AD7147PACPZ-1RL Analog Devices Inc, AD7147PACPZ-1RL Datasheet - Page 13

• Manufacturer Part Number: AD7147PACPZ-1RL
• Description: CAPACITANCE TO DIGITAL CONVERTER
• Manufacturer: Analog Devices Inc
• Series: CapTouch™r
• Type: Capacitive Sensor Controllerr

Specifications of AD7147PACPZ-1RL

• Resolution (bits): 16 b
• Data Interface: I²C, Serial
• Voltage Supply Source: Single Supply
• Voltage - Supply: 2.6 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-LFCSP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sampling Rate (per Second): -
• Lead Free Status / Rohs Status: Compliant

Full Power Mode
In full power mode, all sections of the AD7147 remain fully
powered and converting at all times. While a sensor is being
touched, the AD7147 processes the sensor data. If no sensor is
touched, the AD7147 measures the ambient capacitance level
and uses this data for the on-chip compensation routines. In full
power mode, the AD7147 converts at a constant rate. See the
CDC Conversion Sequence Time section for more information.
Low Power Mode
When AD7147 is in low power mode, the POWER_MODE bits
are set to 10 upon device initialization. If the external sensors
are not touched, the AD7147 reduces its conversion frequency,
thereby greatly reducing its power consumption. The part remains
in a reduced power state while the sensors are not touched. The
AD7147 performs a conversion after a delay defined by the
LP_CONV_DELAY bits, and it uses this data to update the
compensation logic and check if the sensors are active. The
LP_CONV_DELAY bits set the delay between conversions to
200 ms, 400 ms, 600 ms, or 800 ms.
In low power mode, the total current consumption of the AD7147
is an average of the current used during a conversion and the
current used while the AD7147 is waiting for the next conversion
to begin. For example, when LP_CONV_DELAY is 400 ms, the
AD7147 typically uses 0.85 mA of current for 36 ms and 14 μA
of current for 400 ms during the conversion interval. (Note that
these conversion timings can be altered through the register
CONVERSION SEQUENCE
UPDATE COMPENSATION
EVERY LP_CONV_DELAY
LOGIC DATA PATH
Figure 22. Low Power Mode Operation, AD7147
NO
AND INITIALIZATION
POWER_MODE = 10
AD7147 SETUP
TOUCHED?
SENSOR
ANY
YES
YES
CONVERSION SEQUENCE
EVERY 9/18/36ms FOR
SENSOR READBACK
PROXIMITY TIMER
ANY SENSOR
COUNTDOWN
TOUCHED?
NO
TIMEOUT
Rev. B | Page 13 of 72
settings. See the CDC Conversion Sequence Time section for
more information.)
The time for the AD7147 to transition from a full power state to
a reduced power state after the user stops touching the external
sensors is configurable. The PWR_DOWN_TIMEOUT bits (in
the Ambient Compensation Control 0 (AMB_COMP_CTRL0)
Register at Address 0x002) control the time delay before the
AD7147 transitions to the reduced power state after the user
stops touching the sensors.
Latency from Touch to Response
In low power mode, the AD7147 remains in a low power state
until any one of the external sensors are touched. When a
sensor is touched, the AD7147 begins a conversion sequence
every 36 ms to read back data from the sensors. This means that
the latency between the user touching the sensor, and the AD7147
responding, is a maximum of LP_CONV_DELAY ms.
Low Latency from Touch to Response
In low power mode, the AD7147P model remains in a low power
state until proximity is detected on any one of the external sensors.
When proximity is detected, the AD714P begins a conversion
sequence every 36 ms, or 18 ms, or 9 ms to readback data from the
sensors. The latency between first touch and the AD7147P
responding is much reduced, compared to the AD7147, because
the part is already in a full power state by the time the user has
touched the sensor.
CONVERSION SEQUENCE
UPDATE COMPENSATION
EVERY LP_CONV_DELAY
LOGIC DATA PATH
Figure 23. Low Power Mode Operation, AD7147P
NO
AND INITIALIZATION
POWER_MODE = 10
AD7147P SETUP
TO SENSOR?
PROXIMITY
USER IN
YES
CONVERSION SEQUENCE
YES
EVERY 9/18/36ms FOR
SENSOR READBACK
PROXIMITY TIMER
COUNTDOWN
TO SENSOR?
PROXIMITY
USER IN
NO
AD7147
TIMEOUT