Datasheet

PIC18(L)F1XK22
DS41365E-page 240  2009-2011 Microchip Technology Inc.
20.2 FVR Reference Module
The FVR 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 VREFCON0 register to ‘1’. The FVR
can be routed to the comparators or an ADC input
channel.
20.2.1 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 VREFCON0 register also
indicates that the FVR has been operating long enough
to be stable. See Section 25.0 “Electrical
Specifications” for the minimum delay requirement.
FIGURE 20-1: VOLTAGE REFERENCE BLOCK DIAGRAM
FVR1S<1:0>
X1
X2
X4
2
FVR
+
_
FVR1EN
FVR1ST
1.024V Fixed
Reference
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
D1EN
D1LPS
R
D1EN
D1LPS