BQ24072T: Voltage spike with USB and battery

Hi Adrianus,

Welcome to E2E!

Do you have information on the voltage rating on the capacitor? It looks like you have minimal capacitance on the OUT pin and I'm wondering if the capacitance derating resulted in a smaller equivalent capacitance. Are you able to try a unit with a 10 uF capacitance? 

Do you also have information on the load that you can share?

Best Regards,

Anthony Pham

Oh also additional question, is this the BQ24072 or the BQ24072T? On working units, do you see charging? I see the schematic is configured for BQ24072 (non T version). 

Best Regards,

Anthony Pham

Thanks, the exploded capacitor was not the bypass for the OUT pin, but the bypass for another chip. I can try with 10uF and see what happens.

The output is connected to a motor driver and a LDO to power a microcontroller. The motor driver was in sleep and the microcontroller was in idle, basically no significant load.

I'll add the measurements later when I have them.

Regards,

Adrianus

My bad, it is the non T version. When I connect both inputs, it charges.

Regards,

Adrianus

Hi Adrianus,

No worries, thanks for confirming the non T version. It shouldn't affect what you're seeing.

Adrianus Enrico Barus said:

I'll add the measurements later when I have them.

Awesome thanks! Looking forward to your update. 

Best Regards,

Anthony Pham

Hi,

I have replaced the capacitor and done a measurement. The result is pretty much the same. The spike still occurs occasionally.voltage_spike_10uf.pdf

Regards,

Adrianus

Hi Adrianus,

Adrianus Enrico Barus said:

The spike still occurs occasionally

When you say occasionally, do you mean even after plugging in the USB? 

Adrianus Enrico Barus said:

VIN is connected to USB via a standard phone charger

Is it possible to try with a few other USB sources?

Are you able to disconnect your load and see if the behavior is the same?

Best Regards,

Anthony Pham

Hi,

Anthony P Pham said:

When you say occasionally, do you mean even after plugging in the USB? 

This only happens during the USB connection process.

Anthony P Pham said:

Are you able to disconnect your load and see if the behavior is the same?

It is the same.

Anthony P Pham said:

Is it possible to try with a few other USB sources?

I've tried using a power bank and USB from a PC. It seems there is no significant spike using either source. Using a different phone charger still causes a spike.

Regards,

Adrianus

Hi Adrianus,

Adrianus Enrico Barus said:

Using a different phone charger still causes a spike.

Is this the same phone charger that you used in the beginning? Do you know the specs of the phone charger? 

USB standards keep any USB output to be 5 V +/- 10% and so I'm wondering if the behavior you're seeing follows from the type of phone charger that you're using. 

Are you able to share what kind of phone charger you're using?

Best Regards,

Anthony Pham