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| 型號： | pic12ce674 |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | 8-Pin, 8-Bit CMOS Microcontroller with A/D Converter(具A/D轉(zhuǎn)換器和EEPROM數(shù)據(jù)存儲器的8位微控制器) |
| 中文描述： | 8引腳，8位CMOS微控制器與A / D轉(zhuǎn)換器（具的A / D轉(zhuǎn)換器和EEPROM的數(shù)據(jù)存儲器的8位微控制器） |
| 文件頁數(shù)： | 40/112頁 |
| 文件大小： | 1205K |
| 代理商： | PIC12CE674 |
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PIC12CE67X
DS40181A-page 40
Preliminary
1998 Microchip Technology Inc.
8.1
For the A/D converter to meet its specified accuracy,
the charge holding capacitor (C
HOLD
) must be allowed
to fully charge to the input channel voltage level. The
analog input model is shown in Figure 8-4. The source
impedance (R
S
) and the internal sampling switch (R
SS
)
impedance directly affect the time required to charge
the capacitor C
HOLD
. The sampling switch (R
SS
)
impedance varies over the device voltage (V
DD
), see
Figure 8-4.
The maximum recommended imped-
ance for analog sources is 10 k
. After the analog
input channel is selected (changed) this acquisition
must be done before the conversion can be started.
To calculate the minimum acquisition time, Equation 8-
1 may be used. This equation assumes that 1/2 LSb
error is used (512 steps for the A/D). The 1/2 LSb error
is the maximum error allowed for the A/D to meet its
specified resolution.
A/D Sampling Requirements
EQUATION 8-1:
A/D MINIMUM CHARGING
TIME
V
HOLD
= (V
REF
- (V
REF
/512)) (1 - e
(-Tc/C
HOLD
(R
IC
+ R
SS
+ R
S
))
)
or
Tc = -(51.2 pF)(1 k
+ R
SS
+ R
S
) ln(1/511)
Example 8-1 shows the calculation of the minimum
required acquisition time T
ACQ
. This calculation is
based on the following system assumptions.
Rs = 10 k
1/2 LSb error
V
DD
= 5V
→
Rss = 7 k
Temp (system max.) = 50
°
C
V
HOLD
= 0 @ t = 0
EXAMPLE 8-1:
CALCULATING THE
MINIMUM REQUIRED
SAMPLE TIME
T
ACQ
= Amplifier Settling Time +
Holding Capacitor Charging Time +
Temperature Coefficient
T
ACQ
= 5
μ
s + Tc + [(Temp - 25
°
C)(0.05
μ
s/
°
C)]
T
C
=
-C
HOLD
(R
IC
+ R
SS
+ R
S
) ln(1/512)
-51.2 pF (1 k
+ 7 k
+ 10 k
) ln(0.0020)
-51.2 pF (18 k
) ln(0.0020)
-0.921
μ
s (-6.2146)
5.724
μ
s
T
ACQ
= 5
μ
s + 5.724
μ
s + [(50
°
C - 25
°
C)(0.05
μ
s/
°
C)]
10.724
μ
s + 1.25
μ
s
11.974
μ
s
Note 1:
The reference voltage (V
REF
) has no
effect on the equation, since it cancels
itself out.
Note 2:
The charge holding capacitor (C
HOLD
) is
not discharged after each conversion.
Note 3:
The maximum recommended impedance
for analog sources is 10 k
. This is
required to meet the pin leakage specifi-
cation.
Note 4:
After a conversion has completed, a
2.0 T
AD
delay must complete before
acquisition can begin again. During this
time the holding capacitor is not con-
nected to the selected A/D input channel.
FIGURE 8-4:
ANALOG INPUT MODEL
C
PIN
5 pF
VA
Rs
RAx
V
DD
V
T
= 0.6V
V
T
= 0.6V
I leakage
±
500 nA
R
IC
≤
1k
Sampling
SS
R
SS
HOLD
C
= 51.2 pF
V
SS
6V
5V
4V
3V
2V
Sampling Switch
( k
)
5 6 7 8 9 10 11
V
DD
Legend C
PIN
V
T
I leakage
R
IC
SS
C
HOLD
= input capacitance
= threshold voltage
= leakage current at the pin due to
various junctions
= interconnect resistance
= sampling switch
= sample/hold capacitance (from DAC)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| PIC12CE674/JW | 功能描述:8位微控制器 -MCU 3.5KB 128 RAM 6 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 |
| PIC12CE674-04/JM | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:8-Pin, 8-Bit CMOS Microcontroller with A/D Converter |
| PIC12CE674-04/JW | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:8-Pin, 8-Bit CMOS Microcontroller with A/D Converter and EEPROM Data Memory |
| PIC12CE674-04/P | 功能描述:8位微控制器 -MCU 3.5KB 128 RAM 6 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 |
| PIC12CE674-04/P | 制造商:Microchip Technology Inc 功能描述:IC 8BIT CMOS MCU 12CE674 DIP8 |
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