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LM27222: Use High side drive only

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Guru 21045 points
Part Number: LM27222
Other Parts Discussed in Thread: UCC27222, TPS28225, UCC27282, UCC27212

Hi Team,

 

We are looking for High side driver but can’t find TI’s High side driver.

Therefore, we would like to use High side of LM27222(Half bridge) only at the following conditions.

Could you please let us know if you have any concern (LM27222 has any problem)?

And, could you please let us know if you have a recommended other solution?

 

[Conditions]

 

 

Regards,

Kanemaru

  • 0
    TI__Mastermind 21245 points

    Hello Kanemaru,

    TI does not have a high side only driver at this time, but many half bridge drivers can be operated as high side only. I have a couple of concerns on the UCC27222 however. This part is indicated as not for new designs, so I would recommend alternative parts as the high side driver. Also the UCC27222 has predictive drive which is a function to set the dead time of the high side and low side drive. I see the VDD range is shown as 4V to 6.85V, but the UCC27222 maximum UVLO is 4.4V. This is a concern with a 4V minimum VCC or VDD unless the VCC with be higher when the driver starts switching.

    I would recommend a standard half bridge driver specifically the UCC27282 which can operate with only the HI input active. The LI input can be grounded and the HO output will follow the HI input. The minimum recommended VDD on this part is 5.5V however. The TPS28225 does have a lower UVLO threshold and can operate with a recommended VDD range of 4.5V to 8V. The UCC27212 has a low UVLO as well and can operate with 5V VDD. See the comparison table below.


    Please confirm if this addresses your questions of if you have additional questions you can post on this thread.

    Regards,


  • 0 in reply to Richard Herring
    Guru 21045 points

    Hi Richard-san,

     

    Thank you for your prompt reply and detail information.

    We would like to use UCC28255 at the following conditions.

    I understand that this circuit don’t have concern.

    Is my understanding correct?


     

    Regards,

    Kanemaru

  • 0 in reply to Hide
    TI__Mastermind 21245 points

    Hello Kanemaru,

    The TPS28225 should work as a high side driver with the conditions shown. Make sure the PWM input signal has fast rise and fall times of <50ns.

    For any high side driver with a bootstrap high side bias, it is important that the switch node, or PHASE pin transitions close to ground after turn off of the high side FET. The boot capacitor is charged from VDD when PHASE switches close to ground.

    Please confirm if this addresses your questions, or you can post additional questions on this thread.

    Regards,

  • 0 in reply to Richard Herring
    Guru 21045 points

    Hi Richard-san,

    According to the datasheet comment, I understand that "rise and fall times of  <250ns" (not <50ns).

    Is my understanding correct?

    Regards,

    Kanemaru

  • 0 in reply to Hide
    TI__Mastermind 21245 points

    Hello Kanemaru,

    The datasheet of the TPS28225 does mention the statement of the rise and fall time of the PWM signal and references 250ns. I see in the parameter table for the 3-state shutdown hold off time, tHLD_R, that the typical value is 250ns.

    I would recommend margin on the rising and falling time of the input PWM signal. The 250ns is a typical value in the datasheet table, and I would recommend margin to avoid any tri state detection. I would certainly recommend a 2:1 margin at least so 100ns rise and fall should be OK.

    Please confirm if this addresses your concerns, or you can post additional questions on this thread.

    Regards,

  • 0 in reply to Richard Herring
    Guru 21045 points

    Hi Richard-san,

    Thank you for always kind support and detail information.

    I understand. Thank you very much.

    Regards,

    Kanemaru