TPS40425_15 Datasheet, PDF (69/95 Pages) Texas Instruments – TPS40425 Dual Output, 2-Phase, Stackable PMBus™ Synchronous Buck Driverless Controller with Adaptive Voltage Scaling (AVS) Bus

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TPS40425
SLUSBO6A – JANUARY 2014 – REVISED JULY 2014
Bits
Field Name
3
TX2
2:1
PAYLOAD<1:0>
0
SLEW
Description
(Format: binary)
Default: 0b
AVS Double Transmission Check Select
This bit is used to force the AVS slave to require any AVS command to be issued twice before it is
acted upon.
0: Every commit-write actually takes effect as indicated by the AVS Master.
1: Every commit-write attempt must be performed twice for it to take effect.
This bit should not change while AVS is enabled.
(Format: binary)
Default: 01b
AVS Payload Configuration
This bit-field determines the number of bits that the device uses for sending “Voltage” in an AVS
read frame, as well as the number of bits that the device expects in an AVS write frame.
Considering that TPS40425’s encoding for the DAC voltage requires 10 bits, the setting for 8 bits
is not acceptable .
00: 8-bit voltage – Reserved, not to be used in TPS40425.
01: 10-bit voltage, the minimum size (and the default setting).
10: 12-bit voltage. Allowed.
11: 16-bit voltage. Allowed.
This bit field should not change while AVS is enabled.
(Format: binary)
Default: 0b
AVS Slew rate select
This bit is used to select between fast (default) and slow AVS transition rates by adjusting the slew
rate of the error-amplifier reference voltage VREF.
0: Fast AVS slew rate selected (200 mV / 30 µs)
1: Slow AVS rate selected (2 mV / 30 µs – slowest soft-start rate)
Table 15 summarizes the various mode transitions.
INITIAL MODE
AVS
AVS
AVS
AVS
AVS
AVS_STARTUP
AVS_STARTUP
AVS_STARTUP
AVS_STARTUP
PMBus
PMBus
PMBus
PMBus
Table 15. Mode State Transitions
INPUT
CONDITIONS
AVS_EN AVS_STUP
X
X
1
0
1
1
0
X
X
1
X
1
1
0
1
1
0
X
X
X
0
X
1
0
1
1
IF THIS EVENT
OCCURS
No power-cycle
Power cycle
Power cycle
Power cycle
No power cycle
No power cycle
With or without power cycle
Power cycle
Power cycle
No power cycle
Power cycle
Power cycle
Power cycle
FINAL
MODE
AVS
AVS
AVS_STARTUP
PMBus
AVS_STARTUP
AVS_STARTUP
AVS
AVS_STARTUP
PMBus
PMBus
PMBus
AVS
AVS_STARTUP
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