MAX3646 데이터 시트보기 (PDF) - Maxim Integrated

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MAX3646

155Mbps to 622Mbps SFF/SFP Laser Driver with Extinction Ratio Control

Maxim Integrated 

155Mbps to 622Mbps SFF/SFP

Laser Driver with Extinction Ratio Control

Table 2. Circuit Responses to Various Single-Point Faults

PIN

CIRCUIT RESPONSE TO OVERVOLTATGE OR

SHORT TO VCC

TX_FAULT Does not affect laser power.

TX_DISABLE Modulation and bias currents are disabled.

The optical average power increases and a fault occurs

IN+

if VPC_MON exceeds the threshold. The APC loop

responds by decreasing the bias current.

The optical average power decreases and the APC loop

IN-

responds by increasing the bias current. A fault state

occurs if VBC_MON exceeds the threshold voltage.

MD

This disables bias current. A fault state occurs.

CIRCUIT RESPONSE TO UNDERVOLTAGE OR

SHORT TO GROUND

Does not affect laser power.

Normal condition for circuit operation.

The optical average power decreases and the APC loop

responds by increasing the bias current. A fault state

occurs if VBC_MON exceeds the threshold voltage.

The optical average power increases and a fault occurs

if VPC_MON exceeds the threshold. The APC loop

responds by decreasing the bias current.

The APC circuit responds by increasing the bias current

until a fault is detected, then a fault* state occurs.

SHUTDOWN

Does not affect laser power. If the shutdown circuitry is

used, the laser current is disabled.

Does not affect laser power.

BIAS

In this condition, the laser forward voltage is 0V and no

light is emitted.

Fault state* occurs. If the shutdown circuitry is used, the

laser current is disabled.

OUT+

The APC circuit responds by increasing the bias current Fault state* occurs. If the shutdown circuitry is used, the

until a fault is detected, then a fault state* occurs.

laser current is disabled.

OUT-

PC_MON

BC_MON

Does not affect laser power.

Fault state* occurs.

Fault state* occurs.

Does not affect laser power.

Does not affect laser power.

Does not affect laser power.

APCFILT1 IBIAS increases until VBC_MON exceeds the threshold

voltage.

IBIAS increases until VBC_MON exceeds the threshold

voltage.

APCFILT2

IBIAS increases until VBC_MON exceeds the threshold

voltage.

IBIAS increases until VBC_MON exceeds the threshold

voltage.

MODSET Does not affect laser power.

Fault state* occurs.

APCSET Does not affect laser power.

Fault state* occurs.

*A fault state asserts the TX_FAULT pin, disables the modulation and bias currents, and asserts the SHUTDOWN pin.

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