AC-DC input buffer
First Claim
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1. A circuit, comprising:
- a capacitance element having an input and an output;
a direct current input buffer having an input and an output, wherein the input of the direct current input buffer is coupled to the input of the capacitance element and the output of the direct current input buffer is coupled to the output of the capacitance element;
a feedback circuit coupled to the direct current input buffer, the feedback circuit is operable to change the output of the direct current output buffer to match the input of the direct current input buffer responsive to determining the output of the direct current input buffer does not match the input of the direct current input buffer;
a delay circuit coupled to the feedback circuit, the delay circuit is configured to turn off the feedback circuit a predetermined amount of time after the output of the direct current input buffer is changed to match the input of the direct current input buffer; and
an output buffer coupled to the output of the direct current input buffer and the output of the capacitance element.
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Abstract
An inverting input buffer that uses the best features of an AC input buffer (low delay, high speed, high input voltage swing range) and a DC input buffer (stability, reliability, ‘automatic’ high and low data setup, input VIL and VIH “Voltage Input Low” and “Voltage Input High” margins). The delay though the buffer with a nominal load is very small. Optionally, a voltage tolerant input circuit is coupled to the DC input, which enables the DC input buffer to tolerate higher voltage swings, thus allowing a single buffer to switch both high (e.g. 2.5 volts-5 volts in a 1.2 volt system) and low input voltages (e.g. below 2.5 volts in a 1.2 volt system).
12 Citations
17 Claims
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1. A circuit, comprising:
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a capacitance element having an input and an output; a direct current input buffer having an input and an output, wherein the input of the direct current input buffer is coupled to the input of the capacitance element and the output of the direct current input buffer is coupled to the output of the capacitance element; a feedback circuit coupled to the direct current input buffer, the feedback circuit is operable to change the output of the direct current output buffer to match the input of the direct current input buffer responsive to determining the output of the direct current input buffer does not match the input of the direct current input buffer; a delay circuit coupled to the feedback circuit, the delay circuit is configured to turn off the feedback circuit a predetermined amount of time after the output of the direct current input buffer is changed to match the input of the direct current input buffer; and an output buffer coupled to the output of the direct current input buffer and the output of the capacitance element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A circuit, comprising:
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inverting means; means for capacitively coupling an input signal to the inverter means; means for direct current buffering the input signal to the inverter means in parallel with the means for capacitively coupling, the means for direct current buffering having an input and an output; means for providing feedback to the means for direct current buffering, the means for providing feedback is operable to provide feedback to the means for direct current buffering responsive to the output of the means for providing feedback not matching the input of the means for direct current buffering; and delay means for turning off the means for providing feedback a predetermined amount of time after the output of the means for direct current buffering has been changed to match the input of the means for direct current buffering. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A method, comprising:
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applying a signal to an input of a buffer through a capacitance element; and applying the signal to the input of the buffer through a direct current (DC) buffer coupled in parallel with the capacitance element concurrently to applying the signal to the capacitance element; applying a feedback signal to the DC buffer responsive to determining an output of the DC buffer does not match the signal at the input of the DC buffer; and turning off the feedback signal a predetermined amount of time after applying the feedback signal. - View Dependent Claims (16, 17)
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Specification