參數(shù)資料
型號: PIC16C642
廠商: Microchip Technology Inc.
英文描述: 8-Bit EPROM Microcontrollers with Analog Comparators(每個I/O口有25mA驅(qū)動/吸收電流,可編程Vref,微控制器)
中文描述: 8位EPROM微控制器與模擬比較器(每個的I / O口有25毫安驅(qū)動/吸收電流,可編程Vref的,微控制器)
文件頁數(shù): 54/136頁
文件大小: 837K
代理商: PIC16C642
PIC16C64X & PIC16C66X
DS30559A-page 54
Preliminary
1996 Microchip Technology Inc.
8.1
Configuring the Voltage Reference
The Voltage Reference Module 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
Then V
REF
= (VR3:VR0/24) V
If VRR = 0
Then V
REF
= (V
DD
1/4) + (VR3:VR0/32) V
The settling time of the Voltage Reference must be
considered
when
changing
(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
DD
= 5.0V.
DD
DD
the
V
REF
output
EXAMPLE 8-1:
VOLTAGE REFERENCE
CONFIGURATION
MOVLW 0x02 ; 4 inputs muxed
MOVWF CMCON ; to 2 comparators
BSF STATUS,RP0 ; Select Bank 1
MOVLW 0x07 ; RA3:RA0 to outputs
MOVWF TRISA ;
MOVLW 0xA6 ; enable Vref low
MOVWF VRCON ; range, VR3:VR0 = 6
BCF STATUS,RP0 ; Select Bank 0
CALL DELAY_10
μ
s ; 10
μ
s delay
8.2
Voltage Reference Accuracy/Error
The full range of V
the construction of the module. The transistors on the
top and bottom of the resistor ladder network
(Figure 8-2) keep V
REF
from approaching V
The Voltage Reference is V
SS
to V
DD
cannot be realized due to
SS
or V
DD
.
DD
derived and therefore,
the V
absolute accuracy of the Voltage Reference can be
found in Table 12-3.
REF
output changes with fluctuations in V
DD
. The
8.3
Operation During Sleep
When the device wakes up from sleep through an
interrupt or a Watchdog Timer time-out, the contents of
the VRCON register are not affected. To minimize
current consumption in SLEEP mode, the Voltage
Reference Module should be disabled.
8.4
Effects of a Reset
A device reset disables the Voltage Reference by clear-
ing bit VREN (VRCON<7>). This reset also
disconnects the reference from the RA2 pin by clearing
bit VROE (VRCON<6>) and selects the high voltage
range by clearing bit VRR (VRCON<5>). The V
value select bits, VRCON<3:0>, are also cleared.
REF
8.5
Connection Considerations
The Voltage Reference Module operates independently
of the comparator module. The output of the reference
generator may be connected to the RA2 pin if the
TRISA<2> bit is set and bit VROE is set. Enabling the
Voltage Reference output onto the RA2 pin with an
input signal present will increase current consumption.
Connecting RA2 as a digital output with V
will also increase current consumption.
The RA2 pin can be used as a simple D/A output with
limited drive capability. Due to the limited drive
capability, a buffer must be used in conjunction with the
Voltage Reference output for external connections to
V
REF
. Figure 8-3 shows an example buffering
technique.
REF
enabled
FIGURE 8-3:
VOLTAGE REFERENCE OUTPUT BUFFER EXAMPLE
TABLE 8-1:
REGISTERS ASSOCIATED WITH VOLTAGE REFERENCE
Address
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value On
POR,
BOR
Value on
all other
resets
9Fh
VRCON
VREN
VROE
VRR
VR3
VR2
VR1
VR0
000- 0000
000- 0000
1Fh
CMCON
C2OUT
C1OUT
CIS
CM2
CM1
CM0
00-- 0000
00-- 0000
85h
TRISA
TRISA5
TRISA4
TRISA3
TRISA2
TRISA1
TRISA0
--11 1111
--11 1111
Note 1: R is dependent upon the Voltage Reference Configuration VRCON<3:0> and VRCON<5>.
V
REF
output
Voltage
Reference
Output
Impedance
R
(1)
Pin RA2
V
REF
Module
PIC16C662
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PIC16C642-04E/SO 功能描述:8位微控制器 -MCU 7KB 176 RAM 22 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT
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