MAX3964C/DW(2002) Просмотр технического описания (PDF) - Maxim Integrated

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MAX3964C/DW
(Rev.:2002)

+3.0V to +5.5V, 125Mbps to 266Mbps Limiting Amplifiers with Loss-of-Signal Detector A

Maxim Integrated 

+3.0V to +5.5V, 125Mbps to 266Mbps

Limiting Amplifiers with Loss-of-Signal Detector

sensitivity. The offset-correction circuitry is less sensi-

tive to variations of input duty cycle (for example, the

40% to 60% duty cycle encountered in 4B/5B coding)

when the input is less than 30mVp-p.

Loss-of-Signal Comparator

The LOS comparator indicates when the input signal

power is below the programmed LOS threshold. To

ensure supply and temperature independence, VTH is

generated by a 1.2V bandgap reference. The op amp’s

external gain-setting resistors (R1 and R2) can be

chosen to set VTH between 1.2V and 2.4V. To ensure

chatter-free operation, the LOS comparator is designed

with approximately 5dB of hysteresis.

Squelch

The squelch function disables the data outputs by forc-

ing OUT- low and OUT+ high during a LOS condition.

This function ensures that when there is a loss of sig-

nal, the limiting amplifier (and all downstream devices)

does not respond to input noise or corrupt data.

Connect SQUELCH to GND or leave it unconnected to

disable squelch. Connect SQUELCH to VCC to enable

data squelching.

Applications Information

Program the LOS Threshold

Figure 2 provides information for selecting the LOS

threshold voltage (VTH). If R1 is 100kΩ and if the

responsivities of the photodiode and preamplifier are

known, then the value of R2 can be selected from

Figure 2 to provide LOS assert at the desired input

power.

Select Capacitors

A typical MAX3964/MAX3965/MAX3968 implementation

requires four external capacitors (CAZ, CFILTER, and

two input coupling capacitors). For all applications up

to 266Mbps, Maxim recommends the following:

CAZ = 27nF

CFILTER = 10nF

CIN = 10nF

Wire Bonding

For high-current density and reliable operation, the

MAX3964 series uses gold metalization. Diepad size is

4mils square with a 6mil pitch. Die thickness is 15mils.

120

200kV/W

100

80

100kV/W

60

30kV/W

20kV/W

40

15kV/W

20

10kV/W

0

-40 -38 -36 -34 -32 -30 -28 -26

OPTICAL INPUT POWER AT LOS ASSERT (dBm)

Figure 2. LOS Assert Programming Resistor vs. LOS Assert

Power (for various PIN-TIA gains )

PART

MAX3964

MAX3965

MAX3968

Selector Guide

DATA RATE (Mbps)

125 to 155

125 to 155

125 to 266

LOS OUTPUTS

PECL

TTL

PECL

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