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LMG5200: Deadtime generation: are the inputs Schmitt?

Piotr Wyderski
Prodigy 150 points
Part Number: LMG5200
Other Parts Discussed in Thread: LM5041, LMG1205

Hi,

I would like to use LMG5200 as a buck power stage controlled by LM5041. The HD and LD outputs of LM5041 are specified to be CMOS buffers swinging between 0 and 5V. The LD is just an inverted version of HD (per figure 3 in the datasheet), so no deadtime is included. The datasheet of LMG5200 says that the part does not generate deadtime either, so an external circuit needs to be implemented. So far so good, a diode+resistor+capacitor generator per channel should do the job. And a Schmitt trigger, of course. For obvious reasons I would like to keep this circuitry as simple as possible, so the question is whether the inputs of LMG5200 are equipped with one already. On one hand there is no single instance of the word "Schmitt" in the datasheet, but on the other hand the Table 6.5  on page 5 explicitly specifies very precise V_IH and V_IL values and adds "V_HYS Hysteresis between rising and falling threshold  [400mV]". So, can I rely on the thresholds/hysteresis and waive the need for an external Schmitt buffer?


  • 0
    TI__Expert 3225 points

    Hello Piotr,

    Yes the input is a Schmitt buffer based circuit. Actually the driver is very similar to LMG1205, and you can also refer to that driver to understand the circuit scheme. Please let me know if you need any other information. Thanks!

    Best regards,

    Lixing

    Systems Engineer, GaN

    Texas Instruments 

  • 0 in reply to Lixing Fu
    Prodigy 150 points

    Hi Lixing,

    thank you very much for you reply, that's a great news. It certainly solves my issue, but can I suggest that you amend the LMG5200 datasheet to highlight the fact? There is no

    indication of this in the text and Figure 10 is similarly misleading (the symbols indicate plain buffers, not the Schmitt-capable ones). No other users should infer this behaviour from Table 6.5 in the future, IMHO.

    Thanks again and best regards, Piotr

  • 0 in reply to Piotr Wyderski
    TI__Expert 3225 points

    Thank you so much Piotr. In our next revision of LMG5200 datasheet we will taken the suggestions into consideration and make it clear to customers.

    Thanks and regards,

    Lixing