Part Number: SN74CBT3251
I have a question regarding SN74CBT3251D:
1.The datasheet doesn't seem to specify what the Vout max is(when using a 5V supply), nor what the Vout min is.
In an application we're seeing the output voltage range to be 1.1 to 4.2V (when 0 to 5V is expected).
Is there something limiting the voltages a part from the I*R drop of the passing FET?
Since these are passive FET switches, Vout is not a valid spec since the voltage on the output of the switch is dependent on the input voltage and the on-state resistance of the FET.
There are three main architectures for bidirectional passive FET signal switches.
2) NFET in parallel with PFET
3) NFET with the gate biased by a charge pump
1) will pass signals from 0 V to Vcc - ~1V
2) will pass signals from 0V to Vcc
3) will pass signals from 0 V to slightly beyond Vcc
This application note selecting the right TI signal switch goes into more detail on the different switch types and the reason the on-state resistances are different.
The SN74CBTXXXX devices are the NFET type which means the on-state resistance gets increasingly high as the input voltage approaches Vcc. This is why you are only seeing about 4.2 V at the output with input at 5V and Vcc at 5V. If you would like to support 0 to 5V you will need to use the SN74CB3Q3251.
What are you connecting to the signal switch? You may also be interested in the new TMUX1208.
We are glad that we were able to resolve this issue, and will now proceed to close this thread.
If you have further questions related to this thread, you may click "Ask a related question" below. The newly created question will be automatically linked to this question.
In reply to Adam Torma:
In reply to Alberto Doronzo:
Alberto, The closet p2p device in a 16 pin SOIC package I found that will support voltages from 0 to Vcc is the SN74CBTLV3251. This device supply voltage goes up to 3.6 V. Thank you, Adam
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with respect to these materials. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.