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

John Shen1

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.

over 4 years ago

0 David_Wang over 4 years ago

TI__Intellectual 1465 points

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

0 John Shen1 over 4 years ago in reply to David_Wang

Prodigy 60 points

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

0 David_Wang over 4 years ago in reply to John Shen1

TI__Intellectual 1465 points

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

0 John Shen1 over 4 years ago in reply to David_Wang

Prodigy 60 points

Thanks a lot, David. You are very helpful.

Regards

John

Switches & multiplexers

Switches & multiplexers forum

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