Electronic digital logic circuitry – Interface – Supply voltage level shifting
Patent
1996-08-20
1998-10-27
Santamauro, Jon
Electronic digital logic circuitry
Interface
Supply voltage level shifting
326 58, 326 86, H03K 19185
Patent
active
058282319
ABSTRACT:
A low voltage driver circuit capable of interfacing with a high voltage node. The high voltage tolerant input/output circuit of the present invention has a first stage operating at a low voltage integrated circuit standard and a second stage capable of operating at both the low voltage and a high voltage integrated circuit standard. The second stage operates at high voltage during the tristate mode and at low voltage during an active mode. The second stage uses an output driver having a p-type pull-up transistor coupled to an input/output pad. The input/output pad interfaces with a high voltage or mixed voltage network. An isolator circuit is coupled between the first stage and the second stage for voltage isolation when the second stage is operating at high voltage. A charger circuit maintains the high voltage on a gate of the p-type pull-up transistor during the tristate mode and the low voltage during the active mode. The charger also decreases the voltage on the gate of the p-type pull-up transistor in advance of a transition from the tristate to the active mode. The p-type transistors in the circuit which are exposed to the high voltage have their NWELLs coupled to the high voltage. This configuration prevents the back flow of current from the high voltage network to the second stage and protects the p-type transistors in the circuit from latch up.
REFERENCES:
patent: 4963766 (1990-10-01), Lundberg
patent: 5144165 (1992-09-01), Dhong et al.
patent: 5543733 (1996-08-01), Mattos et al.
patent: 5644265 (1997-07-01), Austin et al.
Altera Corporation, "A 3.3-V Programmable Logic Device that Addresses Low Power Supply and Interface Trends" by Rakesh Patel et al., Custom Integrated Circuits Conference (CICC), Santa Clara, California, May 5-8, 1997.
Harms Jeanette S.
Santamauro Jon
Xilinx , Inc.
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