An auxiliary core supply voltage circuit for improved power supply sequencing

摘要

A diode reference circuit 18 biases a transistor 20 to provide an IC core with an auxiliary low voltage power supply on node 16 before the main IC core low power supply circuit begins to operate, at which time the transistor is cut off by the voltage at its emitter. The reference circuit and transistor are powered from the higher voltage supply 14 for the IC's I/O circuits. The automatic provision of an auxiliary low voltage supply for the core eases power supply sequencing constraints. If the core is unpowered the I/O drivers may suffer bus contention. Random application of supply voltages can result in latch-up. The diodes 28 may be Schottky or silicon diodes. The transistor 20 may be of NPN, PNP, MOS, or pHEMT type.