advertisement Electronic Circuit Breaker in Small DFN Package Eliminates Sense
Resistor – Design Note 402
SH Lim
Introduction
Traditionally, an Electronic Circuit Breaker (ECB) comprises a MOSFET, a MOSFET controller and a current sense
resistor. The LTCВ® 4213 does away with the sense resistor
by using the RDS(ON) of the external MOSFET. The result
is a simple, small solution that offers a significant low
insertion loss advantage at low operating load voltage.
The LTC4213 features two circuit breaking responses to
varying overload conditions with three selectable trip
thresholds and a high side drive for an external N-channel MOSFET switch.
Overcurrent Protection
The SENSEP and SENSEN pins monitor the load current via the RDS(ON) of the external MOSFET and serve
as inputs to two internal comparators—SLOWCOMP
and FASTCOMP—with trip points at VCB and VCB(FAST),
respectively. The circuit breaker trips when an overcurrent fault causes a substantial voltage drop across the
MOSFET. An overload current exceeding VCB/RDS(ON)
causes SLOWCOMP to trip the circuit breaker after a 16Вµs
delay. In the event of a severe overload or short-circuit
current exceeding VCB(FAST)/RDS(ON), the FASTCOMP
trips the circuit breaker within 1Вµs, protecting both the
MOSFET and the load. …