Electronic Design

Electronic Circuit Breaker Senses On-Resistance Voltage Drops, Eliminating Sense Resistor

Electronic circuit breakers typically rely on the drop across an external resistor to sense overcurrents. Instead, Linear Technology's LTC4213 senses the drop across the on-resistance (RDS(ON)) in the external MOSFET that provides power to the load. It's less precise than the resistor method, but it's simpler and cheaper, and it wastes less power in low-voltage applications.

The LTC4213 operates over a bias supply range from 2.3 to 6 V. When bias supply voltage and the ON pin are high, the gate drive to the external MOSFET starts charging after a debounce delay. The circuit breaker is armed once the external MOSFET is fully turned on. After that, the chip provides dual level and dual response-time functions by pin-strapping.

With the selector pin at ground, the breaker trips in 16 µs if the drain-source drop exceeds 25 mV and in 1 µs if it exceeds 100 mV. The trip values are 50 and 175 mV with the selector pin floating and 100 and 325 mV with the selector pin at VCC.

In 12-lead DFN, pricing starts at $1.50 each in 1000-piece quantities.

Linear Technology

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