AD5272 - how tall is the resistence per step ?

Hello dear forum users,

I'm new here and new at the topic digital potentiometer.

I need a digital potentiometer which I want control through I2C with my Arduino Uno to change the voltage at the LM723 voltage resistor feedback.

Now I need to know, how big is the resistance of the AD5272 per step.

Do you know how big is it ?

How all is the tolerance between the values?

How big is the difference between min, typically and max value ?

I hope you can help me or give a advice what to do better.

Sincerely,

Petr94

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  • 0
    •  Analog Employees 
    on Jul 23, 2015 12:33 AM over 5 years ago

    Hi Petr,

    A couple of questions:

    • What is the 7-bit I2C device address that you are using?
    • What are the states of pins A1 and A0?
    • How is the 0x2C address implemented?
    • Could you get a scope shot of the SDA and SCL lines of your circuits?
    • What is your digipot's end-to-end resistance value?

    Take note that the 16-bit word consists of two unused bits, which should be set to zero, followed by four control bits and 10 RDAC data bits (note that for the AD5274 only, the lower two RDAC data bits are don’t care if the RDAC register is read from or written to), and data is loaded MSB first (Bit 15).

    You would have to use command number 1 on Table 12 to be able to write to the RDAC.

    You will then compute for the approximate code for the digipot to have a value of 100 ohms. If you have a 20k ohm digipot, you may use code 3 or code 4 to have a resistance between approximately 93 ohms and 113 ohms, wiper resistance included.

    Regards,

    Mark

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  • 0
    •  Analog Employees 
    on Jul 23, 2015 12:33 AM over 5 years ago

    Hi Petr,

    A couple of questions:

    • What is the 7-bit I2C device address that you are using?
    • What are the states of pins A1 and A0?
    • How is the 0x2C address implemented?
    • Could you get a scope shot of the SDA and SCL lines of your circuits?
    • What is your digipot's end-to-end resistance value?

    Take note that the 16-bit word consists of two unused bits, which should be set to zero, followed by four control bits and 10 RDAC data bits (note that for the AD5274 only, the lower two RDAC data bits are don’t care if the RDAC register is read from or written to), and data is loaded MSB first (Bit 15).

    You would have to use command number 1 on Table 12 to be able to write to the RDAC.

    You will then compute for the approximate code for the digipot to have a value of 100 ohms. If you have a 20k ohm digipot, you may use code 3 or code 4 to have a resistance between approximately 93 ohms and 113 ohms, wiper resistance included.

    Regards,

    Mark

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