参数资料
型号: AD7142ACPZ-1REEL
厂商: Analog Devices Inc
文件页数: 25/73页
文件大小: 0K
描述: IC CAP-TO-DGTL CONV PROG 32LFCSP
标准包装: 1
类型: 电容数字转换器
分辨率(位): 16 b
采样率(每秒): 250k
数据接口: 串行
电压电源: 单电源
电源电压: 2.6 V ~ 3.6 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 32-VFQFN 裸露焊盘,CSP
供应商设备封装: 32-LFCSP-VQ
包装: 标准包装
产品目录页面: 781 (CN2011-ZH PDF)
其它名称: AD7142ACPZ-1REELDKR
AD7142
Rev. A | Page 30 of 72
OUTPUTS
EXCITATION SOURCE
The excitation source onboard the AD7142 is a square wave
source with a frequency of 250 kHz. This excitation source
forms the electric field between the transmitter and receiver in
the external capacitance sensor PCB. The source is output from
the AD7142 on two pins, the SRC pin and the SRC pin (outputs
an inverted version of the source square wave). The SRC signal
offsets large external sensor capacitances. SRC is not used in the
majority of applications.
The source output can be disabled from both output pins
separately by writing to the control register bits (Address
0x000[13:12]). Setting Bit 12 in this register to 1 disables the
source output on the SRC pin. Setting Bit 13 in this register to 1
disables the inverted source output on the SRC pin.
CSHIELD OUTPUT
To prevent leakage from the external capacitance sensors, the
sensor traces can be shielded. The AD7142 has a voltage output
that can be used as the potential for any shield traces, CSHIELD.
The CSHIELD voltage is equal to AVDD/2.
The CSHIELD potential is derived from the output of the AD7142
internal amplifier, and is of equal potential to the CIN input
lines. Because the shield is at the same potential as the sensor
traces, no leakage to ground occurs. To eliminate any ringing on
the CSHIELD output, connect a 10 nF capacitor between the
CSHIELD pin and ground. This capacitor is required, whether
CSHIELD is used in the application or not.
For most applications, CSHIELD is not used, and a ground plane is
used instead around the sensors.
GPIO
The AD7142 has one GPIO pin located at Pin 26. It can be
configured as an input or an output. The GPIO_SETUP
Bits[13:12] in the interrupt enable register determine how the
GPIO pin is configured.
Table 15. GPIO_SETUP Bits
GPIO_SETUP
GPIO Configuration
00
GPIO disabled
01
Input
10
Output low
11
Output high
When the GPIO is configured as an output, the voltage level on
the pin is set to either a low level or a high level, as defined by
the GPIO_SETUP bits shown in Table 15.
When the GPIO is configured as an input, the
GPIO_INPUT_CONFIG bits in the interrupt enable register
determine the response of the AD7142 to a signal on the GPIO
pin. The GPIO can be configured as either active high or active
low, as well as either edge-triggered or level-triggered, as listed
Table 16. GPIO_INPUT_CONFIG Bits
GPIO_INPUT_CONFIG
GPIO Configuration
00
Triggered on negative level (active low)
01
Triggered on positive edge (active high)
10
Triggered on negative edge (active low)
11
Triggered on positive level (active high)
When GPIO is configured as an input, it triggers the interrupt
output on the AD7142. Table 14 lists the interrupt output
behavior for each of the GPIO configuration setups.
USING THE GPIO TO TURN ON/OFF AN LED
The GPIO on the AD7142 can be used to turn on and off LEDs
by setting the GPIO as either output high or low. Setting the
GPIO output high turns on the LED; setting the GPIO output
low turns off the LED. The GPIO pin connects to a transistor
that provides the drive current for the LED. Suitable transistors
include the KTC3875.
AD7142
GPIO
VCC
KTC3875
OR SIMILAR
05
70
2-
0
6
1
Figure 45. Controlling LEDs Using the GPIO
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