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PDF AD7889 Data sheet ( Hoja de datos )
| Número de pieza | AD7889 | |
| Descripción | Low Voltage Controller | |
| Fabricantes | Analog Devices | |
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Data Sheet
Low Voltage Controller for Touch Screens
AD7879/AD7889
FEATURES
4-wire touch screen interface
1.6 V to 3.6 V operation
Median and averaging filter to reduce noise
Automatic conversion sequencer and timer
User-programmable conversion parameters
Auxiliary analog input/battery monitor (0.5 V to 5 V)
1 optional GPIO
Interrupt outputs (INT, PENIRQ)
Touch-pressure measurement
Wake-up on touch function
Shutdown mode: 6 μA maximum
12-ball, 1.6 mm × 2 mm WLCSP
16-lead, 4 mm × 4 mm LFCSP
APPLICATIONS
Personal digital assistants
Smart handheld devices
Touch screen monitors
Point-of-sale terminals
Medical devices
Cell phones
GENERAL DESCRIPTION
The AD7879/AD7889 are 12-bit successive approximation
analog-to-digital converters (SAR ADCs) with a synchronous
serial interface and low on-resistance switches for driving 4-wire
resistive touch screens. The AD7879/AD7889 work with a very
low power supply—a single 1.6 V to 3.6 V supply—and feature a
throughput rate of 105 kSPS. The devices include a shutdown
mode that reduces current consumption to less than 6 μA.
To reduce the effects of noise from LCDs and other sources, the
AD7879/AD7889 contain a preprocessing block. The
preprocessing function consists of a median filter and an
averaging filter. The combination of these two filters provides a
more robust solution, discarding the spurious noise in the signal
and keeping only the data of interest. The size of both filters is
programmable. Other user-programmable conversion controls
include variable acquisition time and first conversion delay; up
to 16 averages can be taken per conversion. The AD7879/AD7889
can run in slave mode or standalone (master) mode, using an
automatic conversion sequencer and timer.
FUNCTIONAL BLOCK DIAGRAM
VCC/REF
X+
X–
Y+
Y–
GND
REF–
TEMPERATURE
SENSOR
X– Y– X+ Y+
REF– REF+
12-BIT
SAR ADC
AD7879/
AD7879-1
AD7889/
AD7889-1
RESULT
REGISTERS
CONTROL
REGISTERS
TO
RESULT
REGISTERS
SERIAL PORT
CS/ DIN/ DOUT/ SCL
ADD0 ADD1 SDA
Figure 1.
SEQUENCER
AND TIMER
The AD7879/AD7889 have a programmable pin that can
operate as an auxiliary input to the ADCs, as a battery monitor,
or as a general-purpose input/output (GPIO). In addition, a
programmable interrupt output can operate in three modes: as a
general-purpose interrupt to signal when new data is available
(DAV), as an interrupt to indicate when limits are exceeded
(INT), or as a pen-down interrupt when the screen is touched
(PENIRQ). The AD7879/AD7889 offer temperature
measurement and touch pressure measurement.
The AD7879 is available in a 12-ball, 1.6 mm × 2 mm WLCSP
and in a 16-lead, 4 mm × 4 mm LFCSP. The AD7889 is available
in a backside coated version of the WLCSP. Both devices support
an SPI interface (AD7879/AD7889) or an I2C interface (AD7879-1/
AD7889-1).
Note that throughout this data sheet, multifunction pins, such
as PENIRQ/INT/DAV, are referred to either by the entire pin
name or by a single function of the pin, for example, PENIRQ,
when only that function is relevant.
Rev. D
Document Feedback
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 ©2008–2016 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
1 page  
Data Sheet
AD7879/AD7889
I2C TIMING SPECIFICATIONS (AD7879-1/AD7889-1)
VCC = 1.6 V to 3.6 V, TA = −40°C to +85°C, unless otherwise noted. Sample tested at 25°C to ensure compliance. All input signals are
timed from a voltage level of 1.4 V.
Table 3.
Parameter1
fSCL
t1
t2
t3
t4
t5
t6
t7
t8
tR
tF
Limit
400
0.6
1.3
0.6
100
300
0.6
0.6
1.3
300
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.
SCL
t2 tR
t1
t5
SDA
t8
STOP START
tF
t3
t4
t1
t7
START
Figure 3. Detailed I2C Timing Diagram
t6
STOP
Rev. D | Page 5 of 40
5 Page 
Data Sheet
1400
1200
1000
800
600
400
200
0
2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 3.6
VCC (V)
Figure 19. Temperature Code vs. VCC for 25°C
0
–20
–40
–60
–80
–100
–120
–140
–160
SNR = 61.58dB
THD = 72.34dB
FREQUENCY (Hz)
Figure 20. Typical FFT Plot for the Auxiliary Channels at a 25 kHz Sampling
Rate and a 1 kHz Input Frequency
AD7879/AD7889
MEAN: –1.98893
SD: 0.475534
250
200
150
100
50
0
–4
–3 –2 –1
ERROR (%)
0
Figure 21. Typical Uncalibrated Accuracy for the Battery Channel (25°C)
Rev. D | Page 11 of 40
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet AD7889.PDF ] | |
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