Texas Instruments ADS8688ATDBT

Overview

ADS8688AT from Texas Instruments is a 16-bit, 500-kSPS, 8-channel SAR analog-to-digital converter with integrated analog front-end, ±20-V input overvoltage protection, 1-MΩ constant resistive input impedance, and programmable bipolar/unipolar input ranges (±10.24 V to ±0.64 V and 10.24 V to 1.28 V). It serves as the core data acquisition engine in high-reliability industrial measurement systems requiring channel-independent precision scaling.

For engineers reviewing the ADS8688AT datasheet, ADS8688AT pinout, ADS8688AT application, or ADS8688AT equivalent, this device delivers verified performance across –55°C to +125°C, supports SPI daisy-chaining for multi-channel scalability, integrates a 4.096-V reference with 6 ppm/°C drift, and enables direct sensor connection without external signal conditioning.

Technical Context

The ADS8688AT implements an 8-channel analog multiplexer with auto-scan and manual-scan modes, each channel featuring independent programmable gain and input range selection via internal PGA. Its SAR architecture achieves 500-kSPS aggregate throughput with no pipeline latency, enabling real-time control loop sampling.

Each channel includes dedicated OVP circuitry rated to ±20 V, a second-order LPF for anti-aliasing, and matched input impedance (1 MΩ ±15%) across all ranges. The integrated 4.096-V reference drives both ADC conversion and ALARM threshold generation, with separate REFCAP and REFIO pins for low-noise decoupling.

Key Specifications

Pinout & Package

TSSOP-38 package (9.7 mm × 4.4 mm) with exposed thermal pad; 38-pin surface-mount footprint optimized for industrial PCB layouts with analog/digital ground separation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit multichannel SAR ADC applications.

Compared with ADS8698IPWR and AD7606C-18BSTZ, the ADS8688AT uniquely combines extended temperature operation, channel-independent programmable ranges, integrated reference, and ±20-V OVP in a single TSSOP-38 package-making it optimal for ruggedized, mixed-signal industrial data acquisition where flexibility and reliability are prioritized over raw bit count or speed.

Availability

ADS8688AT is available at Aetrix Electronics and suitable for power automation, protection relay, and PLC analog input module designs requiring stable component supply across extended temperature and long product lifecycles.

Supply support for ADS8688AT 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

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in precision data converters and industrial-grade ICs.

The ADS8688AT belongs to TI's high-reliability data acquisition portfolio, designed specifically for mission-critical industrial sensing applications demanding wide temperature operation, robust input protection, and flexible signal conditioning in compact form factors.

FAQ

What input voltage ranges does the ADS8688AT support per channel?

The ADS8688AT supports eight channel-independent programmable input ranges: bipolar options of ±10.24 V, ±5.12 V, ±2.56 V, ±1.28 V, and ±0.64 V; and unipolar options of 10.24 V, 5.12 V, 2.56 V, and 1.28 V. Each channel can be configured individually via SPI register writes, enabling mixed-range monitoring-for example, channel 0 set to ±10.24 V for motor voltage and channel 3 set to 0–5 V for temperature sensor output-without external hardware changes. This flexibility is implemented using internal PGA gain stages trimmed at wafer test.

How does the ADS8688AT handle overvoltage conditions on its analog inputs?

The ADS8688AT features integrated input overvoltage protection rated to ±20 V when AVDD = 5 V, and ±11 V when AVDD is floating. This protection operates independently per channel and clamps fault currents internally, preventing damage during transients such as lightning-induced surges or wiring errors in field installations. Unlike external TVS-based solutions, this OVP maintains signal integrity up to ±10.24 V full-scale and introduces no leakage or offset shift during normal operation-verified across –55°C to +125°C per TI SBAS813 characterization data.

Can the ADS8688AT operate with an external reference, and how is it configured?

Yes, the ADS8688AT supports external reference operation via the REFSEL pin. When REFSEL is driven high, the internal 4.096-V reference is disabled and REFIO becomes an input accepting 4.046–4.146 V external reference voltage. This mode allows use of ultra-low-drift references (e.g., LT6657) for metrology-grade applications. The internal reference remains available as backup, and switching between internal/external modes requires no power cycle-only a change in REFSEL logic level and appropriate decoupling on REFIO and REFCAP per Section 6.5 of the ADS8688AT datasheet.

What is the purpose of the AUX_IN channel on the ADS8688AT?

The AUX_IN channel on the ADS8688AT is a dedicated 16-bit auxiliary analog input that shares the same SAR core and reference as the primary 8-channel ADC but operates independently. It accepts 0–VREF (0–4.096 V) unipolar signals and provides identical performance specs: 92-dB SNR, ±1.5-LSB INL, and 87-dB SINAD. Its primary use cases include diagnostic monitoring (e.g., measuring internal supply rails), secondary sensor inputs (e.g., humidity alongside temperature), or calibration reference tracking-without consuming one of the main eight programmable channels.

Does the ADS8688AT support daisy-chaining, and what is required to implement it?

Yes, the ADS8688AT supports SPI daisy-chaining using the DAISY pin. To configure daisy-chain mode, connect the SDO of one device to the SDI of the next, tie all CS lines together, and drive DAISY low on the first device and high on all subsequent devices. Each device shifts out its 16-bit conversion result sequentially on a single SDO line, reducing GPIO count and PCB routing complexity. Up to 16 devices can be chained, with total frame length equal to 16 × number of devices bits-verified in TI's SBAS813 timing diagrams and functional description sections.