PAC1721 datasheet(23/92 Pages) MICROCHIP

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DS-20007088A-page 23

PAC1721

When switching to Single-shot mode, any triggers are

ignored until the conversion cycle is complete. When

changing from a continuous sample mode to Single-

shot mode, an extra conversion occurs. The extra

conversion does not occur when switching between

continuous sampling or between various Single-shot

operational modes.

4.9.1

SINGLE-SHOT MODE

In Single-shot mode, PAC1721 samples and converts

VBUS and VSENSE measurements and then calculates

VPOWER. These actions are done in a single sequence.

By default, PAC1721 operates in continuous 1,024 sps

sample mode. To switch to Single-shot mode, set the

following bits in the CONTROL register:

Enter the Sleep state:

SAMPLE_MODE[3:0] = 1110b or 1111b

Switch to the Single-shot mode:

SAMPLE_MODE[3:0] = 0110b

After completing the single-shot measurements and

calculations, PAC1721 enters the Sleep state. Issue a

Refresh (any) command to read the most recent data.

Generally, single-shot conversion commands are not

issued one after the other. Replace single-shot conver-

sions with a continuous sample rate in scenarios where

conversions need to occur in short succession.

4.9.1.1

Single-shot Average Mode

In Single-shot Average mode, PAC1721 issues a single

Refresh command to collect the programmed number

of VBUS or VSENSE samples. The gathered samples are

averaged and the result is stored in the VBUS_AVG or

VSENSE_AVG register, while the VBUS and VSENSE

registers hold the most recent results of the VBUS and

VSENSE conversions. Averaging reduces noise and

offset in the result. In this mode, all averaged samples

are added to the accumulator, while the accumulator

count is incremented by the configured amount each

time a Refresh command triggers another single-shot

average acquisition and conversion.

To enter Single-shot Average mode from the Sleep

state, set the following bits in the CONTROL register:

• SAMPLE_MODE[3:0] = 0111b

4.9.1.2

Single-shot Awake Mode

In Single-shot Awake mode, PAC1721 does not enter

Sleep state after the conversion cycle completes. This

results in a higher quiescent current, but allows

PAC1721 to start converting samples much faster after

it receives the command to initiate the conversion.

To enter Single-shot Awake mode from the Sleep state,

set the following bits in the CONTROL register:

• SAMPLE_MODE[3:0] = 1000b

4.9.1.3

Single-shot Awake Average Mode

The Single-shot Awake Average mode works similarly

to Single-shot Awake mode, but with PAC1721 taking

the programmed amount of samples to average.

See Section 4.9.1, Note 2.

To enter Single-shot Awake Average mode from the

Sleep state, set the following bits in the CONTROL

• SAMPLE_MODE[3:0] = 1001b

4.9.1.4

GPIO Triggered Single-shot Awake

Mode

In General Purpose Input/Output (GPIO) Triggered

Single-shot Awake mode, PAC1721 can use pin A0 or

A1 as a GPIO input to signal the start of a conversion.

This mode is similar to the Single-shot Awake mode in

that PAC1721 does not enter into any low power state

and thus has a fast reaction time when triggered. The

time-limiting factor is the internal 16 kHz oscillator that

monitors the A0/A1 inputs.

Note 1: First enter Sleep state and then switch

to the desired Single-shot mode. This

resolves any situations where the

current conversion cycle impacts the

accumulator count. For details on the

Sleep state, see Section 4.2.6.

2: If PAC1721 enters Single-shot Awake

mode from either the low-power state

or from another Single-shot mode, the

initial Single-shot Awake conversion

adds a wake-up delay that allows the

internal digital logic to fully exit the low-

power state.

3: After entering Single-shot mode, the

first refresh-type command issued

must be a Refresh. Do not issue a

Refresh_V or Refresh_G instead of a

Refresh command.

Note:

After issuing a Refresh (any) command,

wait for a conversion cycle to complete

before starting the next single-shot

conversion.

Note:

The A0/A1 pin must be configured as

GPIO input for the trigger to occur and

the signal must be active high. For

details, see Section 4.2.10.

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