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LMG1210: Please review the schematic

Part Number: LMG1210

Hello TI experts,

my customer drew their schematic with LMG1210. Could you review it?

and here are some questions ;

1. input signal (PWM) is 7MHz (low 0V, high 5V). what are optimized values for R145 and R146 for minimizing dead time?

2. You can see D9 between BST and HB. customer wants to use 1SS416, which Vr is 30V. is it okay for the circuit? and is there any minimum value for Vr?

1SS416CT.pdf

3. my customer made LVTTL signal for EN pin. is it okay to operate?

Please check these issues. Thanks.

Best regards,

Chase

  • Hi Chase

    1. for a minimum dead time of 0.8ns typ use a 1.78Mohm resistor 

    2. The VR needs to be higher that VHB-VDD. this should be close to Vbus. There will also be some overshoot transient, but 30V should be plenty for 17V + transient.

    3. As long as the EN pin is getting a stable signal when the driver is operating then there is no issue.

    Further comments: the bootstrap capacitor (C324) is too large for the FET being driven. In this case a 100nF capacitor should work. Additionally, the VDD bypass capacitor (C240) must be at least 10x the size of the bootstrap capacitor. if C324 is switched to 100nF capacitor, the current 1uF for C240 is sufficient for the application.

    Thanks,

    Daniel W

  • Dear Daniel,

    Thank you for your support. I will discuss it with my customer, and reply if I have another question.

    and here are some questions about layout. Could you check it for me please?

    As you see, layout example in the datasheet shows that VSS thermal pad is connected to other VSS on the TOP layer through no.7 pin.

    But in the customer's layout, VSS thermal pad is connected to other VSS on the TOP layer through no.3 pin.

    We have to confirm that it is okay or might have some problem. (cause they don't have enough time so minimize the risk before they make gerber and real PCB.)

    Please check this issue. Thanks.

    Best regards,

    Chase

  • Hi Chase,

    As seen in the datasheet layout example, the best way is to have both VSS pins closely connected. In the example, this is done through the pad, and appears to be similarly connected in the customer design. I do not expect any issue with this.

    Thanks,

    Daniel W

  • Dear Daniel,

    Thank you for your support. I will discuss it with my customer.

    Best regards,

    Chase