PIC12F1840 View Datasheet(PDF) - Microchip Technology
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MFG CO.
'PIC12F1840' PDF : 410 Pages View PDF
PIC12(L)F1840
17.0 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 pins
• VDD supply voltage
• FVR (Fixed Voltage Reference)
The output of the DAC can be configured to supply a
reference voltage to the following:
• Comparator positive input
• ADC input channel
• DACOUT pin
• Capacitive Sensing (CPS) module
The Digital-to-Analog Converter (DAC) can be enabled
by setting the DACEN bit of the DACCON0 register.
17.1 Output Voltage Selection
The DAC has 32 voltage level ranges. The 32 levels
are set with the DACR<4:0> bits of the DACCON1
register.
The DAC output voltage is determined by the following
equations:
EQUATION 17-1: DAC OUTPUT VOLTAGE
IF DACEN = 1
VOUT
=
VSOURCE+
–
VSOURCE-
D-----A----C----2-R--5----4---:--0----
+
VSOURCE-
IF DACEN = 0 & DACLPS = 1 & DACR[4:0] = 11111
VOUT = VSOURCE +
IF DACEN = 0 & DACLPS = 0 & DACR[4:0] = 00000
VOUT = VSOURCE –
VSOURCE+ = VDD, VREF, or FVR BUFFER 2
VSOURCE- = VSS
17.2 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 be found in Section 30.0 “Electrical
Specifications”.
17.3 DAC Voltage Reference Output
The DAC can be output to the DACOUT pin by setting
the DACOE bit of the DACCON0 register to ‘1’.
Selecting the DAC reference voltage for output on the
DACOUT pin automatically overrides the digital output
buffer and digital input threshold detector functions of
that pin. Reading the DACOUT pin when it has been
configured 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 DACOUT. Figure 17-2 shows
an example buffering technique.
2011-2012 Microchip Technology Inc.
DS41441C-page 133
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