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LTC2972

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ON_OFF_CONFIG

The ON_OFF_CONFIG command configures the combination of CONTROL pin input and PMBus commands needed

to turn the LTC2972 on/off, including the power-on behavior, as shown in the following table. This command register

responds to the global page command (PAGE = 0xFF). After the part has initialized, an additional comparator monitors

VIN_SNS. The VIN_ON threshold must be exceeded before the output power sequencing can begin. After VIN is ini-

tially applied, the part will typically require tINIT to initialize and begin the TON_DELAY timer. The readback of voltages

and currents may require an additional wait for tUPDATE_ADC. A minimum tOFF_MIN wait time must be observed for any

CONTROL pin used toggle to turn the unit off and then back on.

ON_OFF_CONFIG Data Contents

BIT(S) SYMBOL

OPERATION

b[7:5] Reserved

Don’t care. Always returns 0.

b[4] On_off_config_controlled_on

Control default autonomous power up operation.

0: Unit powers up regardless of the CONTROL pin or OPERATION value. Unit always powers up with

sequencing. To turn unit on without sequencing, set TON_DELAY = 0.

1: Unit does not power up unless commanded by the CONTROL pin and/or the OPERATION command on the

serial bus. If On_off_config[3:2] = 00, the unit never powers up.

b[3] On_off_config_use_pmbus

Controls how the unit responds to commands received via the serial bus.

0: Unit ignores the Operation_control[1:0].

1: Unit responds to Operation_control[1:0]. Depending on On_off_config_use_control, the unit may also

require the CONTROL pin to be asserted for the unit to start.

b[2] On_off_config_use_control

Controls how unit responds to the CONTROL pin.

0: Unit ignores the CONTROL pin.

1: Unit requires the CONTROL pin to be asserted to start the unit. Depending on On_off_config_use_pmbus

the OPERATION command may also be required to instruct the device to start.

b[1] Reserved

Not supported. Always returns 1.

b[0] On_off_config_control_fast_off CONTROL pin turn off action when commanding the unit to turn off.

0: Use the programmed TOFF_DELAY.

1: Turn off the output and stop transferring energy as quickly as possible. The device does not sink current in

order to decrease the output voltage fall time.

MFR_CONFIG_LTC2972

This command is used to configure various manufacturer specific operating parameters for each channel.

PMBus COMMAND DESCRIPTION

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