Automotive-Grade Current-Sense Amplifier

Maxim introduces the MAX9937, a high-side current-sense amplifier that uses external resistors to set the voltage gain for maximum design flexibility. The MAX9937 protects against accidental application of battery voltage in the reverse (wrong) direction and against inductive kickback transients and spikes (load dump) of -20V to +40V. These safeguards are a major concern in automotive electronic control units (ECUs), which are used to monitor currents in the modules that control electronic power steering, 4-wheel drive, and antilock braking systems; it even watches the fuse box so as to monitor problems.

The MAX9937 input common-mode range is 4V to 28V and is independent of the VCC supply voltage, which can operate at 2.7V to 5.5V. When VCC is 5V, the supply current is a low 20µA. When VCC is 0V, the input bias current at the sense resistor is only 1µA to minimize battery drain when the ECU is off. Voltage gain is set by the ratio of two external resistors to their accuracy. Input offset voltage (VOS) is a low ±1.2mV (max). The MAX9937 is available in tiny, 3mm x 3mm, 5-pin SC70 package that is lead- and halide-free, thereby RoHS-compliant. This amplifier is fully specified over the -40°C to +125°C automotive temperature range. Prices start at $0.58 (1000-up, FOB USA).