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Hi,
I have a requirement to drive a Triac from the MCU powered by the LV2862. The AC supply is typ 24Vac @ Rc terminal with respect to C terminal. The Triac is driven as follows. The MCU GND is always regulated at Rc - 3V3. Basically the DC/DC output follows the Rc keeping 3V3 below that.
How can I configure the DC/DC convertor and its input?
Cheers,
Kaushalya
Hi,
Do you think below configuration will be workable for you?
Regards,
Hongjia
Hi Hongjia,
Thanks for your reply. This is the standard way of implementing a DC/DC section and unfortunately my Triac gate drive is different to this. As you can see in my diagram, the MT1 terminal is connected to Live (or Rc). What I can think is if we have a negative buck out of LV2862, then we can have something like this.
What do you think? Can we config LV2862 as a negative buck like this?
Cheers,
Kaushalya
Hi,
Yes LV2862 can be used to generate a negative voltage using IBB. You can refer to more details in the apps note: Working With Inverting Buck-Boost Converters. https://www.ti.com/lit/an/snva856b/snva856b.pdf?ts=1691059181403&ref_url=https%253A%252F%252Fwww.google.com%252F
Also I re-draw the system configuration as below. I think it should work for you.
Regards,
Hongjia
Hi Hongjia,
Thanks again. I have looked into that app note. I have tried simulating the design and have made the mistake of wiring VIN directly to SHDN. The VIN was dropping down to 0V in one half cycle. It is fixed now and I can see my VOUT with respect to GND is +3V3. As VOUT is same as Rc, I get regulated -3V3 with respect to Rc now. So all good.
Thanks for your support.
Cheers,
Kaushalya