Patent ID: 7397296

Claim:
An apparatus including a power supply detection circuit biased by at least two power supply voltages for controlling a signal driver circuit, comprising: a circuit reference electrode; a first power supply electrode to convey a first power supply voltage; a second power supply electrode to convey a second power supply voltage; first amplifier circuitry coupled between said circuit reference and first power supply electrodes, and responsive to said first power supply voltage and a first signal having at least asserted and de-asserted signal states by providing a second signal having corresponding signal states; second amplifier circuitry including first and second output signal electrodes, coupled between said circuit reference and second power supply electrodes and to said first amplifier circuitry, and responsive to said second power supply voltage and said second signal by providing, via said first and second output signal electrodes, a differential signal having asserted and de-asserted signal states corresponding to said first asserted and de-asserted signal states; a first capacitance coupled between said circuit reference electrode and said first output signal electrode; a second capacitance coupled between said second power supply electrode and said second output signal electrode; and voltage clamp circuitry coupled to said circuit reference electrode and said first and second output signal electrodes, and responsive to at least a portion of said differential signal by selectively clamping said first output signal electrode at one of a plurality of voltages in relation to said differential signal states.