TIDA-010936: Some questions about the schematic

Clément Letonnelier

Part Number: TIDA-010936
Other Parts Discussed in Thread: LMG2100R044

Tool/software:

Hi,

We have checked this reference design and have few questions as we intend to use the LMG2100R044 and the AMC0106M05DENR in our design.

In the LMG2100R044 datasheet, we saw that on the bootstrap, there shall either be a capacitor or a resistor + capacitor.
On the design, we see a capacitor in parallel with a resistor + capacitor.
In the design guide, you are only talking about the resistor + capacitor.
What do you recommend to do ?
On the phase C, the bootstrap is used to supply the AMC0106, which is interesting and we would like to do the same.
So same question about the bootstrap, do you recommend to only put the resistor + capacitor or the capacitor or both ?

In any case, we would be interested to understand both.

Best regards,

Clément

4 months ago

0 Jerome Shan 4 months ago

TI__Intellectual 1600 points

Hi Clement,

Thank you for reaching out to us on these questions.

These resistors are for different purposes.

1. In application circuit of LMG2100, the resistor here is used to adjust the switching slew rate of the GaN FET. When we not use it, the GaN FET will switching with the highest dV/dt it can achieve.

2. In the application circuit of AMC0106, this resistor is used to limit the max charging current to the 4.7uF capacitor and reduce the voltage ripple on the 0.1uF capacitor out-side the HB-HS pins. We can also refer to the datasheet of AMC0106M05 figure 7-1 in page 15 for the recommended application circuit: both the "0.1uF" and the "4.7uF + resistor" are used.

Best regards,

Jerome Shan

0 Clément Letonnelier 4 months ago in reply to Jerome Shan

Expert 2786 points

Hi Jerome,

So despite what is stated in the schematic, both are in fact not mounted at the same type right ?
Understood.

Clément

0 Jerome Shan 4 months ago in reply to Clément Letonnelier

TI__Intellectual 1600 points

Hi Clement,

For the first one beside LMG2100, if you do not need to tune the switching slew rate, remove this resistor can help to reduce the layout loop of the circuit. Or else, leave a 0 Ohm one in first design may help on debug stage for potential issues.

For the second one, better keep this resistor in circuit as in most cases it is adopted.

Best regards,

Jerome Shan

0 Clément Letonnelier 4 months ago in reply to Jerome Shan

Expert 2786 points

Jerome,

For the first one, we should yes indeed.

But in that case I should remove the first capacitor.

Clément

0 Jerome Shan 4 months ago in reply to Clément Letonnelier

TI__Intellectual 1600 points

Hi Clement,

That's much wiser.

Then make C40 and R15 close to LMG2100. Make C14 close to AMC0106.

Best regards,

Jerome Shan

0 Clément Letonnelier 4 months ago in reply to Jerome Shan

Expert 2786 points

Jerome,

You meant C41/R15 close to the LMG right ?

Clément

0 Jerome Shan 4 months ago in reply to Clément Letonnelier

TI__Intellectual 1600 points

Hi Clement,

Yes, but if you remove C41, only use C40 and R15, then they both must be close to the LMG2100.

Did you mean to remove C41 (as the first capacitor)?

Best regards,

Jerome Shan

0 Clément Letonnelier 4 months ago in reply to Jerome Shan

Expert 2786 points

Jerome,

Not at all, I was speaking for the phase A and B which are not using the scheme due to the acquisition with an INA.

So I was rather refering at removing C23 and replacing R7 by a 0 ohm as you suggested.

For C40/C41, I was rather considering keeping both, an put C40 close to the AMC from what I understand from your previous messages.

Clément

0 Jerome Shan 4 months ago in reply to Clément Letonnelier

TI__Intellectual 1600 points

Hi Clement,

You mean C27 for C23 just now, am I correct?

I agree with you to keep both C40 & C41, and put C40 close to AMC.

Best regards,

Jerome

0 Clément Letonnelier 4 months ago in reply to Jerome Shan

Expert 2786 points

Yes I meant that, sorry... getting tired.

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TIDA-010936: Some questions about the schematic