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SN74LVC1G3157: Could devices like the SN74CBT3125C or SN74LVC1G3157 have something like -2.5V at GND and 2.5V at VCC and operate normally?

Adam Torma
Mastermind 45370 points
Part Number: SN74LVC1G3157
Other Parts Discussed in Thread: SN74CBT3125C, , TMUX1133, TS12A4516

E2E, 

Could devices like the SN74CBT3125C or SN74LVC1G3157  have something like -2.5V at GND and 2.5V at VCC and operate normally? I need to pass a -2.5V to 2.5V square wave signal through it.

 

Any Switch do you recommend can achieve this operation?

Perhaps https://www.ti.com/product/TS12A4516?

Thank you,

Adam

  • 0
    Guru 267180 points

    From the point of view of the device itself, all voltages at the pins are measured relative to the GND pin.

    So as long as the signal has a voltage somewhere between the voltage at the GND pin and the voltage at the VCC pin, this will work. However, the control inputs must receive a valid logic-level voltage; if the logic low level is 2.5 V above the GND pin, then this is not valid.

  • 0
    TI__Mastermind 46317 points

    Hi Adam,

    So in general the answer is yes, you can put a -2.5V signal on the GND pin and 2.5V on the VDD pin and as long as

    VDD - GND <= Recommended Operating Supply Voltage Max there shouldn't be an issue. This being said the logic levels of the part are controlled by the VDD - GND voltage, so the logic levels are now referenced starting at -2.5V instead of 0. 

    The SN74CBT3125C will not work for your application as it is an NFET switch, meaning it can't pass rail to rail signals. So with VDD = 2.5V it will clip at 2.5V - Vt, where Vt is the threshold voltage of the transistor. 

    The  SN74LVC1G3157 can possibly work for your application, but it depends on the frequency of the signal, the bandwidth of the SN74LVC1G3157 is 340MHz. 

    The newest part we have could fit the application is the TMUX1133, with the lowest Ron (typ. 4 Ohms at +/-2.5V)  for the power supply. It does have a lower bandwidth of only 220MHz and also this is a three channel device. 

    The TS12A4516 also works in this application with a higher Ron than the TMUX1133 but a higher bandwidth (464MHz).

    I'd recommend the TMUX1133 or the TS12A4516 for this application. 

    Best Regards,

    Parker Dodson