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Wats the difference between these 2 configurations?

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ericmar

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As the title, Wats the difference between the following 2 configurations of using a Digital potentiometer?

POT.jpg


Thanks,
Eric
 

Not much. If you use 5494 or 5495 that has a full potentiometer you can use the first configuration and if you have 5496 or 5497 that is only a variable resistor use the second one. The benefit of the second one is that you avoid direct connection of the input to the power supply. The 5498 and 5499 have both a pot and a variable resistor.
 

In second configuration,the H side is left floating which can attract some noise.
In my opinion second configuration will work better if we short h- andw- side.
 

I don't know the characteristics of the Maxim devices but a general rule is that DC current through the wiper contact must be avoided because in the long term it can affect the contact resistance. For carbon potentiometers, this is even worse because the carbon layer is degraded by DC current through the wiper contact. So, the second configuration is more prone to long term wear. Furthermore, in that configuration, it is good practice to connect the H and W sides (this will reduce the output noise due to the variable contact resistance of the wiper).
 

Well, if the feedback resistors (the ones connected to the - input in the opamps) are the same, the range of input and output voltages are different. While in figure 12 the input voltage ranges from 0V to 5V, in figure 13 the input voltae ranges from 0V to a voltage lower than 5V, the maximum input voltage depends on value of the resistance in series with the potentiometer and the potentiometer itself in figure 13. As a concecuence the outputs will have proportional values. The second circuit is employed for limitting the ouput voltage to a value usually for protection measures.

Sal
 

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