SN74CBT3125: Are the two FETs, PMOSFET and NMOSFET combined in SN74CBT3125 datasheet case?

Kazuya Nakai59

Guru 21155 points

Part Number: SN74CBT3125
Other Parts Discussed in Thread: TMUX1111, SN74LV4066A

Hello guys,

One of my customers is considering using SN74CBT3125 for their new products.

At this moment, they have the following question.

Could you please give me your reply?

Q. SN74CBT3125 datasheet (Ver. SCDS021I) shows logic diagram on page 2.

We can see one FET only at 1 channel SW.

In other analog datasheet, we often see two FETs, PMOSFET and NMOSFET as the SW in block diagram.

Are the two FETs, PMOSFET and NMOSFET combined and written as one FET in SN74CBT3125 datasheet case?

Your reply would be much appreciated.

Best regards,

Kazuya.

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 298500 points

CBT devices are very old and were designed for TTL signals, which do not go near 5 V. So they have only a single N-channel MOSFET.

For rail-to-rail signals, use an analog switch like the TMUX1111, or SN74LV4066A (with inverted control signals).

0 Bryan Marshall over 3 years ago

TI__Genius 10974 points

Hi Kazuya,

Our switches and multiplexers can have several different architectures depending on what the device is being designed to do. In this instance, the SN74CBT3125 uses a single NFET architecture. We have a helpful digital selection guide I have linked below that goes into detail on how each family was designed (CBT family in this case) if you are curious and would like more information on these kinds of devices.

https://www.ti.com/lit/ml/scdb006a/scdb006a.pdf?ts=1637172271313&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FSN74CBT3125

Thanks!

Bryan

0 Kazuya Nakai59 over 3 years ago in reply to Clemens Ladisch

Guru 21155 points

Hello Clemens,

Thank you very much for your reply.

I understood that SN74CBT3125 can't handle rail-to-rail signal because the device uses single Nch-MOSFET.

Your reply is very helpful for the customer and me.

Thank you again and best regards,

Kazuya.

0 Kazuya Nakai59 over 3 years ago in reply to Bryan Marshall

Guru 21155 points

Hi Bryan,

Thank you very much for your reply.

The selection guide is very helpful. I will tell the link to the customer and I will utilize the guide for switch device selecting.

Thank you again and best regards,

Kazuya.

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SN74CBT3125: Are the two FETs, PMOSFET and NMOSFET combined in SN74CBT3125 datasheet case?