PAC1721 datasheet(43/92 Pages) MICROCHIP

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DS-20007088A-page 43

PAC1721

bit 55:0

VACC[55:0]: The Accumulator (VACC) stores, by default, the accumulated sum of VPOWER calculations.

It can accumulate VBUS or VSENSE measurements if the ACC_CONFIG[1:0] bits in the CONTROL

The stored values are 56-bit unsigned numbers, unless either VBUS or VSENSE is configured to have a

Bipolar range. In that case, the values are stored using 55 bits and one sign bit (2’s complement).

A Refresh command resets the register, while a Refresh_V does not.

When changing the type of results (VBUS, VSENSE or VPOWER) accumulated in the VACC register using

a Refresh_V command, already accumulated results are not reset. This results in the VACC register

containing both new and old values. Send a Refresh command to completely reset the register.

This register uses 12 bits to store VBUS and VSENSE results and 24 bits for VPOWER calculations.

Note 1: Power is always calculated using signed numbers for VBUS and VSENSE. However, if both

VBUS and VSENSE are measured using the default unipolar mode, power is reported as an

unsigned number. This can cause very small discrepancies between a manual comparison

of VBUS × VSENSE and the results that PAC1721 calculates and accumulates for VPOWER.

PAC1721 performs calculations using more bits than the reported results for VBUS and

VSENSE. Thus, in some cases, values stored in the VPOWER and VACC registers are more

accurate than calculations using the values stored in the VBUS and VSENSE registers.

2: This register accumulates both positive and negative values even in Unipolar mode. Thus,

if negative or near zero currents are measured, send a Refresh command to ensure the

correct accumulated values are stored.

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