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LMZ23610: LMZ23610 Switcher module with enable.

umamaheswar peta
Expert 1370 points
Part Number: LMZ23610

Hi,

One of our customer is using LMZ23610 Switcher module with enable.

They want the output only when VIN is greater than 21V.

w.r.t  Section 8.2.2.2,  12.7 kΩ for RENB and 42.2 kΩ for RENT resulting in a rising UVLO of 5.51 V. Note that this divider presents 4.62 V to the EN input when VIN is raised to 20 V. Here, Raising Threshold Ven(rising) from formula gives 5.42V.

 

Now, with 12.7 kΩ for RENB and 196.6 kΩ for RENT results in a rising UVLO of 21 V (my desired value). Note that this divider presents 1.274 V to the EN input when VIN is raised to 21 V. Here, Raising Threshold Ven(rising) from formula gives 19.23V.

 

I am finding some mismatch with formula.

Pl. clarify. requirement is to enable the output when V input crosses 21V.

  • 0
    TI__Guru 50120 points

    Hi,

    Thank you for pointing this discrepancy out. I would recommend using Equation 2 as this takes into account the 2MOhm internal resistor. I will ping the apps engineer who wrote the datasheet.

    Regards,

    Jimmy 

  • 0 in reply to Jimmy Hua
    Expert 1370 points
    Hi Jimmy,
    Thanks for your reply.
    In equation 2, there is no variable related to Cut off voltage. So, how shall I arrive at values for my desired spec?
    My spec is Vin when it reaches 21V, my output should be generated.
    Pl. suggest the R values for this requirement.
    Best Regards,
    Uma mahesh
  • 0 in reply to umamaheswar peta
    TI__Guru 50120 points

    Hi,

    When you ramp up your input supply from 0 to finally input voltage, the device will turn on after exceeding Ven(rising). Alternatively if you ramp down from steady input voltage to 0V the device will turn off after voltage is below Ven(falling).

    If you want to have a Vin UVLO at 21V perhaps you can pick RENT=218kOhms if RENB = 12.7KOhms. 

    Regards,

    Jimmy