PMBus 6-Channel Power-Supply Manager

37

MFR_FAULT_RETRY (DAh)

The MFR_FAULT_RETRY command sets the delay time between a power supply being shut down by a fault response

and the power supply restarting. This command sets the retry time delay in multiples of 1ms. This command value is

used for all fault responses that require delay retry. If global supplies are being sequenced off, the retry delay time does

not begin until the last global channel is turned off. The 2 data bytes are in DIRECT format. When MFR_FAULT_RETRY

= 0000h, the device restarts the power supply at the next available time period.

MFR_NV_FAULT_LOG (DCh)

Each time the MFR_NV_FAULT_LOG command is executed, the device returns a block of 255 bytes containing one

of the 15 nonvolatile fault logs. The MFR_NV_FAULT_LOG command must be executed 15 times to dump the com-

plete nonvolatile fault log. If the returned fault log is all FFs, this indicates that this fault log has not been written by the

device. As the device is operating, it is reading the latest operating conditions for voltage, current, and temperature,

and it is updating the status registers. All this information is stored in on-board RAM. When a fault is detected (if so

enabled in MFR_FAULT_RESPONSE), the device automatically logs this information to one of the 15 nonvolatile fault

logs. After 15 faults have been written, bit 0 of STATUS_CML is set and the host must clear the fault log by setting the

CLEAR_NV_FAULT_LOG bit in MFR_MODE before any additional faults are logged. All the latest status information is

logged as well as eight readings of voltage from the last 800ms in 100ms increments and four readings of current from

the last 800ms of operation. If a power supply is not enabled to measure either current or voltage or if a temperature

sensor is disabled, the associated fault log position returns 0000h.

There is a FAULT_LOG_COUNT (16-bit counter) at the beginning of each fault log that indicates which fault log is

the latest. This counter rolls over should more than 65,535 faults be logged. This counter is not cleared when the

CLEAR_NV_FAULT_LOG bit in MFR_MODE is toggled. The 255 bytes returned by the MFR_NV_FAULT_LOG com-

mand are described in Table 24.

Table 23. MFR_FAULT_RESPONSE Codes

Note: ALERT is asserted if enabled when a new status bit is set. A status bit is latched the first time a particular fault or warning

occurs.

RESPONSE

SETTING

[1:0]

FAULT RESPONSE

11

•

Set the corresponding fault bit in the appropriate status register.

•

Log fault into MFR_NV_FAULT_LOG if NV_LOG = 1.

•

Continue power-supply operation.

10

•

Set the corresponding fault bit in the appropriate status register.

•

Log fault into MFR_NV_FAULT_LOG if NV_LOG = 1.

•

If GLOBAL = 1, assert the FAULT output until faults on all GLOBAL supplies clear and MFR_FAULT_RETRY

expires.

•

Shut down the power supply by deasserting the PSEN output. Wait for the time configured in

MFR_FAULT_RETRY and restart the supply. If GLOBAL = 1, all enabled power supplies with GLOBAL = 1

are shut down in sequence as configured with TOFF_DELAY, or they are all shut down immediately as con-

figured by bit 0 in ON_OFF_CONFIG. Wait for the time configured in MFR_FAULT_RETRY and restart sup-

plies in sequence as configured with TON_DELAY.

01

•

Set the corresponding fault bit in the appropriate status register.

•

Log fault into MFR_NV_FAULT_LOG if NV_LOG = 1.

•

If GLOBAL = 1, assert the FAULT output until power supplies are restarted by the user.

•

Latch-off the power supply by deasserting the PSEN output. If GLOBAL = 1, all enabled power supplies with

GLOBAL = 1 are either shut down in sequence as configured with TOFF_DELAY, or they are all shut down

immediately as configured by bit 0 in ON_OFF_CONFIG.

00

•

Set the corresponding fault bit in the appropriate status register.

•

Continue power-supply operation.