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Original question:

CD4052B

CD4052B: CD4052B large on-state resistance?

Louis Fournier18
Prodigy 20 points
Part Number: CD4052B
Other Parts Discussed in Thread: SN74CB3Q3253, SN74LV4052A, TS5A3159

Hello everybody,

I'm using two CD4052B for MUX/DEMUX. I use only +3.3V as Vdd and connect INH, Vee and Vss to the GND.

My problem is that input voltage is not same as output. I assume there is some voltage loss but from input high level (3.3V), the output is about 2.75V and after DEMUX the final voltage of the output signal is about 1.68V. Then my signal is crushed and cannot drive anything. I would like to know if I forgot something.

My wish is to do the least modification as possible.
Is somebody have an idea? I could provide schematic if required.

Thanks in advance.
Best regards,


Louis F.

  • 0
    TI__Mastermind 45455 points

    Louis,

    What application are you using the CD4052B device?  It may help other people on the forum if you post a schematic or diagram.

    The CD4052 will have a higher series resistance with lower power supply voltage. 

    If you use the 5 V spec as an example you can expect the results you are seeing if you are driving ~1mA through the switch.  The voltage drop across the device with 1mA current is expected to be 470mV.  How much current are you driving through the switch?  What do you have connected to either side of the switch?

    Why did you choose the CD4052B?  An alternative device I found filtering on ti.com selection tool for 2-channel, 4:1 device, with lower on-state resistance will be the SN74CB3Q3253.

    Thank you,

    Adam

  • 0 in reply to Adam Torma
    Prodigy 20 points

    Hello Adam,

    Thank you for your answer. My application consist in multiplexing trigger signals for CCD input signal and demultiplexing the multiplexed signal to a specific CCD (there are several CCD).

    I'm driving a current about 1mA through the switch. I saw that the Rds is higher when you have a lower Vdd (than 5V for example).

    At the end of the switch connection, I have an optocoupler to protect the output stage. But voltage and current is to low and I cannot set the LED on to set the right output.

    Here is the application screenshot:


    Thanks to your help, I found a component: SN74LV4052A and it seems to be good for replacement (exactly same pinout as CD4052B) but low Rds and lower power supply. Do you think it could be a good compromise to avoid heavy hardware modification?

  • 0 in reply to Louis Fournier18
    TI__Mastermind 45455 points

    Louis,

    Is CCD charge-coupled device image sensor which are the camera 1/23 in the drawing above? 

    Yes, generally the Rdson will increase as the Vcc decreases for the CD4052B (transmission gate NFET in parallel with PFET) which is true for all transmission gate and single NFET type switches.  This relation is not true for switches with charge pumps biasing the gate voltage.  More information on the different switch types can be found in the first couple of pages in this application note.

    Yes, the SN74LV4052 will have lower Rdson in 10s of ohms at 3.3 Vcc vs the CD4052B which will be 100s of ohms.

     

    Seeing that you are only using 1-channel 3:1 configuration in your system another choice for the future would be the TS5A3159 which has Rdson <1 ohm.

    Thank you,

    Adam