Texas Instruments ADS7818EB/250

Overview

ADS7818EB/250 from Burr-Brown (now Texas Instruments) is a 12-bit successive approximation register (SAR) analog-to-digital converter with integrated 2.5V bandgap reference, differential input, and synchronous serial interface. It delivers 500kHz throughput at 11mW, operates from a single +5V supply, and guarantees no missing codes across –40°C to +85°C. It is used in portable spectrum analyzers and battery-powered data loggers requiring high-speed, low-power digitization.

For engineers reviewing the ADS7818EB/250 datasheet, ADS7818EB/250 pinout, ADS7818EB/250 application, or ADS7818EB/250 equivalent, key selection considerations include its 500kHz sampling rate, ±1 LSB integral linearity, MSOP-8 package compatibility, differential input architecture, and internal reference overdrive capability - all critical for precision remote sensing and isolated data acquisition designs.

Technical Context

The ADS7818EB/250 implements a capacitive redistribution SAR architecture with on-chip sample/hold, eliminating external hold circuitry. Its conversion timing is asynchronous to the clock via the CONV control line, enabling flexible SPI-like or DSP-synchronized operation modes including LSB-first output and short-cycle termination.

It features dual reference operation: internal 2.5V ±20ppm/°C reference (yielding 0–5V input range) or external reference (2.0–2.55V) applied through a 10kΩ ±30% series resistor. The VREF pin requires 0.1µF ceramic + 2.2µF tantalum bypassing to suppress SAR-induced glitches and maintain 72dB SNR.

Key Specifications

Pinout & Package

ADS7818EB/250 is packaged in an MSOP-8 (3.0mm × 3.0mm, 0.65mm pitch) surface-mount package, optimized for space-constrained 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 ADS7816EB/250, ADS7818EB/250 provides 2.5× higher throughput at identical linearity and package compatibility; compared with ADS8320EB/250, it trades 4-bit resolution for 5× faster sampling - making ADS7818EB/250 optimal for bandwidth-critical, battery-operated instrumentation where 12-bit fidelity is sufficient.

Availability

ADS7818EB/250 is available at Aetrix Electronics and suitable for portable spectrum analyzers, battery-powered data loggers, wireless communication baseband interfaces, and DSP-based digital signal processing systems requiring stable component supply and industrial temperature qualification.

Supply support for ADS7818EB/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

Burr-Brown Corporation, acquired by Texas Instruments in 2000, specialized in high-precision analog signal conditioning and data conversion ICs for industrial, medical, and test equipment markets.

The ADS7818EB/250 belongs to Burr-Brown's high-speed, low-power SAR ADC product line designed specifically for portable and isolated data acquisition systems demanding accuracy, small size, and minimal power consumption.

FAQ

What is the maximum sampling rate supported by the ADS7818EB/250?

The ADS7818EB/250 supports a maximum throughput rate of 500kHz, achieved with an 8MHz clock input (16 cycles per conversion). At this rate, conversion time is 1.625µs and acquisition time is 350ns. Lower rates (e.g., 100kHz) reduce power dissipation to 9mW while maintaining full 12-bit performance. The device remains functional down to 12.5Hz throughput, though not recommended for precision applications due to increased noise susceptibility.

Does the ADS7818EB/250 require an external reference voltage?

No, the ADS7818EB/250 includes an internal 2.5V bandgap reference with ±20ppm/°C drift, enabling immediate operation with 0–5V input range. However, the VREF pin can be overdriven with an external 2.0–2.55V reference to improve temperature stability or set custom full-scale ranges (e.g., 2.048V for 1mV/LSB). External references must drive the internal 10kΩ ±30% series resistor and be properly bypassed.

How does the CONV pin control power-down mode on the ADS7818EB/250?

The ADS7818EB/250 enters power-down mode when the CONV pin is held LOW during conversion and remains LOW at the start of the 13th clock cycle. Power-down reduces supply current to 0.5mA (2.5mW), and the device resumes full operation on the next rising edge of CONV - with the first conversion valid and no pipeline delay. This feature enables significant energy savings in intermittent-sampling applications.

Can the ADS7818EB/250 output data in LSB-first format?

Yes, the ADS7818EB/250 supports LSB-first serial output. To enable it, assert CONV HIGH during the 12th clock cycle and then pull it LOW during the 13th clock cycle (when D0, the LSB, is transmitted). The subsequent 11 clocks repeat the 12-bit result LSB-first. This mode is useful for direct interface with microcontrollers lacking MSB-first shift register support, avoiding firmware bit-reversal overhead.

What is the absolute input voltage range allowed on the +In and –In pins of the ADS7818EB/250?

The ADS7818EB/250 specifies an absolute input voltage range of –0.2V to VCC + 0.2V (i.e., –0.2V to +5.2V at +5V supply) for +In, and –0.2V to +0.2V for –In. Exceeding these ranges risks damaging the input ESD protection structure or degrading linearity. The –In pin is intended for remote ground sensing, not full-scale differential input - true differential signals must be level-shifted to meet these constraints.