Analog Devices Inc. AD7873ARQ

Overview

AD7873ARQ from Analog Devices is a 12-bit successive approximation ADC optimized for 4-wire resistive touch screen digitizer systems, featuring integrated low-on-resistance switches (X+/X−/Y+/Y−), on-chip 2.5 V reference, direct 0 V to 6 V battery monitoring, and −40°C to +85°C temperature sensing. It operates from a single 2.2 V to 5.25 V supply with 125 kSPS throughput and ratiometric conversion to reject switch resistance errors.

For engineers reviewing the AD7873ARQ datasheet, AD7873ARQ pinout, AD7873ARQ application, or AD7873ARQ equivalent, key selection considerations include its QSOP-16 package compatibility, PENIRQ interrupt signaling, differential temperature measurement capability, and support for both internal and external reference configurations in portable HMI designs.

Technical Context

The AD7873ARQ integrates a 6-to-1 analog multiplexer, track-and-hold amplifier, SAR core, and serial interface in a single chip. Its switch drivers enable direct X/Y coordinate excitation and Z-pressure measurement via coordinated X+/Y− and X−/Y+ switching sequences.

It supports dual reference modes: internal 2.5 V ±15 ppm/°C reference (shut down to save power) or external 1 V to VCC reference. Conversion uses straight binary coding with LSB = VREF/4096, and timing is synchronized to DCLK with 12 DCLK-cycle conversion time and 3-cycle acquisition window.

Key Specifications

Pinout & Package

AD7873ARQ is packaged in a 16-lead QSOP (Quarter Size Outline Package) with 0.15 inch body width and standard 0.025 inch lead pitch. Pin 1 is marked by a dot or beveled corner.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar touch screen digitizer applications.

Compared with ADS7843IPWR and TSC2007IPWR, the AD7873ARQ uniquely combines touch digitization, battery monitoring, and differential temperature sensing in a single SPI-compatible QSOP package - enabling compact, self-contained HMI subsystems without external support components.

Availability

AD7873ARQ is available at Aetrix Electronics and suitable for personal digital assistants, smart hand-held devices, and point-of-sale terminals requiring stable component supply and long-term industrial availability.

Supply support for AD7873ARQ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices is a global leader in high-performance analog, mixed-signal, and digital signal processing semiconductors, headquartered in Norwood, MA.

The AD7873ARQ belongs to Analog Devices' precision data acquisition product line, designed specifically for low-power, high-accuracy touch screen controller applications in portable and industrial human-machine interfaces.

FAQ

What is the function of the PENIRQ pin on the AD7873ARQ?

The PENIRQ pin on the AD7873ARQ is an open-drain CMOS interrupt output that asserts low when touch contact is detected on the connected 4-wire resistive panel. It requires an external 10 kΩ to 100 kΩ pull-up resistor and enables the host processor to enter low-power sleep mode until touch activity occurs - a key feature for extending battery life in portable AD7873ARQ-based systems.

Does the AD7873ARQ support external reference voltage, and what is its valid range?

Yes, the AD7873ARQ supports external reference voltage applied to the VREF pin over a 1 V to VCC range. When using an external reference, the analog input range becomes 0 V to VREF, and specifications such as gain error and noise are referenced to that external value. The internal 2.5 V reference can be disabled to reduce power consumption, making the AD7873ARQ adaptable to systems requiring custom scaling or tighter voltage tolerances.

How does the AD7873ARQ perform touch pressure (Z-axis) measurement?

The AD7873ARQ performs touch pressure measurement by sequentially configuring its internal switches to measure two voltages: Z1 (X+ driven, Y− sensed) and Z2 (Y+ driven, X− sensed). The ratio Z1/Z2 is proportional to touch force. This method leverages the AD7873ARQ's integrated 6-to-1 MUX and ratiometric architecture to reject common-mode errors - delivering repeatable pressure data without external amplifiers or calibration in the AD7873ARQ design.

What package type is used for the AD7873ARQ, and how does it differ from other AD7873 variants?

The AD7873ARQ uses a 16-lead QSOP (Quarter Size Outline Package) with 0.15 inch body width. Unlike the AD7873ARM (TSSOP) or AD7873ACP (LFCSP), the AD7873ARQ variant is optimized for through-hole or fine-pitch surface-mount assembly in cost-sensitive industrial and consumer applications. All variants share identical electrical specifications and pinout mapping, ensuring drop-in compatibility across package types in the AD7873 family.

Can the AD7873ARQ operate from a 2.2 V supply, and what performance trade-offs apply?

Yes, the AD7873ARQ is fully specified to operate from a 2.2 V supply, though its maximum throughput rate decreases to approximately 100 kSPS at that voltage (per Figure 9). At 2.2 V, the internal 2.5 V reference remains functional, but external reference operation is limited to 1 V to 2.2 V range. Power dissipation drops to ~0.9 mW in normal mode, making the AD7873ARQ suitable for ultra-low-voltage battery-powered devices where 12-bit resolution and integrated features outweigh peak speed requirements.