Precision, Wide Voltage Range, Gain Selectable Funnel Amplifier

The LT1997-2 is an attenuating (funnel) difference amplifier that can be used to translate large differential signals to the low voltage range compatible with ADCs. It combines a precision operational amplifier with highly-matched resistors to form a one-chip solution to attenuate and level shift voltages accurately using no external components. It comes with three standard pin-selectable gain options (0.1, 0.2 and 0.25), which can be further combined to form gains from 0.0455 to 0.55 (attenuations of 1.82 to 22) with accuracy of 0.006% (60ppm). The LT1997-2 also works across a very wide input common-mode voltage range (±255V), enabling robust operation in demanding industrial environments. Its excellent resistor matching results in a common mode rejection ratio of greater than 105dB.

The resistors maintain their excellent matching over temperature; the matching temperature coefficient is guaranteed less than 1ppm/°C. The resistors are extremely linear with voltage, resulting in a gain nonlinearity of less than 2ppm.

The LT1997-2 is fully specified at 5V and ±15V supplies and from −40°C to 125°C. The device is available in space saving 16-lead MSOP and 4mm × 4mm DFN14 packages.

APPLICATIONS

* High Voltage to Low Voltage Level Translation

* ADC Driver

* Bidirectional Wide Common Mode Range Voltage and Current Sensing

* Industrial Data-Acquisition Front-Ends

* Replacement for Isolation Circuits

* Differential to Single-Ended Conversion

* Precision Attenuation: Gain = 0.1, 0.2, 0.25

* ±255V Common Mode Voltage Range

* 105dB Minimum CMRR (Gain = 0.1)

* 0.006% (60ppm) Maximum Gain Error

* 1ppm/°C Maximum Gain Error Drift

* 2ppm Maximum Gain Nonlinearity

* Wide Supply Voltage Range: 3.3V to 50V