參數(shù)資料
型號： PIC16F785
廠商： Microchip Technology Inc.
英文描述： 20-Pin Flash-Based 8-Bit CMOS Microcontroller with Two-Phase Asychronous Feedback PWM, Dual High-Speed Comparators and Dual Operational Amplifiers
中文描述： 20引腳基于閃存的8兩相異步反饋的PWM，雙高位CMOS微控制器的高速比較器和雙運算放大器
文件頁數(shù)： 85/178頁
文件大?。?/td> 1620K
代理商： PIC16F785
2004 Microchip Technology Inc.
Preliminary
DS41249A-page 83
PIC16F785
12.2
A/D Acquisition Requirements
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 12-4. 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 12-4.
The maximum recom-
mended impedance for analog sources is 10 k
.
As
the impedance is decreased, the acquisition time may
be decreased. 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 12-1
may be used. This equation assumes that 1/2 LSb error is
used (1024 steps for the A/D). The 1/2 LSb error is the
maximum error allowed for the A/D to meet its specified
resolution.
To calculate the minimum acquisition time, T
ACQ
, see
the
PICmicro
Mid-Range
(DS33023).
Reference
Manual
EQUATION 12-1:
ACQUISITION TIME EXAMPLE
Note 1:
The reference voltage (V
REF
) has no effect on the equation, since it cancels itself out.
2:
The charge holding capacitor (C
HOLD
) is not discharged after each conversion.
3:
The maximum recommended impedance for analog sources is 10 k
. This is required to meet the pin
leakage specification.
T
ACQ
Amplifier Settling Time
T
AMP
T
C
+
2μs
T
C
+
+
Hold Capacitor Charging Time
Temperature Coefficient
+
+
=
T
COFF
Temperature - 25°C
+
[
=
=
(
)
0.05μs/°C
(
)
]
T
C
C
HOLD
R
IC
10pF 1k
R
SS
R
S
+
7k
+
(
)
ln(1/2047)
10k
)
ln(0.0004885)
–
=
+
+
–
=
=
1.37
μs
T
ACQ
2μ
S
1.37μ
S
50°C- 25°C
(
)
0.05μ
S
/°C
(
)
[
]
+
+
=
4.67μ
S
=
V
APPLIED
1
e
RC
–
–
V
APPLIED
1
2047
-----------
–
=
V
APPLIED
1
1
2047
-----------
–
V
CHOLD
=
V
APPLIED
1
e
C
RC
–
–
V
CHOLD
=
;[1] V
CHOLD
charged to within 1/2 lsb
;[2] V
CHOLD
charge response to V
APPLIED
;combining [1] and [2]
Where C
HOLD
is charged to within 1/2 lsb:
Solving for T
C
:
Therefore:
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相關代理商/技術參數(shù)
參數(shù)描述
PIC16F785-E/ML 功能描述:8位微控制器 -MCU 3.5 KB 128 RAM 18I/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 安裝風格:SMD/SMT
PIC16F785-E/P 功能描述:8位微控制器 -MCU 14KB 368 RAM 33 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 安裝風格:SMD/SMT
PIC16F785-E/SO 功能描述:8位微控制器 -MCU 3.5KB FL 128R 18 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 安裝風格:SMD/SMT
PIC16F785-E/SS 功能描述:8位微控制器 -MCU 3.5KB FL 128R 18 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 安裝風格:SMD/SMT
PIC16F785-I/ML 功能描述:8位微控制器 -MCU 3.5 KB 128 RAM 18I/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 安裝風格:SMD/SMT
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