| 摘要 |
A power supply switching circuit ensures stable, timely, and accurate transition between a primary power source and a secondary power source of an integrated circuit. A comparison element of the circuit compares a first voltage signal derived from a primary voltage of the primary power source to a second voltage signal, also derived from the primary voltage but having a different rate of change than the first voltage signal, to generate a compare output signal. The first and second voltage signals are characterized as being equal to each other when the primary voltage is equal to a predetermined crossover point at which the integrated circuit device will be powered by the primary voltage. When the primary voltage is less than the predetermined crossover point, a transistor element of a reference leg of a current mirror of the power supply switching circuit operates in back-bias mode and is sized large enough to ensure that the reference leg generates a large enough current to stabilize operation of the comparison element as the primary voltage ramps up until the primary voltage exceeds the predetermined crossover point.
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