Texas Instruments ADS8325IDRBT

Overview

ADS8325IDRBT from Texas Instruments is a 16-bit, SAR analog-to-digital converter with differential input, SPI/SSI-compatible serial interface, and microPower operation (4.5 mW at 100 kSPS, 1 mW at 10 kSPS). It operates from 2.7 V to 5.5 V, supports external reference voltages from 2.5 V to VDD, and delivers ±1.5 LSB typical integral linearity and 3 LSBPP noise - ideal for precision battery-powered data acquisition in industrial and remote sensing systems.

For engineers reviewing the ADS8325IDRBT datasheet, ADS8325IDRBT pinout, ADS8325IDRBT application, or ADS8325IDRBT equivalent, key selection considerations include its SON-8 package thermal pad handling, differential input common-mode voltage limits (–0.3 V to +0.5 V on –IN), 100 kSPS throughput with 6.667 µs conversion time, and compatibility with low-noise op-amp drivers such as OPA365 per TI's recommended interface circuit.

Technical Context

The ADS8325IDRBT implements a capacitive redistribution SAR architecture with integrated sample-and-hold, enabling single-cycle 16-bit conversions without pipeline delay. Its differential analog front-end accepts inputs up to VREF full-scale while maintaining >5 GΩ input resistance and 45 pF input capacitance during sampling.

It uses an external CMOS/LVCMOS-compatible clock (24 kHz–2.4 MHz) to control conversion timing and serial data output, with CS/SHDN serving dual roles: chip select (active-low) and shutdown enable (high). The DOUT stream outputs straight-binary data MSB-first, synchronized to DCLOCK falling edge, with configurable 3-state behavior.

Key Specifications

Pinout & Package

The ADS8325IDRBT is housed in an 8-pin SON (DRB) package with exposed thermal pad, footprint-compatible with 3×3 mm QFN. The thermal pad is internally connected to substrate and may be tied to analog ground or left floating - but must remain isolated from digital ground.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS8325IDRBT, ADS8326IDRBT trades external reference flexibility for integrated reference convenience and PGA capability, while ADS8860IDRCT offers significantly higher speed and lower noise at the cost of supply voltage inflexibility and higher power consumption.

Availability

ADS8325IDRBT is available at Aetrix Electronics and suitable for battery-operated sensor nodes, isolated industrial data acquisition, and remote data logging modules requiring stable component supply across extended product lifecycles.

Supply support for ADS8325IDRBT 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 low-power signal chain solutions.

The ADS8325 belongs to TI's precision SAR ADC portfolio designed for high-resolution, low-power data acquisition in portable, industrial, and isolated measurement systems - emphasizing accuracy, noise performance, and supply flexibility over raw speed.

FAQ

What is the maximum allowable common-mode voltage on the –IN pin of the ADS8325IDRBT?

The ADS8325IDRBT specifies a strict –0.3 V to +0.5 V operating range for the –IN pin across the full temperature range (–40°C to +85°C). Exceeding this range risks nonmonotonic behavior and degraded INL. This constraint enables precise common-mode rejection when –IN is used as a remote ground reference, but requires careful front-end design to maintain compliance - especially with op-amp driver output swing limitations. The ADS8325IDRBT datasheet Figure 28 details the interaction between VREF and allowable common-mode voltage.

Does the ADS8325IDRBT support unipolar single-ended input configurations?

Yes, the ADS8325IDRBT supports unipolar single-ended operation by tying –IN to a stable common-mode voltage (e.g., VREF/2 or AGND), while driving +IN with the signal. TI's SBAS226C datasheet Figure 31 shows validated circuits using OPA365 buffers. However, differential mode is preferred for noise immunity and offset cancellation. Single-ended use reduces effective resolution due to increased susceptibility to ground bounce and supply noise - the ADS8325IDRBT's 16-bit performance is fully realized only with proper differential layout and matched source impedances.

How does reference voltage selection affect noise performance in the ADS8325IDRBT?

Reference voltage directly scales the ADS8325IDRBT's LSB size and apparent noise floor: at 2.5 V reference, internal noise is ~3 LSBPP (≈114 µVPP), whereas at 5 V it is ~1.5 LSBPP (≈114 µVPP absolute). Since noise amplitude remains constant, lower VREF increases quantization-related noise contribution relative to signal. For example, 2.5 V ref yields 38.15 µV/LSB, making 3 LSBPP equal 114 µVPP; same 114 µVPP at 5 V ref equals only 1.5 LSBPP. Thus, ADS8325IDRBT achieves best effective resolution with highest feasible VREF within system constraints.

Can the ADS8325IDRBT operate with a 3.3 V supply and 2.5 V reference simultaneously?

Yes - the ADS8325IDRBT explicitly supports mixed-supply operation: VDD = 3.3 V and VREF = 2.5 V is a valid configuration per the "ELECTRICAL CHARACTERISTICS: VDD = +2.7V" section. However, this combination degrades DC accuracy: gain error increases to ±33 LSB and offset drift rises to ±3 ppm/°C versus ±12 LSB and ±0.2 ppm/°C at matched 5 V supply/reference. TI's Figure 32 quantifies the trade-off. Use ADS8325IDRBT in this mode only when system-level calibration compensates for the increased errors, or when dynamic performance (e.g., ENOB) remains acceptable for the application.

What is the role of the thermal pad in the ADS8325IDRBT's DRB package?

The exposed thermal pad in the ADS8325IDRBT's SON-8 (DRB) package is internally connected to the silicon substrate and serves two primary functions: improving thermal resistance (RθJA = 45.8°C/W) to limit junction temperature rise during sustained 100 kSPS operation, and providing a low-inductance path for analog ground return. TI recommends connecting it to analog ground - not digital ground - to prevent noise coupling. If PCB layout constraints prevent grounding, the pad may be left floating, though thermal performance will degrade by ~10°C/W. The pad must never be soldered to a plane shared with digital switching currents.