LMZ23610: LMZ23610 EN hysteresis source current value issue

Part Number: LMZ23610

Hi,

       Could you give me the EN hysteresis source current MAX & MIN value,The Value can't be found in datasheet!

        I test my board found that the EN hysteresis source current max value maybe 70uA,

        Test Value is En(on) = 19V,EN(off) = 16V,Attachment is SCH,Pls help me,Thanks!

  • Hello Feng,

    Let me check with the IC design engineer and get back to you.

    Regards,
    Denislav
  • In reply to Denislav Petkov:

    Hello Feng, 

    According to the IC designer, this parameter may vary +/- 15%.

    Regards,

    Denislav

  • In reply to Denislav Petkov:

    Hello Denislav,
    "this parameter may vary +/- 15%" ,Do you have document about this?
    Why is my design error so big,if "this parameter may vary +/- 15%",Could you give me some suggest?
    Thank you!
  • In reply to Feng Ge:

    Hello Feng, 

    I don't have a document about the min/max variation. The typical values in the datasheet represent the most likely parametric norm at TJ = 25°C.

    Here are some questions:

    What is the tolerance on the resistors you are using and how are you measuring the EN current?

    What hysteresis window on VIN are you trying to achieve in your application? 

    Could you please share your board layout?

    Regards, 
    Denislav

  • In reply to Denislav Petkov:

    Hi Denislav,

         I want to konw the min/max variation,Because the datasheet don't show the min/max variation,just show  the TYP value is 13uA

         the tolerance on the resistors is 1%,I did not  measuring the EN current,Just calculated by formula

         I want to enable the device on VIN=22V,Disable on VIN= 21.5V,But data deviation is very large after test,and the gap between different board is very big also!

         PCB refer to your reference design.

  • In reply to Feng Ge:

    Hello Feng,

    It might be the case that the equation given in the datasheet is incomplete or a bit misleading.


     

    This is the snapshot from the datasheet. I did some calculations and figured the following out:

    1. For equation (2), there should say Vin(rising) instead of Ven(rising) . Just one different letter, but that makes a huge difference. The voltage Vin(rising)  for your application is targeted to 22V.

    2. As soon as the current source is ON, it adds an offset voltage. This effectively lowers the Ven threshold. The Ven rising threshold is 1.274V as given in the datasheet. This value is lowered when the current source is ON and can be calculated with equation (3).

    3. The new Ven falling threshold is now 1.274V - 13uA x (Rent || 2Meg || Renb + Renh). It is about 1V, depending on your values.

    4. You can use equation (2) to calculate your Vin falling, but with a new threshold voltage. Instead of 1.274 you now use your calculated value from equation (3). This gives you the falling turnoff voltage.

    Calculations with your values from prior post give me the following results, which match with the measured values

    RENT=680kOhm ; RENB=39kOhm will give you VIN rising = 17.8 V and VIN falling = 13.9 V

    Play with the resistor values and you will get the right hysteresis.

    In my case I tried it with 88.7kOhm and 5.2 kOhm which resulted in VIN rising = 22.1 V and VIN falling = 21.6 V.

    Hope this helps you fix your problem.

    Best regards,

    Michael