TPSM831D31: 8Ch READ_IOUT

Hi,

The READ_IOUT (8Ch) command returns the output current for the selected PAGE (00h) and PHASE (04h).

If PAGE is set to 00h, the current returned by READ_IOUT will correspond to channel A, and if PAGE is set to 01h READ_IOUT will give current for channel B.

READ_IOUT is also a phased register, meaning that the current value returned depends on the value in PHASE. The set value in PHASE will determine which phase on a channel commands will access, or if they will access all phases on a channel at once. For example, a PHASE value of 00h will cause READ_IOUT to return the output current for the first phase on that channel, where channel A or B is set by the PAGE register.

PHASE can be set from 00h to 05h for the 1st through 6th phases on a channel, but should not be set to a higher phase than is present in the design. TPSM831D31 has 3 phases on its 1st channel, and 1 phase on the 2nd. If PHASE is set to FFh, READ_IOUT will return the total current for that channel, summed together from all phases.

IOUT_CAL_GAIN (38h) sets the gain used by the controller to calculate output current from the current sense voltage. The current sense voltage provided by the power stages is expected to increase by 5mV for every additional Amp of current, so IOUT_CAL_GAIN should be left at 5mohm (hex value of D140h) in most cases. In the case that the current sense voltage gain and the controller gain is slightly mismatched, IOUT_CAL_GAIN can be used to tune the controller gain.

You can find additional information on using IOUT_CAL_GAIN to tune current reporting in the datasheet for TPS53681, which is the controller used internal to TPSM831D31, available on TI.com: https://www.ti.com/product/TPS53681 

Regards,

Troy