Power-supply feedthrough protection circuit for 5-volt failsafe CMOS drivers
AssigneeLSI Logic Corporation
InventorMichael Braiman
Life of this patent
Estimating the term…
Abstract
A power supply feedthrough protection circuit which solves the problem of voltage feedthrough from a bus cable charging a chip power-supply beyond acceptable transistor limits. The circuit continuously senses the chip power-supply, compares the supply to an acceptable threshold, and provides a low-impedance current path as soon as the power-supply exceeds the threshold. The circuit allows a driver to draw current from the cable, in a controlled manner, and provides that the power supply is therefore never allowed to exceed the maximum allowable limit for transistors.
Claims16
A power supply feedthrough protection circuit configured to receive a chip power supply, a reference voltage, and driver control signal, and configured to provide an output, said power supply feedthrough protection circuit comprising:
- a resistor divider which is configured to receive the chip power supply and divide the chip power supply to a reduced voltage to be compared to the reference voltage;
- means for comparing the reduced voltage to the reference voltage to determine whether the chip power supply exceeds an acceptable threshold;
- a driver which includes a pair of transistors and a series termination resistor, said pair of transistors comprising an n-channel transistor and a p-channel transistor and configured to receive the driver control signals;
- and means for providing a low-impedance current path when it is determined that the chip power supply exceeds the threshold.
A power supply feedthrough protection circuit configured to receive a chip power supply, a reference voltage, and driver control signal, and configured to provide an output, said power supply feedthrough protection circuit comprising:
- a resistor divider which is configured to receive the chip power supply and divide the chip power supply to a reduced voltage to be compared to the reference voltage;
- an amplifier which is configured to receive the reduced voltage and the reference voltage, wherein the amplifier has an output and the circuit further comprises a transistor which is connected to the output of the amplifier and is configured to turn on and provide a path for current to flow from the output of the circuit, to ground, said circuit, further comprising a driver which includes a pair of transistors and a series termination resistor, said pair of transistors comprising an n-channel transistor and a p-channel transistor and configured to receive the driver control signals, said circuit further comprising a capacitor connected to the resistor divider, said capacitor configured to provide bandlimiting to prevent normal switching noise from triggering the circuit, wherein the circuit is configured to operate in a fault and a non-fault condition, wherein in the fault condition, the output of the circuit is connected to a voltage from which the chip voltage supply is derived.
A power supply feedthrough protection circuit configured to receive a chip power supply, a reference voltage, and driver control signals, and configured to provide an output, said power supply feedthrough protection at comprising means for continuously sensing the chip power supply;
- means for comparing the chip power supply to the reference voltage to determine whether the chip power supply exceeds an acceptable threshold;
- and a p-channel field effect transistor having its source and/or well connected to the chip power supply and a current path from the output through the p-channel transistor's source and/or well to the chip power supply.
Dependencies are inferred from the claim text.