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Q: BQ24072 - EN1/2 Pull-down Resistors
1 ) here is another question about BQ24072 EN1/EN2 control pins:
The wording for EN1/EN2 pins in the PIN FUNCTIONS table states that there are internal pull down resistors of value 285KOhms. But soon after comes a warning not to leave these pins unconnected for proper operation. So the question is whether these 285KOhm pull down resistors guarantee a “00” mode (100mA USB100 mode) for EN1/EN1 or we must connect external pull down resistors (what value? 100K? 47K?) to guarantee 100mA mode. Please remember that these control signals are connected to GPIO pins of a processor but in the first moments after 5V is applied to IN and before the processor starts up, these GPIO pins may be undefined/floating so that EN1/EN2 are effectively “unconnected” and their function is defined by the 285K pull downs or external pull downs, if required and present. A: BQ24072
A1) Typically the internal pull down is good by itself, but the internal 285k pull down resistor may not be enough if the signal trace to these pins are routed in a big loop around something noisy. Also if the GPIO during power-up is not high impedance, then this may force the pin momentarily into an undesired state, but the part would only be doing what is requested and should return to its desired state once the GPIO has the correct output.
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