External components provide true shutdown for boost converter

the step-up Switching-converter Circuit in figure 1 presents a familiar problem:if you Shut down boost converter ic_{1 by pulling its  input Low, external inductor l< Sub id= "Id1901448-49-sub" >1 and forward-biased Schottky diode d1 allow the Load To continue drawing. For battery-powered applications so present a heavy load-300 MA, for example-this unwanted dc-current path may quickly d Rain the battery. Adding an N-channel MOSFET, q1, and a 100-kωresistor, r1, solves T He problem by opening the unwanted current path during shutdown. The resulting circuit is suitable for battery-powered-system applications in which a microcontroller handles the Power man agement.}

Asserting a low logic level on the input simultaneously shuts down the switching converter, a MAX756, and turns off the M Osfet, thereby blocking load current by removing the load ' s ground connection. When the signal deasserts, the 100-kωpullup resistor turns on the MOSFET by pulling the MOSFET's Gate high. With its ground reconnected, the load then draws current from the activated Boost-converter circuit.

For optimum results in high load currents, select a logic-level MOSFETs for Q1 that presents a reasonably low on-resistance . The MOSFET ' s Drain-to-source breakdown voltage should also be able to withstand at least twice the maximum output voltage You expect from the boost converter. If necessary, you can reduce the MOSFET's effective on-resistance by connecting and more MOSFETs in parallel.

External provide true shutdown for boost converter