AD7143ACPZ Analog Devices Inc, AD7143ACPZ Datasheet - Page 12

IC, CDC, 16BIT, SMD, LFCSP-16, 7143

AD7143ACPZ

Manufacturer Part Number
AD7143ACPZ
Description
IC, CDC, 16BIT, SMD, LFCSP-16, 7143
Manufacturer
Analog Devices Inc
Datasheet

Specifications of AD7143ACPZ

Supply Voltage Range
2.6V To 3.6V
Operating Temperature Range
-40°C To +85°C
Digital Ic Case Style
LFCSP
No. Of Pins
16
Svhc
No SVHC (18-Jun-2010)
Package / Case
LFCSP
Base Number
7143
Ic Function
Programmable Controller For Capacitance Touch Sensors
Rohs Compliant
Yes
Lead Free Status / RoHS Status
Lead free / RoHS Compliant

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AD7143
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 AD7143.
If the application requires high resolution sensors, such as scroll
bars or wheels, software is required that runs on the host
processor. (No software is required for button sensors.) The
memory requirements for the host depend upon the sensor, and
are typically 9 kB of code and 600 bytes of data memory.
Analog Devices supplies the sensor PCB footprint design
libraries to the customer based on the customer’s specifications,
and supplies any necessary software on an open-source basis.
OPERATING MODES
The AD7143 has three operating modes. Full power mode,
where the device is always fully powered, is suited for applications
where power is not a concern. One example is game consoles
that have an ac power supply. Low power mode, where the part
automatically powers down, is tailored to give significant power
savings over 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 (Bit 0 and Bit 1) of the control
register set the operating mode on the AD7143. The control
register is at Address 0x000. Table 6 shows the POWER_MODE
settings for each operating mode. To put the AD7143 into
shutdown mode, set the POWER_MODE bits to either 01 or 11.
Table 6. POWER_MODE Settings
POWER_MODE Bits
00
01
10
11
The power-on default setting of the POWER_MODE bits is 00,
full power mode.
SENSOR PCB
Figure 18. Three Part Capacitance Sensing Solution
S1
S2
S3
S4
S5
S6
S7
S8
8
AD7143
SRC
Operating Mode
Full power mode
Full shutdown mode
Low power mode
Full shutdown mode
I
2
C
HOST PROCESSOR
600 BYTES RAM
9kB ROM
1 MIPS
Rev. 0 | Page 12 of 56
Full Power Mode
In full power mode, all sections of the AD7143 remain fully
powered at all times. While a sensor is being touched, the
AD7143 processes the sensor data. If no sensor is touched, the
AD7143 measures the ambient capacitance level and uses this
data for the on-chip compensation routines. In full power
mode, the AD7143 converts at a constant rate. See the CDC
Conversion Sequence Time section for more information.
Low Power Mode
When in low power mode, the AD7143 POWER_MODE bits
are set to 10 upon device initialization. If the external sensors
are not touched, the AD7143 reduces its conversion frequency,
thereby greatly reducing its power consumption. The part
remains in a reduced power state when the sensors are not
touched. Every LP_CONV_DELAY ms (200 ms, 400 ms, 600
ms or 800 ms), the AD7143 performs a conversion and uses this
data to update the compensation logic. When an external
sensor is touched, the AD7143 begins a conversion sequence
every 25 ms to read back data from the sensors.
In low power mode, the total current consumption of the
AD7143 is an average of the current used during a conversion,
and the current used while the AD7143 is waiting for the next
conversion to begin. For example, when LP_CONV_DELAY is
400 ms, the AD7143 typically uses 0.9 mA current for 25 ms
and 15 μA for 400 ms of the conversion interval. Note that these
conversion timings can be altered through the register settings.
See the CDC Conversion Sequence Time section for more
information.
The time taken for the AD7143 to go from a full power state to
a reduced power state, once the user stops touching the external
sensors, is configurable. Once the sensors are not touched, the
PWR_DWN_TIMEOUT bits, in the Ambient Compensation
Ctrl 0 Register at Address 0x002, control the amount of time
necessary for the device to return to a reduced power state.
EVERY LP_CONV_DELAY ms
CONVERSION SEQUENCE
UPDATE COMPENSATION
LOGIC DATA PATH
Figure 19. Low Power Mode Operation
NO
AND INITIALIZATION
POWER_MODE = 10
AD7143 SETUP
TOUCHED?
SENSOR
ANY
YES
YES
CONVERSION SEQUENCE
SENSOR READBACK
PROXIMITY TIMER
EVERY 25ms FOR
COUNT DOWN
ANY SENSOR
TOUCHED?
NO
TIMEOUT

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