PAC1721 datasheet(15/92 Pages) MICROCHIP

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DS-20007088A-page 15

PAC1721

Internal values continue to update according to the

sample rate selected in the CONTROL register.

Note:

Issue a Refresh command to save the

results of the most recently completed

conversion cycle to the VBUS, VSENSE

and VPOWER registers. Otherwise, the

results of the conversion are discarded. For

more details, see Register 6-1.

4.2.3

REFRESH_G COMMAND

The Refresh_G command is identical in all aspects to

the Refresh command, with added compatibility for the

I2C General Call address (0000 000b).

Using Refresh_G, the host issues a single Refresh

command to all PAC1721 devices in the system. The

data from this Refresh_G command is read device by

device to capture a snapshot of system power and

energy for all PAC1721 units.

Besides the General Call address, Refresh_G can also

be issued with a valid target address. In this scenario,

only the PAC1721 device with the specified target

address receives the command. For more details, see

4.2.4

REFRESH_V COMMAND

To read VSENSE and VBUS measurements, as well as

the most recent power calculation and/or accumulator

values and accumulator count without resetting the

accumulators, issue a Refresh_V command.

To ensure data registers are ready-to-read by the host,

wait for one conversion cycle to complete after issuing

a Refresh_V command. Input sampling, data conver-

sion and power integration are not interrupted and

continue as set by the CONTROL register. Data regis-

ters remain available to read until the next Refresh or

Refresh_V command is issued.

Note:

The accumulator and accumulator count

are not reset when issuing a Refresh_V.

Refresh_V can activate changes to the CONTROL

Refresh_V command activates these changes without

resetting the accumulators or the accumulator count.

For more details, see Register 6-22.

4.2.5

AUTO-REFRESH

The Auto-refresh function speeds up the transition time

from the Conversion-complete state to Ready-to-read

state.

To enable Auto-refresh, set the AUTO_REFRESH[1:0]

bits in the CONTROL register. When these bits are set,

PAC1721 performs a Limited Refresh: only the values

stored in the data registers migrate to the I2C domain

(populate I2C registers). For details, see Register 6-2.

The following registers require a manual Refresh (any)

command to update their values. They cannot be

updated while the Auto-refresh function is enabled.

•CONTROL

• NEG_PWR_FSR

•SLOW

• SLOW_ALERT0

• GPIO_ALERT1

• ACC_FULL_LIMIT

• ALERT_ENABLE

• ACC_COUNT_PRESET

• VACC_PRESET

When Auto-refresh is enabled, all manual Refresh

(any) commands are ignored, except when setting the

AUTO_REFRESH[1:0] bits in the CONTROL register.

To activate register changes that require a Refresh

(any) command, first set the AUTO_REFRESH[1:0]

bits to 00b. This disables Auto-refresh and allows to

change registers. Next, issue a manual Refresh (any)

command to activate these changes.

Auto-refresh does not trigger when communicating to

PAC1721 or another device on the I2C bus. To ensure

that the conversion cycle has completed and there is

new data available to read, set up the Conversion

Complete alert:

In the CONTROL register, set pin A0 or A1 to

function as ALERT pin:

A0 → SLOW_ALERT0[1:0] = 00b

A1 → GPIO_ALERT1[1:0] = 00b

Enable the Conversion Complete alert:

ALERT_ENABLE register → ALERT_CC = 1b

Assign the alert to the A0 or A1 pin:

A0: SLOW_ALERT0 register → ALERT_CC0 = 1b

A1: GPIO_ALERT1 register → ALERT_CC1 = 1b

The next conversion cycle overwrites the data if not

read by the time the new cycle completes.

Note 1: While enabled, Auto-refresh overrules

all other refresh commands (Refresh,

Refresh_G and Refresh_V).

2: Do not enable Auto-refresh when using

Single-shot sample modes.

3: If the CONTROL register no longer

corresponds to the CONTROL_ACT

only if both registers match.

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