Maxim Integrated Products has introduced the MAX9928/MAX9929 low-cost, current-sense amplifiers for monitoring charge and discharge currents. These devices use a rail-to-rail input stage to achieve a wide, -0.1V to +28V, input common-mode range. This unique architecture offers true ground sensing and high-side current sensing in the same IC with unidirectional or bidirectional (charge/discharge) 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 20microamps of quiescent current from an independent, +2.5V to +5.5V supply voltage, the MAX9928/MAX9929 are also ideal for battery-powered handheld devices.
These precision amplifiers have less than 400microvolts 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: 2microamps/mV and 5microamps/mV. The user is free to 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 20V/V and 50V/V.
Both devices include a digital sign output that indicates the direction of current flow, allowing the user to maximize the output-voltage swing and utilize an ADC's full input range for measuring charge and discharge currents. An internal comparator uses low offset voltage and hysteresis to ensure that the direction of the sign bit is correct and unambiguous.
Maxim Integrated Products
