AMC1301: Floating voltage

Hirotaka Matsumoto

Part Number: AMC1301
Other Parts Discussed in Thread: TL431, TIDA-00366

Hi all

Would you mind if we ask AMC1301?

We have basic question about floating voltage on the datasheet P1 Simplified Schematic.
The voltage VDD1 is supplied using Zener diode or TL431 between VDD1 pin and GND pin.
In case of no Load or no low-side gate operation, it seems that there is no current path from Zener diode's cathod to anode.
Is our recognition correct?

Kind regards

Hirotaka Matsumoto

over 7 years ago

0 Tom Hendrick over 7 years ago

TI__Guru**** 181021 points

Hi Matsumoto-san,

The 'floating supply' would actually be referenced to the GND1 pin in this case so it's only floating with respect to the the system ground. That voltage source would be the high side gate driver power supply. Please do let me know if that is still not clear to you.

0 Hirotaka Matsumoto over 7 years ago in reply to Tom Hendrick

Guru 27585 points

Tom san

Thank you for your reply.
And then, we apologize that our explanation makes you confuse.
Please refer to the attachment file.
And then could you give us your opinion?
20180313_AMC1301_VDD1(Floating voltage).pdf

Kind regards,

Hirotaka Matsumoto

0 Tom Hendrick over 7 years ago in reply to Hirotaka Matsumoto

TI__Guru**** 181021 points

Hi Matsumoto-san,

Thanks for the picture, I am aware of that TI Design, but I'm not the author of it. The configuration there is quite similar to the simplified schematic shown on page 1 of the AMC1301 datasheet. What is not shown in that screen capture is the shunt resistor. You can see that on the cover sheet of the schematic document associated with TIDA-00366. You are correct though, if the high side gate drive voltage is not present, there would be no current flow through the TL431. This has no bearing though on the lower switch or the load, U_TOP_REF is the connection point between the upper and lower IGBT's.

0 Hirotaka Matsumoto over 7 years ago in reply to Tom Hendrick

Guru 27585 points

Tom san

Thank you for your comment!

OK, we got it.

Kind regards,

Hirotaka Matsumoto

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AMC1301: Floating voltage