Patent ID: 7786765

Claim:
A low voltage shutdown circuit, comprising: an input node for receiving a voltage V in to be monitored; first and second voltage-to-current converters arranged to receive V in at respective inputs and to convert V in to currents I 1 and I 2 at respective outputs, said converters having respective voltage-to-current transfer functions which intersect at a predetermined non-zero threshold voltage V th , wherein said first and second voltage-to-current converters comprise: first and second resistors connected in series between V in and a first node, the junction between said first and second resistors being a second node; a first bipolar transistor connected between said first node and a circuit common point, said transistor's base directly connected to said second node; a second bipolar transistor connected to form a current mirror with said first bipolar transistor, the current conducted by said second bipolar transistor being I 1 ; and a third bipolar transistor having its base directly connected to said first node and its emitter connected to said circuit common point, the current conducted by said third bipolar transistor being I 2 ; and a current comparison circuit arranged to produce an output which is in a first state when I 1 <I 2 and in a second state when I 1 >I 2 such that said output toggles when V in falls below V th .