Current-Sense Amplifiers Provide -0.1 V to +28 V Input Range October 13, 2008
Two current-sense amplifiers use a rail-to-rail input stage to achieve a wide, -0.1 V to +28 V common-mode input range. The MAX9928/MAX9929 architecture combines true ground sensing and high-side current sensing in the same IC with unidirectional or bidirectional current-monitoring capability. This is useful for monitoring batteries in deep discharge, as well as the supercapacitors that are commonly used as emergency backup supplies in hybrid cars. Consuming only 20 µA of quiescent current from an independent, 2.5- to 5.5-V supply voltage, the amplifiers are also well suited for battery-powered handheld devices. They have less than 400 µV of offset voltage, and include on-chip, laser-trimmed, gain-setting resistors for better than 1% gain accuracy. The MAX9928 is a current-output device and is available in two transconductance gain options: 2 µA/mV and 5 µA/mV. Users select the output resistor to convert the current to a voltage to match the input range of an ADC. The MAX9929 is a voltage-output device with fixed-gain options of 20 V/V and 50 V/V. The MAX9928 and MAX9929 are fully specified over the -40°C to +125°C automotive temperature range, and are available in 1 mm x 1.5 mm, 6-bump UCSP and 8-pin microMAX packages. Prices start at $0.85 for 1000-unit quantities. MAXIM INTEGRATED PRODUCTS, Sunnyvale, CA. (800) 998-8800.
