VND7140AJ-E最大电流如何获得

大家好，

我有一个关于VND7140AJ-E的问题，我已将其纳入我们公司的设计中。我多次阅读数据表，因为芯片的最大电流并没有真正说明，就像“内部限制”一样。所以我检查了Iliml和Ilimh参数，他们说明了4Atyp和12Atyp。我需要最大4A，所以这对我的应用来说应该足够了。

该芯片还具有28V的最大电压，足以满足我的24V使用需求。我们组装了电路板并将其放在测试台上。但令我惊讶的是，我不能超过1Amp。我一直试图找出问题所在，所以我取消了VND7140周围的所有组件，并将输入的占空比设置为100％。还是只有1A。

当VND7140在板上时，我注意到的另一件事是，当我降低占空比时，它会持续一秒钟，然后进入故障模式。我认为这可能是因为它测量输出端的低电压，这是由于一组电容器用于将PWM信号转换为模拟DC。这很奇怪，因为数据表没有说明这种保护，并且从电力供应中提取的电流不超过1A。

我测量了恒定电流负载的输出电流。

有没有人有任何想法为什么显示这种行为，最重要的是如何获得当前我真正需要的。

带着敬意，
Michel van der Breggen
#max-current #protection＃vnd7140



以下为原文




Hello All,

i have a question about the VND7140AJ-E which i have incorperated into a design of our company. I read the datasheet several times, because the maximum current of the chip is not really stated as such, just as ''internally limited''. So i checked the Iliml and Ilimh parameters and they stated 4Atyp and 12Atyp. I need 4A max, so this should be more than enough for my application.  

The chip also has a maximum voltage of 28V which is enough for my 24V usage. We assembled the boards and I put it on the testbench. But to my surprise i can't get more than 1Amp out of it. I have been trying to figure out what is wrong, so I took off all the components which are around the VND7140 and i put the dutycycle on the input to 100%. Still just 1A.

Another thing i noticed while the VND7140 was on the board is that when i lowered the dutycycle it would go on for a second and then drop into failure mode. I thought this could be due to the fact that it measures a low voltage on the output, which is due to a set of capacitors used to change the PWM signal into analog DC. Which is strange since the datasheet doesn't state such protection and there is no more then 1A being drawn from the powersupply.  

I measured the output current which a constant current load.  

Does anybody have any ideas why this behaviour is being displayed and most of all how to get the current i really need.

With regards,
Michel van der Breggen  
#max-current #protection #vnd7140