AD637 usage notes

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Preface

AD637 yes ADI company , Its Chinese name is also called a chip produced by adenault Semiconductor Technology Co., Ltd , So as a user , We only care about how to use it , So the most important thing for us is to read his chip manual . Here is a brief record of its use .

One 、 Schematic diagram of chip manual

This bipolar application circuit is widely used in the chip manual , Why is it called bipolar （ Never mind , I don't know either , That's how he named it ）.

1.1 AD Circuit diagram of

that AD The circuit diagram of is also drawn for you , among C4 It's a filter capacitor ,C3 and C7 Is the average capacitance ,C3=C7=2.2*C4

So what is the conclusion ：

C4 The bigger it is , The smaller the ripple , But the slower the conversion speed , The error becomes smaller .

C4 The smaller it is , The larger the ripple , But the faster the conversion , The error becomes larger .

It's easy to understand , The smaller the ripple , The error must be smaller , vice versa , Of course, if you get something, you will lose something , If you want speed, the ripple will be big , Want precision , Then the speed is slow . Of course, choose a more neutral one , It's not slow , The ripple is not big .

So what is the theoretical basis ？ Of course, it's the chip manual , It says C4,C3 and C7 For setup time （ That is, the conversion time ） Influence .

This is the page , If you are interested, you can download it and have a look , Link to the chip manual
AD637 Chip manual

Two 、 test result

2.1. On the market AD637

Testing conditions ： The signal generator gives 1Vrms, after AD637, Then use an oscilloscope to observe . What the theory observes is 1V.
notes ： Relationship between peak value and effective value
Because the peak value of sine wave is the effective value √2 times . The peak to peak is 2 Times the peak , Therefore, it is a valid value 2.828(2√2) times .
　　 Peak to peak value refers to the difference between the highest value and the lowest value of the signal in a cycle , Is the range between maximum and minimum . It describes the size of the variation range of the signal value .

Module user manual response <200ms, Actually, it's probably 250ms. The output amplitude is 1V No problem , The ripple is also small , Because its output filter capacitance is relatively large .

2.2 AD637 Self made circuit

Then we weld one by ourselves according to the above schematic diagram and parameters .


response time Probably 10ms, The output amplitude is 1V No problem . The ripple is a little bigger than the one above , But it doesn't affect , Within the range of error .
According to the above schematic diagram , Measurable 20mVrms-7Vrms The input signal of , And the error is within the acceptable range .

summary

Okay , This is the sharing , I hope I can help you , Say more than do , Try it yourself .