Line Card

AD7873: Touch Screen Digitizer

 2009-06-12

【Basic Info】

【Product Feature】

* 4-Wire touch screen interface
* On-chip temperature sensor:
* –40°C to +85°C
* On-chip 2.5 V reference
* Direct battery measurement (0 V to 6 V)
* Touch-pressure measurement
* Specified throughput rate of 125 kSPS
* Single supply, VCC of 2.2 V to 5.25 V
* Ratiometric conversion
* High-speed sSerial interface
* Programmable 8- or 12-bit resolution
* One auxiliary analog input
* Shutdown mode: 1 µA max
Resolution (Bits): 12bit
T-Put Rate: 125kSPS
# Chan: 6
Supply V: Single(+3),Single(+3.3)
Pwr Diss: 1.4mW
Sleep Pwr Diss: 3.6µW
Ain Range: Uni (Vref),Uni 2.5V
Ref Int/Ext: Int/Ext
Product Description: 4-Wire Resistive Touch Screen Controller w/ Temp Sensor, 2.5V Ref, and Aux & Battery Inputs

【Application】

* Personal digital assistants
* Smart hand-held devices
* Touch screen monitors
* Point-of-sale terminals
* Pagers

【Overview】

The AD7873 is a 12-bit successive approximation ADC with a synchronous serial interface and low on resistance switches for driving touch screens. The AD7873 operates from a single 2.2 V to 5.25 V power supply and features throughput rates greater than 125 kSPS.

The AD7873 features direct battery measurement, temperature measurement, and touch pressure measurement. The AD7873 also has an on-board reference of 2.5 V that can be used for the auxiliary input, battery monitor, and temperature measurement modes. When not in use, the internal reference can be shut down to conserve power. An external reference can also be applied and can be varied from 1 V to VCC and 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 AD7873 features on-board switches. This, coupled with low power and high speed operation, makes the 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), a 16-lead, thin shrink small outline package (TSSOP), and a 16-lead, lead frame chip scale package (LFCSP).

Product Highlights
* Ratiometric conversion mode available, eliminating errors due to on-board switch resistances.
* On-board temperature sensor: −40°C to +85°C.
* Battery monitor input.
* Touch pressure measurement capability.
* Low power consumption of 1.37 mW maximum with the reference off, or 2.41 mW typical with the reference on, at 125 kSPS and VCC at 3.6 V.
* Package options include 4 mm × 4 mm LFCSP.
* Analog input range from 0 V to VREF.
* Versatile serial I/O ports.