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Original question:

LM5020: LM5022 for design question

LM5020: Alternate/upgrade to LM5020 for 30V-57V Vin isolated flyback application

Devesh Agarwal
Prodigy 80 points
Part Number: LM5020
Other Parts Discussed in Thread: LM2904, LM258, , LM5022, LM51561, LM5156

We are using LM5020MM-1 in an existing isolated flyback topology.

Vin is 27V to 57V. Max Iin is 900mA. Output is 12V 4A in one model, and 24V 2.5A in another model. We use an EFD core transformer, and an LTV357 opto-coupler based feedback control.

Freq is 300KHz. +/- 50KHz.

Max duty cycle right now is around 49% but while we would like to retain the possibility of going higher till about 60%, it is not a desirable feature, not a critical one.

We have also implemented an external short-circuit protection and a dithering circuit using LM258/LM2904.

It is our design and is about 12 years old.

We find availability of LM5020 to be a challenge, and are looking to upgrade the design.

May I ask for suggestions for a cost effective current-mode controller that we can transition the design to? Pricing around $1.00 will be best.

One part we are considering is LM5022 and MAX17595ATE+. Is there any other TI controller which is newer in design, that will meet our technical, cost and availability requirements.

If we can get built-in hiccup short-circuit protection and built-in dithering, that will be most desirable. 

Thanks in advance

  • 0
    TI__Guru* 76815 points

    Hi Devesh,

    Thank you for reaching out and considering our solutions.  I would recommend the LM5156 or LM5156x, which can be considered as an improved version of the LM5020:  higher driver strength, smaller current sense working voltage, option of a robust hiccup mode with the LM51561, and options of spread spectrum to mitigate EMI, just name a few.   We also have design tools to help you to get a good start point in your new designs.

    https://www.ti.com/lit/zip/snvc240

    Thanks,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Prodigy 80 points

    Ni Hao YouHao.

    Thanks so much. It is so nice to hear from you, again. I don't know if you recall, Srini Menon who was the FAE for NSC in Bangalore back in 2008 or so, arranged a conf call between you, myself, and my design engineer Vignesh that solved all the issues we were having with the LM5020 with our HighPoE splitter at the time. 

    Will certainly look at LM51561. Looks very similar to the MAX17595 we are using in another module.

    Would you have any insight in to the availability issue on LM51561? I see there is no inventory available for us to even get a sample for testing.

    Best regards