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Original question:

LM76003: Ven rising and falling hysteresis

LM76003: VEN rising and falling thresholds

Andreas Nestler
Intellectual 350 points
Part Number: LM76003
Other Parts Discussed in Thread: LM76005

Hello,

The same question came up in the forum but w/o clarification within this forum. I do not understand the mismatch between the EC data and the description in the text:

  • VENH in the text should be VEN_VOUT_H from EC data (typical value) = 1.204 V
  • VENL in the text should be VEN_VOUT_H - VEN_VOUT_HYS (typical value) =( 1.204 - 0.15) V

Howevr, in the text VENH = 1.218V and VENL = 0.99V is used. What is the background of those values? I know for worst case analysis I have to consider the extreme values for VEN_VOUT_H. For hysteresis only a typical value specification exists.

Furthermore the values in the application section (above) are not in line with the section 7.3.4 in datasheet:

For this I would use the EC data. How to cope with the different values?

Thanks and best regards

Andreas N.

  • 0
    Intellectual 350 points

    The EN rising threshold of 1.218 V in section 8.2.2.12 Undervoltage lockout must be an error if reverse calculate the EN threshold by re-arranged equation 29 with RENT=315k and RENB=100k.

    I have also compared the description with the LM76005 device datasheet, which lists other data in application section (8.2.2.12) than LM76003 datasheet. The EC data of LM76005 is identical to LM76003 specification for enable threshold.

    The only remaining issue from my point of view is the VENL = 0.99V in both datasheets (LM76003 and LM76005), which I cannot understand from EC data. From EC data I calculate a value of 1.204V - 0.15V = 1.054 V (typical) and not 0.99 V (typical).  Even though the UVLO threshold will not be critical at all in most application this issue shall be clarified.

    BR Andreas

  • 0 in reply to Andreas Nestler
    TI__Guru 59025 points

    Hello

    I agree that the data sheet has some errors and confusing data and calculations.

    I will speak with the Applications manager and we will see what we can do to fix the

    situation.  The 0.99V comes from: 1.14V - 0.15V = 0.99V

    Thanks

  • 0 in reply to Frank De Stasi
    Intellectual 350 points

    Hello Frank,

    I agree with the last calculated value. However the 0.99V is mentioned as typical UVLO threshold and the 1.14 V is the minimum enable threshold. To calculate the typical UVLO threshold (to switch off) I would use the typical enable threshold minus the hysteresis. Therefore, I think this does not really match to each other.

    Regards Andreas

  • 0 in reply to Andreas Nestler
    TI__Guru 59025 points

    Hello

    Yes; thank you for bringing these issues to our attention.

    Thanks