RESET Timing of HX2LP and its Effect on External Power Supply – KBA222745

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Question:

What is the minimum value of the capacitor that can be used on the RESET pin of HX2LP? What effect does the capacitor have on the usage of external power supply?

 

Answer:

The RC values used on the RESET pin of HX2LP must make sure that sufficient timing is provided for the supply to ramp up and stabilize before the chip is taken out of reset. The datasheet recommends the usage of 100 kΩ resistor and 0.1 µF capacitor on the RESET pin.

 

But, if HX2LP is self-powered and the ramp-up of the external power supply is very slow, there can be enumeration issues because the chip might be taken out of reset before the supply voltage stabilizes. Hence, in such situations, it is recommended to increase the value of capacitance to meet the timing specifications.