參數(shù)資料
型號: PIC18F442T-E/ML
廠商: Microchip Technology
文件頁數(shù): 120/134頁
文件大?。?/td> 0K
描述: IC MCU FLASH 8KX16 EE A/D 44QFN
標(biāo)準(zhǔn)包裝: 1,600
系列: PIC® 18F
核心處理器: PIC
芯體尺寸: 8-位
速度: 40MHz
連通性: I²C,SPI,UART/USART
外圍設(shè)備: 欠壓檢測/復(fù)位,LVD,POR,PWM,WDT
輸入/輸出數(shù): 34
程序存儲器容量: 16KB(8K x 16)
程序存儲器類型: 閃存
EEPROM 大?。?/td> 256 x 8
RAM 容量: 768 x 8
電壓 - 電源 (Vcc/Vdd): 4.2 V ~ 5.5 V
數(shù)據(jù)轉(zhuǎn)換器: A/D 8x10b
振蕩器型: 外部
工作溫度: -40°C ~ 125°C
封裝/外殼: 44-VQFN 裸露焊盤
包裝: 帶卷 (TR)
PIC16C9XX
DS30444E - page 86
1997 Microchip Technology Inc.
12.5
A/D Operation During Sleep
The A/D module can operate during SLEEP mode. This
requires that the A/D clock source be set to RC
(ADCS1:ADCS0 = 11). When the RC clock source is
selected, the A/D module waits one instruction cycle
before starting the conversion. This allows the SLEEP
instruction to be executed, which eliminates all digital
switching noise from the conversion. When the conver-
sion is completed the GO/DONE bit will be cleared, and
the result loaded into the ADRES register. If the A/D
interrupt is enabled, the device will wake-up from
SLEEP. If the A/D interrupt is not enabled, the A/D mod-
ule will then be turned off, although the ADON bit will
remain set.
When the A/D clock source is another clock option (not
RC), a SLEEP instruction will cause the present conver-
sion to be aborted and the A/D module to be turned off,
though the ADON bit will remain set.
Turning off the A/D places the A/D module in its lowest
current consumption state.
12.6
A/D Accuracy/Error
The absolute accuracy specied for the A/D converter
includes the sum of all contributions for quantization
error, integral error, differential error, full scale error, off-
set error, and monotonicity. It is dened as the maxi-
mum deviation from an actual transition versus an ideal
transition for any code. The absolute error of the A/D
converter is specied at <
±1 LSb for VDD = VREF (over
the device’s specied operating range). However, the
accuracy of the A/D converter will degrade as VDD
diverges from VREF.
For a given range of analog inputs, the output digital
code will be the same. This is due to the quantization of
the analog input to a digital code. Quantization error is
typically
± 1/2 LSb and is inherent in the analog to dig-
ital conversion process. The only way to reduce quanti-
zation error is to increase the resolution of the A/D
converter.
Offset error measures the rst actual transition of a
code versus the rst ideal transition of a code. Offset
error shifts the entire transfer function. Offset error can
be calibrated out of a system or introduced into a sys-
tem through the interaction of the total leakage current
and source impedance at the analog input.
Gain error measures the maximum deviation of the last
actual transition and the last ideal transition adjusted for
offset error. This error appears as a change in slope of
the transfer function. The difference in gain error to full
Note:
For the A/D module to operate in SLEEP,
the A/D clock source must be set to RC
(ADCS1:ADCS0 = 11). To perform an A/D
conversion in SLEEP, ensure the SLEEP
instruction immediately follows the instruc-
tion that sets the GO/DONE bit.
scale error is that full scale does not take offset error
into account. Gain error can be calibrated out in soft-
ware.
Linearity error refers to the uniformity of the code
changes. Linearity errors cannot be calibrated out of
the system. Integral non-linearity error measures the
actual code transition versus the ideal code transition
adjusted by the gain error for each code.
Differential non-linearity measures the maximum actual
code width versus the ideal code width. This measure
is unadjusted.
The maximum pin leakage current is
± 1 A.
In systems where the device frequency is low, use of
the A/D RC clock is preferred. At moderate to high fre-
quencies, TAD should be derived from the device oscil-
lator. TAD must not violate the minimum and should be
≤ 8 s for preferred operation. This is because TAD,
when derived from TOSC, is kept away from on-chip
phase clock transitions. This reduces, to a large extent,
the effects of digital switching noise. This is not possible
with the RC derived clock. The loss of accuracy due to
digital switching noise can be signicant if many I/O
pins are active.
In systems where the device will enter SLEEP mode
after the start of the A/D conversion, the RC clock
source selection is required. In this mode, the digital
noise from the modules in SLEEP are stopped. This
method gives high accuracy.
12.7
Effects of a RESET
A device reset forces all registers to their reset state.
This forces the A/D module to be turned off, and any
conversion is aborted.
The value that is in the ADRES register is not modied
for a Power-on Reset. The ADRES register will contain
unknown data after a Power-on Reset.
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