PIC16F1508TESSQTO datasheet(149/384 Pages) MICROCHIP

149 / 384 page

 2011 Microchip Technology Inc.

Preliminary

DS41609A-page 149

PIC16(L)F1508/9

16.0 DIGITAL-TO-ANALOG

CONVERTER (DAC) MODULE

The Digital-to-Analog Converter supplies a variable

voltage reference, ratiometric with the input source,

with 32 selectable output levels.

The input of the DAC can be connected to:

•External VREF+ pin

•VDD supply voltage

The output of the DAC can be configured to supply a

reference voltage to the following:

• Comparator positive input

• ADC input channel

•DACOUT1 pin

•DACOUT2 pin

The Digital-to-Analog Converter (DAC) can be enabled

by setting the DACEN bit of the DACCON0 register.

16.1

Output Voltage Selection

The DAC has 32 voltage level ranges. The 32 levels

are set with the DACR<4:0> bits of the DACCON1

The DAC output voltage is determined by the following

equations:

EQUATION 16-1:

DAC OUTPUT VOLTAGE

16.2

Ratiometric Output Level

The DAC output value is derived using a resistor ladder

with each end of the ladder tied to a positive and

negative voltage reference input source. If the voltage

of either input source fluctuates, a similar fluctuation will

result in the DAC output value.

The value of the individual resistors within the ladder

can

found

Section 29.0

“Electrical

Specifications”

16.3

DAC Voltage Reference Output

The DAC voltage can be output to the DACOUT1 and

DACOUT2 pins by setting the respective DACOE1 and

DACOE2 pins of the DACCON0 register. Selecting the

DAC reference voltage for output on either DACOUTx

pin automatically overrides the digital output buffer and

digital input threshold detector functions of that pin.

Reading the DACOUTx pin when it has been config-

ured for DAC reference voltage output will always

return a ‘0’.

Due to the limited current drive capability, a buffer must

be used on the DAC voltage reference output for

external connections to either DACOUTx pin.

Figure 16-2 shows an example buffering technique.

IF DACEN = 1

IF DACEN = 0 and DACLPS = 1 and DACR[4:0] = 11111

VOUT

VSOURCE +

IF DACEN = 0 and DACLPS = 0 and DACR[4:0] = 00000

VOUT

VSOURCE –

VSOURCE+ = VDD, VREF, or FVR BUFFER 2

VSOURCE- = VSS

VOUT

VSOURCE+VSOURCE-

–

 DACR 4:0



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







VSOURCE-

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