Texas Instruments ADS7824U

Overview

ADS7824U from Burr-Brown (now Texas Instruments) is a 12-bit, 4-channel successive-approximation analog-to-digital converter with ±10V input range, internal +2.5V reference, and parallel/serial digital interface. It achieves 25µs max complete conversion cycle, ±0.5 LSB max INL/DNL, and operates from single +5V supply. Used in industrial data acquisition systems requiring multichannel precision sampling at up to 40kHz throughput.

For engineers reviewing the ADS7824U datasheet, ADS7824U pinout, ADS7824U application, or ADS7824U equivalent, key selection considerations include its dual-output mode (parallel byte-selectable or serial MSB-first), continuous conversion capability across four channels, power-down mode (50µW), and SOIC-28 industrial temperature rating (–40°C to +85°C).

Technical Context

The ADS7824U integrates a 4-channel analog multiplexer, track-and-hold amplifier, 12-bit SAR core, internal trimmed scaling resistors for ±10V range, and a dual-mode digital interface. Its laser-trimmed resistor network ensures ±0.1% channel-to-channel matching and stable full-scale error drift of ±2 ppm/°C.

Conversion is initiated via CS/R/C edge-triggered control logic, with BUSY signaling completion. In continuous mode (CONTC = HIGH), it autonomously sequences through AIN0–AIN3 while maintaining 25µs per-channel throughput - enabled by internal clock generation and synchronized serial output using DATACLK/SDATA/EXT-INT control.

Key Specifications

Pinout & Package

ADS7824U is housed in a 28-pin SOIC package (package drawing 217), 0.300" wide, with standard JEDEC MS-012AC dimensions and gull-wing leads. Thermal resistance θ_JA = 75°C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 12-bit multichannel ADC applications.

Compared with ADS7824U, ADS7825U trades speed and power efficiency for resolution, while AD7824BRZ sacrifices integration for vendor diversification - making ADS7824U optimal for cost-constrained, high-throughput industrial DAQ where internal reference and continuous mode are critical.

Availability

ADS7824U is available at Aetrix Electronics and suitable for industrial process monitoring, motor control feedback, portable data loggers, and test & measurement equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ADS7824U 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

Burr-Brown Corporation, acquired by Texas Instruments in 2000, specialized in precision analog ICs including data converters, amplifiers, and references for industrial and instrumentation markets.

The ADS7824U belongs to Burr-Brown's legacy high-accuracy sampling ADC product line, designed specifically for multichannel industrial data acquisition systems demanding ±10V input compatibility, low power, and dual digital interface flexibility.

FAQ

What is the maximum sampling rate achievable with the ADS7824U in continuous conversion mode?

The ADS7824U achieves a 40kHz throughput rate in continuous conversion mode, meaning it completes one full 12-bit conversion every 25µs. Since it sequences automatically across four channels (AIN0–AIN3), each channel is sampled at 10kHz - sufficient for real-time monitoring of motor currents, vibration spectra, or process variables in industrial control systems. This rate is guaranteed across the full –40°C to +85°C operating range.

Does the ADS7824U require an external reference voltage, or can it operate with its internal reference?

The ADS7824U can operate with its internal +2.5V reference, eliminating the need for an external reference IC. The internal reference is specified at ±0.25% initial accuracy and ±2 ppm/°C drift, and requires a 2.2µF tantalum capacitor from CAP pin to AGND2. External reference operation is also supported (2.3V–2.7V range), but doing so forfeits the guaranteed ±0.5 LSB linearity unless the external reference meets stringent noise and stability requirements.

How does the ADS7824U handle channel addressing and sequencing in continuous mode?

In continuous mode (CONTC = HIGH), the ADS7824U automatically increments its internal channel counter after each conversion, cycling sequentially through AIN0 → AIN1 → AIN2 → AIN3 → AIN0. Channel address outputs A0 and A1 reflect the currently selected input, allowing host systems to synchronize data capture. No external address control is needed - the device manages multiplexer timing, acquisition, and conversion autonomously as long as CS, R/C, and PWRD remain LOW.

What are the key timing constraints for reading parallel data from the ADS7824U without corruption?

To read parallel data reliably from the ADS7824U, BUSY rising edge must be used to latch valid data: when BYTE = LOW, D7–D0 present the 8 MSBs; when BYTE = HIGH, they present the 4 LSBs (with D4 as LSB). Bus access time is 83ns, and data remains valid for ≥20ns after BUSY rises. Attempting to read before BUSY rises or beyond 60ns after will yield indeterminate values. Also, toggling BYTE while CS = LOW and R/C = HIGH changes the byte presented without initiating new conversion.

Can the ADS7824U interface directly with a microcontroller lacking a dedicated SPI peripheral?

Yes - the ADS7824U's serial interface does not require a hardware SPI peripheral. When PAR/SER = LOW and EXT/INT = LOW, it outputs MSB-first two's complement data on SDATA synchronized to its internal 900kHz DATACLK, with SYNC pulse marking frame start. A GPIO-based bit-banging routine can sample SDATA on DATACLK edges. For external clocking (EXT/INT = HIGH), any MCU GPIO can generate DATACLK up to 10MHz, and SDATA is sampled on both edges - enabling flexible software-controlled serial reads without dedicated peripherals.