 dB

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

_______________________________________________________________________________________ 3

200

300

250

400

350

550

500

450

600

-40 0-20 20406080100

INPUT-REFERRED RMS NOISE

vs. TEMPERATURE

MAX3864 toc01

JUNCTION TEMPERATURE (°C)

INPUT-REFERRED NOISE (nA

RMS

)

CIN = 1.5pF

CIN = 1.0pF

CIN = 0.5pF

CIN IS SOURCE CAPACITANCE
PRESENTED TO DIE, INCLUDES
PACKAGE PARASITIC, PIN DIODE,
AND PARASITIC INTERCONNECT
CAPACITANCE.

50

55

65

60

70

75

FREQUENCY RESPONSE

MAX3864 toc02

FREQUENCY (MHz)

TRANSIMPEDANCE (dBΩ)

110010 1k 10k

0

30

20

10

40

50

60

70

80

90

100

10 100 1000 10,000

DETERMINISTIC JITTER

vs. INPUT AMPLITUDE

MAX3864 toc03

INPUT CURRENT AMPLITUDE (µAp-p)

PEAK-TO-PEAK JITTER (ps)

0

300

200

100

400

500

600

700

800

900

1000

1 10 100 1000

INPUT-REFERRED RMS NOISE CURRENT

vs. DC INPUT CURRENT

MAX3864 toc04

DC INPUT CURRENT (µA)

INPUT-REFERRED NOISE (nA

RMS

)

60

63

62

61

65

64

69

68

67

66

70

-40-200 20406080100

SMALL-SIGNAL TRANSIMPEDANCE

vs. TEMPERATURE

MAX3864 toc05

AMBIENT TEMPERATURE (°C)

TRANSIMPEDANCE dBΩ)

1.4

1.6

1.5

1.9

1.8

1.7

2.2

2.1

2.0

2.3

-40 0 20-20 40 60 80 100

BANDWIDTH vs. TEMPERATURE

MAX3864 toc06

JUNCTION TEMPERATURE (°C)

BANDWIDTH (GHz)

CIN = 1.5pF

CIN = 1.0pF

CIN = 0.5pF

CIN IS SOURCE CAPACITANCE
PRESENTED TO DIE, INCLUDES
PACKAGE PARASITIC, PIN DIODE,
AND PARASITIC INTERCONNECT
CAPACITANCE.

300

360

340

320

400

380

480

460

440

420

500

-40-200 20406080100

DIFFERENTIAL OUTPUT AMPLITUDE

vs. TEMPERATURE

MAX3864 toc07

AMBIENT TEMPERATURE (°C)

DIFFERENTIAL OUTPUT AMPLITUDE (mVp-p)

INPUT = 2mA

EYE DIAGRAM (INPUT = 2mAp-p)

MAX3864 toc11

80ps/div

50mV/div

INPUT = 2

13

-1 PRBS WITH 72 CID

V

CC

= 3.0V AT TA = -40°C

EYE DIAGRAM (INPUT = 2mAp-p)

MAX3864 toc12

80ps/div

50mV/div

INPUT = 2

13

-1 PRBS WITH 72 CID

V

CC

= 3.13V AT TA = -40°C

Typical Operating Characteristics

(V

CC

= 3.3V, TA = +25°C and MAX3864 EV kit source capacitance = 0.85pF, unless otherwise noted).

MAX3864

Detailed Description

The MAX3864 transimpedance amplifier is designed for

2.5Gbps fiber optic applications. As shown in Figure 1,

the MAX3864 comprises a transimpedance amplifier, a
voltage amplifier, an output buffer, an output filter, and
a DC cancellation circuit.

Transimpedance Amplifier

The signal current at the input flows into the summing
node of a high-gain amplifier. Shunt feedback through
RFconverts this current to a voltage. Schottky diodes
clamp the output voltage for large input currents
(Figure 2).

Voltage Amplifier

The voltage amplifier converts single-ended signals to
differential signals and introduces a voltage gain.

Output Buffer

The output buffer provides a back-terminated voltage
output. The buffer is designed to drive a 100Ω differen­tial load between OUT+ and OUT-. The output voltage
is divided between internal 50Ω load resistors and the
external load resistor. In the typical operating circuit,
this creates a voltage-divider with a ratio of 1/2. The
MAX3864 can also be terminated with higher output
impedances, which increases gain and output voltage
swings.

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

4 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

V

CC

= 3.3V, TA = +25°C and MAX3864 EV kit source capacitance = 0.85pF, unless otherwise noted).

Pin Description

200

100

0

-100

-200

-100 0-50 50 100

DC TRANSFER FUNCTION

MAX3864 toc10

INPUT CURRENT (µA)

DIFFERENTIAL OUITPUT VOLTAGE (mVp-p)

EYE DIAGRAM (INPUT = 20µAp-p)

MAX3864 toc09

80ps/div

10mV/div

INPUT = 223 -1 PRBS

PIN NAME FUNCTION

1VCCSupply Voltage

2 N.C. No Connection

3 IN Amplifier Input

4 FILTER

Provides bias voltage for the photodiode through a 750Ω 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.

5 GND Ground

6 OUT- Inverting Output. Current flowing into IN causes V

OUT-

to decrease.

7 OUT+ Noninverting Output. Current flowing into IN causes V

OUT+

to increase.

8 GND Ground

EYE DIAGRAM (INPUT = 2mAp-p)

MAX3864 toc08

80ps/div

50mV/div

INPUT = 223 -1 PRBS

For optimum supply-noise rejection, the MAX3864
should be terminated with a differential load. If a single­ended output is required, the unused output should be
terminated with 50Ω to VCC. The MAX3864 will not drive
a DC-coupled, 50Ω grounded load.

Output Filter

The MAX3864 includes a one-pole lowpass filter that
limits the circuit bandwidth and improves noise perfor­mance.

DC Cancellation Circuit

The DC cancellation circuit uses low-frequency 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 (PWD) on large input signals.

The DC cancellation circuit is internally compensated
and therefore does not require external capacitors. This
circuit minimizes PWD for data sequences that exhibit a
50% duty cycle and mark density. A duty cycle or mark
density significantly different from 50% causes the
MAX3864 to generate PWD.

DC cancellation current is drawn from the input and
creates noise. For low-level signals with little or no DC
component, this is not a problem. Amplifier noise will
increase for signals with significant DC component (see
Typical Operating Characteristics).

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

_______________________________________________________________________________________ 5

VOLTAGE

AMPLIFIER

TRANSIMPEDANCE

AMPLIFIER

OUTPUT
BUFFER

OUTPUT

FILTER

OUT+

50Ω

50Ω

OUT-

V

CC

RF = 1k

V

CC

LOWPASS FILTER

750Ω

FILTER

IN

GND

DC CANCELLATION

CIRCUIT

DISABLE

MAX3864

Figure 1. Functional Diagram

AMPLITUDE

OUTPUT (LARGE SIGNALS)

TIME

OUTPUT (SMALL SIGNALS)

Figure 2. Limited Output

AMPLITUDE INPUT FROM PHOTODIODE

TIME

INPUT (AFTER DC CANCELLATION)

Figure 3. DC Cancellation Effect on Input

Applications Information

Optical Power Relations

Many of the MAX3864 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. Figure 4 shows relations that

are helpful for converting optical power to input signal
when designing with the MAX3864.

Optical power relations are shown in Table 1; the defini­tions are true if the average duty cycle and mark densi­ty of the input data are 50%.

Optical Sensitivity Calculations

The MAX3864 input-referred RMS noise current (IN)
generally determines the receiver sensitivity. To obtain
a system bit-error rate (BER) of 1E-10, the minimum sig­nal-to-noise ratio (SNR) is 12.7. The input sensitivity,
expressed in average power, can be estimated as:

where ρ is the photodiode responsivity, including fiber­to-photodiode coupling efficiency in A/W and I

N

in µA.

For example, if SNR = 12.7, I

N

= 0.490µA, re= 10, and

ρ = 1, then sensitivity is -24dBm.

Input Optical Overload

The overload is the largest input that the MAX3864
accepts while meeting deterministic jitter specifications.
The optical overload can be estimated in terms of aver­age power with the following equation (assumes
r

e

= ∞):

Optical Linear Range

The MAX3864 has high gain, which limits the outputs
when the input signal exceeds 40µAp-p. The MAX3864
operates in a linear range for inputs not exceeding:

Layout Considerations

Use good high-frequency design and layout techniques.
The use of a multilayer circuit board with separate ground
and power planes is recommended. Connect the GND
pins to the ground plane with the shortest possible traces.

Noise performance and bandwidth will be adversely
affected by capacitance at the IN pin. Minimize capaci­tance on this pin, and select a low-capacitance photodi­ode. Assembling the MAX3864 in die form using chip and
wire technology provides the best possible performance.
Figure 5 shows the recommended layout for a TO
header.

The SO package version of the MAX3864 is offered as an
easy way to characterize the circuit and to become famil­iar with the circuit’s operation, but it does not offer opti­mum performance. When using the SO version of the
MAX3864, the package capacitance adds approximately

0.3pF at the input. The PC board between the MAX3864
input and the photodiode also adds parasitic capaci­tance. Keep the input line short, and remove power and
ground planes beneath it.

GND

Connect GND as close to the AC ground of the photode­tector diode as possible. The photodetector AC ground is
usually the ground of the filter capacitor from the photode­tector cathode. The total loop (from GND, through the
bypass capacitor and the diode, and back to IN) should
be no more than approximately 1/5th of a wavelength.

Overload 10log

2mAp - p 1000

2

dBm=

×













ρ

Sensitivity=10log

SNR

2

dBm

×+

()

−

()

×













Ir

r

Ne

e

1

1 1000ρ

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

6 _______________________________________________________________________________________

PO

PI

P

AVG

TIME

POWER

P

IN

Figure 4. Optical Power Relations

PARAMETER SYMBOL RELATION

Average Power P

AVE

P

AVE

= (P0 + P1) / 2

Extinction Ratio r

e

re = P1 / P

0

Optical Power of a 1 P

1

P1 = 2P

AVEre

/ (re + 1)

Optical Power of a 0 P

0

P0 = 2P

AVE

/ (re + 1)

Signal Amplitude P

IN

PIN = P1 - P0 = 2P

AVE

(re - 1) / (re + 1)

Table 1. Optical Power Relations

Note: Assuming a 50% average input duty cycle and mark

density.

Linear Range = 10log

4-

2

dBm

0 1 1000

1

µ+

()

×

−

()













Ap p r

r

e

e

ρ

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

_______________________________________________________________________________________ 7

IN

V

CC

V

CC

GND

200Ω

Figure 6. Equivalent Input Circuit

CASE IS GROUND

TOP VIEW OF TO-46 HEADER

C

FILTER

V

CC

PHOTODIODE

MAX3864

OUT+

OUT-

Figure 5. Suggested Layout for TO-46 Header

Photodiode Filter

Supply voltage noise at the photodiode cathode pro­duces a current I = CPD∆V / ∆t, which reduces the
receiver sensitivity (CPDis the photodiode capaci­tance). The filter resistor of the MAX3864, 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
C

FILTER

and CPD. The input noise current due to sup­ply noise is (assuming the filter capacitor is much larg­er than the photodiode capacitance):

If the amount of tolerable noise is known, the filter
capacitor can be easily selected:

For example, with a maximum noise voltage equal to
100mVp-p, CPD= 0.85pF, R

FILTER

= 750Ω, and I

NOISE

selected to be 250nA (half of the MAX3864’s input noise):

Wire Bonding

For high current density and reliable operation, the
MAX3864 uses gold metalization. Connections to the
die should be made with gold wire only, using ball­bonding. Wedge bonding is not recommended. Die
thickness is typically 15mils (0.375mm).

C=

100mV

FILTER

()()

()( )

=

085

750 250

453

.pF

nA

pF

Ω

C=

V

FILTER

NOISE

()()

()()

C

RI

PD

FILTER NOISE

I=

V

NOISE

NOISE

()()

()()

C

RC

PD

FILTER FILTER

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

8 _______________________________________________________________________________________

V

CC

OUT+

OUT-

GND

50Ω 50Ω

Figure 7. Equivalent Output Circuit

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

_______________________________________________________________________________________ 9

30mils

50mils

1.27mm

OUT+

GND

OUT-

GND

V

CC

INPUT FILTER

(0.762mm)

Chip Information

TRANSISTOR COUNT: 320

PROCESS: BIPOLAR (SILICON GERMANIUM)

Chip Topography

Package Information

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

10 ______________________________________________________________________________________

SOICN.EPS

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

______________________________________________________________________________________ 11

NOTES

MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range
Transimpedance Preamplifier

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.

12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

NOTES