LTM4686BIVPBF datasheet(101/130 Pages) AD

101 / 130 page

LTM4686B

101

Rev. 0

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APPENDIX C: PMBUS COMMAND DETAILS

Table 24. VOUT_OV_FAULT_RESPONSE Data Byte Contents

BITS DESCRIPTION

VALUE MEANING

7:6

Response

For all values of bits [7:6], the LTM4686B:

• Sets the corresponding fault bit in the status commands and

• Notifies the host by asserting ALERT pin, unless masked.

The fault bit, once set, is cleared only when one or more of the

following events occurs:

• The device receives a CLEAR_FAULTS command.

• The output is commanded through the RUNn pin, the OPERATION

command, or the combined action of the RUNn pin and

OPERATION command, to turn off and then to turn back on, or

• Bias power is removed and reapplied to the LTM4686B.

Part performs OV pull down only (i.e., turns off the top

MOSFET and turns on lower MOSFET while VOUT is >

VOUT_OV_FAULT)

The PMBus device continues operation for the delay time

specified by bits [2:0] and the delay time unit specified for that

particular fault. If the fault condition is still present at the end of

the delay time, the unit responds as programmed in the Retry

Setting (bits [5:3]).

The device shuts down immediately (disables the output) and

responds according to the retry setting in bits [5:3].

Not supported. Writing this value will generate a CML fault.

5:3

Retry Setting

000–110 The unit does not attempt to restart. The output remains

disabled until the fault is cleared until the device is commanded

OFF bias power is removed.

111

The PMBus device attempts to restart continuously, without

limitation, until it is commanded OFF (by the RUNn pin or

OPERATION command or both), bias power is removed, or

another fault condition causes the unit to shut down without

retry. Note: The retry interval is set by the MFR_RETRY_DELAY

command.

2:0

Delay Time

XXX

The delay time in 10µs increments. This delay time determines

how long the controller continues operating after a fault is

detected. Only valid for deglitched off state

VOUT_UV_FAULT_RESPONSE

The VOUT_UV_FAULT_RESPONSE command instructs the device on what action to take in response to an output

undervoltage fault. The data byte is in the format given in Table 25.

The device also:

• Sets the VOUT bit in the STATUS_WORD

• Sets the VOUT undervoltage fault bit in the STATUS_VOUT command

• Notifies the host by asserting ALERT pin, unless masked.

The UV fault and warn are masked until the following criteria are achieved:

1) The TON_MAX_FAULT_LIMIT has been reached

2) The TON_DELAY sequence has completed

3) The TON_RISE sequence has completed

4) The VOUT_UV_FAULT_LIMIT threshold has been reached

5) The IOUT_OC_FAULT_LIMIT is not present

The UV fault and warn are masked whenever the channel is not active.

The UV fault and warn are masked during TON_RISE and TOFF_FALL sequencing.

This command has one data byte.

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