AD633 squaring/single power supply issue

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Atlas5

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Hello,

I am trying to preform the squaring of a sin wave using a AD633 multiplier using OrCAD. So far, I am following the method that the datasheet produces for squaring the input. The only difference is that I am trying to use a single power supply instead of two seperate ones. Can anyone give me advice on how I can change the curcuit so that I can get the right output.

Also, attached is my simplified circuit which shows the multiplier on top and the power function (simulation). The current result picture shows the result I am getting if using the multiplier. The last picture shows the result I get by using the power function in OrCAD. Let me know if you need more information.

Thanks.
 
hi,
Normally pin 5 is connected the -V supply. your diagram shows it 'floating', try connecting pin 5 to 0V.

I suspect it will not work to specification as its designed for dual supply operation.
 
ericgibbs said:
hi,
Normally pin 5 is connected the -V supply. your diagram shows it 'floating', try connecting pin 5 to 0V.

I suspect it will not work to specification as its designed for dual supply operation.
Click to expand...

Thank you for the reply.

At the moment pin 5 is connected to ground with a 0.1uF cap to help regulate it.

As of working for speculations, I was just wondering if there is a way to make it work so that it can use a single power supply instead of a dual one.
 
Atlas5 said:
At the moment pin 5 is connected to ground with a 0.1uF cap to help regulate it.

As of working for speculations, I was just wondering if there is a way to make it work so that it can use a single power supply instead of a dual one.
Click to expand...
A capacitor does not regulate, it filters. You need a connection to ground to carry the IC operating current. Capacitors provide a block to DC.

The operating input and output range of the AD633 is within 3V to 4V of either supply voltage (see Fig. 6 in the data sheet). Thus for operation on a single supply, the input and output voltages can go no lower than 3-4V above ground or no higher then 3-4V below the supply voltage. If you can maintain the input and output signals within that range, then it should work with a single supply, although at lower voltages, the accuracy may suffer. It will obviously not work properly down to ground with a single supply.
 
Thank you for your reply.

crutschow said:
A capacitor does not regulate, it filters. You need a connection to ground to carry the IC operating current. Capacitors provide a block to DC.
Click to expand...

You are correct it does filter as filter would be the better word for this.


Hmmm. I see then. If that is the case then would my application work better if I use the adl5391 multiplier instead since I can connect it to ground and use a single power supply of 5V.
 
Last edited:
Atlas5 said:
Hmmm. I see then. If that is the case then would my application work better if I use the adl5391 multiplier instead since I can connect it to ground and use a single power supply of 5V.
Click to expand...
Yes, that would appear to be a better device for single supply operation it the accuracy meets your requirements.
 
crutschow said:
Yes, that would appear to be a better device for single supply operation it the accuracy meets your requirements.
Click to expand...

Alright. I was wondering if you would know where I could find a PSPICE model of the part since I cannot seem to find it online.
 
Since Analog Devices does not offer a spice model for the adl5391, I suspect there is none available.
 
crutschow said:
Since Analog Devices does not offer a spice model for the adl5391, I suspect there is none available.
Click to expand...

If that is the case then are there any alternatives since I would like to simulate the multiplier so that I can confirm that it works.
 
Don't know of any off hand. You need to search the multiplier vendors to see if they have a part you can use that also has a Spice model available.
 
That hasnt been an easy task since I have spending a good amount of time trying to find one but I had no luck so far.
 
After some more searching I think I will have to go and use the dual power supply for the AD633. The only difference is that I will use another chip called MAX868 which is a Regulated, Adjustable -2x Inverting Charge Pump. From my understanding I can use this chip to invert a positive power supply and invert it to a negative power supply but doubled. In this regard I would have to use a voltage divider to bring the voltage back down to -5V since that is where I would need it. Anyway, let me know if this could work too or if you have any other suggestions.

Here is the link to the chip's datasheet.
https://www.electro-tech-online.com/custompdfs/2012/05/MAX868.pdf
 
The "voltage divider" you need is used to regulate the output voltage as shown in Figure 4 of the data sheet. For R1 = R2 and adding the dotted line connection, the output voltage will be the negative of the input voltage.
 
Ah I see. I will try that out then and see how that will work in my application. If there are any other suggestions on getting a negative power supply through a positive power supply or another method as a "more affordable" solution to my issue then I would love to hear it.

Thanks.
 
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