TPS61196: PCBA is failing generate VBoost and Switching Frequency at MOSFET Q1

Hi Tyrique,

May I know what is the input voltage? And have you checked EN and PWM when powering on?

BR

Patrick

The input Voltage we are providing is 12V and we have verified that we are seeing PWM and EN at their expected values during power on. The enable is approximately 6V and we are currently testing with the PWM pulled up to try and see any output at all. We are running the EVAL module with the exact same inputs and set up and functions properly.

Hi Tyrique,

Have you measured the voltage of REF? And could you please also capture the waveform of IFBx during start-up? Thanks

BR

Patrick

I am currently viewing 4.25V from REF pin 21. We noted that a 1 uF capacitor was being used on my board so we replaced this capacitor with a 0.3uF capacitor and we are still viewing the same voltage. What could be causing this? I will send a capture of the IFB as soon as possible.

Hi Tyrique,

I don't think the 4.25V is as expected, please try with a 2.2uF on this REF pin as datasheet recommended.

BR

Patrick

I agree as the data sheet says that 3.1V is the maximum tolerance, I will attempt to place a 2.2uF in place but I am unsure if this will change the functionality or voltage seen at this pin in the circuit due to the fact that the same voltage was seen with a 1uF capacitor and a 0.3uF capacitor. 

Do you have any thoughts on why this could be happening? Would component layout or spacing on a PCB affect the functionality of this circuit?

Hi Tyrique,

Refer to datasheet "7.3.5 Power-up Sequencing and Soft Start-up" capture, the REF capacitance is recommended to be within 1uF to 4.7uF. So I think the 2.2uF is worth trying as it also be the capacitance on our EVM. 

You can also capture the waveform of IFB to see if there will be the "unused channel detection" pulse.

BR

Patrick