PAC1933T-ISLASHJQ. datasheet(21/62 Pages) MICROCHIP

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DS20005850C-page 21

PAC1932/3/4

Data conversion and processing is performed for each

active channel in sequential fashion until all active

channels have been converted, completing the

conversion 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.

4.3

Conversion Cycle Controls

4.3.1

REDUCING THE NUMBER OF

CHANNELS TO BE SAMPLED

Program Register 6-10 CHANNEL_DIS and SMBus

(Address 1Ch) to reduce the number of channels that

are active. The sample rate is unaffected, but power

dissipation is reduced very slightly if some channels

are disabled. Any or all channels may be disabled; if

all channels are disabled, the device goes into Sleep

mode. When a channel is disabled due to register

programming in the PAC1934 or due to factory

programming on the PAC1932 and PAC1933, the auto

incrementing pointer will skip these channels by

default

(see

Section 5.5

“Auto-Incrementing

Pointer”

4.3.2

SINGLE SHOT MODE

The Control register also allows the device to operate

in Single Shot mode. In Single Shot mode, all active

channels will sample and convert once, followed by

results being calculated. The accumulator and

accumulator count operate the same as for continuous

conversion mode, accumulating each single shot

power calculation and incrementing the accumulator

count. The conversion cycle will start when the

REFRESH

command

(or

REFRESH_V

REFRESH_G) is sent.

After the single shot measurements and calculations

are complete, the device will go into Sleep mode. A

REFRESH, REFRESH_G or REFRESH_V command

may be sent to read the data. The user needs to wait

3 ms

after

the

REFRESH

command

before

commanding another Single Shot conversion by

means of sending one of the REFRESH commands.

This is because a 1 ms delay is required between

REFRESH commands, and coming out of Sleep

requires 2 ms.

4.4

Alert Functionality

The Alert functionality can serve two purposes: to

notify the system that a conversion cycle for all active

channels is complete, or to notify the system that the

accumulator or accumulator count has overflowed.

4.4.1

USING THE ALERT FUNCTION

To use the ALERT function, configure the SLOW pin to

function as ALERT using Register 6-2 CTRL Register

(Address 01h). For this configuration, the ALERT pin

must have a pull-up to VDD I/O (it will function as an

open drain output). If a pull-up resistor is attached to

the pin for Alert functionality, the device will power up

in Slow mode. Any of the four sample rates can be

programmed using Register 6-2 CTRL Register

(Address 01h).

The Alert function for Accumulator Overflow can also

be used without reconfiguring the SLOW pin, by

monitoring the OVF bit in Register 6-2 CTRL Register

(Address 01h).

4.4.2

ALERT AFTER COMPLETE

CONVERSION

has an ALERT_CC bit that can be used

to enable the ALERT_CC function. If this bit is set, the

ALERT pin will go low for 5 μS after each complete

conversion cycle is complete.

4.4.3

ALERT ON ACCUMULATOR

OVERFLOW

If the ALERT function is enabled, and any of the

accumulators or the accumulator count overflows, the

ALERT pin may be used to notify the system. To

enable this trigger for the ALERT pin, bit 1 in the

CTRL Register (Address 01h) must be

set. Note that the OVF bit in the Register 6-2 CTRL

overflows occur.

4.4.4

CLEARING ALERT AND OVF

When the Alert function has been tripped by

accumulator or accumulator count overflow, it will

remain asserted until a REFRESH command is

received. REFRESH_G will also clear the OVF bit and

the Alert function, but REFRESH_V will not.

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