PIC16F707-ESLASHML datasheet(121/284 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

Preliminary

DS41418A-page 121

PIC16F707/PIC16LF707

16.4

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 CPSxRM bit of the CPSxCON0 register. See

Section 16.3

“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 accom-

plished by configuring the CPSxRNG <1:0> bits in the

CPSxCON0 register. See Table 16-2 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 16-2 shows a more detailed drawing of the

current sources and comparators associated with the

oscillator.

16.5

Timer Resources

To measure the change in frequency of the capacitive

sensing oscillator, a fixed time base is required. For the

period of the fixed time base, the capacitive sensing

oscillator is used to clock either TimerA/B or Timer1/3

(for CPSA/B, respectively). The frequency of the

capacitive sensing oscillator is equal to the number of

counts in the timer divided by the period of the fixed

time base.

16.6

Fixed Time Base

To measure the frequency of the capacitive sensing

oscillator, a fixed time base is required. Any timer

resource or software loop can be used to establish the

fixed time base. It is up to the end user to determine the

method in which the fixed time base is generated.

TABLE 16-2:

POWER MODE SELECTION

CPSxRM

Range

CPSxRNG<1:0>

Mode

Nominal Current (1)

Low

Off

0.0 µA

Low

0.1 µA

Medium

1.2 µA

High

18 µA

High

Noise Detection

0.0 µA

Low

9 µA

Medium

30 µA

High

100 µA

Note:

See Section 25.0 “Electrical Specifications” for more information.

Note:

The fixed time base can not be generated

by the timer resource that the capacitive

sensing oscillator is clocking.

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