MAX3766EEP 查看數據表（PDF） - Maxim Integrated

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MAX3766EEP

622Mbps LAN/WAN Laser Driver w

Maxim Integrated 

622Mbps LAN/WAN Laser Driver with

Automatic Power Control and Safety Shutdown

VCC

OR

ENABLE

VCC

MAX809MEUR-T

RESET

ENABLE

MAX3766*

SAFETY

CSAFETY

*IN LATCHED SHUTDOWN

CONFIGURATION

Figure 6. Reset Pulse Generator

If PC board space is not a constraint, Maxim recom-

mends enabling the transmitter with a reset-pulse gen-

erator, such as the MAX809, which generates a reset

signal after VCC reaches 4.5V (Figure 6). This method

ensures that the transmitter starts correctly, even if the

supply ramps very slowly.

__________________Design Procedure

Select Laser

Select a communications-grade laser with a rise time of

0.5ns or better for 622Mbps applications. The voltage

swing at the OUT+ pin affects the output waveform,

and is largely determined by the laser resistance,

inductance, and modulation current. To obtain the

MAX3766’s AC specifications, the output voltage at

OUT+ must remain above VCC - 2.5V at all times.

An approximation for the minimum voltage at OUT+ is

given by the following equation (Table 1):

( ) VOUT(MIN) = VCC(MIN) - VLASER - IMOD



RL

+

RD

+

L

tr





Select a laser that meets the output voltage criteria. A

high-efficiency laser requires low modulation current

and generates low voltage swing at OUT+. Laser pack-

age inductance can be reduced by trimming leads.

Typical package leads have inductance of 25nH per

inch (1nH/mm). A compensation filter network can also

be used to reduce ringing, edge speed, and voltage

swing.

Table 1. Output Voltage Approximation

VARIABLE

VOUT(MIN)

VCC(MIN)

VLASER

RL

IOUT

RD

L

tr

DESCRIPTION

Approximation for the lowest voltage at the OUT+ pin

Minimum power supply

Laser forward voltage at operating power

Laser dynamic resistance

Laser modulation current

Any damping resistance or line termination in series with the laser

(but not in series with BIAS)

Total series inductance of laser, laser package, and board traces to the

MAX3766

20% to 80% rise time of the laser modulation current, filtered by a

compensation network

TYPICAL VALUE

2.2V

4.5V

1.3V

3Ω

30mA

10Ω

6nH

300ps

(20% to 80%)

______________________________________________________________________________________ 11

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