This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • Resolved

SN74CBT3125: Power the switch chip from an I/O pin output

Prodigy 40 points

Replies: 4

Views: 76

Part Number: SN74CBT3125

Can we connect the VCC pin of this SN74CBT3125 switch chip to an I/O pin of a 430 MCU? In other words, can we use the I/O pin output of a 430 MCU  to supply the power to the switch chip? What we want to do is to control the power supply of the switch chip using a 430 MCU.  We are not sure:  1. How much current will the switch chip draw from its VCC pin when its VCC voltage is about 2.8-3.0V.   2. Whether the SN74CBT3125 switch can work properly under 2.8V VCC.  The datasheet says  the recommended power supply is 4V.  2.8V is quite far from 4V.  3. What is the output current of the I/O pin of a 430 MCU, assuming the 430 MCU is powered by a 3V power supply?  Thanks a lot for the help.

  • Hi, John,

    Unfortunately, the SN74CBT3125 requires at least 4V to operate properly. 

    For 4ch. SPST configuration, you may consider the the newly device such as the TMUX1111 (VDDMIN= 1.08V) or TMUX1511 (VDDMIN= 1.5V).

    I/O pin of 430 MCU can typically source up to 6mA of current, which is much higher than the current consumption of these switches. You will have no problem supplying the devices using the MCU's GPIO.

    Thanks,
    David

  • In reply to David_Wang:

    Hello David,

    Thanks a lot for the quick response. Your answer did solve my question. Just one more thing: when using MCU’s I/O pin to provide power for the switch chip, do we need to connect a 1uF capacitor from the I/O pin to ground so to make the power source more stable?

    Regards

    John

  • In reply to John Shen1:

    Hi, John,

    Yes. It's always a good idea to have a decoupling cap on the power supply to stabilize the switch operation. 

    Thanks,
    David

  • In reply to David_Wang:

    Thanks a lot, David. You are very helpful.

    Regards

    John

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.