I/O cell configuration for multiple I/O standards
AssigneeAltera Corporation
InventorsCameron McClintock, Richard G. Cliff, Bonnie I. Wang
Life of this patent
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Abstract
Circuitry is provided to individually configure each I/O of an integrated circuit to be compatible with a different LVTTL I/O standards. This can be done with only one I/O supply voltage, where that voltage is the highest of the I/O voltages needed in a particular application. The circuitry operates by regulating the output voltage of the I/O cell so that it is above the VOH and below the maximum VIH for the LVTTL standard for which it will comply with. Since each I/O cell is individually configurable, any I/O can drive out to any LVTTL specification.
Claims40
An integrated circuit comprising:
- a first transistor coupled between a supply voltage and a first node, wherein a control electrode of the first transistor is coupled to a reference voltage;
- and
- a second transistor coupled between the first node and an output pad of the integrated circuit, wherein the reference voltage is less than the supply voltage and greater than a VSS voltage of the integrated circuit, and a voltage output high level at the pad will be determined by the reference voltage.
An integrated circuit comprising:
- a first transistor coupled between a supply voltage and a first node, wherein a control electrode of the first transistor is coupled to a reference voltage;
- and
- a second transistor coupled between the first node and an output pad of the integrated circuit, wherein a voltage output high level at the pad will be the lesser of the reference voltage level or the supply voltage, and in normal operation, the first transistor is not fully on.
An integrated circuit comprising:
- a first transistor coupled between a supply voltage and a first node, wherein a control electrode of the first transistor is coupled to a reference voltage;
- and
- a second transistor coupled between the first node and an output pad of the integrated circuit, wherein a voltage output high level at the output pad is selectable based on the reference voltage, and in normal operation the reference voltage is less than the supply voltage.
An integrated circuit comprising:
- a first transistor coupled between a supply voltage and a first node, wherein a control electrode of the first transistor is coupled to a reference voltage;
- and
- a second transistor coupled between the first node and an output pad of the integrated circuit, wherein a voltage output high level at the pad will be the lesser of the reference voltage level or the supply voltage, wherein the reference voltage level is selected to be a desired voltage output high level at the pad plus a VTN1 voltage, and the desired voltage high level is below the supply voltage and greater than a VSS voltage of the integrated circuit.
Dependencies are inferred from the claim text.