Analog Devices Inc. AD7575AQ

Overview

AD7575AQ from Analog Devices is an 8-bit successive approximation analog-to-digital converter (ADC) with integrated track-and-hold, designed for unipolar single-supply operation at +5 V. It achieves a 5 µs conversion time using a 4 MHz external clock, supports 0 to 2.46 V input range (with 1.23 V reference), delivers ±1 LSB total unadjusted error, and interfaces directly to 8-bit microprocessors via CS/RD control logic. It is used in real-time data acquisition systems digitizing audio-band signals up to 50 kHz.

For engineers reviewing the AD7575AQ datasheet, AD7575AQ pinout, AD7575AQ application, or AD7575AQ equivalent, key selection considerations include its LC2MOS process-based low power (15 mW typ), 100 ns data access time, built-in track/hold eliminating external hold capacitors, and compatibility with Z80H, 8085A-2, 6502B, 68B09, and TMS32010 processors in Slow Memory or ROM interface modes.

Technical Context

The AD7575AQ employs a successive approximation register (SAR) architecture with on-chip DAC and comparator, synchronized by either internal RC oscillator or external 4 MHz clock. Its track-and-hold captures input signals on the third falling edge of CLK after CS and RD assertion, enabling full-scale digitization of 50 kHz sine waves (386 mV/µs slew rate).

Control logic supports two microprocessor interface modes: Slow Memory (using BUSY to force WAIT state) and ROM (non-blocking, dual-read sequence). The TP pin must be hard-wired HIGH; it is reserved for factory test and not functional in application circuits.

Key Specifications

Pinout & Package

AD7575AQ is packaged in an 18-lead Cerdip (Q-18) hermetic ceramic DIP with 0.3" width, rated for –25°C to +85°C operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit SAR ADC applications.

Compared with MAX160BCPP and ADS7822U, the AD7575AQ uniquely combines single +5 V operation, integrated track/hold, 5 µs conversion, and parallel 8-bit bus interface-making it optimal for legacy microprocessor systems requiring minimal support components and deterministic timing.

Availability

AD7575AQ is available at Aetrix Electronics and suitable for industrial data acquisition, audio digitization, microcontroller instrumentation, and embedded process control requiring stable component supply across extended temperature ranges.

Supply support for AD7575AQ 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 AD7575AQ belongs to the AD7575 family of LC2MOS 8-bit ADCs, engineered for cost-sensitive, microprocessor-centric data acquisition where single-supply operation, integrated track/hold, and parallel bus compatibility are essential.

FAQ

What is the maximum input signal frequency the AD7575AQ can accurately digitize?

The AD7575AQ supports full-power digitization of input signals up to 50 kHz - corresponding to a 2.46 V peak-to-peak sine wave with 386 mV/µs slew rate. This is enabled by its on-chip track-and-hold function. For signals beyond this bandwidth, amplitude accuracy degrades due to slew-rate limiting, even if sampled above the Nyquist rate. The AD7575AQ datasheet confirms this specification applies across its rated temperature range (–25°C to +85°C) and is independent of whether internal or external clocking is used.

Does the AD7575AQ require external calibration for typical use?

No, the AD7575AQ does not require external offset or gain calibration in most applications because its total unadjusted error is specified at ±1 LSB max over temperature - sufficient for monotonicity and no missing codes. The AD7575AQ's low zero and full-scale errors (±1/2 LSB offset, ±1 LSB full-scale) mean system-level adjustments are unnecessary unless sub-LSB precision is mandated. Calibration procedures documented in the datasheet are provided for edge-case metrology applications, not routine deployment.

Can the AD7575AQ operate with an external reference other than 1.23 V?

Yes, the AD7575AQ accepts any stable reference between 1.17 V and 1.29 V (±5% of 1.23 V), as specified in the Absolute Maximum Ratings and Electrical Characteristics tables. Input range scales linearly: V_IN = 0 to 2×V_REF. Using a 2.048 V reference, for example, extends full-scale input to 4.096 V but reduces LSB size to ~16 mV and may affect SNR and linearity per the device's reference input impedance profile (6–18 kΩ, code-dependent). The AD7575AQ's performance remains guaranteed only within the ±5% tolerance band.

What is the function of the TP pin on the AD7575AQ, and how should it be connected?

The TP (Test Pin) on the AD7575AQ is reserved exclusively for factory testing and must be hard-wired to a logic HIGH level (e.g., +5 V via 10 kΩ pull-up) in all applications. It is not a functional signal path, has no electrical role in conversion or interface timing, and must never be left floating or driven actively. The AD7575AQ datasheet explicitly warns against using TP as a feedthrough on double-sided PCBs - doing so risks compromising device reliability or measurement integrity.

How does the AD7575AQ interface with the TMS32010 DSP processor?

The AD7575AQ interfaces with the TMS32010 DSP using the ROM interface mode: conversion starts on the first IN A, PA instruction (asserting CS and RD), and result data is read on the second IN A, PA instruction. The AD7575AQ's 100 ns data access time and 5 µs conversion meet TMS32010 timing at up to 18 MHz clock rates. The BUSY pin can optionally generate an interrupt when conversion completes. This configuration is validated in Analog Devices' Application Note and Figure 8 of the AD7575AQ datasheet.