LTM4686BIVPBF datasheet(24/130 Pages) AD

24 / 130 page

LTM4686B

Rev. 0

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OPERATION

its switching frequency to a clock signal supplied to

its SYNC pin when MFR_CONFIG_ALL[4] = 1b. These

parameters can be configured at SVIN power-up accord-

ing to resistor-pin strapping of the FSWPHCFG pin, pro-

vided MFR_CONFIG_ALL[6] = 0b.

Output voltage turn-on and turn-off sequencing and

associated watchdog timers, namely:

• Output voltage turn-on delay time (the time delay

from the LTM4686B being commanded to turn

on, e.g., by the RUNn pin toggling from logic

low to high, before switching action commences.

TON_DELAYn).

• Output voltage soft-start ramp-up time (TON_RISEn).

• The amount of time (TON_MAX_FAULT_LIMITn)

permitted to elapse after the LTM4686B is com-

manded to turn on, e.g., by the RUNn pin toggling

from logic low to high, after which, if the output

voltage fails to exceed the output undervoltage

fault threshold (VOUT_UV_FAULT_LIMITn), the

LTM4686B’s output (VOUTn) is declared to have not

come up in a timely manner.

• The LTM4686B’s response to any such afore-

mentioned TON_MAX_FAULT_LIMITn event

(TON_MAX_FAULT_RESPONSEn).

• Output voltage soft-stop ramp-down time

(TOFF_FALLn).

• Output voltage turn-off delay time (the time delay

from the LTM4686B being commanded to turn off,

e.g., by the RUNn pin toggling from logic high to low,

before switching action ceases. TOFF_DELAYn).

• When commanded to turn off its output—or,

when turning off its output in response to a fault—

configuring whether the LTM4686B’s output (VOUTn)

becomes high impedance (“High-Z” or “three

state”—turning off both MTn and MBn in the power

stage). (“Immediate Off”, ON_OFF_CONFIGn[0] = 1b

vs configuring the output voltage to be ramped down

according to TOFF_FALLn and/or TOFF_DELAYn set-

tings, ON_OFF_CONFIGn[0] = 0b).

• The amount of time (TOFF_MAX_WARN_LIMITn)

permitted to elapse after the LTM4686B is supposed

to have turned off its output, i.e., at the end of the

period dictated by TOFF_FALLn, after which, If the

output voltage has not fallen below 12.5% of the

former target voltage of regulation, the LTM4686B’s

output (VOUTn) is declared to have not powered

down in a timely manner.

Configurable output voltage restart time. Subsequent to

theRUNn pinbeingpulledlow,theLTM4686BpullsRUNn

logic low, itself, and the output cannot be restarted until a

minimum time has elapsed—the restart delay time. This

delay assures proper sequencing of all system rails. The

minimum restart delay processed by the LTM4686B is

the longer of (TOFF_DELAYn + TOFF_FALLn + 136ms)

vs the commanded MFR_RESTART_DELAYn register

value. At the end of this delay, the LTM4686B releases

its RUNn pin.

Configurable fault-hiccup retry delay time. When a

fault occurs in which the LTM4686B’s fault response

behavior to that fault is to reattempt power-up of its out-

put voltage after said fault ceases to be present (e.g.,

“Infinite Retry”), the delay time for the LTM4686B to

re-engage switching action is the longer of the MFR_

RETRY_DELAYn time vs the time required for the out-

put to decay below 12.5% of the formerly commanded

output voltage value (unless this latter most criteria, i.e.,

requiring the output to decay below 12.5% is negated by

the setting of MFR_CHAN_CONFIGn[0] to “1b”—which

is the LTM4686B’s factory-NVM default setting).

Output over/undervoltage fault responses (VOUT_OV_

FAULT_RESPONSEn, VOUT_UV_FAULT_RESPONSEn).

Time-averaged current limit warning and instanta-

neous peak (cycle-by-cycle) fault thresholds, and

fault response (IOUT_OC_WARN_LIMITn, IOUT_OC_

FAULT_LIMITn, IOUT_OC_FAULT_RESPONSEn).

Channel (VOUT0, VOUT1) overtemperature warning

and fault thresholds, and fault response (OT_WARN_

LIMITn, OT_FAULT_LIMITn, OT_FAULT_RESPONSEn).

Channel (VOUT0, VOUT1) undertemperature fault

thresholds and fault response (UT_FAULT_LIMITn,

UT_FAULT_RESPONSEn).

LTM4686BIVPBF 数据表(PDF) 24 Page - Analog Devices

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