LM46002AQ

xxhhzz

LM46002AQ [Copy link]

 

Has anyone used this power chip (LM46002AQPWPR)? The design is to output 12V (input wide voltage 3.9-24V). Now it is measured that no matter how much the input is, the output is about 4V, and the FB pin is about 1V. Can anyone check if there is a problem with the circuit? ? ? ?

whuer

Is there a screenshot of the actual PCB so that the problem cannot be seen?

xxhhzz

whuer posted on 2019-6-10 13:34 Is there a screenshot of the actual PCB so that I can't see the problem

xxhhzz

whuer posted on 2019-6-10 13:34 Is there a screenshot of the actual PCB so that I can't see the problem

Hello, this is the PCB diagram

qiushenghua

What is the input voltage?

The material you selected is a single Buck circuit, which can only output 12V when the input is >12V.

xxhhzz

qiushenghua posted on 2019-6-10 14:40 What is the input voltage? The material you chose is a single Buck circuit, and it can only output 12V when the input is >12V.

When the input is greater than 12V, the output is also about 4V. That is, no matter whether the input is greater than or less than 12V, the output is about 4V. I am also very surprised.

qiushenghua

R77=1M

R78=255k

FB=1.011V

Isn't the output voltage around 4.9V?

1.011/255*(1000+255)=4.9757

xxhhzz

qiushenghua posted on 2019-6-10 14:48 R77=1M R78=255k FB=1.011V The output voltage is about 4.9V, right? 1.011/255*（1000+255）=4.97 ...

Then according to the parameters in the technical data,

is not correct.

xxhhzz

qiushenghua posted on 2019-6-10 14:48 R77=1M R78=255k FB=1.011V The output voltage is about 4.9V, right? 1.011/255*（1000+255）=4.97 ...

I calculated it wrong just now. It is correct according to the parameters. What does it mean that the output can only be 12V if the input is greater than 12V?

qiushenghua

xxhhzz posted on 2019-6-10 15:01 I calculated it wrong just now. It is correct according to the parameters. What does it mean that the output can only be 12V if the input is greater than 12V?

That is, the chip you choose can only step down the voltage from a structural point of view, and the output voltage can only be equal to or lower than the input voltage.

If you want a wide voltage (3-24V), then it is wrong to choose this material.

By the way, do you want to use our chip?

qiushenghua

xxhhzz posted on 2019-6-10 15:01 I calculated it wrong just now. It is correct according to the parameters. What does it mean that the output can only be 12V if the input is greater than 12V?

I have sent you a private message, please check your inbox

qiushenghua

The value of C61 in the schematic is also wrong. It should be a capacitor in the pF range, not 47uF.

In addition, R80 should not be pasted with 0 ohm. R80 is a pull-up resistor. Pasting a 0 ohm resistor may burn the chip.

xxhhzz

qiushenghua posted on 2019-6-10 15:07 That is, the chip you chose can only step down the voltage from the structure, and the output voltage can only be equal to or lower than the input voltage. You need a wide voltage (3- ...

No, this chip should be a buck-boost chip (3.5V-60V wide voltage input), which company is yours?

qiushenghua

http://www.ti.com.cn/product/cn/LM46002

LM46002 3.5 – 60V 2A Low Quiescent Current Step-Down Converter

The title is the buck converter.

We have sent you specifications for some of our products before.

https://bbs.eeworld.com.cn/forum.php?mod=redirect&goto=findpost&ptid=1077964&pid=2872272&fromuid=354619

Which material is suitable for you depends on the power requirements of your current design.

阿卡时间段

First of all, the power topology here is a BUCK step-down structure. If you want to get a 12V voltage input, it must be higher than 12V. Secondly, adjusting the FB resistor voltage divider can naturally get the required voltage.