Allgemeine Beschreibung

The MAX44244/MAX44245/MAX44248 family of parts provide ultra-precision, low-noise, zero-drift single/quad/dual operational amplifiers featuring very low-power operation with a wide supply range. The devices incorporate a patented auto-zero circuit that constantly measures and compensates the input offset to eliminate drift over time and temperature as well as the effect of 1/f noise. These devices also feature integrated EMI filters to reduce high-frequency signal demodulation on the output. The op amps operate from either a single 2.7V to 36V supply or dual ±1.35V to ±18V supply. The devices are unity-gain stable with a 1MHz gain-bandwidth product and a low 90µA supply current per amplifier.

The low offset and noise specifications and high supply range make the devices ideal for sensor interfaces and transmitters.The devices are available in µMAX, SO, SOT23, and TSSOP packages and are specified over the -40°C to +125°C automotive operating temperature range.

Anwendungen

Sensors Interfaces

4mA to 20mA and 0 to10V Transmitters

PLC Analog I/O Modules

Weight Scales

Portable Medical Devices

 

Vorteile und Merkmale

Reduces Power for Sensitive Precision Applications

Low 90µA Quiescent Current per Amplifier

Eliminates the Cost of Calibration with Increased

Accuracy with Maxim’s Patented Autozero Circuitry

Very Low Input Voltage Offset 7.5µV (max)

Low 30nV/°C Offset Drift (max)

Low Noise Ideal for Sensor Interfaces and

Transmitters

50nV/√Hz at 1kHz

0.5µVP-P from 0.1Hz to 10Hz

1MHz Gain-Bandwidth Product

EMI Suppression Circuitry

Schiene-zu-Schiene-Ausgang

Wide Supply for High-Voltage Front Ends

2.7V to 36V Supply Range

µMAX, SO, SOT23, TSSOP Packages

 

Detaillierte Beschreibung

The MAX44244/MAX44245/MAX44248 are highprecision amplifiers with less than 2µV (typ) input-referred offset and low input voltage-noise density at 10Hz. 1/f noise, in fact, is eliminated to improve the performance in low-frequency applications. These characteristics are achieved through an auto-zeroing technique that cancels the input offset voltage and 1/f noise of the amplifier. External Noise Suppression in EMI Form These devices have input EMI filters to prevent effects of radio frequency interference on the output. The EMI filters comprise passive devices that present significant higher impedance to higher frequency signals. See the EMIRR vs. Frequency graph in the Typical Operating Characteristics section for details.High Supply Voltage Range The devices feature 90µA current consumption per channel and a voltage supply range from either 2.7V to 36V single supply or ±1.35V to ±18V split supply.

 

Anwendungen Informationen

The devices feature ultra-high precision operational amplifiers with a high supply voltage range designed for load cell, medical instrumentation, and precision instrument applications.4–20mA Current-Loop Communication Industrial environments typically have a large amount of broadcast electromagnetic interference (EMI) from highvoltage transients and switching motors. This combined with long cables for sensor communication leads to high-voltage noise on communication lines. Current-Loop communication is resistant to this noise because the EMI induced current is low. This configuration also allows for low-power sensor applications to be powered from the communication lines.

 

Layout Guidelines

The MAX44244/MAX44245/MAX44248 feature ultra-low input offset voltage and noise. Therefore, to get optimum performance follow the layout guidelines. Avoid temperature tradients at the junction of two dissimilar metals. The most common dissimilar metals used on a PCB are solder-to-component lead and solder-to-board trace. Dissimilar metals create a local thermocouple. A variation in temperature across the board can cause an additional offset due to Seebeck effect at the solder junctions. To minimize the Seebeck effect, place the amplifier away from potential heat sources on the board, if possible. Orient the resistors such that both the ends are heated equally. It is a good practice to match the input signal path to ensure that the type and number of thermoelectric juntions remain the same. For example, consider using dummy 0Ω resistors oriented in such a way that the thermoelectric source, due to the real resistors in the signal path, are cancelled. It is recommended to flood the PCB with ground plane. The ground plane ensures that heat is distributed uniformly reducing the potential offset voltage degradation due to Seebeck effect.