Can I safely use a MOSFET switch at the input of a MC33063 boost regulator?
There isn't an enable on the MC33063.

There are two ways that this could be done:

With a PMOS high side switch on the Vcc line which would switch the entire part on and off (and also allow very low current leakage) 


P-Channel MOSFET high side switch

Or another potential way (which I have not verified on this device but should work) would be to drive the COMP pin higher than 1.25V. The downside would be that the MC33063 would be using quiescent current with the switching disabled.

During normal operation, the feedback pin is regulated to 1.25V, if the COMP pin is significantly higher than 1.25V then switching operation stops. If the pin voltage is pulled up by a mosfet, then the voltage could be pulled up to more than the 1.275V threshold voltage of the COMP pin and operation would stop (even with a 3.3V Vcc on the mosfet, you could use a higher Vcc if needed, the COMP pin is tolerant to 40V). I would test this idea in spice before using. 







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