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PDF AD7147 Data sheet ( Hoja de datos )
| Número de pieza | AD7147 | |
| Descripción | CapTouch Programmable Controller | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AD7147 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
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CapTouch™ Programmable Controller for
Single-Electrode Capacitance Sensors
AD7147
www.daFtaEsAhTeeUt4RuE.cSom
Programmable capacitance-to-digital converter (CDC)
Femtofarad resolution
13 capacitance sensor inputs
9 ms update rate, all 13 sensor inputs
No external RC components required
Automatic conversion sequencer
On-chip automatic calibration logic
Automatic compensation for environmental changes
Automatic adaptive threshold and sensitivity levels
Register map is compatible with the AD7142
On-chip RAM to store calibration data
SPI-compatible (serial-peripheral-interface-compatible)
serial interface (AD7147)
I2C-compatible serial interface (AD7147-1)
Separate VDRIVE level for serial interface
Interrupt output and general-purpose input/output (GPIO)
24-lead, 4 mm × 4 mm LFCSP
2.6 V to 3.3 V supply voltage
Low operating current
Full power mode: 1 mA
Low power mode: 21.5 μA
APPLICATIONS
Cell phones
Personal music and multimedia players
Smart handheld devices
Television, A/V, and remote controls
Gaming consoles
Digital still cameras
GENERAL DESCRIPTION
The AD7147 is designed for use with capacitance sensors
implementing functions such as buttons, scroll bars, and
wheels. The sensors need only one PCB layer, enabling ultra
thin applications.
The AD7147 is an integrated CDC with on-chip environmental
calibration. The CDC has 13 inputs channeled through a switch
matrix to a 16-bit, 250 kHz sigma-delta (∑-Δ) converter. The CDC
is capable of sensing changes in the capacitance of the external
sensors and uses this information to register a sensor activation.
By programming the registers, the user has full control over the
CDC setup.
High resolution sensors require minor software to run on the
host processor.
CIN0 19
CIN1 20
CIN2 21
CIN3 22
CIN4 23
CIN5 24
CIN6 1
CIN7 2
CIN8 3
CIN9 4
CIN10 5
CIN11 6
CIN12 7
FUNCTIONAL BLOCK DIAGRAM
ACSHIELD VCC
8 11
GND
10
BIAS
9
POWER-ON
RESET LOGIC
EXCITATION
SOURCE
AD7147
CALIBRATION
RAM
16-BIT
Σ-Δ
CDC
CALIBRATION
ENGINE
CONTROL
AND DATA
REGISTERS
VDRIVE 12
SERIAL INTERFACE
AND CONTROL LOGIC
INTERRUPT
AND GPIO
LOGIC
13 14 15 16
SDO/ SDI/ SCLK CS/
SDA ADD0
ADD1
17
INT
Figure 1. AD7147 Block Diagram
18 GPIO
The AD7147 is designed for single-electrode capacitance
sensors (grounded sensors). There is an active shield output to
minimize noise pickup in the sensor.
The AD7147 has on-chip calibration logic to compensate for
changes in the ambient environment. The calibration sequence
is performed automatically and at continuous intervals as long
as the sensors are not touched. This ensures that there are no
false or nonregistering touches on the external sensors due to
a changing environment.
The AD7147 has an SPI-compatible serial interface, and the
AD7147-1 has an I2C®-compatible serial interface. Both parts have
an interrupt output, as well as a GPIO. There is a VDRIVE pin to set
the voltage level for the serial interface independent of VCC.
The AD7147 is available in a 24-lead, 4 mm × 4 mm LFCSP and
operates from a 2.6 V to 3.6 V supply. The operating current con-
sumption in low power mode is typically 26 μA for 13 sensors.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2007 Analog Devices, Inc. All rights reserved.
1 page  
AD7147
SPI TIMING SPECIFICATIONS (AD7147)
TA = −40°C to +85°C, VDRIVE = 1.65 V to 3.6 V, and VCC = 2.6 V to 3.6 V, unless otherwise noted. Sample tested at 25°C to ensure
compliance. All input signals are specified with tR = tF = 5 ns (10% to 90% of VCC) and timed from a voltage level of 1.6 V.
Table 4. SPI Timing Specifications
www.daPtarsahmeeet4teur.com
Limit
fSCLK
5
t1 5
t2 20
t3 20
t4 15
t5 15
t6 20
t7 16
t8 15
Unit
MHz max
ns min
ns min
ns min
ns min
ns min
ns max
ns max
ns min
Description
SCLK frequency
CS falling edge to first SCLK falling edge
SCLK high pulse width
SCLK low pulse width
SDI setup time
SDI hold time
SDO access time after SCLK falling edge
CS rising edge to SDO high impedance
SCLK rising edge to CS high
CS
SCLK
SDI
SDO
t1 t2
1
t4
t5
MSB
t3
23
15 16
1
2
LSB
t6
MSB
Figure 2. SPI Detailed Timing Diagram
t8
15 16
t7
LSB
Rev. 0 | Page 5 of 68
5 Page 
THEORY OF OPERATION
The AD7147 and AD7147-1 are CDCs with on-chip
environmental compensation. They are intended for use in
portable systems requiring high resolution user input. The
www.daintatsehrneealt4cuir.ccoumitry consists of a 16-bit, ∑-Δ converter that can
change a capacitive input signal into a digital value. There are
13 input pins, CIN0 to CIN12, on the AD7147 or AD7147-1. A
switch matrix routes the input signals to the CDC. The result of
each capacitance-to-digital conversion is stored in on-chip
registers. The host subsequently reads the results over the serial
interface. The AD7147 has an SPI interface, and the AD7147-1
has an I2C interface, ensuring that the parts are compatible with
a wide range of host processors. AD7147 refers to both the
AD7147 and AD7147-1, unless otherwise noted, from this
point forward in this data sheet.
The AD7147 interfaces with up to 13 external capacitance
sensors. These sensors can be arranged as buttons, scroll bars,
or wheels, or as a combination of sensor types. The external
sensors consist of an electrode on a single- or multiple-layer
PCB that interfaces directly to the AD7147.
The AD7147 can be set up to implement any set of input
sensors by programming the on-chip registers. The registers can
also be programmed to control features such as averaging,
offsets, and gains for each of the external sensors. There is an
on-chip sequencer that controls how each of the capacitance
inputs is polled.
The AD7147 has on-chip digital logic and 528 words of RAM
that are used for environmental compensation. The effects of
humidity, temperature, and other environmental factors can
affect the operation of capacitance sensors. Transparent to the
user, the AD7147 performs continuous calibration to compen-
sate for these effects, allowing the AD7147 to consistently
provide error-free results.
The AD7147 requires a companion algorithm that runs on the
host or another microcontroller to implement high resolution
sensor functions, such as scroll bars or wheels. However, no
companion algorithm is required to implement buttons. Button
sensors are implemented on chip, entirely in digital logic.
The AD7147 can be programmed to operate in either full power
mode or low power automatic wake-up mode. The automatic
wake-up mode is particularly suited for portable devices that
AD7147
require low power operation to provide the user with significant
power savings and full functionality.
The AD7147 has an interrupt output, INT, to indicate when
new data has been placed into the registers. INT is used to
interrupt the host on sensor activation. The AD7147 operates
from a 2.6 V to 3.6 V supply and is available in a 24-lead, 4 mm ×
4 mm LFCSP.
CAPACITANCE-SENSING THEORY
The AD7147 measures capacitance changes from single-electrode
sensors. The sensor electrode on the PCB comprises one plate
of a virtual capacitor. The other plate of the capacitor is the user’s
finger, which is grounded with respect to the sensor input.
The AD7147 first outputs an excitation signal to charge the
plate of the capacitor. When the user comes close to the sensor,
the virtual capacitor is formed, with the user acting as the second
capacitor plate.
PLASTIC COVER
SENSOR PCB
Σ-Δ
ADC
16-BIT
DATA
AD7147
EXCITATION
SIGNAL
250kHz
Figure 19. Capacitance-Sensing Method
A square wave excitation signal is applied to CINx during
the conversion, and the modulator continuously samples the
charge going through CINx. The output of the modulator is
processed via a digital filter, and the resulting digital data is
stored in the CDC_RESULT_Sx registers for each conversion
stage, at Address 0x00B to Address 0x016.
Rev. 0 | Page 11 of 68
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet AD7147.PDF ] | |
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