MAX34440 datasheet(21/43 Pages) MAXIM

21 / 43 page

PMBus 6-Channel Power-Supply Manager

Fault Management and Reporting

For reporting faults/warnings to the host on a real-time

basis, the device asserts the open-drain ALERT pin (if

enabled in MFR_MODE) and sets the appropriate bit in

the various status registers. On recognition of the ALERT

assertion, the host or system manager is expected to poll

the I2C bus to determine the device asserting ALERT.

The host sends the SMBus ARA (0001 100). The device

ACKs the SMBus ARA, transmits its slave address, and

deasserts ALERT. The system controller then communi-

cates with PMBus commands to retrieve the fault/warn-

ing status information from the device.

See the individual command sections for more details.

Faults and warnings that are latched in the status regis-

ters are cleared when any one of the following conditions

occurs:

• ACLEAR_FAULTScommandisreceived.

• TheRST pin is toggled.

• Biaspowertothedeviceisremovedandthenreapplied.

One or more latched-off power supplies is only restarted

when one of the following occurs:

• The output is commanded through the CONTROL

pin, the OPERATION command, or the combined

action of the CONTROL pin and OPERATION com-

mand to turn off and then turn back on.

• TheRST pin is toggled.

• Biaspowertothedeviceisremovedandthenreapplied.

A power supply is not allowed to turn on if any faults the

supply responds to are detected. Only after the faults

clear is the power supply allowed to turn on. When global

supplies are being sequenced on, a fault on any of the

supplies keeps all supplies from being turned on.

A system-wide power-up (OPERATION command is

received to turn the supplies on when PAGE is 255 or the

CONTROL pin is toggled to turn on the supplies) allows

all enabled power supplies to power-up. If any faults are

detected once the supplies start to turn on, the response

of MFR_FAULT_RESPONSE is performed.

The device responds to fault conditions accord-

ing to the manufacturer fault response command

(MFR_FAULT_RESPONSE). This command byte deter-

mines how the device should respond to each particular

fault. Table 5 illustrates the required conditions and fault

actions for specific parameters.

System Watchdog Timer

The device uses an internal watchdog timer that is inter-

nally reset every 5ms. In the event that the device is

locked up and this watchdog reset does not occur after

500ms, the device automatically resets. After the reset

occurs, the device reloads all configuration values that

were stored to flash and begins normal operation. After

the reset, the device also does the following:

1) Sets the NONE OF THE ABOVE bit in STATUS_BYTE.

2) Sets the NONE OF THE ABOVE and MFR bits in

STATUS_WORD.

3) Sets the WATCHDOG bit in STATUS_MFR_SPECIFIC.

4) Notifies the host through ALERT assertion (if enabled

in MFR_MODE).

Table 5. Device Parametric Monitoring States

PARAMETER

REQUIRED CONDITIONS FOR ACTIVE MONITORING

ACTION DURING A FAULT

Overvoltage

Power Supply Enabled (TON_MAX_FAULT_LIMIT ≠ 0000h)

Continue Monitoring

Undervoltage

•

Power Supply Enabled (TON_MAX_FAULT_LIMIT ≠ 0000h)

•

PSEN Output is Active

•

Channel’s VOUT Must Have Exceeded VOUT_UV_FAULT During

Channel Power-Up

Stop Monitoring While the Power

Supply is Off

Overcurrent

•

Power Supply Enabled (TON_MAX_FAULT_LIMIT ≠ 0000h)

•

Current Monitoring Enabled (IOUT_OC_FAULT_LIMIT ≠ 0000h)

Continue Monitoring

Power-Up Time

Power Supply Enabled (TON_MAX_FAULT_LIMIT ≠ 0000h)

Monitor Only During Power-On

Overtemperature

Temp Sensor Enabled (ENABLE in MFR_TEMP_SENSOR_CONFIG = 1)

Continue Monitoring

MAX34440 Datasheet(PDF) 21 Page - Maxim Integrated Products

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