Abstract: A level shifter circuit includes an input circuit, an inverter, a pull-up circuit, and a pull-down circuit. The input circuit generates a pull-up signal in response to an input signal using charge from a supply voltage. The inverter inverts the input signal to generate a pull-down signal. The inverter comprises complementary transistors that receive charge from the supply voltage. The pull-up circuit pulls a level shifted output signal of the level shifter circuit to the supply voltage in response to the pull-up signal. The pull-down circuit pulls the level shifted output signal to a low voltage in response to the pull-down signal.

Abstract: More accurate signal detection circuitry in serial interfaces, particularly on a programmable integrated circuit device, such as a PLD, includes a high-speed, high-resolution, high-bandwidth comparator, along with digital filtering, to reduce the effect of process, temperature or supply variations. The comparator is used to compare a direct input signal with a programmable reference voltage, and, in a preferred embodiment, can detect the signal level within 8 mV accuracy. The output of the comparator may then be digitally filtered. Preferably, both a high-pass digital filter and a low-pass analog filter may be used to eliminate glitches and low-frequency noise. Preferably, the digital filters are programmable to adjust the sensitivity to noise. The filtered output is then latched and output to indicate receipt or loss of signal. This signal detect circuitry can operate reliably at data rates as high as 7 Gbps.