Datasheet

PIC18F/LF1XK50
DS41350E-page 246 Preliminary  2010 Microchip Technology Inc.
21.2 FVR Reference Module
The FVR reference is a stable fixed voltage reference,
independent of V
DD, with a nominal output voltage of
1.024V. This reference can be enabled by setting the
FVR1EN bit of the REFCON0 register to ‘1’. The FVR
voltage reference can be routed to the comparators or
an ADC input channel.
21.2.1 FVR STABILIZATION PERIOD
When the Fixed Voltage Reference module is enabled, it
will require some time for the reference and its amplifier
circuits to stabilize. The user program must include a
small delay routine to allow the module to settle. The
FVR1ST stable bit of the REFCON0 register also
indicates that the FVR reference has been operating long
enough to be stable. See Section 27.0 “Electrical
Specifications” for the minimum delay requirement.
FIGURE 21-1: VOLTAGE REFERENCE BLOCK DIAGRAM
16-to-1 MUX
DAC1R<4:0>
R
VDD
VREF+
D1PSS<1:0> = 00
D1NSS = 0
VREF-
D1NSS = 1
R
R
R
R
R
R
32 Steps
V
REF
FVR1
D1PSS<1:0> = 01
D1PSS<1:0> = 10
CV
REF pin
DAC1OE
FVR1S<1:0>
X1
X2
X4
2
FVR
+
_
FVR1EN
FVR1ST
1.024V Fixed
Reference
D1EN
D1LPS
R
D1EN
D1LPS