41594B datasheet(294/372 Pages) MICROCHIP

294 / 372 page

PIC12LF1840T48A

DS41594B-page 294

Preliminary

 2011-2012 Microchip Technology Inc.

27.4

Power Modes

The capacitive sensing oscillator can operate in one of

seven different power modes. The power modes are

separated into two ranges; the low range and the high

range.

When the oscillator’s low range is selected, the fixed

internal voltage references of the capacitive sensing

oscillator are being used. When the oscillator’s high

range is selected, the variable voltage references

supplied by the FVR and DAC modules are being used.

Selection between the voltage references is controlled

by the CPSRM bit of the CPSCON0 register. See

Section 27.3

“Voltage

References”

for

information.

Within each range there are three distinct Power modes;

low, medium and high. Current consumption is dependent

upon the range and mode selected. Selecting Power

modes within each range is accomplished by configuring

the CPSRNG <1:0> bits in the CPSCON0 register. See

Table 27-1 for proper Power mode selection.

The remaining mode is a Noise Detection mode that

resides within the high range. The Noise Detection

mode is unique in that it disables the sinking and sourc-

ing of current on the analog pin but leaves the rest of

the oscillator circuitry active. This reduces the oscilla-

tion frequency on the analog pin to zero and also

greatly reduces the current consumed by the oscillator

module.

When noise is introduced onto the pin, the oscillator is

driven at the frequency determined by the noise. This

produces a detectable signal at the comparator output,

indicating the presence of activity on the pin.

Figure 27-2 shows a more detailed drawing of the

current sources and comparators associated with the

oscillator.

TABLE 27-1:

POWER MODE SELECTION

CPSRM

Range

CPSRNG<1:0>

Mode

Nominal Current(1)

Low

Off

0.0

A

Low

0.1

A

Medium

1.2

A

High

A

High

Noise Detection

0.0

A

Low

A

Medium

A

High

100

A

Note 1:

See Section 31.0 “Electrical Specifications” for more information.

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