TPS92641EVM: TPS92641

Hello, I have drawn a board by myself. When there is no load, the VREF is detected to have 3V, and the Ron has no waveform. Then I put on the power and the LED didn't light up. I found that the U3 MOS had been short-circuited.

1: Is there any problem with my schematic design?

2: How to avoid the re-burning of the pipe?

Thank you very much

Hello, after taking apart the detection, MOS is not broken. The SW foot of 92641 and GND have been short-circuited internally. Why does this happen?

I change a new 92641 SW, there is no short circuit, but I do not take the case of load, the input voltage 16-22V adjustment. VCC voltage is always 8.5V, SW is always 7V (vCC-7V has a big differential pressure). When normal condition SW foot voltage is VCC-7V left and right? What should be my current problem?

and I test LG have PWM wave,but HG  Maintain 7V level 。

I changed the R9 resistance down and the R12 resistance up. RON and LG have waveforms, but HG has no waveforms

Thank you very much

Hello,

You have UVLO set to turn on at 40V, if you are applying 16-22V it will not turn on.  R3 would have to increase to 10 Kohm or higher to turn on below 16V.

I don't see anything wrong with your schematic.  I don't know what you are doing with the connections on J4.

I don't understand "2: How to avoid the re-burning of the pipe?"

Best Regards,

Hello, J4 is not connected. Today, by changing the parameters, we got the situation that HL and RON have waveforms, but HG have no waveforms. How can we analyze this situation? Thank you very much.

Hello,

What is 'HL'?

What is your load?

Best Regards,

oh , LG and RON have waveforms, but HG have no waveforms. and no-load。I don't know where to analyze the problem

Hello,

It needs a load to regulate current.

Best Regards,

Hello, for fear of burning lamp beads, I connect 1K resistor as the load, and I change the circuit board parameters as follows，The +VIN is 30V.

Ron waves are formed as follows（blue about 250k）

HG and LG waves are formed as follow,The waveform is abnormal(bule is HG ,yellow is LG)

The HG and LG waveforms when I remove the R1 resistor are shown below(bule is LG ,yellow is HG)

I find that the waveform driving MOS is abnormal, so how can I solve this problem? Thank you very much.

Hello,

The second picture I do not understand, how can it be 2V per division and when the voltage drops the upper MOSFET is on?  The gate voltage must go high for the upper MOSFET to turn on.  How are you connected to the upper gate to measure it?  To me that looks like the upper MOSFET is turning off before the lower MOSFET turns on however the signals are so noisy you really cannot tell what is going on.

The third waveform appears to be the upper MOSFET current limit causing it to shut off.  It measures the MOSFET Vds voltage when on and if it is too high it shuts off, two pulses like that and it shuts down for a length of time, this is in the datasheet.  R1 removed makes it so the MOSFET cannot turn on.

You cannot troubleshoot a current regulator without the proper load.  This device does not regulate voltage so a 1 Kohm resistor isn't a proper load for this.  If you are worried about burning up LEDs get a number of power diodes in series for a load.

I would recommend getting the EVM to try.

Best Regards,

hello ,MOS waveform with LED is much more beautiful, but why does HG voltage go to 0, normally it should not be a whole raised waveform?

Thanks very much.