LTM4686BIVPBF datasheet(37/130 Pages) AD

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LTM4686B

Rev. 0

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are used to determine the appropriate response to

an overtemperature and undertemperature condition,

respectively.

The fault responses are:

Ignore

Shut Down Immediately—Latch Off

Shut Down Immediately—Retry Indefinitely using the

Time Interval Specified in MFR_RETRY_DELAYn

See Table 28.

RESPONSES TO EXTERNAL FAULTS

When either GPIOn pin is pulled low, the OTHER bit is

set in the STATUS_WORD command, the appropriate bit

is set in the STATUS_MFR_SPECIFC command, and the

ALERT pin is pulled low. Responses are not deglitched.

Each channel can be configured to ignore or shut down

then retry in response to its GPIOn pin going low by modi-

fying the MFR_GPIO_RESPONSEn command. To avoid

the ALERT pin asserting low when GPIOn is pulled low,

assert bit 1 of MFR_CHAN_CONFIGn, or mask the ALERT

using the SMBALERT_MASK command.

FAULT LOGGING

The LTM4686B has fault logging capability. Data is logged

into memory in the order shown in Table 30. The data to

be stored in the fault log is being continuously stored in

internal volatile memory. When a fault event occurs, the

recording into internal volatile memory is halted, the fault

log information is available from the MFR_FAULT_LOG

command, and the contents of the internal memory are

copied into EEPROM. Fault logging is allowed at tempera-

tures above 85°C; however, retention of 10 years is not

guaranteed. When the die temperature exceeds 130°C the

fault logging is delayed until the die temperature drops

below 125°C. After the fault condition that created the

fault log event has been removed, clear the fault before the

fault log data is erased, or else the part will immediately

issue another fault log.

OPERATION

When the LTM4686B powers-up, it checks the EEPROM

for a valid fault log. If a valid fault log exists in EEPROM,

the “Valid Fault Log” bit in the STATUS_MFR_SPECIFIC

command will be set and an ALERT event will be gen-

erated. Also, fault logging will be blocked until the

LTM4686B has received a MFR_FAULT_LOG_CLEAR

command before fault logging will be re-enabled.

The information is stored in EEPROM in the event of

any fault that disables the controller on either channel.

An external GPIOn pulling low will not trigger a fault

logging event.

BUS TIMEOUT PROTECTION

The LTM4686B implements a timeout feature to avoid

hanging the serial interface. The data packet timer begins

at the first START event before the device address write

byte. Data packet information must be completed within

25ms or the LTM4686B will three-state the bus and ignore

the given data packet. If more time is required, assert

bit 3 of MFR_CONFIG_ALL to allow typical bus timeouts

of 255ms. Data packet information includes the device

address byte write, command byte, repeat start event (if a

read operation), device address byte read (if a read opera-

tion), all data bytes and the PEC byte if applicable.

The LTM4686B allows longer PMBus timeouts for block

read data packets. This timeout is proportional to the

length of the block read. The additional block read timeout

applies primarily to the MFR_FAULT_LOG command. In

no circumstances will the timeout period be less than the

tTIMEOUT_SMB specification of 32ms (typical).

The user is encouraged to use as high a clock rate

as possible to maintain efficient data packet transfer

between all devices sharing the serial bus interface. The

LTM4686B supports the full PMBus frequency range

from 10kHz to 400kHz.

LTM4686BIVPBF 数据表(PDF) 37 Page - Analog Devices

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