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Original question:

BQ24308: Question about CE

BQ24308: BQ24308: Vin 5-6V ; Vout Fail

Star Xu
Genius 9645 points
Part Number: BQ24308

Hi 

The customer design with BQ24308. 

At the beginning, when Vin >= 5.1V, Vout will not be able to pull up always, it is pulled Low immediately, repeating all the time.

When use Vin<=5V, Vout output is normal. At this time, increase Vin to  6V the output Vout still normally, and the OVP function is normal.

Why the VIN is between 5-6v, VOUT abnormal?

Thanks

Star

  • 0
    TI__Guru 54715 points

    Hi Star,

    The BQ24308 will turn off from one of 3 causes:

    1. OV, this is very fast
    2. OC, this is slower and subject to the blanking delay
    3. The part overheats

    It seems unlikely the part is hot controlled by voltage. Look at the signals at turn on to tell if it is turning off after the tBLANK delay from a current at startup triggered at the slightly higher voltage, or if the turn off is fast like the over voltage delay.  Compare to the waveforms in the data sheet figure 21 for OCP or figure 15 for OV.

    They might also look at the supply response to a load such as connection to see if it overshoots vs the increase in load from adjusting the voltage.   Check the placement and performance of the input capacitor.  See the data sheet section 9.2.2.3 Selection of Input and Output Bypass Capacitors and the 11.1 Layout Guidelines.  Check for noise on the supply which might be at a lower voltage when the setting is lower and stabilized by the input capacitor when connected successfully and the voltage is increased.