参数资料
型号: PIC16C621-20/SS
元件分类: 微控制器/微处理器
英文描述: 8-BIT, OTPROM, 20 MHz, RISC MICROCONTROLLER, PDSO20
封装: 0.209 INCH, PLASTIC, MO-150, SSOP-20
文件页数: 60/121页
文件大小: 1202K
代理商: PIC16C621-20/SS
1999 Microchip Technology Inc.
DS30235H-page 43
PIC16C62X
8.0
VOLTAGE REFERENCE
MODULE
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 VREF values and has a power-down function to
conserve power when the reference is not being used.
The VRCON register controls the operation of the
reference as shown in Register 8-1. The block diagram
is given in Figure 8-1.
8.1
Configuring the Voltage Reference
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:
if VRR = 1: VREF = (VR<3:0>/24) x VDD
if VRR = 0: VREF = (VDD x 1/4) + (VR<3:0>/32) x VDD
The setting time of the Voltage Reference must be
considered
when
changing
the
VREF
output
(Table 12-1). Example 8-1 shows an example of how to
configure the Voltage Reference for an output voltage
of 1.25V with VDD = 5.0V.
REGISTER 8-1:
VRCON REGISTER(ADDRESS 9Fh)
FIGURE 8-1:
VOLTAGE REFERENCE BLOCK DIAGRAM
R/W-0
U-0
R/W-0
VREN
VROE
VRR
—VR3
VR2
VR1
VR0
R
= Readable bit
W = Writable bit
U
= Unimplemented bit, read
as ’0’
- n = Value at POR reset
- x = Unknown at POR reset
bit7
bit0
bit 7:
VREN: VREF Enable
1
= VREF circuit powered on
0
= VREF circuit powered down, no IDD drain
bit 6:
VROE: VREF Output Enable
1
= VREF is output on RA2 pin
0
= VREF is disconnected from RA2 pin
bit 5:
VRR: VREF Range selection
1
= Low Range
0
= High Range
bit 4:
Unimplemented: Read as ’0’
bit 3-0: VR<3:0>: VREF value selection 0
≤ VR [3:0] ≤ 15
when VRR = 1: VREF = (VR<3:0>/ 24) * VDD
when VRR = 0: VREF = 1/4 * VDD + (VR<3:0>/ 32) * VDD
Note:
R is defined in Table 12-2.
VRR
8R
VR3
VR0
(From VRCON<3:0>)
16-1 Analog Mux
8R
R
VREN
VREF
16 Stages
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