Ultra-Low Offset/Drift, Precision Instrumentation Amplifiers with REF Buffer

The MAX4208/MAX4209 ultra-low offset and drift instrumentation amplifiers feature exceptional precision specifications, low power consumption, rail-to-rail output, excellent gain-bandwidth product, and buffered REFIN/MODE input in a very small µMAX® package. These devices use a spread-spectrum, autozeroing technique that constantly measures and corrects the input offset, eliminating drift over time and temperature and the effect of 1/f noise. This technique achieves less than 20µV offset voltage, allows ground-sensing capability, provides ultra-low CMOS input bias current and increased common-mode rejection performance.

The MAX4208/MAX4209 provide high-impedance inputs optimized for small-signal differential voltages (±100mV). All devices provide a gain-bandwidth product of 750kHz.

The MAX4208 provides an adjustable gain with two external resistors or unity gain with FB connected to OUT. The MAX4209 is available with a fixed gain of 100V/V with ±0.03% (typ) accuracy. Both devices include a reference input (REF) to level-shift the output, allowing for bipolar signals in single-supply applications. In both devices, REFIN/MODE is an input to a precision unity-gain buffer, which sets the REF voltage to level-shift the output. The internal REF buffer allows the reference to be set by a simple resistive divider or an ADC reference without any loading error.

The MAX4208/MAX4209 operate with a 2.85V to 5.5V single-supply voltage and consume only 750µA of quiescent current (when the internal buffer is off) and only 1.4µA in shutdown mode. These amplifiers also operate with ±2.5V dual supplies with REF connected to ground and REFIN/MODE to VSS. The MAX4208/MAX4209 are available in space-saving 8-pin µMAX packages and are specified over the automotive operating temperature range (-40°C to +125°C).

Applications

* Battery-Powered Medical Equipment * Differential Voltage Amplification * Industrial Process Control * Notebook Computers * Precision Low-Side Current Sense * Strain-Gauge Amplifiers

* Spread-Spectrum, Auto-Zero Instrumentation Amplifiers Improve DC Characteristics to Maximize Sensor Performance

* Input Offset Voltage: ±20µV (max) at +25°C

* ±0.25% (max) Gain Error

* Low 0.2µV/°C Offset Voltage Drift

* 1pA CMOS Input Bias Current

* True Ground Sensing with Rail-to-Rail Output

* 750kHz Gain-Bandwidth Product

* Buffered REF Input for High Accuracy and Bipolar Operation

* Low Power Operation Supports Remote Sensing and Battery-Powered Applications

* 2.85V to 5.5V Single-Supply Operation (or ±1.425V to ±2.75V Dual Supplies)

* 750µA Supply Current

* 1.4µA Shutdown Mode

* Adjustable (MAX4208) and Fixed Gain of 100 (MAX4209) Provide Design Flexibility