Accelerating the Voltage Fall on the Downstream VBUS lines of HX2LP


Question: When the hub is unplugged or powered off, due to the large capacitors placed on the downstream VBUS lines, the voltage on these lines fall very slowly. How do we reduce this discharge time?

Answer: Placing a bleeder resistor of 100k-150k ohm on the downstream VBUS lines of HX2LP (or the VBUS pin of the downstream device ) will increase the discharge rate of the capacitors and will cause the VBUS to drop down faster. When choosing a value for the bleeder resistor, care should be taken that the suspend current draw limit of 500uA is not exceeded by placing the resistor.