LTC4449 datasheet(83/108 Pages) LINER

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LTC3882-1

Rev A

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These commands can be used to establish required on/off sequencing for any number of system power supply rails.

MFR_RESTART_DELAY

The MFR_RESTART DELAY command specifies the minimum PWM off time (RUN low) in milliseconds. The LTC3882-1

will actively hold its RUN pin low for this length of time if a falling RUN edge is detected. After this delay, a standard

start-up sequence can be initiated. A minimum of TOFF_DELAY + TOFF_FALL + 136ms is recommended for this com-

mand value. Valid value range is 136ms to 65.52 seconds. The LTC3882-1 uses a resolution of 16ms for this command

and will not produce delays outside of this range.

This command has two data bytes in Linear_5s_11s format.

TON_DELAY

The TON_DELAY command sets the delay, in milliseconds, between a start condition and the beginning of the output

voltage rise. Values from 0ms to 83 seconds are considered valid, and the LTC3882-1 will not produce delays outside

of this range.

This command has two data bytes in Linear_5s_11s format.

TON_RISE

The TON_RISE command sets the desired time, in milliseconds, from the point the output starts to rise until it enters

the regulation band. Values from 0 seconds to 1.3 seconds are considered valid, and the LTC3882-1 will not produce

rise times outside of this range. Values of TON_RISE less than 0.25ms or resulting slopes greater than 4V/ms will

result in an output step to the commanded voltage limited only by PWM analog loop response.

This command has two data bytes in Linear_5s_11s format.

OUTPUT TIMING, DELAYS, AND RAMPING

COMMAND NAME

CMD

CODE DESCRIPTION

TYPE

PAGED

DATA

FORMAT UNITS NVM

DEFAULT

VALUE

MFR_RESTART_DELAY

0xDC Minimum time RUN pin is held low by the

LTC3882-1.

R/W Word

L11

500ms

0xFBE8

TON_DELAY

0x60 Delay from RUN pin or OPERATION on

command to TON_RISE ramp start.

R/W Word

L11

0.0ms

0x8000

TON_RISE

0x61 Time for VOUT to rise from 0V to

VOUT_COMMAND after TON_DELAY.

R/W Word

L11

8.0ms

0xD200

TON_MAX_FAULT_LIMIT

0x62 Maximum time for VOUT to rise above

VOUT_UV_FAULT_LIMIT after TON_DELAY.

R/W Word

L11

10.0ms

0xD280

VOUT_TRANSITION_RATE

0x27 VOUT slew rate for programmed output

changes.

R/W Word

L11

V/ms

0.25V/ms

0xAA00

TOFF_DELAY

0x64 Delay from RUN pin or OPERATION off

command to TOFF_FALL ramp start.

R/W Word

L11

0.0ms

0x8000

TOFF_FALL

0x65 Time for VOUT to fall to 0V from

VOUT_COMMAND after TOFF_DELAY.

R/W Word

L11

8.0ms

0xD200

TOFF_MAX_WARN_LIMIT

0x66 Maximum time for VOUT to decay below

12.5% of VOUT_COMMAND after TOFF_FALL

completes.

R/W Word

L11

150ms

0xF258

Related commands: MFR_RETRY_DELAY, STATUS_VOUT, SMBALERT_MASK, TON_MAX_FAULT_RESPONSE, MFR_CHAN_CONFIG_LTC3882-1,

MFR_PWM_MODE_LTC3882-1

PMBus COMMAND DETAILS (Output Timing, Delays, and Ramping)

LTC4449 Datasheet(PDF) 83 Page - Linear Technology

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