30 Dec 11

The new MCP6N11 is the first instrumentation amplifier introduced from Microchip. This amplifier’s new gain setting feature by using an extra pin (VFG) differs from the traditional approach of setting gain of connecting a feedback component from the output directly to the inverting input. This new pin connects to the inverting input of the second input stage. The output voltage (VOUT) can be shifted by the voltage applied to a reference voltage pin (VREF). This pin connects to the non-inverting input of the second input stage.

This provides an improvement for many characteristics, such as gain error and drift-over temperature. This chip can be ordered in one of several minimum gain options (1, 2, 5, 10, and 100 V/V), depending on the application. Other parameters, such as input offset voltage and input noise, can be optimized with this minimum gain feature.

The MCP6N11 can operate from a single supply with a voltage range of 1.8V to 5.5V. It offers rail-to-rail input and output performance with no common mode crossover distortion on the inputs. The Common Mode Rejection Ratio (CMRR) and the Power Supply Rejection Ratio (PSRR) are both over 94 dB over the range of operation. All devices are fully specified from -40°C to +125°C.

This new instrumentation amp features Microchip’s mCal technology, which is an on-chip calibration circuit that can compensate for offset voltage changes and provides an accurate way to minimize offset drift over time and temperature. The MCP6N11 uses CMOS circuitry for low-power operation while providing a gain bandwidth product of 500 kHz, and it features a hardware shutdown pin (EN/CAL) for even more power savings. Whenever this pin is low, the part is in a low power mode and the output is high impedance.  When this pin goes high, the calibration procedure begins, and then the amplifier resumes normal operation.

These features would make the MCP6N11 ideal for many portable sensor and signal conditioning applications that use small batteries. The diagram below shows a typical application using a Wheatstone bridge (strain gage) sensor: