Texas Instruments ADS7822U

Overview

ADS7822U from Texas Instruments is a 12-bit successive approximation register (SAR) analog-to-digital converter with pseudo-differential input, 200kHz maximum throughput, 2.7V–5.25V supply range, and SO-8 package. It delivers 1.6mW power consumption at full rate and supports external reference voltages from 50mV to VCC-ideal for low-power remote data acquisition systems.

For engineers reviewing the ADS7822U datasheet, ADS7822U pinout, ADS7822U application, or ADS7822U equivalent, key selection criteria include its microPower operation at 7.5–200kHz sample rates, CMOS-compatible serial interface timing, ±2 LSB integral linearity over –40°C to +85°C, and SO-8 footprint compatibility with board-level space constraints in battery-powered instrumentation.

Technical Context

The ADS7822U implements a capacitive redistribution SAR architecture on 0.6μm CMOS, integrating sample/hold functionality without external components. Its conversion cycle requires exactly 12 clock cycles after a 1.5-cycle acquisition window, with data output synchronized to DCLOCK falling edges and no pipeline delay.

It uses a synchronous 3-wire serial interface (CS/SHDN, DCLOCK, DOUT) supporting straight-binary output, MSB-first transmission, and optional LSB-first continuation. The pseudo-differential input (+In/–In) captures voltage difference during hold mode, with –In limited to –0.2V to +1.0V for remote ground sensing-not true differential rejection.

Key Specifications

Pinout & Package

ADS7822U is housed in an SO-8 (D package) surface-mount package with standard 150-mil body width and 1.27mm pitch. Pin 1 is marked by a beveled corner or dot.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS7822UB and ADS7822UC, the ADS7822U provides optimal cost-performance balance for industrial and portable applications where ±2 LSB linearity is sufficient-avoiding premium pricing while retaining identical timing, power, and layout compatibility.

Availability

ADS7822U is available at Aetrix Electronics and suitable for battery-operated systems, remote data acquisition modules, and isolated industrial monitoring requiring stable component supply and long-term manufacturability.

Supply support for ADS7822U 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 design.

The ADS7822U belongs to TI's legacy precision SAR ADC product line, engineered specifically for ultra-low-power, space-constrained applications including portable instrumentation and distributed sensing-prioritizing micropower efficiency over high-speed parallel interfaces.

FAQ

What is the minimum supply voltage required for guaranteed operation of the ADS7822U?

The ADS7822U is specified for guaranteed performance from 2.7V to 5.25V. While functional operation is documented down to 2.0V, the 2.7V lower limit ensures full 75kHz throughput, ±2 LSB integral linearity, and 1.5-cycle acquisition time across –40°C to +85°C. Below 2.7V, maximum sample rate decreases and timing margins tighten-designs relying on ADS7822U must maintain VCC ≥2.7V for production compliance.

How does the pseudo-differential input of the ADS7822U differ from a true differential input stage?

The ADS7822U's pseudo-differential input samples the voltage difference between +In and –In during hold mode but does not reject common-mode signals beyond the –In pin's limited range (–0.2V to +1.0V). Unlike true differential ADCs, it lacks matched input paths and common-mode feedback-so it cannot suppress noise equally present on both pins. The –In pin serves primarily for remote ground sensing, not noise cancellation, making ADS7822U unsuitable for high-noise industrial bus environments without external conditioning.

Can the ADS7822U operate with a 3.3V supply and 2.5V external reference simultaneously?

Yes-the ADS7822U fully supports mixed-supply operation: VCC = 3.3V and VREF = 2.5V is a validated configuration per TI's SBAS062C datasheet. This setup yields 0.61mV LSB size, maintains ±2 LSB linearity, and draws ~200μA quiescent current at 75kHz. The 2.5V reference must be stable and low-noise; the device's reference input impedance exceeds 5GΩ, minimizing loading effects on buffered references.

What happens to the DOUT pin when CS is held high during conversion?

When CS is high, the ADS7822U enters full power-down mode: the analog section disables, the comparator powers off, and DOUT transitions to high-impedance (Hi-Z) state within 40–80ns (per tdis spec). No serial data is output, and internal clocks halt-only 3μA supply current remains. DOUT remains Hi-Z until CS falls low again, at which point the next conversion begins and DOUT drives valid data after the second DCLOCK falling edge.

Is the ADS7822U pin-compatible with other members of the ADS7822 family such as ADS7822EB or ADS7822PC?

No-ADS7822U (SO-8) is not pin-compatible with ADS7822EB (MSOP-8) or ADS7822PC (DIP-8), despite identical pin functions. Package footprints differ: SO-8 has 1.27mm pitch and gull-wing leads; MSOP-8 has 0.5mm pitch and narrow body; DIP-8 is through-hole. Mechanical incompatibility prevents PCB reuse. However, all variants share identical pin numbering and signal mapping-schematic symbols and firmware drivers are interchangeable across packages when layout is revised.