PAC1721 datasheet(19/92 Pages) MICROCHIP

19 / 92 page

 2026 Microchip Technology Inc. and its subsidiaries

DS-20007088A-page 19

PAC1721

Use Equation 4-4 to calculate the real value of VSENSE.

EQUATION 4-4:

4.6

FSR/2 Modes

FSR/2 mode allows the use of a reduced FSR. This can

be divided by a factor of two for VSENSE and/or VBUS

and it can be selected for both voltages by configuring

the NEG_PWR_FSR register:

•VBUS → CFG_VB[1:0] = 10b

•VSENSE → CFG_VS[1:0] = 10b

4.7

ADC Measurements, Offset and

Averaging

PAC1721 is primarily used for energy measurements

where many power calculations are accumulated. This

is inherently an averaging process. Individual voltage

and current measurements can also benefit from aver-

aging to reduce noise and offset. The averaged values

are internally calculated for VBUS and VSENSE.

Rolling averages of the most recent samples are stored

in the VBUS_AVG and VSENSE_AVG registers. The

rolling averages update internally after every complete

conversion cycle, while readable registers are updated

using Refresh (any) commands. Use these averaged

results to obtain the most accurate, lowest noise

measurements.

Results from both VBUS and VSENSE ADCs are 12-bit

2's complement signed numbers. Conversion results

are stored as unipolar or bipolar numbers based on

NEG_PWR_FSR register settings. Besides measuring

bipolar currents (charging/discharging) and voltages

that can drop below ground level, bipolar numbers can

give more accurate results for very small values that

may actually be negative for some readings. For more

details, see Register 6-20.

PAC1721 calculates the mean value for both VBUS and

VSENSE by averaging the most recent voltage samples.

The number of samples (measurements) included in

the rolling average is determined by the AVERAGE[2:0]

bits in the CONTROL register. By default, these bits are

set to 001b, equivalent to using the most recent eight

measurements to determine rolling averages.

PAC1721 stores the rolling averages of the most recent

VBUS and VSENSE samples in the VBUS_AVG and

VSENSE_AVG registers. After POR, these registers

start representing accurate voltage averages only after

the minimum required number of samples/completed

conversion cycles is reached. Set the AVERAGE[2:0]

bits in the CONTROL register so that PAC1721 uses

the most recent 4, 8, 16, 32, 64 or 128 samples when

calculating the rolling VBUS and VSENSE averages. For

more details, see Register 6-2.

The VBUS_AVG and VSENSE_AVG registers update

after every completed conversion cycle. Refresh (any)

commands update these registers like any readable

TABLE 4-1:

FSR/2 – VBUS

VBUS Range

FSR = 9V, FSR/2 = 4.5V

Unipolar 0-FSR

2.2 mV/LSB

Bipolar ± FSR

4.4 mV/LSB

Bipolar ± FSR/2

2.2 mV/LSB

TABLE 4-2:

FSR/2 – VSENSE

VSENSE Range

FSR = 100 mV, FSR/2 = 50 mV

Unipolar 0-FSR

24.414 µV/LSB

Bipolar ± FSR

48.828 µV/LSB

Bipolar ± FSR/2

24.414 µV/LSB

Where:

VSENSE = Sense Voltage (V)

LSB(VSENSE) = LSBs of the VSENSE measurement

FSVSENSE = Full Scale Voltage for VSENSE (V):

• 100 mV for Unipolar mode

• 200 mV for Bipolar mode

• 100 mV for Bipolar FSR/2 mode

212 = 12-bit Resolution Denominator

CONV(VSENSE) = Converted analog-to-digital value, from

hexadecimal to decimal, read from the

VSENSE register

LSB VSENSE



FSVSENSE

-------------------------

VSENSE

LSB VSENSE

 CONV VSENSE





Note:

Using the full resolution of the device

can impact NEG_PWR_FSR register

settings. For example, if conversion

results are stored as unipolar numbers

and a negative value is converted, the

average result includes the signed

negative value and produces a different

value than just averaging the VBUS or

VSENSE register.

PAC1721 Datasheet(PDF) 19 Page - Microchip Technology

PAC1721 Datasheet(HTML) 19 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92

Datasheet Download

Link URL