PAC1941T-1ESLASH4MX. datasheet(30/96 Pages) MICROCHIP

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PAC194X

DS20006543A-page 30

 2021 Microchip Technology Inc.

5.13.3

ALTERNATIVE USES FOR THE

ACCUMULATOR

For the PAC194X, the accumulator may be used to

accumulate VSENSE or VBUS values instead of

VPOWER values for any channel. This functionality is

invoked by setting bits in Register 7-19.

Setting the accumulator for a channel to accumulate

VSENSE values gives a measure of accumulated

current, which is equivalent to charge. This allows the

accumulator to be used as a coulomb counter.

For either VSENSE or VBUS, many samples may be

accumulated on chip and the result collected by the

host and divided by the accumulator counter count

value to yield an average value with a very long inte-

gration time to reduce noise. This feature is also very

useful for system calibration, allowing many averages

to be accumulated for fast averaging/noise reduction.

Calibration time can be further reduced by combining

this with the Fast mode.

5.14

Conversion Cycles

A conversion cycle for the device consists of the

analog-to-digital conversion being complete for all

channels (including the real-time calibration that is part

of each conversion cycle). Immediately following the

data conversion, the power results are calculated for

that channel and the power value is added to the accu-

mulator. Averaged values for VSENSE and VBUS are

also updated internally as part of each conversion

cycle.

Data conversion and processing are performed for

each active channel in sequential fashion until all

active channels are converted, completing the conver-

sion cycle for the device. The sequential sampling of

each channel, along with the calculation time and any

sleep time needed to set the overall sampling rate, is

referred to as a round robin sampling period.

5.15

Conversion Cycle Controls

5.15.1

REDUCING THE NUMBER OF

CHANNELS TO BE SAMPLED

channels that are active. The sample rate is unaf-

fected, but power dissipation is reduced if some chan-

nels are disabled. Any or all channels may be

disabled; if all channels are disabled, the device goes

into Sleep mode.

5.15.2

BURST MODE

For the PAC194X, Burst mode is added for faster

sampling. In this mode, the round robin sequencer

enables each active channel sequentially and restarts

the round robin sequence again without sleeping in

between as it normally does. The fifth channel that is

used for offset canceling is not sampled in this mode,

the previous value for offset canceling is repeatedly

used, so sampling will not be as accurate if this mode

is used for long periods of time, especially if

temperature changes, although the 8X average

accuracy will not be significantly affected.

The effective sampling mode changes with the number

of active channels, as shown in Table 5-3. The Burst

mode is enabled by setting a bit in Register 7-2.

5.15.3

FAST MODE

Fast mode is also a mode for faster sampling. It is

similar to Burst mode, only in Fast Mode, the fifth

channel is converted and used for continuous offset

correction.

The effective sampling mode changes with the number

of active channels, as shown in Table 5-4. The Burst

mode is enabled by setting a bit in Register 7-2.

TABLE 5-3:

BURST MODE ENABLED

Active

Channels

Sampling Frequency

1024*5/1 = 5120 SPS

1024*5/2 = 2560 SPS

1024*5/3 = 1706 SPS

1024*5/4 = 1280 SPS

TABLE 5-4:

FAST MODE ENABLED

Active

Channels

Sampling Frequency

1024*5/2 = 2560 SPS

1024*5/3 = 1706.6 SPS

1024*5/4 = 1280 SPS

1024*5/5 = 1024 SPS

PAC1941T-1E/4MX. Datasheet(PDF) 30 Page - Microchip Technology

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