Texas Instruments ADS7835E/250

Overview

ADS7835E/250 from Texas Instruments (formerly Burr-Brown) is a 12-bit, 500kHz throughput SAR analog-to-digital converter with integrated sample-and-hold, internal 2.5V reference, and synchronous serial interface. It operates from a single +5V supply, delivers ±2.5V bipolar input range, and achieves 72dB SNR at 10kHz - ideal for portable spectrum analyzers and multi-channel data loggers.

For engineers reviewing the ADS7835E/250 datasheet, ADS7835E/250 pinout, ADS7835E/250 application, or ADS7835E/250 equivalent, key selection considerations include guaranteed no-missing-codes performance, power-down mode reducing dissipation to 2.5mW, MSOP-8 package compatibility with space-constrained PCB layouts, and binary two's complement output format requiring precise timing control of CONV and CLK signals.

Technical Context

The ADS7835E/250 implements a capacitive redistribution SAR architecture fabricated in 0.6µm CMOS, enabling inherent sample-and-hold functionality without external components. Its conversion timing is controlled asynchronously by the CONV signal, independent of CLK edges for sample/hold transitions.

It supports dual serial data formats: MSB-first (default) and LSB-first (enabled via specific CONV edge sequencing), with clock frequency scalable from 200kHz to 8MHz to achieve 12.5kHz–500kHz throughput rates. The internal 2.5V bandgap reference drives the CDAC and allows overdriving with external 2.3V–2.9V references for improved temperature stability.

Key Specifications

Pinout & Package

ADS7835E/250 is housed in an MSOP-8 package (3.0mm × 3.0mm, 0.65mm pitch), optimized for compact, high-density PCB layouts in portable instrumentation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ADS7835EB/250, the ADS7835E/250 trades 1 LSB linearity for cost savings while retaining identical timing, packaging, and power-down behavior; versus ADS8320E/250, it offers 5× higher throughput and +5V compatibility at the expense of resolution and modern SPI framing.

Availability

ADS7835E/250 is available at Aetrix Electronics and suitable for portable instrumentation, wireless test equipment, and multi-channel data acquisition systems requiring stable component supply across extended product lifecycles.

Supply support for ADS7835E/250 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 acquired Burr-Brown in 2000 and maintains its precision analog portfolio, emphasizing high-performance data converters for industrial, medical, and test equipment markets.

The ADS7835E/250 belongs to TI's legacy high-speed SAR ADC family designed specifically for battery-powered, space-constrained measurement systems needing 12-bit accuracy at 500kHz with minimal external components.

FAQ

What is the absolute maximum input voltage range for the ADS7835E/250?

The ADS7835E/250 specifies an absolute maximum analog input voltage of –5.3V to +5.3V when operating from a +5V supply. Exceeding this range risks permanent damage. The functional input range is ±2.5V with the internal reference enabled, or ±VREF when using an external reference between 2.3V and 2.9V. Always ensure input signals remain within absolute ratings even during power-up/power-down sequences.

Does the ADS7835E/250 require an external clock, and what are the valid frequency and timing constraints?

Yes, the ADS7835E/250 requires an external clock on the CLK pin, with valid frequencies from 200kHz to 8MHz. Minimum HIGH and LOW times must each be ≥50ns, and the clock period must be ≥125ns. The clock duty cycle is not critical. For 500kHz throughput, a 8MHz clock with 16 cycles per conversion is used; lower throughput rates use proportionally fewer clock cycles or gated clocking to enter power-down mode between conversions.

How does the power-down mode work on the ADS7835E/250, and how quickly does it recover?

The ADS7835E/250 enters power-down mode when CONV remains LOW during conversion and is still LOW at the start of the 13th clock cycle. It exits power-down on the rising edge of CONV, requiring ≥tACQ (350ns) in the HIGH state to fully power up internal nodes and sample the input accurately. The first conversion after wake-up is valid - no latency penalty - making it suitable for burst-mode acquisition in battery-powered devices.

Can the ADS7835E/250 interface directly with a TI TMS320C54x DSP, and which pins map to which signals?

Yes, the ADS7835E/250 interfaces directly with TI TMS320C54x DSPs using the Buffered Serial Port (BSP). Connect CONV to BFSX (frame sync), CLK to BCLKX (bit clock), and DATA to BDR (data receive). This mapping leverages the ADS7835E/250's MSB-first synchronous serial protocol and eliminates glue logic. Ensure proper timing alignment per the BSP's frame synchronization requirements and ADS7835E/250's tCKCH/tCKCS setup/hold constraints.

What is the purpose of the dual GND pins (Pins 3 and 4) on the ADS7835E/250, and how should they be routed?

Pins 3 and 4 on the ADS7835E/250 are separate analog and digital ground connections, respectively. They must both be connected to a low-impedance, unified system ground plane - not isolated. Their separation minimizes digital switching noise from the serial interface (CLK, DATA, CONV) from coupling into the sensitive analog input path (AIN, VREF). Use short, direct traces and avoid routing digital signals over the analog ground region to preserve 72dB SNR performance.