LTC2975_15 Datasheet, PDF (51/104 Pages) Linear Technology – 4-Channel PMBus Power System Manager Featuring Accurate Input Current and Energy Measurement

LTC2975
PMBus Command Description
VOUT_MODE
This command is read only and specifies the mode and exponent for all commands with a L16 data format. See
Data Formats on page 27.
VOUT_MODE Data Contents
BIT(S) SYMBOL
OPERATION
b[7:5] Vout_mode_type
Reports linear mode. Hard-wired to 000b.
b[4:0] Vout_mode_parameter Linear mode exponent. 5-bit two’s complement integer. Hardwired to 0x13 (–13 decimal).
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 voltage
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
This command register allows the user to directly program the 10-bit DAC. Manual DAC writes require the channel
to be in the ON state,TON_RISE to have expired and MFR_CONFIG_LTC2975 b[5:4] = 10b or 11b. Writing MFR_
CONFIG_LTC2975 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_LTC2975 b[5:4] = 00b or 01b.
MFR_DAC Data Contents
BIT(S) SYMBOL
OPERATION
b[15:10] Reserved
Read only, always returns 0.
b[9:0] Mfr_dac_direct_val DAC code value.
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