LM5180-Q1: LM5180-Q1

Daniel Melo

Part Number: LM5180-Q1
Other Parts Discussed in Thread: LM5180

Tool/software:

I am having troubles with my output voltage. The output voltage varies in accordance with the input voltage. I wanted the output to be 5V but its 7.11V and if I increase the input voltage the output increases and if i decrease the input voltage the output decreases. Below is the representation of the circuit in pspice for TI.

11 months ago

0 Ray DiCecco 11 months ago

TI__Genius 11350 points

Hi Daniel, very sorry for the delay in response as much of the team has been out of office this week.

Let me know if you're still having an issue and a product expert will respond within one business day. In the meantime, please fill in the LM5180-Q1 calculator so we are aligned on your intended design parameters.

Regards,

Ray

0 Daniel Melo 11 months ago in reply to Ray DiCecco

Prodigy 20 points

Hi Ray,

No worries. I am still having issues.

I'll start filling out the LM5180-Q1 calculator.

Thanks,

Daniel

0 Ray DiCecco 11 months ago in reply to Daniel Melo

TI__Genius 11350 points

Sounds good Daniel.

One thing I should mention, the LM5180 is a primary-side regulated (PSR) flyback, if you don't have an LDO on the output, you may have to add dummy load or a Zener clamp to the output for proper regulation at no load or very light load. I'm not sure if that's where you're having the issue or not, but I wanted to mention it.

Ray

0 Manuel Alva Hernandez 11 months ago in reply to Daniel Melo

TI__Genius 15646 points

Hi Daniel,

If you are running the simulation at no load condition, Vout will be higher than Vout set point. You need a zener diode to clamp Vout voltage at no load. This is because LM5180-Q1 switches at a fsw_min=12kHz. Zener clamp voltage is recommended to be at least 5% higher than Vout set point. You can also use s dummy load; you can set the value of the dummy resistor considering the standby losses of the system P_standby=Vout_noload^2/R_dummy

Thank you

0 Daniel Melo 11 months ago in reply to Manuel Alva Hernandez

Prodigy 20 points

There is a load in my design. The Output is feeding two other LDOs. I also placed a load on the dummy resistor.

0 Manuel Alva Hernandez 11 months ago in reply to Daniel Melo

TI__Genius 15646 points

Hi Daniel,

Please, share waveforms of (SW-GND), (VIN-GND), (VOUT-GNDS) and (FB-GND) to check for any issues. Please also zoom in on the waveforms so we can check one switching period.

Thank you

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LM5180-Q1: LM5180-Q1