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LMG1210: Suitable components for the gate driver

Jonathan Navor
Genius 9475 points
Part Number: LMG1210

Hi Experts,

We need your assistance with this customer's query below.

As they would like to know more about LMG1210 - High-Speed gate driver,.I can see that this driver supports up to 50MHz switching speeds. For bootstrapping circuit, what are the recommended parts for the bootstrap diode if operating at the maximum rated switching speed?

In the datasheet, the recommendation for very low on-time is to use synchronous bootstrap, if in case we want to go for a diode, can we use it? Which part would be suitable?

Please let me know if you need any other information from the customer. 

Thank you in advance.

Best regards,

Jonathan

  • 0
    TI__Intellectual 2100 points

    Hi Jonathan,

    Thank you for reaching out! You will want to use a Schottky diode with a low forward voltage drop and low junction capacitance. The diode should be chosen such that it is capable of handling peak transient currents at start-up, and the voltage rating is above the DC link voltage with some margin for overshoot. This diode must be able to reverse bias fast enough to block charges from the boot cap flowing to the VDD supply.

    Is 50 MHz the targeted switching frequency for this application? Also, are you able to share more information on the end application? The team actually has some content available on Optimizing Efficiency Through Dead Time Control with the LMG1210 driver, and techniques you can use to help minimize dead time and achieve a higher switching frequency.

    Please let me know if you have any questions!

    Best,

    Alex Weaver

  • 0 in reply to Alex Weaver
    TI__Genius 9475 points

    Hi Alex,

    Thank you for your support. Here is our customer's follow up question.

    Yes, the target is to use the device (LMG1210) to its maximum rated frequency. Your information is useful, however, I am not able to find a fast diode that can have less than 2-3 ns of recovery time and which can handle up to 1A of peak current.

    But if you have some recommended diode parts which can be used with your device LMG1210 when used at its maximum rated frequency, this would help (could be from the range of TI products or from other manufacturers too).

    Best regards,

    Jonathan

  • 0 in reply to Jonathan Navor
    TI__Intellectual 2100 points

    Hi Jonathan,

    What bus voltage are you planning to operate the device at? Also, what duty cycle are you expecting? This information will help the team better understand your circuit.

    The LMG1210 EVM uses the BAT46WJ Schottky diode, and this could be a helpful starting point for your search. The EVM is actually rated for 15MHz, but mentions that the EPC2001 GaN FET is a large FET (high Qg) and limits the switching frequency of the EVM:

    In addition to the optimizing efficiency through dead time control document, the team also has a document available on optimizing multi-MHz gate driver design. Pages 3 and 4 of this document discuss reverse recovery and some of the trade-offs and considerations of the Schottky diode as well as a PN junction diode.

    Please let me know if you have any additional questions!

    Best,

    Alex Weaver

  • 0 in reply to Alex Weaver
    TI__Genius 9475 points

    Hi Alex,

    Our customer would like to evaluate this device at 50MHz, with 100V input for a buck. The diode you mentioned has about 5.9ns of reverse recovery time. Can you please confirm if this device can support the 50MHz operation of LMG1210?

    Thank you for your usual support.

    Best regards,

    Jonathan

  • 0 in reply to Jonathan Navor
    TI__Mastermind 23025 points

    Hello Jonathan,

    Alex is out of the office at the moment, he will respond to your questions by tomorrow.

  • 0 in reply to Jonathan Navor
    TI__Intellectual 2100 points

    Hi Jonathan,

    Here is an image of the LMG1210EVM switching at 50% duty cycle, 50MHz, and no bus voltage:

    I cannot guarantee the Schottky diode's performance, but the waveform helps capture the capabilities of the EVM's BAT46WJ diode. As I previously mentioned, choosing a Schottky diode with a low forward voltage drop and low junction capacitance as well as following the guidelines from the "optimizing multi-Mhz gate driver design" article will help maximize the switching frequency capability. 

    Best,

    Alex Weaver