Texas Instruments ADS820U

Overview

ADS820U from Texas Instruments is a monolithic 10-bit, 20MHz pipeline analog-to-digital converter with internal track-and-hold, reference, and power-down functionality. It operates from a single +5V supply, supports differential or single-ended inputs, delivers 60dB SNR and ±0.2LSB differential linearity error at 10MHz, and targets high-fidelity video digitizing and IF baseband sampling.

For engineers reviewing the ADS820U datasheet, ADS820U pinout, ADS820U application, or ADS820U equivalent, key selection considerations include its 65MHz analog input bandwidth, 6.5-clock-cycle latency, TTL/HCT-compatible CMOS outputs, SO-28 package compatibility, and differential linearity performance validated across –40°C to +85°C.

Technical Context

The ADS820U implements a 9-stage pipelined architecture with 2-bit quantizers per stage and digital error correction logic to guarantee no missing codes and ±0.2LSB DNL at full 20MHz sample rate. Its fully differential track-and-hold accepts ±1.25V to ±3.25V differential input range centered at +2.25V common-mode voltage.

Conversion timing is synchronized to a 50% duty cycle external clock with ≤2ns rise/fall time; aperture jitter is 7ps rms and aperture delay is 2ns. Output coding is selectable between Straight Offset Binary (SOB) and Binary Two's Complement (BTC) via MSBI pin, with 3-state output control via OE pin.

Key Specifications

Pinout & Package

ADS820U is housed in a 28-pin Small Outline (SO-28) package with exposed pad thermal enhancement (θ_JA = 75°C/W). Pin assignments are optimized for analog/digital separation: ground pins (1,14,25,28) and +VS pins (15,17,20,24) are distributed to minimize supply noise coupling; differential analog inputs (26,27) and reference bypass terminals (21,22,23) are grouped for controlled-impedance routing.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed ADC applications.

Compared with ADS830U and MAX1186ECM+, the ADS820U offers optimal balance of 10-bit resolution, integrated reference, SO-28 compatibility, and verified 20MSPS performance for video and communications front-ends - avoiding both external component overhead and layout rework.

Availability

ADS820U is available at Aetrix Electronics and suitable for video digitizing, CCD imaging, and IF/baseband sampling applications requiring stable component supply and long-term industrial availability.

Supply support for ADS820U 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, embedded processing, and high-performance data converters with over 50 years of innovation in precision signal chain solutions.

The ADS820U belongs to TI's high-speed pipeline ADC product line, engineered specifically for demanding video, imaging, and communications systems where resolution, speed, and analog integrity must coexist within tight power and board-area constraints.

FAQ

What is the maximum sampling rate supported by the ADS820U?

The ADS820U supports a maximum sampling rate of 20 million samples per second (20MSPS), specified across its full operating temperature range of –40°C to +85°C. This rate is validated with a 50% duty cycle clock having ≤2ns rise/fall times. At this rate, the ADS820U maintains 60dB SNR and ±0.2LSB differential linearity error, making it suitable for real-time video and IF digitization tasks where timing accuracy and spectral purity are critical. The ADS820U achieves this performance using its 9-stage pipelined architecture with digital error correction.

Does the ADS820U require external reference components?

No, the ADS820U does not require external reference components for basic operation because it integrates precision +1.25V and +3.25V reference buffers. These internal references establish a 4V_p-p differential full-scale input range centered at +2.25V common-mode voltage. External 0.1µF bypass capacitors on REFB (pin 21), CM (pin 22), and REFT (pin 23) are mandatory for stability, but no external voltage references or trimming networks are needed. The ADS820U can also accept external references if higher accuracy or adjustable full-scale range is required.

How is the output data format selected on the ADS820U?

The ADS820U output data format is selected via the MSBI (Most Significant Bit Inversion) pin (pin 19). When MSBI is LOW or floating (default, due to internal pull-down), the device outputs Straight Offset Binary (SOB) coding where full-scale positive input yields 1111111111. When MSBI is driven HIGH, it outputs Binary Two's Complement (BTC) coding where the MSB is inverted - e.g., full-scale positive becomes 0111111111. This selection is static during conversion and affects all 10 output bits (B1–B10). The ADS820U does not support dynamic format switching mid-conversion.

What is the purpose of the OE (Output Enable) pin on the ADS820U?

On the ADS820U, the OE (Output Enable) pin (pin 18) controls the 3-state output drivers for the 10-bit parallel digital bus (pins B1–B10). When OE is driven HIGH, all outputs enter high-impedance state - electrically disconnecting them from the data bus to prevent contention during shared-bus operation or test modes. When OE is LOW or floating (default, due to internal pull-down), outputs are actively driven with TTL/HCT-compatible logic levels. OE is not intended for dynamic toggling during active conversion cycles, as it may introduce timing uncertainty in data capture.

Can the ADS820U accept single-ended analog inputs?

Yes, the ADS820U can accept single-ended analog inputs by connecting the complementary input (IN, pin 27) to the common-mode voltage (CM, pin 22) while driving the primary input (IN, pin 26) with a 0.25V to 4.25V signal. This configuration yields a 4V_p-p single-ended full-scale range but increases even-order harmonic distortion - particularly above 5MHz - due to reduced common-mode rejection. For best performance in video or communications applications, Texas Instruments recommends differential drive using transformer or op-amp circuits, as documented in the ADS820U datasheet application sections.