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    MCP4261 burnt and hot after power on half hour

    Tested a MCP4261 by MEGA2560, the MCP became hot after half hour, what's wrong?

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    Re: MCP4261 burnt and hot after power on half hour

    Hi,

    Use a symbol with the correct pin counting order.

    Klaus
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    Re: MCP4261 burnt and hot after power on half hour

    Quote Originally Posted by KlausST View Post
    Hi,

    Use a symbol with the correct pin counting order.

    Klaus
    Thank you Klaus,

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    Re: MCP4261 burnt and hot after power on half hour

    maybe you have a wiper close to +V end of resistor and tied to ground.
    that could put 5V across the wiper resistance of about 75 ohm, for about 6.6 mA and 300 mW.
    that seems excessive

    are both IC's powered between the same 5V and the same ground?
    a mismatch there could be an issue

    sorry. grasping at straws here.
    is there any additional information you can provide?



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    Re: MCP4261 burnt and hot after power on half hour

    Quote Originally Posted by wwfeldman View Post
    maybe you have a wiper close to +V end of resistor and tied to ground.
    that could put 5V across the wiper resistance of about 75 ohm, for about 6.6 mA and 300 mW.
    that seems excessive

    are both IC's powered between the same 5V and the same ground?
    a mismatch there could be an issue

    sorry. grasping at straws here.
    is there any additional information you can provide?
    Thank you.
    The MCP uaed a 5V supply, and MEGA used USB power, both GNG together.



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    Re: MCP4261 burnt and hot after power on half hour

    so they both use 5V
    I would not expect that to be too much of a problem, since the grounds are tied together

    try the circuit for a little while using only usb power
    potential problem - if your usb can't provide sufficient current, so if you have a powered hub, use that to power the circuit

    since it isn't clear what the wipers are attached to, if you can, put the wipers near the center of their range

    so, what are the wipers attached to?



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    Re: MCP4261 burnt and hot after power on half hour

    laoadam, what wwfeldman is suggesting is that the fault is not in the (confusing) schematic you show but due to something connected to the P0W or P1W pins. The device is a dual potentiometer intended to output a voltage on the 'W' pin but it is not capable of supplying much current in to or out of a connected device.

    Do you have something connected to the P0W or P1W pins?

    Brian.
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    Re: MCP4261 burnt and hot after power on half hour

    Thank you wwfeldman and betwixt.
    Both P0W and P1W connected a 4.7k + LED for each, for testing only for now.



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    Re: MCP4261 burnt and hot after power on half hour

    at maximum output voltage on the wiper, 5 V, less about 2 V drop on the LED, leaves 3V/4700 ohm.
    you won't see the LED light up - suggest you reduce resistance

    however, there is another constraint:
    according to the data sheet, maximum current through A, W or B is 2.5 mA
    for a wiper at maximum (5V), less 2 V drop on LED, leaves 3V and 2.5 mA - resistor then 1200 ohm
    look close to see the LED on.

    you might want the wiper to drive a small transistor (2N2222A ? ) and let the transistor drive the LED
    can get more V and more current - use 5V and about 330 ohms then LED to collector.
    this should make the LED bright and not be a big load on the mcp42...



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