LP2951: LP2951 ERROR FUNCTION FAILED

ZUO XIAOWEI

Part Number: LP2951

Dear sir/madam

Now I use LP2951-50DRGR to provide a fixed output of 5V in my system. I found a description in the datasheet that ERROR will go low when Vout drops 6% of its norminal value. I calculate that 5V * 94% equals to 4.7V. It means that when the Vout is below 4.7V, then ERROR PIN will go low. Now I connect a resistor of 33ohm between Vout and GND, then I found that the Vout = 4.4V, but the ERROR does NOT go low, still provide 4.98V. So I will find your help.

I attached the schematic, using png form in the attachment, the circuit works like that, let me explain as below:

when I provide 12V as input, then LP2951 is powered. It will output 5V in the OUTPUT PIN. Now LED4 and LED2 should be lighted. When I press the buttow, a 33-ohm resistor is connected. Now the current is over 100mA. So the Vout should drop. And I measured the output voltage, the value is 4.4V, but ERROR PIN is still as high as 4.98V.

Thanks and looking forward to your reply.

BR,

Joey

3 天前

0 Taylor 1 天前

TI__Guru 53745 points

您好，

已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

0 Eric Ba 1 天前

TI__Expert 6920 points

Hi Joey,

Could you please removeR12 and R11, and short them directly and remove C1 to let the connection open? And then have the same test.

B.R.

Eric

0 ZUO XIAOWEI 1 天前回复 Eric Ba

Prodigy 10 points

Hi Eric

I have made a mistake and now I have already got the correct result.

The L1 has a voltage drop, so when I measured VCC5, I have got the value of 4.4V, but LP2951 still provided 5V output at the OUTPUT PIN.

Then I increased the output current until the OUTPUT PIN had only 4.4V, then ERROR PIN had a low output.

Finally I use one magnetic beads (ferrite) to instead of L1, and get the threshold value, it is 4.7v, below this value, ERROR has a low output, while above this value, ERROR has a high output.

So R11, R12 and C1 does not have any impact on this circuit.

Thanks for your reply.

BR,

Joey

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LP2951: LP2951 ERROR FUNCTION FAILED