Bidirectional level shifting interface circuit
First Claim
1. A bidirectional level shifting interface circuit comprising:
- first and second I/O ports;
a first FET having a channel connected between said first and second I/O ports, said first I/O port being including means for coupling to a third I/O port of a first digital circuit operating at a relatively low power supply voltage, and said second I/O port being including means for coupling to a fourth I/O port of a second digital circuit operating at a relatively high power supply voltage, said channel passing communication signals in each direction between said first and second digital circuits; and
latching circuit means, biased by the relatively high voltage power supply, having an output connected to said second I/O port, and having a control input responsive to the voltage at said first or second I/O ports, for latching said second I/O port at sufficient voltage to drive said second digital circuit at binary one level in response to the transmission by said first digital circuit of a binary one signal toward said second digital circuit via said first and second I/O ports.
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Accused Products
Abstract
A bidirectional level shifting interface circuit has first and second I/O ports and an FET with a drain-source channel connected between the first and second I/O ports. The first I/O port is connected to an I/O port of a first digital circuit operating at a relatively low supply voltage, and the second I/O port is connected to an I/O port of a second digital circuit operating at a relatively high supply voltage. This channel passes communication signals in each direction between the first and second digital circuit. A latching circuit comprising a P Channel FET is biased by the relatively high voltage supply, has an output connected to the second I/O port, and has a control input. The interface circuit further comprises an inverter circuit having a control input connected to the second I/O port and an inverted output connected to the control input of the latching FET such that when the second I/O port exhibits a binary one voltage caused by the first digital circuit, the inverted output exhibits a binary zero voltage to activate the P Channel FET to latch the second I/O port at sufficient voltage to drive the second digital circuit at binary one level.
72 Citations
21 Claims
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1. A bidirectional level shifting interface circuit comprising:
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first and second I/O ports; a first FET having a channel connected between said first and second I/O ports, said first I/O port being including means for coupling to a third I/O port of a first digital circuit operating at a relatively low power supply voltage, and said second I/O port being including means for coupling to a fourth I/O port of a second digital circuit operating at a relatively high power supply voltage, said channel passing communication signals in each direction between said first and second digital circuits; and latching circuit means, biased by the relatively high voltage power supply, having an output connected to said second I/O port, and having a control input responsive to the voltage at said first or second I/O ports, for latching said second I/O port at sufficient voltage to drive said second digital circuit at binary one level in response to the transmission by said first digital circuit of a binary one signal toward said second digital circuit via said first and second I/O ports. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A bidirectional communication system comprising:
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a first digital circuit operating at a relatively low power supply voltage and having a first I/O port; a second digital circuit operating at a relatively high power supply voltage and having a second I/O port; a first transmission line connected at one end to said first I/O port; a second transmission line connected at one end to said second I/O port; and a bidirectional level shifting interface circuit comprising; a third I/O port connected to the other end of said first transmission line; a fourth I/O port connected to the other end of said second transmission line; an FET having a channel connected between said third and fourth I/O ports; and latching circuit means, biased by the relatively high voltage power supply, having an output connected to said fourth I/O port, and a control input responsive to the voltage at said third or fourth I/O ports for latching said fourth I/O port at sufficient voltage to drive said second digital circuit at binary one voltage in response to the transmission by said first digital circuit of a binary one signal toward said second digital circuit via said third and fourth I/O ports. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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Specification