A patented 4-milliohm internal lead-frame resistor that produces near-zero insertion losses is a key element in the LM3812 and LM3813 high-precision current-gauge ICs. The chips are intended for use in battery fuel monitors, motion-control diagnostics and load-current sensing of power sources. Their low insertion losses, which eliminate the need for external sense elements, are particularly important when measuring high currents.The LM3812 senses current on the high side of the load, while the LM3813 handles low-side sensing. Both measure current flow with virtually no insertion loss in the measurement line. Voltages across the lead-frame resistor are measured by a delta-sigma converter; that measurement is converted to a PWM digital output that indicates current magnitude and direction and is fed to a microcontroller. PWM accuracy at room temperature is rated at ±2%.
Company: NATIONAL SEMICONDUCTOR CORP.
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