LM5113: LM5113QDPRRQ1

Aswanth Mohanan

Part Number: LM5113

Tool/software:

This is the schematic diagram of the LM5113 I used. When I apply HIGH to the HI pin and LOW to the LI pin (with HIGH = 3.3 V in my case), the HS pin only rises up to 2.56 V. Then, when I set HI = 0 and LI = 1, the HS pin goes to 0 V, which works correctly. But in the first condition, it doesn’t work, and my phase output stays at 2.56 V instead of 5 V. Can anyone help me debug this issue? I have already tried removing the zener at the OL pins and changing the gate resistor from 340 Ω to 10 Ω, but the issue remains.

28 days ago

0 Annabelle Alemand 28 days ago

TI__Prodigy 710 points

Hello Aswanth,

It sounds like the bootstrap circuit may not be charging correctly. With LI=1, please measure HB and HB-HS (both should be ~equal to VDD). And then with HI=1, please probe HB, HS, HB-HS and gate. Depending on the behavior of these waveforms, the problem could be with the bootstrap capacitor, bootstrap diode, or trace between HB-HS. Please see this App Note on choosing a size for Cboot (https://www.ti.com/lit/an/slua887a/slua887a.pdf?ts=1755626756020).

Also, we do recommend a larger bypass capacitor between ground and the 0.1uF capacitor. The 0.1uF capacitor should be as close to the VDD pin as possible. You can find more details in the LM5113(-Q1) schematic review template on TI.com under Design & development (https://www.ti.com/product/LM5113-Q1#design-tools-simulation).

Please let me know if the issue does not resolve and we can look into it further.

Thanks,

Annabelle

0 Aswanth Mohanan 25 days ago in reply to Annabelle Alemand

Prodigy 20 points

HB_HS is 0v when HI = 1 and LI = 0, Also i had made the c vdd to 1uF according to the datasheet

0 Aswanth Mohanan 25 days ago in reply to Aswanth Mohanan

Prodigy 20 points

Also i have make bootstrapping circuit resistor to 10ohm

0 Annabelle Alemand 25 days ago in reply to Aswanth Mohanan

TI__Prodigy 710 points

Hi Aswanth,

Have you confirmed that there is no issue with your diode? If HB-HS is at 0V when HI=1, that means the bootstrap did not charge while the low side was on, so the high side will not be able to turn on.

1. Set LI=1, HI=0 for a few us and measure HB-HS. It should be around 5V, but if it's at 0V, the bootstrap charge path is broken. Please also measure HS to GND and share both of these waveforms with me please.

2. Please check your diode, ensuring that anode is to VDD and cathode to HB. If you're unsure, replace it if possible to see if that fixes the issue.

Thanks,

Annabelle

0 Annabelle Alemand 14 days ago in reply to Annabelle Alemand

TI__Prodigy 710 points

Hi Aswanth,

Were you able to resolve this issue?

Thanks,

Annabelle

0 Annabelle Alemand 8 days ago in reply to Annabelle Alemand

TI__Prodigy 710 points

Hi Aswanth,

I am going to go ahead and close this thread due to inactivity. If you have any further questions, please start a new thread.

Thanks,

Annabelle

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LM5113: LM5113QDPRRQ1