0 Members and 1 Guest are viewing this topic.
What about stability? Like getting desired output (250mA) at lower input (under 4.5V)? Pick a different chip.Tim
Just use something else, like for example : AOZ1280 (3.6v min, 26v max, cheap... 60 cents at 25qty, 30 cents at 1k) : https://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AOZ1280CI/785-1277-1-ND/2769845^ however be aware that max duty cycle is 87% so you'll need at least 4.2v to get 3.3v stable ... still you should get at least 4.2v from usb, so it should be fine. it's worth knowing if you want to use a lithium (3.7..4.2v battery), you wouldn't get 3.3v quite right.
Richtek RT7294C (max 18v in, but 4.3v min, synchronous rectifier so you save on separate diode) : https://www.digikey.com/product-detail/en/richtek-usa-inc/RT7294CGJ6F/1028-1507-1-ND/5724414RT8299ZQW for 3v..24v in, synchronous : https://www.digikey.com/product-detail/en/richtek-usa-inc/RT8299ZQW/1028-1158-1-ND/3078161
I am looking for switching frequency of 1.4MHz or more.Thanks for pointing me to AOZ1280
Quote from: fossil on February 01, 2019, 11:25:10 amI am looking for switching frequency of 1.4MHz or more.Thanks for pointing me to AOZ1280Shouldn't make your decisions on frequency alone, 500kHz is already quite high. You'll need slightly bigger inductors, but they'll still be reasonably small and cheap. The benefit is it's a sync rectifier, so you save some money and pcb space by not having to use a diode... so it works out in the end.
It could also work with 700kHz RT8258 which has same pinout but being non syncronous rectifier would need a diode (you can have the footprint on board and just not populate it if you use the sync rectifier version) : https://www.digikey.com/product-detail/en/richtek-usa-inc/RT8258GJ6/1028-1044-2-ND/2546043