JAJSQ97J may 2009 – january 2021 XIO2001
PRODUCTION DATA
PCI Express WAKE is an open-drain output from the XIO2001 that is driven low to re-activate the PCI Express link hierarchy’s main power rails and reference clocks. This PCI Express side-band signal is connected to the WAKE input on the upstream PCIe device. WAKE is operational during both the main power state and VAUX power state.
Since WAKE is an open-drain output, a system side pullup resistor is required to prevent the signal from floating. The drive capability of this open-drain output is 4 mA. Therefore, the value of the selected pullup resistor must be large enough to assure a logic low signal level at the receiver. A robust system design will select a pullup resistor value that de-rates the output driver current capability by a minimum of 50%. At 3.3 V with a de-rated drive current equal to 2 mA, the minimum resistor value is 1.65 k Ω . Larger resistor values are recommended to reduce the current drain on the VAUX supply.