MAX3867 Ver la hoja de datos (PDF) - Maxim Integrated

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componentes Descripción

Fabricante

MAX3867

+3.3V, 2.5Gbps SDH/SONET Laser Driver with Automatic Power Control

Maxim Integrated 

+3.3V, 2.5Gbps SDH/SONET Laser Driver

with Automatic Power Control

VCC

LATCH

MAX3867

DATA

CLK

DQ

0

MUX

1

ENABLE

172X

MODSET

RMODSET

BIASMAX

RBIASMAX

LP

OUT+

IMOD

OUT-

LP

CD

RD

CF

RF

25Ω

VCC

IBIAS BIAS

40X

5X

MD

FAILURE

DETECTOR

CAPC

FAIL

CAPC

IMD

APCSET

RAPCSET

1000pF

Figure 4. Functional Diagram

laser package is used to convert the optical power into

a photocurrent. The APC loop adjusts the laser bias

current so that the monitor current is matched to a ref-

erence current set by RAPCSET. The time constant of

the APC loop is determined by an external capacitor

(CAPC). To eliminate the pattern-dependent jitter asso-

ciated with the APC loop-time constant, and to guaran-

tee loop stability, the recommended value for CAPC is

0.1µF.

When the APC loop is functioning, the maximum allow-

able bias current is set by an external resistor, RBIASMAX.

An APC failure flag (FAIL) is set low when the bias current

can no longer be adjusted to achieve the desired aver-

age optical power. To filter out the APC loop noise, use

an external capacitor at APCFILT with a recommended

value of 0.1µF.

APC closed-loop operation requires the user to set three

currents with external resistors connected between

ground and BIASMAX, MODSET, and APCSET. Detailed

guidelines for these resistor settings are described in

the Design Procedure section.

Open-Loop Operation

If necessary, the MAX3867 is fully operational without

APC. In this case, the laser current is directly set by two

external resistors connected from ground to BIASMAX

8 _______________________________________________________________________________________

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