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LTC2972

2972fa

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MFR_IOUT_CAL_GAIN_TAU_INV Data Content

Bit(s) Symbol

Operation

b[15:0] Mfr_iout_cal_gain_tau_inv

Values ≤ 0 set MFR_T_SELF_HEAT to zero.

Values ≥ 1 set MFR_T_SELF_HEAT to MFR_IOUT_CAL_GAIN_THETA • READ_IOUT • (VISENSEP – VISENSEM).

TON_DELAY, TON_RISE, TON_MAX_FAULT_LIMIT and TOFF_DELAY

These commands share the same format and provide sequencing and timer fault and warning delays in ms.

TON_DELAY sets the amount of time in milliseconds that a channel waits following the start of an ON sequence before

its VOUT_EN pin enables a DC/DC converter. This delay is counted using SHARE_CLK only.

TON_RISE sets the amount of time in ms that elapses after the power supply has been enabled until the LTC2972’s

DAC soft connects and servos the output voltage to the desired level if Mfr_dac_mode = 00b. This delay is counted

using SHARE_CLK only.

TON_MAX_FAULT_LIMIT is the maximum amount of time that the power supply being controlled by the LTC2972 can

attempt to power up the output without reaching the VOUT_UV_FAULT_LIMIT. If it does not, then a TON_MAX_FAULT

is declared. If the output reaches VOUT_UV_FAULT_LIMIT prior to TON_MAX_FAULT_LIMIT, the LTC2972 unmasks

the VOUT_UV_FAULT_LIMIT threshold. (Note that a value of zero means there is no limit to how long the power supply

can attempt to bring up its output voltage.) This delay is counted using SHARE_CLK only.

TOFF_DELAY is the amount of time that elapses after the CONTROL pin and/or OPERATION command is de-asserted

until the channel is disabled (soft-off). This delay is counted using SHARE_CLK if available, otherwise the internal

oscillator is used.

TON_DELAY and TOFF_DELAY are internally limited to 13.1 seconds, and rounded to the nearest 10µs when smaller

than 655ms, or rounded to the nearest 200µs when larger than 655ms. TON_RISE and TON_MAX_FAULT_LIMIT are

internally limited to 655ms, and rounded to the nearest 10µs. The read value of these commands always returns what

was last written and does not reflect internal limiting.

SEQUENCING TIMING LIMITS AND CLOCK SHARING

COMMAND NAME

CMD

CODE DESCRIPTION

TYPE

PAGED FORMAT UNITS EEPROM

DEFAULT

VALUE

REF

PAGE

TON_DELAY

0x60 Time from CONTROL pin and/or OPERATION

command = ON to VOUT_ENn pin = ON.

R/W Word

L11

1.0

0xBA00

TON_RISE

0x61 Time from when the VOUT_ENn pin goes high until the

LTC2972 optionally soft-connects its DAC and begins

to servo the output voltage to the desired value.

R/W Word

L11

10.0

0xD280

TON_MAX_FAULT_LIMIT 0x62 Maximum time from VOUT_ENn pin on assertion that

an UV condition will be tolerated before a TON_MAX_

FAULT condition results.

R/W Word

L11

15.0

0xD3C0

TOFF_DELAY

0x64 Time from CONTROL pin and/or OPERATION

command = OFF to VOUT_ENn pin = OFF.

R/W Word

L11

1.0

0xBA00

MFR_RESTART_DELAY

0xDC Delay from actual CONTROL active edge to virtual

CONTROL active edge.

R/W Word

L11

400

0xFB20

PMBus COMMAND DESCRIPTION

LTC2972 Datasheet(PDF) 58 Page - Linear Technology

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