Linear Technology LT1999 high-voltage amplifier

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Linear Technology has released the LT1999, a high-voltage amplifier designed for bi-directional current sensing in the presence of fast switching common-mode voltages from -5 to 80. This wide input common-mode range is obtained with standard low-voltage op amp supplies.

A 2 MHz bandwidth enables the device to monitor currents in H-bridge motor controls, switching power supplies, solenoid and battery chargers. To maintain accuracy, even when monitoring motor and solenoid current, it guarantees more than 80 dB of common-mode rejection at 100 kHz. This ensures that the device remains insensitive to the large square wave input common-mode voltages present in these applications.

The amplifier features a buffered output with three fixed-gain options for 10, 20 and 50 V/V. By default, the output voltage is referenced halfway between the supply voltage and ground, enabling the output to indicate both the magnitude and direction of the sensed current.

The output bias level can be set via a separate input. Gain error is guaranteed at less than 0.5% and input offset voltage is guaranteed at less than 1.5 mV over the full temperature range of -40 to 125°C. It operates with an independent 5 V supply voltage, drawing 1.5 mA while active and 10 µA in shutdown mode.