Texas Instruments ADS7835E

Overview

ADS7835E from Burr-Brown (now Texas Instruments) is a 12-bit, 500kHz SAR analog-to-digital converter with integrated sample-and-hold, internal 2.5V reference, ±2.5V bipolar input range, and synchronous serial interface. It operates from a single +5V supply, consumes 17.5mW at full throughput, and supports power-down mode (2.5mW). It is used in portable spectrum analyzers and remote data acquisition systems requiring low-power, isolated digital interfaces.

For engineers reviewing the ADS7835E datasheet, ADS7835E pinout, ADS7835E application, or ADS7835E equivalent, key selection considerations include guaranteed no-missing-codes performance over –40°C to +85°C, MSOP-8 package compatibility, bipolar input handling without external level-shifting, and serial LSB/MSB-first flexibility via CONV timing control.

Technical Context

The ADS7835E implements a capacitive redistribution SAR architecture with on-chip 2.5V bandgap reference and built-in S/H function. Its analog input uses a 2kΩ–2kΩ voltage divider enabling true bipolar operation (–VREF to +VREF) from a single 5V rail, with input impedance switching between ~4kΩ during sampling and ~2kΩ during hold.

Digital interface timing is asynchronous between CONV and CLK: conversion start is edge-triggered by CONV falling, while serial data transfer is clock-synchronized. The device supports three operational modes - full-speed continuous, power-down gated, and short-cycle early-termination - all controlled solely by CONV pulse width and alignment relative to CLK edges.

Key Specifications

Pinout & Package

ADS7835E is housed in an 8-pin MSOP package (drawing 337), with dual ground pins (pins 3 and 4) for noise separation between analog and digital return paths. Pin layout supports compact decoupling: VREF (pin 1) requires 0.1µF ceramic + 2.2µF tantalum; +VCC (pin 8) requires 0.1µF ceramic + 10µF tantalum.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS7835EB and ADS8320EB, the ADS7835E delivers the best balance of 500kHz throughput, 12-bit no-missing-codes assurance, and 17.5mW active power in MSOP-8 - making it the preferred choice for portable, battery-constrained, high-speed data acquisition where moderate linearity (±2 LSB) is sufficient.

Availability

ADS7835E is available at Aetrix Electronics and suitable for portable instrumentation, remote data acquisition, and wireless test equipment requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for ADS7835E 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

Burr-Brown Corporation, acquired by Texas Instruments in 2000, specialized in precision analog ICs including data converters, amplifiers, and references for industrial and instrumentation markets.

The ADS7835E belongs to Burr-Brown's high-speed SAR ADC product line, designed specifically for portable, low-power, bipolar-input measurement systems where serial interface simplicity and guaranteed monotonicity are critical.

FAQ

What is the guaranteed operating temperature range for the ADS7835E?

The ADS7835E is specified and guaranteed over the industrial temperature range of –40°C to +85°C. All key parameters-including integral linearity (±2 LSB), no missing codes, throughput rate (500kHz), and power consumption-are validated across this full range. This makes the ADS7835E suitable for deployment in outdoor instrumentation, automotive test gear, and factory-floor data loggers without derating.

Does the ADS7835E require external components for stable operation?

Yes, the ADS7835E requires specific external passive components: VREF (pin 1) must be bypassed with a 0.1µF ceramic capacitor placed adjacent to the package plus a 2.2µF tantalum capacitor in parallel; +VCC (pin 8) requires a 0.1µF ceramic and 10µF tantalum; and AIN (pin 2) benefits from an external op-amp buffer when driving from high-impedance or reactive sources. These are mandatory for achieving specified SNR, linearity, and acquisition time.

Can the ADS7835E interface directly with a microcontroller SPI peripheral?

The ADS7835E supports SPI-like operation but is not a standard SPI slave: it uses a non-standard 3-wire interface (CONV, CLK, DATA) with timing-controlled mode selection (e.g., LSB-first triggered by CONV pulse). While many MCUs can emulate this timing in GPIO/bit-bang mode, dedicated SPI hardware may require firmware adaptation to manage CONV as a frame-sync signal rather than CS. TI's application note SBAS102 details MCU implementation examples.

What is the purpose of the dual GND pins (pins 3 and 4) on the ADS7835E?

The ADS7835E features separate analog ground (pin 3) and digital ground (pin 4) terminals to isolate noise-sensitive analog circuitry (S/H, CDAC, reference buffer) from digital switching transients (CONV, CLK, DATA). Proper PCB layout requires routing these to distinct ground planes joined at a single point near the ADC's power supply entry to prevent ground bounce from degrading SNR or introducing offset errors in the ADS7835E conversion results.

How does the power-down mode of the ADS7835E affect conversion latency?

The ADS7835E power-down mode introduces zero additional latency: the first conversion after exiting power-down (via rising CONV edge) is fully valid and meets all timing specifications, including acquisition time (350ns) and conversion time (1.625µs). This "instant wake-up" behavior enables aggressive duty-cycling in battery-powered ADS7835E applications without compromising real-time responsiveness or requiring dummy conversions to stabilize internal nodes.