AD7843ARUZ Datasheet, PDF (1/21 Pages) Analog Devices – Touch Screen Digitizer

FEATURES
4-wire touch screen interface
Specified throughput rate of 125 kSPS
Low power consumption:
1.37 mW max at 125 kSPS with VCC = 3.6 V
Single supply, VCC of 2.2 V to 5.25 V
Ratiometric conversion
High speed serial interface
Programmable 8-bit or 12-bit resolution
2 auxiliary analog inputs
Shutdown mode: 1 µA max
16-lead QSOP and TSSOP packages
APPLICATIONS
Personal digital assistants
Smart hand-held devices
Touch screen monitors
Point-of-sales terminals
Pagers
GENERAL DESCRIPTION
The AD7843 is a 12-bit successive approximation ADC with a
synchronous serial interface and low on resistance switches for
driving touch screens. The part operates from a single 2.2 V to
5.25 V power supply and features throughput rates greater than
125 kSPS.
The external reference applied to the AD7843 can be varied
from 1 V to +VCC, while the analog input range is from 0 V to
VREF. The device includes a shutdown mode that reduces the
current consumption to less than 1 µA.
The AD7843 features on-board switches. This, coupled with low
power and high speed operation, make this device ideal for
battery-powered systems such as personal digital assistants with
resistive touch screens, and other portable equipment. The part
is available in a 16-lead 0.15" quarter size outline package
(QSOP) and a 16-lead thin shrink small outline package
(TSSOP).
Rev. B
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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
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registered trademarks are the property of their respective owners.
Touch Screen Digitizer
AD7843
X+
X–
Y+
Y–
IN3
IN4
V_REF
FUNCTIONAL BLOCK DIAGRAM
+V_CC
PENIRQ
AD7843
PEN
INTERRUPT
T/H
4-TO-1
I/P
MUX
COMP
CHARGE
REDISTRIBUTION
DAC
SAR + ADC
CONTROL LOGIC
GND
+V_CC
SPORT
DIN
CS
DOUT DCLK BUSY
Figure 1.
PRODUCT HIGHLIGHTS
1. Ratiometric conversion mode available eliminating errors
due to on-board switch resistances.
2. Maximum current consumption of 380 µA while operating
at 125 kSPS.
3. Power-down options available.
4. Analog input range from 0 V to VREF.
5. Versatile serial I/O port.
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