Texas Instruments ADS8688AIDBTR

Overview

ADS8688AIDBTR from Texas Instruments is a 16-bit, 8-channel, single-supply SAR analog-to-digital converter with integrated analog front-end, ±20 V input overvoltage protection, 500 kSPS aggregate throughput, and software-programmable bipolar/unipolar input ranges up to ±10.24 V. It serves as a high-precision data acquisition IC in industrial PLC analog input modules.

For engineers reviewing the ADS8688AIDBTR datasheet, ADS8688AIDBTR pinout, ADS8688AIDBTR application, or ADS8688AIDBTR equivalent, key selection criteria include channel-independent gain configuration, 1 MΩ constant input impedance across all ranges, on-chip 4.096-V reference with 6 ppm/°C drift, SPI-compatible daisy-chain interface, and operation from –40°C to 125°C.

Technical Context

The ADS8688AIDBTR integrates an 8-channel multiplexer with auto/manual scan modes, per-channel programmable PGA, 2nd-order LPF, and overvoltage protection circuitry before the SAR core. Its architecture supports independent range selection per channel - including ±10.24 V, ±5.12 V, ±2.56 V, ±1.28 V, ±0.64 V, and unipolar variants - all referenced to the internal 4.096-V reference.

It employs a successive approximation register ADC core with 850 ns conversion time and 1150 ns acquisition time, achieving 92 dB SNR and ±0.75 LSB INL at 500 kSPS. The digital interface uses CMOS-level SPI with daisy-chain capability via DAISY pin, supporting 1.65–5.25 V I/O voltage and 17 MHz SCLK.

Key Specifications

Pinout & Package

TSSOP-38 package (9.7 mm × 4.4 mm), thermally enhanced with multiple AGND/DGND pins and dedicated analog/digital supply separation for noise isolation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS8684AIDBTR and AD7606BSTZ, the ADS8688AIDBTR uniquely combines 8-channel flexibility, on-chip 4.096-V reference, ±20 V OVP, and 1 MΩ constant input impedance - reducing external component count and improving field reliability in harsh industrial settings.

Availability

ADS8688AIDBTR is available at Aetrix Electronics and suitable for power automation, protection relays, and PLC analog input modules requiring stable component supply, long-term industrial lifecycle support, and guaranteed traceability.

Supply support for ADS8688AIDBTR 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 company specializing in analog and embedded processing technologies, with leadership in precision data converters and industrial-grade ICs.

The ADS868xA family was designed specifically for high-reliability industrial data acquisition, integrating signal conditioning, protection, and conversion in a single IC to simplify analog front-end design for PLCs, energy meters, and motor drives.

FAQ

What input voltage ranges does the ADS8688AIDBTR support?

The ADS8688AIDBTR supports eight software-selectable bipolar ranges: ±10.24 V, ±5.12 V, ±2.56 V, ±1.28 V, and ±0.64 V; and five unipolar ranges: 0–10.24 V, 0–5.12 V, 0–2.56 V, 0–1.28 V, and 0–0.64 V. Each of its eight analog input channels can be independently configured to any of these ranges, enabling mixed-sensor interfacing without external hardware changes. The ADS8688AIDBTR achieves this using an integrated PGA with factory-trimmed gain accuracy.

Does the ADS8688AIDBTR require an external reference voltage?

No, the ADS8688AIDBTR includes a precision 4.096-V internal reference with 6 ppm/°C temperature drift and 10–22 µF decoupling requirements on REFCAP. REFSEL pin controls reference source: when low, REFIO outputs the internal reference; when high, REFIO accepts an external reference (4.046–4.146 V). This dual-mode capability eliminates mandatory external references while allowing system-level calibration flexibility. The ADS8688AIDBTR's internal reference is fully characterized across –40°C to 125°C.

How does the ADS8688AIDBTR handle overvoltage conditions on analog inputs?

The ADS8688AIDBTR provides robust ±20 V overvoltage protection on all analog input pins (AIN_nP, AIN_nGND) when AVDD is actively powered (low-impedance path), and ±11 V protection when AVDD is floating (high-impedance condition). This protection is implemented via integrated clamping circuitry that routes excess current safely to AVDD or GND without damaging the SAR core or degrading performance. The ADS8688AIDBTR maintains specification compliance after such events, unlike solutions requiring external TVS diodes or series resistors.

Can multiple ADS8688AIDBTR devices be connected on a single SPI bus?

Yes, the ADS8688AIDBTR supports daisy-chain configuration using the DAISY pin and standard SPI signals (CS, SCLK, SDI, SDO). In daisy-chain mode, CS activates the chain, and data propagates serially from device to device - SDO of the first device connects to SDI of the next, with final SDO returning to the host. This eliminates the need for individual chip-select lines and simplifies routing in multi-channel systems. The ADS8688AIDBTR's timing specifications guarantee reliable operation up to 17 MHz SCLK in this topology.

What is the power consumption of the ADS8688AIDBTR during active and standby operation?

The ADS8688AIDBTR consumes 16 mA from AVDD (5 V) during full-speed operation (500 kSPS, internal reference enabled), totaling ~65 mW. In standby mode (RST/PD low), it draws 3–4.5 mA, and in power-down mode, only 3–20 µA. These values are specified across –40°C to 125°C and include all internal circuitry - PGA, reference buffer, and digital logic. The ADS8688AIDBTR's low-power profile supports thermally constrained industrial enclosures and battery-backed data loggers without thermal derating.