Datasheet

( )
= ´ ´ + +
Exponent
IN
V Mantissa 2 1 READ _ VIN _ CAL _ GAIN READ _ VIN _ CAL _ OFFSET
( )
= ´ ´ + +
Exponent
OUT
V Mantissa 2 1 READ _ VOUT _ CAL _ GAIN READ _ VOUT _ CAL _ OFFSET
TPS40400
SLUS930B –APRIL 2011– REVISED OCTOBER 2011 www.ti.com
READ_VIN (88h)
The READ_VIN commands returns two bytes of data in the linear data format that represent the input voltage
applied to the VDD pin of the controller. The data format is as follows:
Command READ_VIN
Format Linear, two's complement binary
Bit Position 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
Access r r r r r r r r r r r r r r r r
Function Exponent Mantissa
Default Value 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0
The input voltage is scaled before it reaches the internal analog to digital converter so that resolution of the input
voltage read back is 31.25mV. The input voltage can be found using Equation 25.
(25)
Exponent
Fixed at –5.
Mantissa
The lower 10 bits are the result of the ADC conversion of the input voltage. The 11
th
bit is fixed at 0 because only
positive numbers are considered valid.
READ_VIN_CAL_GAIN comes from the MFR_SPECIFIC_06 command
READ_VIN_CAL_OFFSET comes from the MFR_SPECIFIC_07 command
READ_VOUT (8Bh)
The READ_VOUT commands returns two bytes of data in the linear data format that represent the output voltage
of the controller. The output voltage is sensed at the ISNS- pin so voltage drop to the load is not accounted for.
The data format is as follows:
Command READ_VOUT
Format Linear, two's complement binary
Bit Position 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
Access r r r r r r r r r r r r r r r r
Function Mantissa
Default Value 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
The setting of the VOUT_MODE affects the results of this command as well. In the TPS40400, VOUT_MODE is
set to linear mode with an exponent of –10 and cannot be altered. The output voltage can be found by:
(26)
Exponent
Fixed at -10 by VOUT_MODE
Mantissa
Bits 13 (bit 5 in high order byte) through 4 are the result of the ADC conversion of the ouput voltage. The
effective LSB using this scheme is 15.625 mV.
READ_VOUT_CAL_GAIN is derived from the MFR_SPECIFIC_05 command
READ_VOUT_CAL_OFFSET is derived from the MFR_SPECIFIC_04 command
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