AD7843 Datasheet, PDF (1/16 Pages) Analog Devices – Touch Screen Digitizer

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FEATURES
4-Wire Touch Screen Interface
Specified Throughput Rate of 125 kSPS
Low Power Consumption:
1.37 mW Max at 125 kSPS with V_CC = 3.6 V
Single Supply, V_CC of 2.2 V to 5.25 V
Ratiometric Conversion
High-Speed Serial Interface
Programmable 8- or 12-Bit Resolution
Two Auxiliary Analog Inputs
Shutdown Mode: 1 ␮A max
16-Lead QSOP and TSSOP Packages
APPLICATIONS
Personal Digital Assistants
Smart Hand-Held Devices
Touch Screen Monitors
Point-of-Sales Terminals
Pagers
Touch Screen Digitizer
AD7843
FUNCTIONAL BLOCK DIAGRAM
+V_CC
PENIRQ
X+
X–
Y+
Y–
IN3
IN4
V_REF
AD7843
PEN
INTERRUPT
T/H
4-TO-1
I/P
MUX
COMP
CHARGE
REDISTRIBUTION
DAC
SAR + ADC
CONTROL LOGIC
GND
+V_CC
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 +V_CC, while the analog input range is from 0 V to
V_REF. 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 (QSOP) pack-
age and a 16-lead Thin Shrink Small Outline (TSSOP) package.
SPORT
DIN
CS
DOUT DCLK
BUSY
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 V_REF.
5. Versatile serial I/O port.
REV. 0
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