Dear Team,
The customer found that they input 5V signal (STRIP0_1A_SW) to SN74CBT3253C but only got 4V at the output.
They want to know why it loss about 1V at the output.
The 5V input signal comes from LED driver's 3.3V signal(STRIP0_1A) and pass through a 3.3V to 5V level shift.
In below figure, the channel one should be "STRIP0_1A_SW" not "STRIP0_1A." It's a typo.
Could you please help to clarify this problem?
Thank you.
Regards,
Jim
Hi Jim,
The SN74CBT/CBT-C family of switches are single NMOS FET switches. In order for the FET to have a low impedance path from drain to source (A to B) the Vgs voltage must be greater than the FETs threshold voltage. With this type of switch you will only be able to pass a signal about 1 V < than the Vcc voltage.
If you want to pass a voltage up to the value of Vcc you will need a different family of switch that has two FETs an NMOS and PMOS in parallel or a switch with a charge pump.
You can look at the new TMUX1209 that provides rail to rail switching in addition to 1.8-V compatible control inputs, Break-before-make, Fail-safe logic.
Thanks
Saminah
