Texas Instruments ADS8668IDBT

Overview

ADS8668IDBT from Texas Instruments is an 8-channel, 12-bit, 500-kSPS successive-approximation register (SAR) analog-to-digital converter with integrated analog front-end, ±20-V input overvoltage protection, 1-MΩ constant resistive input impedance, and on-chip 4.096-V reference. It supports channel-independent programmable bipolar/unipolar input ranges including ±10.24 V, ±5.12 V, and ±2.56 V, and is used in industrial PLC analog input modules requiring high dc precision and robust field connectivity.

For engineers reviewing the ADS8668IDBT datasheet, ADS8668IDBT pinout, ADS8668IDBT application, or ADS8668IDBT equivalent, key selection considerations include its 8-channel single-ended architecture, SPI-compatible daisy-chain interface, –40°C to 125°C operating temperature range, and channel-specific alarm thresholds for real-time monitoring in power automation and protection relay systems.

Technical Context

The ADS8668IDBT integrates a multiplexer with auto/manual scan modes, per-channel programmable gain amplifier (PGA), second-order low-pass filter (LPF), and overvoltage protection (OVP) circuitry before the SAR ADC core. Each of its eight analog input channels features independent configuration of input range, alarm thresholds, and acquisition timing.

It employs a 4.096-V internal reference with ±8 ppm/°C drift and supports external reference via REFIO. The digital interface uses a CMOS-compatible SPI protocol with chip-select (CS), serial clock (SCLK), data-in (SDI), data-out (SDO), and daisy-chain (DAISY) signals - enabling synchronized multi-device acquisition without additional control logic.

Key Specifications

Pinout & Package

TSSOP-38 package (9.7 mm × 4.4 mm) with exposed thermal pad; RoHS-compliant, lead-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS8664IDBT, the ADS8668IDBT delivers double the channel count in the same footprint while retaining identical timing, register compatibility, and protection features; versus AD7606C-18BSTZ, it trades resolution and speed for superior ruggedness, configurability, and embedded fault-response capability in harsh industrial settings.

Availability

ADS8668IDBT is available at Aetrix Electronics and suitable for power automation, protection relays, PLC analog input modules, and motor control feedback systems requiring stable component supply, long-term industrial lifecycle support, and guaranteed traceable sourcing.

Supply support for ADS8668IDBT 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 headquartered in Dallas, Texas, specializing in analog, embedded processing, and power management ICs for industrial, automotive, and communications markets.

The ADS866x family was designed specifically for industrial data acquisition systems requiring integrated signal conditioning, high channel density, and field-rugged operation - targeting applications where reliability under electrical stress and long-term parametric stability are non-negotiable.

FAQ

What is the maximum input voltage the ADS8668IDBT can withstand without damage?

The ADS8668IDBT provides ±20 V overvoltage protection on all analog input pins (AIN_nP and AIN_nGND) when AVDD = 5 V and source impedance is <30 kΩ. This rating is specified in the Absolute Maximum Ratings table and verified across the full –40°C to 125°C temperature range. Exceeding ±20 V may cause permanent damage, and operation above ±11 V is not recommended when AVDD is floating.

Does the ADS8668IDBT require external components for reference decoupling?

Yes, the ADS8668IDBT requires two external decoupling capacitors: a 10–22 µF capacitor between REFIO and REFGND, and another 10–22 µF capacitor between REFCAP and REFGND. These are mandatory per the datasheet's Electrical Characteristics section and ensure stable 4.096-V reference operation with <10 ppm gain error drift. Omitting them degrades SNR and increases gain error variation.

Can the ADS8668IDBT interface directly with a 1.8-V microcontroller?

Yes, the ADS8668IDBT supports digital I/O voltages from 1.65 V to 5.25 V on DVDD, allowing direct connection to 1.8-V logic without level shifters. Its digital inputs (CS, SCLK, SDI, DAISY, REFSEL, RST/PD) accept VIH ≥ 0.7 × DVDD and VIL ≤ 0.3 × DVDD, and outputs (SDO, ALARM) drive VOH ≥ 0.8 × DVDD and VOL ≤ 0.2 × DVDD - fully compliant with 1.8-V CMOS signaling.

How does the ADS8668IDBT handle crosstalk between adjacent input channels?

The ADS8668IDBT achieves >110 dB crosstalk isolation between aggressor and victim channels by combining on-chip 2nd-order LPFs, guarded analog routing, and sequential sampling architecture. Measured per datasheet Figure 7.5, this isolation holds for full-scale sinusoidal inputs up to 10 kHz applied to unselected channels - ensuring accurate readings even when monitoring high-amplitude signals on neighboring inputs.

Is the internal reference of the ADS8668IDBT enabled by default after power-up?

No, the internal 4.096-V reference is disabled by default after power-up. The REFSEL pin must be driven low to enable it, configuring REFIO as an output. When REFSEL is high, REFIO becomes an input for external reference injection. This design prevents conflict during system initialization and allows flexible reference sourcing - the ADS8668IDBT will not generate valid conversions until REFSEL is asserted low and the reference stabilizes (~15 ms turn-on time).