BQ24308: Vin 5-6V ; Vout Fail

你好,我想請問: 

1. 如圖是我的接法. 

2. 剛開始當Vin =5.1以上時 ,Vout 會拉不起來 (掛示波器可以看到它想起來,但又被馬上拉Low,一直重複)(負載已先都拿掉)

3. 承上:使用Vin=5V 以下 ,可以讓Vout 正常輸出 , 此時線上調高Vin 一直到6V 都可以正常輸出Vout ; 也可正常OVP功能..

4. 所以問題是一開始的Vin (5-6V)是因為甚麼原因 , 而讓它判斷一直將Vout 關掉??

謝謝!

Steven

Star Xu：

您好，请参考下面内容：

The BQ24308 will turn off from one of 3 causes:

OV, this is very fast
OC, this is slower and subject to the blanking delay
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