AD7843ARQZ-REEL

Overview

The AD7843ARQZ-REEL is a 12-bit successive approximation analog-to-digital converter (ADC) designed for touch screen digitizer applications. It features a synchronous serial interface and low on-resistance switches for driving resistive touch screens. The device operates from a single 2.2 V to 5.25 V power supply, supporting throughput rates greater than 125 kSPS. It includes two auxiliary analog inputs and a shutdown mode reducing current consumption to less than 1 µA. The part is available in 16-lead QSOP and TSSOP packages.

Feature Summary

• 12-bit resolution with specified throughput rate of 125 kSPS
• Low power consumption: 1.37 mW max at 125 kSPS with VCC = 3.6 V
• Single supply operation from 2.2 V to 5.25 V
• Ratiometric conversion mode eliminating errors due to on-board switch resistances
• Shutdown mode with maximum current consumption of 1 µA

Applications

• Personal digital assistants
• Smart hand-held devices
• Touch screen monitors
• Point-of-sales terminals
• Pagers

Procurement Notes

Verify the specific package type (QSOP or TSSOP) required for the design, as the base model AD7843ARQZ is available in both. Confirm that the REEL suffix indicates tape and reel packaging suitable for automated assembly. Ensure the operating temperature range (-40°C to +85°C) meets system requirements. Check for RoHS compliance status if environmental regulations apply to the final product.

Selection Notes

Select the AD7843ARQZ-REEL when a 12-bit ADC with integrated touch screen drivers is needed. The ratiometric mode is critical for accurate coordinate measurement by negating switch resistance errors. Ensure the external reference voltage is between 1 V and VCC. Consider the 125 kSPS throughput limit and the need for an external clock source via the DCLK pin. Verify that the serial interface timing matches the host controller capabilities.

Part Context

The AD7843 is part of Analog Devices' family of touch screen controllers. It shares functional similarities with the AD7873 but lacks the internal 2.5 V reference and temperature sensor found in the latter. The AD7843 requires an external reference voltage applied to the VREF pin. It is designed for battery-powered portable systems where low power consumption and high speed are prioritized.

Replacement Considerations

The AD7873 is a compatible alternative offering similar performance with added internal reference and temperature sensing capabilities. Ensure pin compatibility and software register configuration differences are addressed during substitution.