Hi,
I've an efficient buck circuit which works well. It has a pin which is grounded disabled the chip, however the voltage coming from this varies (seems to be a % of the input voltage).
My problem is that at the beginning of power on the frequency is low and this causes the circuit to burst 5v, which sometimes locks USB devices or causes them to on/off. Due to tight space I have limited capacitance, but then the amount required to overcome this would be substantial.
I've also played with using two resistors to lessen the voltage difference on the disable pin and a capacitor, but this varies and has not proven reliable.
Are there any other ideas? I'm thinking I could have a small linear regulator with a resistor/capacitor/transistor to switch the pin, but how to discharge the capacitor if the power becomes intermittent?
Cheers!
Andrew
I've an efficient buck circuit which works well. It has a pin which is grounded disabled the chip, however the voltage coming from this varies (seems to be a % of the input voltage).
My problem is that at the beginning of power on the frequency is low and this causes the circuit to burst 5v, which sometimes locks USB devices or causes them to on/off. Due to tight space I have limited capacitance, but then the amount required to overcome this would be substantial.
I've also played with using two resistors to lessen the voltage difference on the disable pin and a capacitor, but this varies and has not proven reliable.
Are there any other ideas? I'm thinking I could have a small linear regulator with a resistor/capacitor/transistor to switch the pin, but how to discharge the capacitor if the power becomes intermittent?
Cheers!
Andrew