Buffer with an output swing created using an over-supply voltage
View Patent ↗A pre-drive circuit with an output buffer that may contain a bootstrap circuit is described. The bootstrap circuit may be configured to output a voltage level greater in magnitude than the supply voltage that the bootstrap circuit is coupled with. The pre-drive circuit may contain a timing circuit. The timing circuit may be configured to at least partially determine when the bootstrap circuit outputs a voltage greater in magnitude than the supply voltage. The pre-drive circuit may also contain a pre-drive buffer circuit. This pre-drive buffer circuit may be capable of three outputs: (1) logical zero, or roughly electrical ground; (2) logical one, or roughly the level of the voltage supply, and (3) an outputted voltage greater than the voltage supply.
1. A circuit comprising:
a timing circuit configured to generate a delayed signal in response to an input signal;
a first pre-drive buffer portion configured to provide a first voltage level to a node in response to a first control signal based on the input signal and the delayed signal; and
a second pre-drive buffer portion configured to provide a second voltage level to the node in response to a second control signal based on the input signal; and
a bootstrap circuit configured to boost the voltage level of the node from the first voltage level to a bootstrapped voltage level in response to a third control signal based on the input signal.
2. The circuit of claim 1 , wherein the timing circuit is a delay circuit.
3. The circuit of claim 2 , wherein the delay circuit is comprised of a series of logic gates.
4. The circuit of claim 1 , wherein the input signal is a clock signal, and the delayed signal generated by the timing circuit is a buffered clock signal.
5. The circuit of claim 1 , wherein the bootstrap circuit is comprised of a MOSFET, wherein a source of the MOSFET is coupled to a drain of the MOSFET.
6. The circuit of claim 5 , wherein the MOSFET is coupled to generate a capacitive charge, and wherein the bootstrapped voltage level is based on the capacitive charge.
7. The circuit as recited in claim 5 , wherein the gate of the MOSFET is coupled to the node.
8. The circuit as recited in claim 5 , wherein a version of the third control signal is provided to the drain and the source of the MOSFET.
9. The circuit of claim 1 , wherein the timing circuit is a delay circuit comprised of a series of inverters.
10. The circuit of claim 1 , further comprising a control logic circuit, wherein the control logic circuit receives at least a first control signal and has an output coupled to the timing circuit.
11. The circuit of claim 1 , further comprising:
an input portion coupled to generate a signal in response to a first control signal, a second control signal, and the input signal,
wherein the timing circuit is coupled to receive the signal from the input portion and further coupled to generate the delayed signal based on the signal received from the input portion.
12. The circuit as recited in claim 1 , wherein the first pre-drive buffer portion and the second pre-drive buffer portion are configured to cause the node to float and the voltage level of the node is boosted to the bootstrapped voltage level, by the bootstrap circuit, while the node floats.
13. The circuit as recited in claim 1 , wherein the first voltage level is provided by a first power supply node and the second voltage level is provided by a ground voltage node, the first voltage level exceeding the second voltage level and the bootstrapped voltage level exceeding the first voltage level.
14. The circuit as recited in claim 1 , wherein the first pre-drive buffer portion comprises a first device of a first type coupled between the node and the first power supply node and the second pre-drive buffer portion comprises a second device of a second type coupled between the node and the ground voltage node.
15. The circuit as recited in claim 14 , wherein the first device includes a gate terminal configured to receive the first control signal and the second device includes a gate terminal configured to receive the second control signal.
16. The circuit as recited in claim 15 , wherein the second control signal is further based on another control signal.
17. A method comprising:
generating a delayed signal in response to an input signal;
providing a first voltage level to a node in response to a first control signal based on the input signal;
providing a second voltage level to the node in response to a second control signal based on the input signal and the delayed signal; and
boosting the voltage level of the node from the second voltage level to a bootstrapped voltage level in response to a third control signal based on the delayed signal.
18. The method, as recited in claim 17 , further comprising:
causing the node to float in response to the first control signal and the second control signal,
wherein the voltage level is boosted to the bootstrapped voltage level while the node floats.
19. An apparatus comprising:
means for generating a delayed signal in response to an input signal;
means for providing a first voltage level to a node in response to a first control signal based on the input signal;
means for providing a second voltage level to the node in response to a second control signal based on the input signal and the delayed signal; and
means for boosting the voltage level of the node from the second voltage level to a bootstrapped voltage level in response to a third control signal based on the delayed signal.