Hi Grizzly and Rikky,
I have updated the schematic based on your suggestions and inputs.
1)For your BAT_SENSE circuit you may want to add some diodes to protect the MCU against BEMF, at least if you are not using batteries only to power that thing.
Ans: I have updated it. Also, could you please recommend a fast switching diode suitable for protecting the MCU from reverse voltage?
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You may use wrong net label, there are both +15VDC and +14VDC.
Ans: Updated, I have corrected the labels accordingly. -
You can use correct label input / output type. At least it will help on DRC.
Ans: Do you mean I should use consistent labeling on every out side of the sheet? -
To provide better thermal sense, you can use the filtered voltage instead of 3.3V, though it is not strictly required.
Ans: Updated, I have applied this change. -
Maybe I’m dumb, but I don’t know what R45 is for?
Ans:
-: Role of R45 (Drain-to-Source Resistor)
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Provides a Discharge Path for Residual Drain Voltage:
- When the MOSFET (Q20, Q18) turns off, some residual charge may remain on the drain due to parasitic capacitance.
- R45 helps discharge this residual voltage, preventing floating or unexpected behavior.
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Aids in Fast Body Diode Recovery:
- If the MOSFET’s body diode conducts, it can stay slightly forward-biased after switching off.
- R45 helps drain this stored charge, improving diode recovery and reducing conduction losses.
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Damps High-Frequency Oscillations:
- MOSFET switching can introduce ringing due to PCB inductance and capacitance.
- R45 helps suppress these oscillations, improving overall circuit stability.
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Smooths Turn-Off Behavior:
- Without R45, the drain-source voltage transition might be abrupt, causing voltage spikes and EMI issues.
- This resistor helps soften the transition, reducing stress on components.
Also, please let me know if you have found any issues or if you have any doubts.
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About the power supply, MP9486A seems much better than XL7500A. Just keep in mind the switching frequency quite high (up to 1MHz) it can be noisy, you should keep the loop area as small as possible.
Ans: Noted, I will optimize the power supply layout to minimize noise and loop area. -
Oh, and don’t try to copy the design for each phase. You can reuse the same schematic for 3 phases.
Ans: Do you mean I should copy and paste the section in the layout and manually adjust the labels?
