High voltage input buffer made by a low voltage process and having a self-adjusting trigger point
AssigneeMotorola, Inc.
InventorJohn Deane Coddington
Life of this patent
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Abstract
A high performance high input voltage input buffer manufacture using a low voltage process contains an input buffer circuit (136) and a level shifter (132). The input buffer (136) will receive an input signal via a chip pad (112). The input signal from trip pad (112) will be provided to an inverter stack (135) that contains or is coupled to protection transistors (116, 114, 110, and 111). The protection transistors are biased by a reference generator (134) which outputs a voltage that is a function of the maximal voltage that can be provided on the chip pad (112). By using the circuit (134), the trigger point of the inverter stack (135) can be dynamically adjusted for any OVDD (110) value whereby input buffer performance is improved and made more flexible.
Claims12
An input buffer comprising:
- an input pad coupled to receive an input signal;
- a first circuit coupled to the input pad, the first circuit coupled to receive the input signal from the input pad, the first circuit comprising:
- a reference voltage generator;
- an inverter coupled to the reference voltage generator, the inverter coupled to receive an external voltage, the inverter having a trigger point which is a function of the external voltage, the inverter comprising:
- a first device having a first node coupled to receive the external voltage;
- a second device having a second node coupled to a second supply voltage;
- a first protection circuit coupled to the first device and coupled to the input pad, the first protection circuit coupled to protect the first device from low voltages, the first protection circuit coupled to the reference voltage generator, and
- a second protection circuit coupled to the second device and coupled to the input pad, the second protection circuit coupled to protect the second device from high voltages, the second protection circuit coupled to the reference voltage generator;
- and
- a level shifter coupled to the inverter, the level shifter coupled to receive a first supply voltage, the level shifter providing an internal voltage indicated by the input signal, wherein the internal voltage is less than the external voltage.
Dependencies are inferred from the claim text.