Tool/software:
Hi TI Experts,
I am currently testing my pcb using LMG2100 for buck-boost converter. I face a big issue that damage the LMG2100, I had damage 5 ICs already. Especially when I apply the PWM in HI and LI side from microcontroller. I have tried using the LMG2100EVM-078 board, it worked without buffer to assert PWM from microcontroller. The PWM just runs in 12.5kHZ. When I check the TIDA-010936 TI use Buffer TXU0304DTR from PWM output to HI/LI.
I noted that in evaluation board LMG2100EVM-078, TIDA-010936, and TIDA-010933, you have pull down resistor of 10kohm in HI and LI side (R13 and R15 in figure below from TIDA-010933 ref design) , but I check in the datasheet there is none mentioning this. Is this required? currently I don't put this pull up resistor, I only put resistor and cap as in R12 and C18 as lowpass filter.
Can you explain why this happening?
Note: The Vin is 24 volt. AGND connect to GND of microcontroller, PGND is forced connected to AGND with 0 ohm resistor as in the design of LMG2100EVM-078 (below). I don't use dead time circuit since the PWM from my microcontroller has the deadtime. Sometimes it works, currently I take out the inductor to see the SW output.
Hi Fajar,
The 10kohm resistor is used for PWM filtering. At 12kHz the high ripple due to inductor current can cause damage but you are testing without inductor right?
Can you share schematic for review?
Best Regards,
Madhur
Dear Madhur,
Thank you for your response. I think so, at first when I connected the inductor with 12kHz PWM damage the MOSFET due to high ripple current. I will use at least 100kHz for the PWM. However, I remember no connected to load so it's open circuit.
Yes, I experience testing without inductor also damage that's why I am suspecting that it is required 10kohm pulldown resistor. However, I did experiments few times without pulldown resistor it was working fine.
I can share the schematic via email, where can I send it?
Best regards,
Fajar
Hi Fajar,
Please share schematic and layout to madhur@ti.com.
Let's continue the conversation over email.
Best Regards,
Madhur
Hi Fajar,
I will take a look and reply to you over email.
Best Regards,
Madhur