Applications Information

Converting Average Optical Power

to Signal Amplitude

Many of the MAX3866’s specifications relate to input

signal amplitude. When working with fiber optic

receivers, the input is usually expressed in terms of

average optical power and extinction ratio. The rela-

tions given in Table 1 are helpful for converting optical

power to input signal when designing with the

MAX3866.

In an optical receiver, the input current to the transim-

pedance amplifier can be found by multiplying the

power relationships in Table 1 with the photodiode

responsivity.

Wire Bonding

Make corrections to the die with gold wire only, using

ball bonding techniques. Die pad size is 4mils (100µm)

square and die thickness is 12mils (~300µm).

Layout Techniques

The MAX3866’s performance can be greatly affected

by circuit board layout and design. Use good high-fre-

quency design techniques, including minimizing

ground inductances and using fixed-impedance trans-

mission lines on all data signals.

2.5Gbps, +3.3V Combined

Transimpedance/Limiting Amplifier

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9

PARAMETER

SYMBOL

RELATION

Average

Power

Extinction

Ratio

Optical Power

of a “1”

P1

Optical Power

of a “0”

P0

Signal

Amplitude

P

= P1 - P0 = 2P

IN

AVE

(re - 1)

(re + 1)

re + 1

Table 1. Optical-Power Relations*

*

Assuming a 50% average input mark density.

Pad Configuration

CPD+

VCCS

VCCS

CHF+

CHF-

LOP

GND

FIL GND IN+

IN-

N.C.

CPD-

GND

GND

INV

PDC

GND

OUT+

OUT-

GND

VCCD

VCCD

0.057"

(1.45mm)

0.066"

(1.68mm)

TRANSISTOR COUNT: 851