AD7843

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- or 12-Bit Resolution Two Auxiliary Analog Inputs Shutdown Mode: 1A max 16-Lead QSOP and TSSOP Packages

Personal Digital Assistants Smart Hand-Held Devices Touch Screen Monitors Point-of-Sales Terminals Pagers

(TA = 25°C unless otherwise noted)
+VCC to GND . . . . . . . . . . . . . . . . . . . . . . . . ....................................... 0.3 V to +7 V
Analog Input Voltage to GND . . . . . . . ......................................0.3 V to VCC + 0.3 V
Digital Input Voltage to GND . . . . . . . .......................................0.3 V to VCC + 0.3 V
Digital Output Voltage to GND . . . . . .........................................0.3 V to VCC + 0.3 V
VREF to GND . . . . . . . . . . . . . . . . . . . ....................................... 0.3 V to VCC + 0.3 V
Input Current to Any Pin Except Supplies2 . . . . ......................................... . . ±10 mA
Operating Temperature Range
Commercial . . . . . . . . . . . . . . . . . . . . . . . ....................................... 40°C to +85°C
Storage Temperature Range . . . . . . . . . . ..................................... 65°C to +150°C
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . ..................................... 150°C
QSOP, TSSOP Package, Power Dissipation . . . . . . .......................................... 450 mW
JA Thermal Impedance . . . . . . . . . . .......................................... 149.97°C/W (QSOP)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......................................... 150.4°C/W (TSSOP)
JC Thermal Impedance . . . . . . . . . . . . .......................................... 38.8°C/W (QSOP)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......................................... 27.6°C/W (TSSOP)
Lead Temperature, Soldering
Vapor Phase (60 secs) . . . . . . . . . . . . . . . . . . . . . . ......................................... 215°C
Infrared (15 secs) . . . . . . . . . . . . . . . . . . . . . . . . . .......................................... 220°C
NOTES
¹Stresses above those listed under Absolute Maximum Rating may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
²Transient currents of up to 100 mA will not cause SCR latch-up.

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 A.

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) package and a 16-lead Thin Shrink Small Outline (TSSOP) package.