CAP1188 datasheet(49/79 Pages) MICROCHIP

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 2015 Microchip Technology Inc.

DS00001620C-page 49

CAP1188

Bit 3-2 - STBY SAMP_TIME[1:0] - Determines the time to take a single sample when the device is in Standby as shown

in Table 6-38.

Bits 1 - 0 - STBY_CY_TIME[2:0] - Determines the overall cycle time for all measured channels during standby operation

as shown in Table 6-39. All measured channels are sampled at the beginning of the cycle time. If additional time is

remaining, the device is placed into a lower power state for the remaining duration of the cycle.

APPLICATION NOTE:

The programmed cycle time is only maintained if the total averaging time for all samples is

less than the programmed cycle. The STBY_AVG[2:0] bits will take priority so that if more

samples are required than would normally be allowed during the cycle time, the cycle time

will be extended as necessary to accommodate the number of samples to be measured.

6.22

Standby Sensitivity Register

The Standby Sensitivity register controls the sensitivity for sensor inputs that are active in Standby.

Bits 2 - 0 - STBY_SENSE[2:0] - Controls the sensitivity for sensor inputs that are active in Standby. The sensitivity set-

tings act to scale the relative delta count value higher or lower based on the system parameters. A setting of 000b is the

most sensitive while a setting of 111b is the least sensitive. At the more sensitive settings, touches are detected for a

smaller delta C corresponding to a “lighter” touch. These settings are more sensitive to noise however and a noisy envi-

ronment may flag more false touches than higher sensitivity levels.

APPLICATION NOTE:

A value of 128x is the most sensitive setting available. At the most sensitivity settings, the

MSB of the Delta Count register represents 64 out of ~25,000 which corresponds to a touch

128

TABLE 6-38:

STBY_SAMP_TIME BIT DECODE

STBY_SAMP_TIME[1:0]

Sampling Time

320us

640us

1.28ms (default)

2.56ms

TABLE 6-39:

STBY_CY_TIME BIT DECODE

STBY_CY_TIME[1:0]

Overall Cycle Time

35ms

70ms (default)

105ms

140ms

TABLE 6-40:

STANDBY SENSITIVITY REGISTER

ADDR

R/W

Default

42h

R/W

Standby Sensitiv-

ity

STBY_SENSE[2:0]

02h

TABLE 6-37:

STBY_AVG BIT DECODE (CONTINUED)

STBY_AVG[2:0]

Number of Samples Taken per

Measurement

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