參數(shù)資料
型號(hào)： AD7147AACBZ-RL
廠商： Analog Devices Inc
文件頁(yè)數(shù)： 17/69頁(yè)
文件大?。?/td> 0K
描述： IC CDC 13CH SPI W/RAM 25WLCSP
產(chǎn)品變化通告： 8mm Carrier Tape Changes 28/Feb/2012
標(biāo)準(zhǔn)包裝： 10,000
系列： CapTouch™
類(lèi)型： 電容數(shù)字轉(zhuǎn)換器
分辨率（位）： 16 b
采樣率（每秒）： 250k
數(shù)據(jù)接口： 串行，SPI?
電壓電源： 單電源
電源電壓： 2.6 V ~ 3.6 V
工作溫度： -40°C ~ 85°C
安裝類(lèi)型： 表面貼裝
封裝/外殼： 25-UFBGA，WLCSP
供應(yīng)商設(shè)備封裝： 25-WLCSP
包裝： 帶卷 (TR)
AD7147A
Rev. B | Page 23 of 68
ENVIRONMENTAL CALIBRATION
CDC
O
UT
P
UT
CO
D
E
S
t
STAGEx_LOW_THRESHOLD
STAGEx_HIGH_THRESHOLD
CDC AMBIENT VALUE
CHANGING ENVIRONMENTAL CONDITIONS
SENSOR 1 INT
ASSERTED
SENSOR 2 INT
ASSERTED
07727-
034
The AD7147A provides on-chip capacitance sensor calibration
to automatically adjust for environmental conditions that have
an effect on the ambient levels of the capacitance sensor. The
output levels of the capacitance sensor are sensitive to tempera-
ture, humidity, and, in some cases, dirt.
The AD7147A achieves optimal and reliable sensor performance
by continuously monitoring the CDC ambient levels and compen-
sating for any environmental changes by adjusting the values of
the STAGEx_HIGH_THRESHOLD registers and the STAGEx_
LOW_THRESHOLD registers as described in the Threshold
Equations section. The CDC ambient level is defined as the
output level of the capacitance sensor during periods when the
user is not approaching or in contact with the sensor.
Figure 34. Ideal Sensor Behavior with a Constant Ambient Level
CAPACITANCE SENSOR BEHAVIOR WITHOUT
CALIBRATION
After the AD7147A is configured, the compensation logic runs
automatically with each conversion when the AD7147A is not
being touched. This allows the AD7147A to compensate for
rapidly changing environmental conditions.
Figure 35 shows the typical behavior of a capacitance sensor when
calibration is not applied and the ambient levels drifting over time
as environmental conditions change. As a result of the initial
threshold levels remaining constant while the ambient levels
drift upward, Sensor 2 fails to detect a user contact in this example.
The ambient compensation control registers provide the host
with access to general setup and controls for the compensation
algorithm. On-chip RAM stores the compensation data for each
conversion stage, as well as setup information specific for each stage.
describes how the AD7147A adaptive calibration algorithm
prevents such errors from occurring.
Figure 34 shows an example of the ideal behavior of a capaci-
tance sensor, where the CDC ambient level remains constant
regardless of the environmental conditions. The CDC output
shown is for a pair of differential button sensors, where one
sensor caused an increase and the other caused a decrease in
measured capacitance when activated. The positive and negative
sensor threshold levels are calculated as a percentage of the
STAGEx_OFFSET_HIGH and STAGEx_OFFSET_LOW values,
and are based on the threshold sensitivity settings and the
ambient value. These values are sufficient to detect a sensor
contact and result in the AD7147A asserting the INT output
when the threshold levels are exceeded.
CD
C
O
U
T
P
UT
CO
D
E
S
t
CDC AMBIENT
VALUE DRIFTING
CHANGING ENVIRONMENTAL CONDITIONS
STAGEx_HIGH_THRESHOLD
STAGEx_LOW_THRESHOLD
SENSOR 1 INT
ASSERTED
SENSOR 2 INT
NOT ASSERTED
07
72
7-
0
35
Figure 35. Typical Sensor Behavior Without Calibration
THRESHOLD EQUATIONS
On-Chip Logic Stage High Threshold
Y
SENSITIVIT
THRESHOLD
POS
HIGH
OFFSET
STAGEx
HIGH
OFFSET
STAGEx
HIGH
OFFSET
STAGEx
AMBIENT
SF
STAGEx
THRESHOLD
HIGH
STAGEx
_
16
4
_
4
_
×
+
=
(1)
On-Chip Logic Stage Low Threshold
Y
SENSITIVIT
THRESHOLD
NEG
LOW
OFFSET
STAGEx
LOW
OFFSET
STAGEx
LOW
OFFSET
STAGEx
AMBIENT
SF
STAGEx
THRESHOLD
LOW
STAGEx
_
16
4
_
4
_
×
+
=
(2)
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AD7147ACPZ-1REEL 功能描述:IC CAP-TO-DGTL CONV PROG 24LFCSP RoHS:是 類(lèi)別:集成電路 (IC) >> 數(shù)據(jù)采集 - ADCs/DAC - 專(zhuān)用型 系列:CapTouch™ 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:50 系列:- 類(lèi)型:數(shù)據(jù)采集系統(tǒng)（DAS） 分辨率（位）:16 b 采樣率（每秒）:21.94k 數(shù)據(jù)接口:MICROWIRE?，QSPI?，串行，SPI? 電壓電源:模擬和數(shù)字 電源電壓:1.8 V ~ 3.6 V 工作溫度:-40°C ~ 85°C 安裝類(lèi)型:表面貼裝 封裝/外殼:40-WFQFN 裸露焊盤(pán) 供應(yīng)商設(shè)備封裝:40-TQFN-EP（6x6） 包裝:托盤(pán)
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