MAX471

19-0335; Rev 2; 12/96 Precision, High-Side Current-Sense Amplifiers _______________General Description The MAX471/MAX472 are complete, bidirectional, highside current-sense amplifiers for portable PCs, telephones, and other systems where battery/DC power-line monitoring is critical. High-side power-line monitoring is especially useful in battery-powered systems, since it does not interfere with the ground paths of the battery chargers or monitors often found in “smart” batteries. The MAX471 has an internal 35mΩ current-sense resistor and measures battery currents up to ±3A. For applications requiring higher current or increased flexibility, the MAX472 functions with external sense and gain-setting resistors. Both devices have a current output that can be converted to a ground-referred voltage with a single resistor, allowing a wide range of battery voltages and currents. An open-collector SIGN output indicates current-flow direction, so the user can monitor whether a battery is being charged or discharged. Both devices operate from 3V to 36V, draw less than 100µA over temperature, and include a 18µA max shutdown mode. ____________________________Features o Complete High-Side Current Sensing o Precision Internal Sense Resistor (MAX471) o 2% Accuracy Over Temperature o Monitors Both Charge and Discharge o 3A Sense Capability with Internal Sense Resistor (MAX471) o Higher Current-Sense Capability with External Sense Resistor (MAX472) o 100µA Max Supply Current o 18µA Max Shutd...