LTC3883 Datasheet, PDF (67/112 Pages) Linear Technology – Single Phase Step-Down DC/DC Controller with Digital Power System Management

LTC3883/LTC3883-1
PMBus Command Details
Table 3. ON_OFF_CONFIG Detailed Command Information
ON_OFF_CONFIG Data Contents
BITS(S) SYMBOL
OPERATION
b[7:5] Reserved
Don’t care. Always returns 0.
b[3] On_off_config_use_pmbus
Controls how the unit responds to commands received via the serial bus.
0: Unit ignores the Operation command b[7:6].
1: Unit responds to Operation command b[7:6]. The unit also requires the RUN pin to be asserted for the
unit to start.
b[0] On_off_config_control_fast_off RUN 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.
Note: A high on the RUN pin is always required to start power conversion. Power conversion will always stop with a low on RUN.
OPERATION
The OPERATION command is used to turn the unit on and off in conjunction with the input from the RUN pin. It is
also used to cause the unit to set the output voltage to the upper or lower MARGIN VOLTAGEs. The unit stays in
the commanded operating mode until a subsequent OPERATION command or change in the state of the RUN pin
instructs the device to change to another mode. If the part is stored in the MARGIN_LOW/HIGH state, the next RESET
or POWER_ON cycle will ramp to that state. If the OPERATION command is modified, for example ON is changed to
MARGIN_LOW, the output will move at a fixed slope set by the VOUT_TRANSITION_RATE.
Margin High (Ignore Faults) and Margin Low (Ignore Faults) operations are not supported by the LTC3883.
The part defaults to the ON state.
This command has one data byte.
Table 4. OPERATION Command Detail Command
OPERATION Data Contents When On_Off_Config_Use_PMBus Enables
Operation_Control
SYMBOL
ACTION
VALUE
BITS
Turn off immediately
0x00
Turn on
0x80
FUNCTION Margin Low
0x98
Margin High
0xA8
Sequence off
0x40
OPERATION Data Contents When On_Off_Config is Configured Such That
OPERATION Command is Not Used to Command Channel On or Off
SYMBOL
ACTION
VALUE
BITS
Output at Nominal
0x80
FUNCTION Margin Low
0x98
Margin High
0xA8
Note: Attempts to write a reserved value will cause a CML fault.
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