AD7142_17 datasheet(15/70 Pages) AD

부품명	AD7142

상세설명	Programmable Controller for Capacitance Touch Sensors

Download	70 Pages

Scroll/Zoom	100%

제조업체	AD [Analog Devices]

홈페이지	http://www.analog.com

Logo

15 / 70 page

Data Sheet

AD7142

Rev. B | Page 15 of 70

CAPACITANCE-TO-DIGITAL CONVERTER

The capacitance-to-digital converter on the AD7142 has a Σ-Δ

architecture with 16-bit resolution. There are 14 possible inputs to

the CDC that are connected to the input of the converter through a

switch matrix. The sampling frequency of the CDC is 250 kHz.

OVERSAMPLING THE CDC OUTPUT

The decimation rate, or oversampling ratio, is determined by

Bits[9:8] of the control register, as listed in Table 9.

Table 9. CDC Decimation Rate

Decimation Bit Value

Decimation Rate

CDC Output Rate

Per Stage

00

256

3.072 ms

01

128

1.536 ms

101

111

1 Do not use this setting.

The decimation process on the AD7142 is an averaging process

where a number of samples are taken and the averaged result is

output. Due to the architecture of the digital filter employed, the

amount of samples taken (per stage) is equal to 3 times the

decimation rate. So 3 × 256 or 3 × 128 samples are averaged to

obtain each stage result.

The decimation process reduces the amount of noise present in

the final CDC result. However, the higher the decimation rate,

the lower the output rate per stage, thus, a trade-off is possible

between a noise-free signal and speed of sampling.

CAPACITANCE SENSOR OFFSET CONTROL

There are two programmable DACs on board the AD7142 to

null any capacitance sensor offsets. These offsets are associated

with printed circuit board capacitance or capacitance due to any

other source, such as connectors. In Figure 22, CIN is the

capacitance of the input sensors, and CBULK is the capacitance

between layers of the sensor PCB. CBULK can be offset using the

on-board DACs.

PLASTIC OVERLAY

SENSOR BOARD

CBULK

CIN

CAPACITIVE SENSOR

Figure 22. Capacitances Around the Sensor PCB

A simplified block diagram in Figure 23 shows how to apply the

STAGE_OFFSET registers to null the offsets. The 7-bit

POS_AFE_OFFSET and NEG_AFE_OFFSET registers program

the offset DAC to provide 0.16 pF resolution offset adjustment

over a range of ±20 pF. Apply the positive and negative offsets

to either the positive or the negative CDC input using the

NEG_AFE_OFFSET register and POS_AFE_OFFSET register.

This process is only required once during the initial capacitance

sensor characterization.

POS_AFE_OFFSET

16-BIT

CDC

NEG_AFE_OFFSET

+DAC

(20pF RANGE)

POS_AFE_OFFSET_SWAP BIT

NEG_AFE_OFFSET_SWAP BIT

7

16

CIN

SRC

CIN_CONNECTION_SETUP

REGISTER

–DAC

(20pF RANGE)

+

_

Figure 23. Analog Front-End Offset Control

CONVERSION SEQUENCER

The AD7142 has an on-chip sequencer to implement conversion

control for the input channels. Up to 12 conversion stages can

be performed in one sequence. Each of the 12 conversion stages

can measure the input from a different sensor. By using the

Bank 2 registers, each stage can be uniquely configured to support

multiple capacitance sensor interface requirements. For example,

a slider sensor can be assigned to STAGE1 through STAGE8,

with a button sensor assigned to STAGE0.

The AD7142 on-chip sequence controller provides conversion

control beginning with STAGE0. Figure 24 shows a block diagram

of the CDC conversion stages and CIN inputs. A conversion

sequence is defined as a sequence of CDC conversions starting

at STAGE0 and ending at the stage determined by the value

programmed in the SEQUENCE_STAGE_NUM register. Depen-

ding on the number and type of capacitance sensors that are

used, not all conversion stages are required. Use the SEQUENCE_

STAGE_NUM register to set the number of conversions in one

sequence, depending on the sensor interface requirements. For

example, this register would be set to 5 if the CIN inputs were

mapped to only six stages. In addition, set the STAGE_CAL_EN

registers according to the number of stages that are used.

유사한 부품 번호 - AD7142_17

제조업체	부품명	데이터시트	상세설명
Analog Devices	AD7142	958Kb / 73P	Programmable Controller for Capacitance Touch Sensors REV. A

More results

유사한 설명 - AD7142_17

제조업체	부품명	데이터시트	상세설명
Analog Devices	AD7142	958Kb / 73P	Programmable Controller for Capacitance Touch Sensors REV. A
	AD7143	1,006Kb / 56P	Programmable Controller for Capacitance Touch Sensors REV. 0
	AD7143	589Kb / 57P	Programmable Controller for Capacitance Touch Sensors
	AD7143	784Kb / 57P	Programmable Controller for Capacitance Touch Sensors REV. 0
	AD7142ACPZ-500RL7	844Kb / 73P	Programmable Controller for Capacitance Touch Sensors REV. A
	AD7148	1Mb / 56P	Programmable Touch Controller for Single Electrode Capacitance Sensors REV. 0
	AD7147	889Kb / 73P	CapTouch Programmable Controller for Single-Electrode Capacitance Sensors REV. D
	AD7147	1Mb / 68P	CapTouch??Programmable Controller for Single-Electrode Capacitance Sensors REV. 0
Texas Instruments	TSC2301	1Mb / 94P	[Old version datasheet] PROGRAMMABLE TOUCH SCREEN CONTROLLER
ON Semiconductor	LC717A30UR	241Kb / 14P	Capacitance?륞igital?륝onverter LSI for Electrostatic Capacitive Touch Sensors November, 2018 ??Rev. 0

More results

AD7142 데이터시트(PDF) 15 Page - Analog Devices

AD7142 데이터시트(HTML) 15 Page - Analog Devices

유사한 부품 번호 - AD7142_17

유사한 설명 - AD7142_17

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

데이터시트 다운로드

링크 URL