MAX3643 查看數據表（PDF） - Maxim Integrated

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MAX3643

155Mbps to 2.5Gbps Burst-Mode Laser Driver

Maxim Integrated 

MAX3643

155Mbps to 2.5Gbps Burst-Mode Laser Driver

BURST-ENABLE (BEN±) IN

≤ 125μs FOR BPON/GPON

INTERNAL MDIN VOLTAGE SAMPLER

BENOUT OUTPUT

3μs

MDOUT

1.2V

100μs

< 2.56mV

Figure 2. Sample-and-Hold Timing Diagram

Enable Input

An LVCMOS input, EN, is provided to disable both bias

and modulation currents under external control. The

maximum time to disable laser current with the EN con-

trol is 375ns.

Setting the Current Limit

A current limiter is provided to protect the laser diode

by shutting down both bias and modulation currents

when total current exceeds a value set by the resistor

connected from IMAX to ground. Do not use less than

3kΩ RIMAX. See the IBIAS + IMOD Current Threshold vs.

RIMAX graph in the Typical Operating Characteristics.

Programming the MODSET and

BIASSET Inputs

To program the laser modulation current using a cur-

rent DAC, connect VMSET to VREF, attach the DAC to

the MODSET pin and set the current according to:

IMOD = IMODSET x 88

To program the laser modulation current using a resis-

tor or digital potentiometer, connect VMSET to VREF,

attach a resistor from the MODSET pin to ground, and

set the current according to:

IMOD

=

1.2V

RMODSET + RMOD

× 88

To program the laser modulation current using a PWM

voltage DAC (requiring a high-impedance load), attach

a DAC output to the VMSET pin, connect a resistor from

the MODSET pin to ground as shown in the Typical

Applications Circuit, and set the current according to:

IMOD

=

VDAC

RMODSET + RMOD

×

88

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