LTM4686BIVPBF datasheet(35/130 Pages) AD

35 / 130 page

LTM4686B

Rev. 0

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OPERATION

will continue to retry. The retry interval is specified by the

MFR_RETRY_DELAY command and prevents damage to

the regulator components by repetitive power cycling. The

MFR_RETRY_DELAY must be greater than 120ms. It can

not exceed 83.88 seconds.

Channel-to-channel fault dependencies can be created by

connecting GPIOn pins together. In the event of an internal

fault, one or more of the channels is configured to pull

the bussed GPIOn pins low. The other channels are then

configured to shut down when the GPIOn pins are pulled

low. For autonomous group retry, the faulted channel is

configured to release the GPIOn pin(s) after a retry interval,

assuming the original fault has cleared. All the channels

in the group then begin a soft-start sequence. If the fault

response is LATCH_OFF, the GPIOn pin remains asserted

low until either the RUN pin is toggled OFF/ON or the part is

commanded OFF/ON. The toggling of the RUN either by the

pin or OFF/ON command will clear faults associated with

the channel. If it is desired to have all faults cleared when

either RUN pin is toggled, set bit 0 of MFR_CONFIG_ALL

to a 1.

The status of all faults and warnings is summarized in the

STATUS_WORD and STATUS_BYTE commands.

RESPONSES TO VOUT AND IOUT FAULTS

VOUT OV and UV conditions are monitored by compara-

tors. The OV and UV limits are set in three ways.

As a Percentage of the VOUT if Using the Resistor

Configuration Pins

In EEPROM if Either Programmed at the Factory or

Through the GUI

By PMBus Command

The IIN and IOUT overcurrent monitors are performed by

ADC readings and calculations. Thus these values are

based on average currents and can have a nominal time

latency of up to 90ms. The IOUT calculation accounts

for the power inductor DCR and the temperature coef-

ficient of the inductor’s copper winding. The input cur-

rent is equal to the sum of output current times the

respective channel duty cycle plus the input offset cur-

rent for each channel. If this calculated input current

exceeds the IIN_OC_WARN_LIMIT the ALERT pin is

pulled low and the IIN_OC_WARN bit is asserted in the

STATUS_INPUT register.

The LTM4686B provides the ability to ignore the fault,

shut down and latch off or shut down and retry indefinitely

(hiccup). The retry interval is set in MFR_RETRY_DELAYn

and can be from 120ms to 83.88 seconds in 1ms incre-

ments. The shutdown for OV/UV and OC can be done

immediately or after a user selectable deglitch time.

Output Overvoltage Fault Response

A programmable overvoltage comparator (OV) guards

against transient overshoots as well as long-term over-

voltages at the output. In such cases, the top MOSFET is

turned off and the bottom MOSFET is turned on until the

overvoltage condition is cleared regardless of the PMBus

VOUT_OV_FAULT_RESPONSEn command byte value.

This hardware level fault response delay is typically 2µs

from the overvoltage condition to BG asserted high. Using

the VOUT_OV_FAULT_RESPONSEn command, the user

can select any of the following behaviors:

OV Pull-Down Only (OV cannot be ignored)

Shut Down (Stop Switching) Immediately—Latch Off

Shut Down Immediately—Retry Indefinitely using the

Time Interval Specified in MFR_RETRY_DELAYn

Either the Latch Off or Retry fault responses can be

deglitched in increments of (0 to 7) • 10µs. See Table 24.

Output Undervoltage Response

The response to an undervoltage comparator output can

be either:

Ignore

Shut Down Immediately—Latch Off

Shut Down Immediately—Retry Indefinitely using the

Time Interval Specified in MFR_RETRY_DELAYn

Either the Latch Off or Retry fault responses can be

deglitched in increments of (0 to 7) • 10µs. See Table 25.

LTM4686BIVPBF 数据表(PDF) 35 Page - Analog Devices

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