PIC12F752 datasheet(112/204 Pages) MICROCHIP

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PIC12F752/HV752

DS41576A-page 112

Preliminary

 2011 Microchip Technology Inc.

14.1

DAC Positive Voltage Source

The DACPSS bit of the DACCON0 register selects the

positive voltage source, VSRC+. The following voltage

sources are available:

•VDD pin (default)

•VREF+ pin

DAC module can select the positive voltage source

using the DACPSS bit of the DACCON0 register. The

default source, DACPSS = 0, connects VDD to the pos-

itive voltage source (VSRC+). VSRC+ can be changed to

the VREF+ pin by setting DACPSS = 1.

14.2

DAC Range Selection

The DACRNG bit of the DACCON0 register selects

between full-range or limited-range DAC output

voltage.

Each range selects the output in 32 equal steps.

In Full-Range mode, the output is (31/32)*VSRC+. In

Limited-Range mode, the maximum VOUT is limited to

6% of VSRC+, (31/512) * VSRC+.

14.3

Ratiometric Output Level

The DAC output value is derived using a resistor ladder

with one end of the ladder tied to the positive voltage

reference and the other end tied to VSS. If the voltage of

the input source fluctuates, a similar fluctuation will

result in the DAC output value.

The resistor values within the ladder can be found in

Section 20.0 “Electrical Specifications”.

14.4

DAC Output Voltage

The DAC output voltage level of the DAC is determined

by the DACRNG and the DACR<4:0> bits of the

DACCON0 and DACCON1 registers, respectively.

Use Equation 14-1 to determine the value of the DAC

output voltage. Example 14-1 illustrates the calculations

of the minimum, maximum and increment size of the

DAC output voltage in Full Range mode. Example 14-2

illustrates the Limited Range mode of the DAC output

voltage values.

EQUATION 14-1:

DAC OUTPUT VOLTAGE

EXAMPLE 14-1:

FULL RANGE MODE

EXAMPLE 14-2:

LIMITED RANGE MODE

VOUT

VSRC+

 DACR 4:0



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













Note:

The value of ‘n’ is determined by the DACRNG bit.

When: DACRNG = 0 (Limited Range mode); n = 9;

DACRNG = 1 (Full Range mode); n = 5.

Given: VSRC = VDD = 5V, DACRNG = 1

VOUT = [VSRC+ * (DACR<4:0>/25)]

Minimum VOUT Calculation:

Maximum VOUT Calculation:

Step Increment Calculation:

DACR<4:0> = 0 0000b, (0d);

DACR<4:0> = 1 1111b, (31d);

DACR<4:0> = 0 0001b, (1d);

VOUT = [5V * (0/32)] = 0V;

VOUT = [5V * (31/32)] = 4.84V;

VOUT = [5V * (1/32)] = 156 mV

Full Range Mode Operation:

VOUT 4.84V, with 32-step increments of 156 mV.

Given: VSRC = VDD = 5V, DACRNG = 0

VOUT = [VSRC+ * (DACR<4:0>/29)]

Minimum VOUT Calculation:

Maximum VOUT Calculation:

Step Increment Calculation:

DACR<4:0> = 0 0000b, (0d);

DACR<4:0> = 1 1111b, (31d);

DACR<4:0> = 0 0001b, (1d);

VOUT = [5V * (0/512)] = 0V;

VOUT = [5V * (31/512)] = 303 mV;

VOUT = [5V * (1/512)] = 9.8 mV

Limited Range Mode Operation:

VOUT 303 mV, with 32-step increments of 9.8 mV.

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