Prestage for an off-chip driver (OCD)
View Patent ↗A prestage for generating a control signal for an output driver of an integrated circuit, wherein the integrated circuit can be provided with a reference potential and a supply potential fixed in relation to the reference potential, comprises an input for receiving an input signal from the integrated circuit, a circuitry for generating an output signal based on the received input signal, an output for outputting the generated output signals as control signal for an output driver as well as a current source, which is effectively connected to the circuitry. Thereby, the circuitry for generating an output signal and the current source are connected in series and connected to a first potential and a second potential such that a prestage potential difference across the series circuit is higher than a supply potential difference between the supply potential and the reference potential. Such a prestage has the advantage that it is less sensitive against variations on the reference potential or the reference potential, respectively, than conventional circuitries and can generate an output signal with well defined rise times.
1. A prestage for generating a control signal for an output driver of an integrated circuit, wherein the integrated circuit can be provided with a reference potential and a supply potential determined in relation to the reference potential, the prestage comprising:
an input for receiving an input signal from the integrated circuit;
a circuitry for generating an output signal based on the received input signal;
an output for outputting the generated output signal as a control signal for the output driver;
a current source, which is effectively connected to the circuitry, wherein the circuitry and the current source are connected in series and connected to a first potential and a second potential such that a prestage potential difference across the series circuit is higher than a supply potential difference between the supply potential and the reference potential;
wherein the circuitry comprises a first supply voltage terminal and a second supply voltage terminal, the current source comprises a current output and a base terminal, wherein the current output is coupled to the first supply voltage terminal, wherein the second potential is applied to the base terminal as base potential, and the first potential is applied to the second supply terminal.
2. The prestage according to claim 1 , wherein the base potential is more negative than the reference potential, wherein the supply potential is more positive than the reference potential and the first potential is equal to the supply potential.
3. The prestage according to claim 1 , wherein the base potential is more positive than the supply potential, wherein the supply potential is more positive than the reference potential and the first potential is equal to the reference potential.
4. The prestage according to claim 1 having a charge pump for generating the base potential.
5. The prestage according to claim 1 having a terminal to which the base potential can be applied.
6. The prestage according to claim 5 , wherein the integrated circuitry comprises a voltage source circuit, which is designed to generate the base potential.
7. The prestage according to claim 1 , wherein the circuitry is a basic CMOS circuit.
8. The prestage according to claim 1 , wherein the prestage is integrated on a chip with the integrated circuit.
9. The prestage according to claim 1 having a current source circuit, which is designed to apply a current source control signal to the current source.
10. The prestage according to claim 9 , wherein the current source circuit is coupled to the base potential of the current source.
11. The prestage according to claim 1 , wherein a logic data value of the input signal is determined by an input voltage of the input signal in relation to the reference potential, and wherein the prestage is designed such that the output signal assumes a current value determined by the current source at a time when the input signal changes the logic data value.