Sunnyvale, Calif. Maxim Integrated Products has introduced the low-cost MAX9928 and MAX9929 current-sense amplifiers for monitoring charge and discharge currents. Consuming only 20 μA of quiescent current from an independent +2.5-V to +5.5-V supply voltage, the devices are well-suited for battery-powered handheld devices.
In addition, these devices use a rail-to-rail input stage to achieve a wide -0.1-V to +28-V 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, Maxim said. This is useful for monitoring batteries in deep discharge as well as supercapacitors that are commonly used as emergency backup supplies in hybrid cars.
These precision amplifiers supply less than 400 microvolts 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 μ/mV and 5μ/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 20 V/V and 50 V/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 use 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.
The MAX9928/MAX9929 devices are fully specified over the -40°C to +125° automotive temperature range. They are available in 1 x 1.5-mm, 6-bump UCSP and 8-pin microMAX packages.
Pricing: Starts at $0.85 (1000-up, FOB USA).
Maxim Integrated Products , 1-800-998-8800, www.maxim-ic.com