PIC16F627-04 Microchip Technology, PIC16F627-04 Datasheet - Page 69

• Manufacturer Part Number: PIC16F627-04
• Description: FLASH-Based 8-Bit CMOS Microcontrollers
• Manufacturer: Microchip Technology

11.0
The Voltage Reference is a 16-tap resistor ladder
network that provides a selectable voltage reference.
The resistor ladder is segmented to provide two ranges
of V
conserve power when the reference is not being used.
The VRCON register controls the operation of the
reference as shown in Figure 11-1. The block diagram
is given in Figure 11-2.
FIGURE 11-1:
FIGURE 11-2: VOLTAGE REFERENCE BLOCK DIAGRAM
1999 Microchip Technology Inc.
bit7
bit 7:
bit 6:
bit 5:
bit 4:
bit 3-0: V
V
R/W-0
REN
REF
Note:
V
REN
VOLTAGE REFERENCE
MODULE
values and has a power-down function to
V
V
V
Unimplemented: Read as '0'
REN
ROE
RR
R
R is defined in Table 12-3.
R/W-0
<3:0>: V
V
: V
1 = V
0 = V
1 = V
0 = V
1 = Low Range
0 = High Range
when V
when V
ROE
: V
: V
V
VRCON REGISTER(ADDRESS 9Fh)
REF
REF
REF
REF
REF
REF
REF
REF
Range selection
REF
RR
RR
Enable
Output Enable
R/W-0
circuit powered on
circuit powered down, no I
is output on RA2 pin
is disconnected from RA2 pin
V
= 1: V
= 0: V
value selection 0
RR
8R
REF
REF
U-0
—
= (V
= 1/4 * V
R
R
<3:0>/ 24) * V
R/W-0
V
R3
DD
V
R
+ (V
R
[3:0]
Preliminary
DD
R
R/W-0
<3:0>/ 32) * V
V
16 Stages
drain
R2
DD
16-1 Analog Mux
15
11.1
The Voltage Reference can output 16 distinct voltage
levels for each range.
The equations used to calculate the output of the
Voltage Reference are as follows:
The setting time of the Voltage Reference must be
considered
(Table 12-2). Example 11-1 shows an example of how
to configure the Voltage Reference for an output volt-
age of 1.25V with V
R/W-0
V
if V
if V
R1
R
RR
RR
DD
= 1: V
= 0: V
Configuring the Voltage Reference
R/W-0
V
R
when
R0
REF
REF
bit0
= (V
= (V
DD
changing
R = Readable bit
W = Writable bit
U = Unimplemented bit, read
-n = Value at POR reset
R
DD
= 5.0V.
<3:0>/24) x V
8R
PIC16F62X
x 1/4) + (V
as ’0’
V
V
R
R
3
0
(From VRCON<3:0>)
the
R
DS40300B-page 69
DD
<3:0>/32) x V
V
V
REF
RR
output
DD