Datasheet

TPS40400

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SLUS930B –APRIL 2011– REVISED OCTOBER 2011

SUPPORTED COMMANDS

The TPS40400 supports the following commands from the PMBus 1.1 specification.

OPERATION (01h)

The OPERATION command is used to turn the device output on or off in conjunction with the input from the

CONTROL pin. It is also used 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 a change in the state of the

CONTROL pin instructs the device to change to another mode.

Command OPERATION

Format Unsigned binary

Bit Position 7 6 5 4 3 2 1 0

Access r/w r r/w r/w r/w r/w r r

Function ON X Margin X X

Default Value 0 0 0 0 0 0 X X

This bit is an enable command to the converter.

• 0: output switching is disabled. Both drivers placed in an off or low state.

• 1: output switching is enabled. The device is allowed to begin power conversion assuming no fault conditions

exist.

Margin

If Margin Low is enabled, load the value from the VOUT_MARGIN_LOW command. If Margin High is enabled,

load the value from the VOUT_MARGIN_HIGH command. (See PMBus specification for more information)

• 00XX: Margin Off

• 0101: Margin Low (Ignore Fault)

• 0110: Margin Low (Act on Fault)

• 1001: Margin High (Ignore Fault)

• 1010: Margin High (Act on Fault)

Note that the reference voltage used for overvoltage, undervoltage detection and power good are derived from

the actual reference voltage in effect at the time. Setting a margin to test for one of these fault conditions does

not work. Testing for these conditions must be done by forcing the FB pin to a voltage that would trip these fault

conditions based on the current reference voltage and the percentage difference from this level set by the

threshold setting commands.

ON_OFF_CONFIG (02h)

The ON_OFF_CONFIG command configures the combination of CNTL pin input and serial bus commands

needed to turn the unit on and off. The contents of this register can be stored to non-volatile memory using the

STORE_DEFAULT_ALL or STORE_DEFAULT_CODE commands.

Command ON_OFF_CONFIG

Format Unsigned binary

Bit Position 7 6 5 4 3 2 1 0

Access r r r r/w r/w r/w r/w r

Function X X X pu cmd cpr pol cpa

Default Value X X X 1 0 1 1 1

The pu bit sets the default to either operate any time power is present or for the on/off to be controlled by CNTL

pin and PMBus OPERATION command. This bit is used in conjunction with the 'cp', 'cmd', and 'on' bits to

determine start up.

Product Folder Link(s) :TPS40400