Voltage Drop When Sending Bluetooth Data/Advertising.

[Farhouse]

Hi to everyone, i will try to explain everything in detail.

I developing a product that is currently in the pre-production stage, and im having some issues with voltage drops.

This si the regulator..

When im the bluetooth is connected and sending data, i see this in the DVDD line.

Each voltaje drop occurs with 20ms delay. And when i disconnet the bluetooth, and the NRF starts Advertising. i see this:

The firmware has a advertising of 265ms, and as you can see the voltaje drops occurs at aprox 270ms each. so i guess that it seems that the regulator cannot supply the current required.

Can someone Advice what should i do? change Capacitor for bigger ones? Another LDO?

Thanks in advance.

[ketiljo]

It's hard to see on the screen shots, how large is the voltage drops you see? Try to  remove L4 and short it and see if that helps. What is the power source to the regulator, V_IN?

[Farhouse]

I will try taking out L4, The V_IN its either VBAT 3.0v-4.2v , or 5v USB. The voltaje drop is almost 50mV.

[hmolesworth]

C17 1uF is really too low; try 47uF and see if that helps. Be aware that low voltage ceramic capacitors are not what they seem; for example a 47uF 5 volt capacitor may only be 15uF at 3 volts. Avoid that issue by using higher voltage ceramics, typically 3 x operating voltage on the capacitor, or use Tantalum instead which don't suffer from that issue. The downside of Tantalum is the material can only be mined on Tuesdays and so there is sometimes a world shortage and high price :-)

[ketiljo]

Plus that tantalum have a high DC leakage current and is not recommended for low current applications.