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AD7147A Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer AD7147A
Beschreibung CapTouch Programmable Controller
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 30 Seiten
AD7147A Datasheet, Funktion
www.DataSheet4U.com
CapTouch Programmable Controller for
Single-Electrode Capacitance Sensors
AD7147A
FEATURES
Programmable capacitance-to-digital converter (CDC)
Femtofarad (ff) 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 AD714x
On-chip RAM to store calibration data
Serial peripheral interface (SPI) (AD7147A)
I2C-compatible serial interface (AD7147A-1)
Separate VDRIVE level for serial interface
Interrupt output and general-purpose input/output (GPIO)
25-ball, 2.3 mm × 2.1 mm WLCSP
2.6 V to 3.6 V supply voltage
Low operating current
Full power mode: 1 mA
Low power mode: 28.96 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 AD7147A CapTouch™ controller is designed for use with
capacitance sensors implementing functions such as buttons,
scroll bars, and wheels. The sensors need only one PCB layer,
enabling ultrathin applications.
The AD7147A is an integrated CDC with on-chip environmen-
tal calibration. The CDC has 13 inputs channeled through a
switch matrix to a 16-bit, 250 kHz sigma-delta (Σ-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 and may require two PCB layers.
CIN0 D3
CIN1 A3
CIN2 B3
CIN3 A4
CIN4 C3
CIN5 A5
CIN6 B4
CIN7 B5
CIN8 C4
CIN9 C5
CIN10 D4
CIN11 D5
CIN12 E5
FUNCTIONAL BLOCK DIAGRAM
ACSHIELD VCC GND
E4 D2 E2
BIAS
E3
POWER-ON
RESET LOGIC
EXCITATION
SOURCE
AD7147A
CALIBRATION
RAM
16-BIT
Σ-Δ
CDC
CALIBRATION
ENGINE
CONTROL
AND DATA
REGISTERS
VDRIVE C2
SERIAL INTERFACE
AND CONTROL LOGIC
INTERRUPT
AND GPIO
LOGIC
B2 NC
A2 GPIO
E1 D1 C1 B1
A1
SDO SDI SCLK CS
(SDA) (ADD0)
(ADD1)
INT
NOTES
1. PIN NAMES IN PARENTHESES ARE FOR THE AD7147A-1.
Figure 1.
The AD7147A is designed for single electrode capacitance
sensors (grounded sensors). There is an active shield output to
minimize noise pickup in the sensor.
The AD7147A 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 AD7147A has an SPI-compatible serial interface, and the
AD7147A-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 AD7147A is available in a 25-ball, 2.3 mm × 2.1 mm
WLCSP and operates from a 2.6 V to 3.6 V supply. The operating
current consumption in low power mode is typically 28.96 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
©2009 Analog Devices, Inc. All rights reserved.






AD7147A Datasheet, Funktion
AD7147A
www.DataSheet4U.com
I2C TIMING SPECIFICATIONS (AD7147A-1)
TA = −40°C to +85°C, sample tested at 25°C to ensure compliance. VDRIVE = 1.65 V to 3.6 V, and VCC = 2.6 V to 3.6 V, unless otherwise
noted. All input signals timed from a voltage level of 1.6 V.
Table 5. I2C Timing Specifications1
Parameter
Limit
fSCLK 400
t1 0.6
t2 1.3
t3 0.6
t4 100
t5 300
t6 0.6
t7 0.6
t8 1.3
tR 300
tF 300
Unit
kHz max
μs min
μs min
μs min
ns min
ns min
μs min
μs min
μs min
ns max
ns max
Description
Start condition hold time, tHD; STA
Clock low period, tLOW
Clock high period, tHIGH
Data setup time, tSU; DAT
Data hold time, tHD; DAT
Stop condition setup time, tSU; STO
Start condition setup time, tSU; STA
Bus-free time between stop and start conditions, tBUF
Clock/data rise time
Clock/data fall time
1 Guaranteed by design, not production tested.
I2C Timing Diagram
SCLK
t2 tR
t1
t5
SDA
t8
STOP START
tF
t3
t4
t1
t7
START
Figure 3. I2C Detailed Timing Diagram
t6
STOP
200µA
IOL
TO OUTPUT
PIN CL
50pF
1.6V
200µA
IOH
Figure 4. Load Circuit for Digital Output Timing Specifications
Rev. 0 | Page 6 of 68

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AD7147A pdf, datenblatt
AD7147A
Registering a Sensor Activation
When a user approaches a sensor, the total capacitance associated
with that sensor changes and is measured by the AD7147A. If
the change causes a set threshold to be exceeded, the AD7147A
interprets this as a sensor activation.
On-chip threshold limits are used to determine when a sensor
activation occurs. Figure 20 shows the change in CDC_RESULT_Sx
when a user activates a sensor. The sensor is deemed to be active
only when the value of CDC_RESULT_Sx is either greater than the
value of STAGEx_HIGH_THRESHOLD or less than the value
of STAGEx_LOW_THRESHOLD.
SENSOR ACTIVE A
STAGEx_HIGH_THRESHOLD
CDC_RESULT_Sx
AMBIENT OR
NO-TOUCH VALUE
STAGEx_LOW_THRESHOLD
SENSOR ACTIVE B
Figure 20. Sensor Activation Thresholds
In Figure 20, two sensor activations are shown. Sensor Active A
occurs when a sensor is connected to the positive input of the
converter. In this case, when a user activates the sensor, there is an
increase in CDC code, and the value of CDC_RESULT_Sx exceeds
that of STAGEx_HIGH_THRESHOLD. Sensor Active B occurs
when the sensor is connected to the negative input of the converter.
In this case, when a user activates the sensor, there is a decrease
in CDC code, and the value of CDC_RESULT_Sx becomes less
than the value of STAGEx_LOW_THRESHOLD.
For each conversion stage, the STAGEx_HIGH_THRESHOLD
and STAGEx_LOW_THRESHOLD registers are in Bank 3.
The values in these registers are updated automatically by the
AD7147A due to its environmental calibration and adaptive
threshold logic.
At power-up, the values in the STAGEx_HIGH_THRESHOLD
and STAGEx_LOW_THRESHOLD registers are the same as those
in the STAGEx_OFFSET_HIGH and STAGEx_OFFSET_LOW
registers in Bank 2. The user must program the STAGEx_OFFSET
_HIGH and STAGEx_OFFSET_LOW registers on device power-
up. See the Environmental Calibration section of the data sheet
for more information.
www.DataSheet4U.com
Complete Solution for Capacitance Sensing
Analog Devices, Inc., provides a complete solution for capacitance
sensing. The two main elements to the solution are the sensor
PCB and the AD7147A.
If the application requires high resolution sensors such as scroll
bars or wheels, software that runs on the host processor is required.
The memory requirements for the host depend on the sensor
and are typically 10 kB of code and 600 bytes of data memory,
depending on the sensor type.
SENSOR PCB
AD7147A
SPI OR I2C
HOST PROCESSOR
1 MIPS
10kB ROM
600 BYTES RAM
Figure 21. Three-Part Capacitance Sensing Solution
Analog Devices supplies the sensor PCB footprint design
libraries to the customer and supplies any necessary software on
an open-source basis.
BIAS PIN
This pin is connected internally to a bias node of the AD7147A.
To ensure correct operation of the AD7147A, connect a 100 nF
capacitor between the BIAS pin and ground. The voltage seen at
the BIAS pin is VCC/2.
OPERATING MODES
The AD7147A has three operating modes. Full power mode, where
the device is always fully powered, is suited for applications where
power is not a concern (for example, game consoles that have an
ac power supply). Low power mode, where the part automatically
powers down when no sensor is active, is tailored to provide
significant power savings compared with full power mode and
is suited for mobile applications, where power must be conserved.
In shutdown mode, the part shuts down completely.
The POWER_MODE Bits[1:0] of the power control register
(PWR_CONTROL, Address 0x000) set the operating mode on
the AD7147A. Table 8 shows the POWER_MODE settings for
each operating mode. To put the AD7147A into shutdown
mode, set the POWER_MODE bits to either 01 or 11.
Table 8. POWER_MODE Settings
POWER_MODE Bits
Operating Mode
00 Full power mode
01 Shutdown mode
10 Low power mode
11 Shutdown mode
The power-on default setting of the POWER_MODE bits is 00,
full power mode.
Rev. 0 | Page 12 of 68

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