National Semiconductor Launches New LM3822 and LM3824 Current Sensors
National Semiconductor Corp. (Santa Clara, CA) announced a pair of high-precision current-gauge ICs for monitoring battery capacity in cellular phones, information appliances and other small portable devices. The LM3822 and LM3824 current sensors are housed in MSOP-8 packages for applications requiring motion-control diagnostics or load-current sensing of power sources.
The LM3822 and LM3824 sensors feature a 3-milliohm internal lead-frame resistor, which produces near-zero insertion losses while eliminating the need for external sense elements. In addition, the output is a PWM digital signal that is universally compatible with all micro-controllers, rated at +/-2 percent. An analog output is also possible with the addition of a simple R-C filter or an external op-amp filter. The integrated delta-sigma converter has the ability to cancel out the sensor's input-offset voltage, which is the largest contributor to measurement error in the micro-volt range. Both ICs sense magnitude and direction of current in ranges of -1.0A to +1.0A, or -2.0A to +2.0A.
Two modes of operation are available. The LM3822 operates in precision mode, averaging current over a 50-millisecond time period at 0.1-percent PWM resolution, while providing immunity to current spikes. The LM3824 operates in high-speed mode, with current averaged over a 6-millisecond time period at 0.8-percent PWM resolution. The LM3822 and LM3824 are currently available in eight-pin MSOP packages at $1.20 each when purchased in 1,000-unit lots.
