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LP8861-Q1: LED Open Fault

Takao Yamamoto
Genius 4135 points

Dear all,

We have understand that switching will be off when open load from Table 3.

Is this correct?

In addition, could you teach about Figure 20?

Why do 'Vout' and 'Vout OTHER LEDs' voltage increase after open LED?

Best regards,

  • 0
    TI__Intellectual 1235 points
    Hi Takao,

    Your understanding is correct. The Open LED fault detects if one or more outputs are below the threshold level AND boost adaptive control has reached maximum voltage.

    This definition helps to explain why the VBOOST and VOUT (other LEDs) need to increase when OPEN LED occurs. There are instances where the output voltage is below the threshold level of LOW_COMP and yet that is not due to OPEN LED. So if OPEN LED event occurs, the first part of the detection is that VOUT goes below threshold value defined by LOW_COMP. The second part of the detection is that LP8861 purposely raises VBOOST/VOUT (other LEDS). The fingerprint that OPEN LED event has truly occurred is that VBOOST value reaches VBOOST set MAX level. At that point (when VBOOST reaches VBOOST set Max) device acknowledge fault (FAUTL goes low).

    I hope that helps.

    Kind Regards,
    David