Other Parts Discussed in Thread: BQ24253, TPS62082, TPS61027, TPS62081,
The system is meant to powered via a single cell 3V7 LiPo battery.
The board is using the BQ24253 as a battery charger / power path management.
This IC is working as intended, it charges the battery at the desired current and provide my system with +VBUS
That +VBUS rail is feeding a 5V Boost Converter (TPS61027), a 3V3 Buck Regulator (TPS62082) and a 1V8 buck Regulator (TPS62081)
The enable line of those 3 IC is common and is provided from a smart push button IC (STM6601). Basically a short press of the button makes that line go high, while a long press makes it go low.
It has been debugged and it is working as intended.
The problem I am experiencing is that there is ripple on my +VBUS rail when those 3 IC are switched on.
I am testing on 2 boards at the moment and the behaviour in not the same. (frequency of the ripple and amplitude are different)
By process of elimination we found out that the ripple was induced by the 5V power rail.
That power rail feeds 2 RGB LEDs and a USB A connector for a host. We are currently using the USB connector for a Wi-Fi dongle.
We are using an Over current protection IC for the USB Host connector (LM3525M-L).
We narrowed the problem down to that IC (LM3525). So when we disable the IC (EN pull HIGH), the ripple disappears but the VBUS line is still noisy.
We can observed the same phenomenon when the Bulk capacitor (C57) is removed and LM3525 is enabled.
We have tried to add a 100uF Electrolytic cap at the input (in parallel with C55) but the ripple is still there.
Can you please ask TI if this is normal behaviour for that IC ?
