請(qǐng)教MT3608升壓芯片電路輸出只有預(yù)設(shè)得到一半是咋回事？

ID:899981 · 發(fā)表于 2022-6-28 15:54

原理圖中15/1.2+1=13.5X0.6=8.1現(xiàn)在輸出4V，量FB=0.3V，應(yīng)該是0.6V才可以

ID:647261 · 發(fā)表于 2022-6-28 16:46

8V輸出什么都不接的時(shí)候也是這樣嗎？
如果是的話，芯片和電感都換新的試試吧

ID:899981 · 發(fā)表于 2022-6-28 16:53

sttt300 發(fā)表于 2022-6-28 16:46
8V輸出什么都不接的時(shí)候也是這樣嗎？
如果是的話，芯片和電感都換新的試試吧

謝謝，是的，啥都沒接。電感不會(huì)壞的吧。不過我兩個(gè)電容都是電解的，不影響吧

ID:647261 · 發(fā)表于 2022-6-28 17:10

ZHAOBAO511 發(fā)表于 2022-6-28 16:53
謝謝，是的，啥都沒接。電感不會(huì)壞的吧。不過我兩個(gè)電容都是電解的，不影響吧

大多情況下，電解電容還是貼片電容都不影響，容值夠就行了
電感也是會(huì)壞的，特別是選的電感過電流不是很充足的時(shí)候，特別容易壞

ID:278840 · 發(fā)表于 2022-6-28 17:33

感覺是沒升壓，二極管壓降0.3V，加電感的壓降差不多4v

ID:401564 · 發(fā)表于 2022-6-28 22:21

個(gè)人感覺,這個(gè)問題是很容易解決的,帖子的審核時(shí)間就有找到問題所在了
1,先看EN腳的電壓有沒有達(dá)到數(shù)據(jù)手冊(cè)的要求電壓
2,換一個(gè)電感試一下,吹一個(gè)電感下來,再換上去,整個(gè)過程不會(huì)超過5分鐘
3,測(cè)量二極管是不是好的
4,如果前面幾步都換不到問題,如果手頭上還有另外一個(gè)芯片,換一個(gè)試一下
以上整個(gè)過程,不會(huì)超過20分鐘

ID:824490 · 發(fā)表于 2022-6-30 10:42

你把R30/R32各放大10倍試試？電感用的對(duì)不對(duì)？電容對(duì)不對(duì)？二極管對(duì)不對(duì)？布局對(duì)不對(duì)？

以下是關(guān)于器件選型的描述：

Setting the Output Voltage
The internal reference VREF is 0.6V (Typical).The
output voltage is divided by a resistor divider,R1 and
R2 to the FB pin. The output voltage is given by
(1 +R1/R2)*Vref=Vout

Inductor Selection
The recommended values of inductor are 4.7 to
22μH. Small size and better efficiency are the major
concerns for portable device, such as MT3608 used
for mobile phone. The inductor should have low core
loss at 1.2MHz and low DCR for better efficiency. To
avoid inductor saturation current rating should be
considered.
Capacitor Selection
Input and output ceramic capacitors of 22μF are
recommended for MT3608 applications. For better
voltage filtering, ceramic capacitors with low ESR
are recommended. X5R and X7R types are suitable
because of their wider voltage and temperature
ranges.
Diode Selection
Schottky diode is a good choice for MT3608
because of its low forward voltage drop and fast
reverses recovery. Using Schottky diode can get
better efficiency. The high speed rectification is also
a good characteristic of Schottky diode for high
switching frequency. Current rating of the diode must
meet the root mean square of the peak current and
output average current multiplication as following :
I D (RMS) ≈ I OUT × I PEAK
The diode’ s reverse breakdown voltage should be
larger than the output voltage.

以下是布局的要求：

Layout Consideration
For best performance of the MT3608, the following
guidelines must be strictly followed.
 Input and Output capacitors should be placed
close to the IC and connected to ground plane
to reduce noise coupling.
 The GND should be connected to a strong
ground plane for heat sinking and noise
protection.
 Keep the main current traces as possible as
short and wide.
 SW node of DC-DC converter is with high
frequency voltage swing. It should be kept at a
small area.
 Place the feedback components as close as
possible to the IC and keep away from the
noisy devices.

ID:284903 · 發(fā)表于 2023-3-5 21:33

這個(gè)我碰到類似問題了，等于沒工作，換了TPS61040上去就好了，MT3608很多假貨，測(cè)管腳電阻是對(duì)的，一上電就擊穿，估計(jì)是廠家的良品篩選下來的

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請(qǐng)教MT3608升壓芯片電路輸出只有預(yù)設(shè)得到一半是咋回事？

請(qǐng)教MT3608升壓芯片電路輸出只有預(yù)設(shè)得到一半是咋回事？