CMOS bidirectional buffer for mixed voltage applications
First Claim
1. An output buffer for connecting a first device supplied with a first voltage to a second device supplied with a second voltage, comprising:
- a first driver for driving a terminal pad up to said second voltage;
a second driver for driving said terminal pad down to a voltage VSS;
at least one pair of push-pull bootstrap control transistors, connected to said first driver, for driving up said first driver to a voltage level based on a bootstrap capacitor having a predetermined capacitance, wherein the voltage level at a node between each said at least one pair of bootstrap control transistors is geater than the sum of said second voltage and a predetermined threshold voltage of said first driver.
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Accused Products
Abstract
In a preferred embodiment of the present invention, a bidirectional buffer connects a first device, such as a CMOS chip having a first voltage, such as VCC, to a second device having a second voltage, such as VDD, through a terminal pad. The buffer includes a bootstrap capacitor to assist in driving up the terminal pad. In particular, the buffer comprises an output and an input portion. The output portion includes a first driver for driving the terminal pad up to VDD and a second driver for driving the terminal pad down to VSS. The first driver includes a pull-up PMOS transistor and a pull-up NMOS transistor connected in series and the second driver includes a pull-down NMOS transistor. Further, preferably one pair of push-pull bootstrap control transistors are connected in parallel to the gate of the pull-up NMOS transistor for quickly driving up the first driver to a voltage level based on the bootstrap capacitor having a predetermined capacitance. The input portion includes an invertor and a protection resistor for protecting the invertor from static charges.
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Citations
34 Claims
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1. An output buffer for connecting a first device supplied with a first voltage to a second device supplied with a second voltage, comprising:
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a first driver for driving a terminal pad up to said second voltage; a second driver for driving said terminal pad down to a voltage VSS; at least one pair of push-pull bootstrap control transistors, connected to said first driver, for driving up said first driver to a voltage level based on a bootstrap capacitor having a predetermined capacitance, wherein the voltage level at a node between each said at least one pair of bootstrap control transistors is geater than the sum of said second voltage and a predetermined threshold voltage of said first driver. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A bidirectional buffer for connecting a first device supplied with a first voltage to a second device supplied with a second voltage, comprising:
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an output portion having; a first driver for driving a terminal pad up to said second voltage; a second driver for driving said terminal pad down to a voltage VSS; at least one pair of push-pull bootstrap control transistors, connected to said first driver, for driving up said first driver to a voltage level due to the effect of a bootstrap capacitor having a predetermined capacitance, wherein the voltage level at a node between each said at least one pair of bootstrap control transistor is greater than the sum of said second voltage and a predetermined threshold voltage of said first driver, and an input portion, connected to the first and second drivers, for receiving signals from a bonding pad. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34)
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Specification