PIC16C620 Microchip Technology, PIC16C620 Datasheet - Page 43

• Manufacturer Part Number: PIC16C620
• Description: EPROM-Based 8-Bit CMOS Microcontroller
• Manufacturer: Microchip Technology

8.0
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 8-1. The block diagram is
given in Figure 8-2.
FIGURE 8-1:
FIGURE 8-2:
1998 Microchip Technology Inc.
bit7
bit 7:
bit 6:
bit 5:
bit 4:
bit 3-0: V
V
R/W-0
REN
REF
V
Note:
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
VOLTAGE REFERENCE BLOCK DIAGRAM
REF
VRCON REGISTER(ADDRESS 9Fh)
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
DD
R3
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
8.1
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 8-1 shows an example of how to
configure the Voltage Reference for an output voltage
of 1.25V with V
R/W-0
V
if V
if V
R1
R
DD
RR
RR
= 1: V
= 0: V
Configuring the Voltage Reference
R/W-0
V
R
when
R0
REF
REF
bit0
DD
= (V
= (V
= 5.0V.
changing
R = Readable bit
W = Writable bit
U = Unimplemented bit,
- n =Value at POR reset
R
DD
<3:0>/24) x V
PIC16C62X
8R
x 1/4) + (V
read as ‘0’
V
V
R
R
3
0
(From VRCON<3:0>)
the
R
DS30235G-page 43
DD
<3:0>/32) x V
V
V
REF
RR
output
DD