LTC2972 datasheet(53/112 Pages) LINER

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LTC2972

2972fa

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VOUT_COMMAND, VOUT_MAX, VOUT_MARGIN_HIGH, VOUT_MARGIN_LOW, VOUT_OV_FAULT_LIMIT,

VOUT_OV_WARN_LIMIT, VOUT_UV_WARN_LIMIT, VOUT_UV_FAULT_LIMIT, POWER_GOOD_ON and

POWER_GOOD_OFF

These commands provide various servo, margining and supervising limits for a channel’s output voltage.

MFR_VOUT_DISCHARGE_THRESHOLD

This register contains the coefficient that multiplies VOUT_COMMAND in order to determine the OFF threshold volt-

age for the associated output. If the output voltage has not decayed below MFR_VOUT_DISCHARGE_THRESHOLD •

VOUT_COMMAND prior to the channel being commanded to enter/re-enter the ON state, the Status_mfr_discharge bit

in the STATUS_MFR_SPECIFIC register will be set and the ALERTB pin will be asserted low. In addition, the channel

will not enter the ON state until the output has decayed below its off-threshold voltage. Setting this to a value greater

than 1.0 effectively disables DISCHARGE_THRESHOLD checking, allowing the channel to turn back on even if it has

not decayed at all.

Other channels can be held-off if a particular output has failed to discharge by using the bidirectional FAULTBn pins

(refer to the MFR_FAULTBn_RESPONSE and MFR_FAULTBn_PROPOGATE registers).

MFR_DAC_STARTUP

This command register programs the 10-bit DAC to a specific DAC code when a channel is enabled with the DAC

set to connect immediately and servo is disabled (MFR_CONFIG_LTC2972 b[5:4] = 10b). This value is loaded from

EEPROM at power-on-reset or after a RESTORE USER_ALL command. After loading, all subsequent DAC values are

set by writing to the MFR_DAC command register. If soft-connect mode is enabled, the value in this register is ignored.

MFR_DAC_STARTUP Data Contents

BIT(S) SYMBOL

OPERATION

b[15:10] Reserved

Read only, always returns 0.

b[9:0] Mfr_dac_startup_val

DAC code value.

MFR_DAC

This command register allows the user to directly program the 10-bit DAC. Manual DAC writes require the chan-

nel to be in the ON state,TON_RISE to have expired and MFR_CONFIG_LTC2972 b[5:4] = 10b or 11b. Writing

MFR_CONFIG_LTC2972 b[5:4] = 10b commands the DAC to hard connect with the value in Mfr_dac_direct_val.

Writing b[5:4] = 11b commands the DAC to soft connect. Once the DAC has soft connected, Mfr_dac_direct_val

returns the value that allowed the DAC to be connected without perturbing the power supply. MFR_DAC writes are

ignored when MFR_CONFIG_LTC2972 b[5:4] = 00b or 01b.

PMBus COMMAND DESCRIPTION

LTC2972 Datasheet(PDF) 53 Page - Linear Technology