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TS5V330C: part use for non-video applications

Part Number: TS5V330C
Other Parts Discussed in Thread: SN74CB3Q3257, SN74CBT3257, SN74CBT3257C, TS5N412, CD74HCT4066

Hi,

I would like to know if we can use this switch generically for analog applications.

I've been using the NXP NX5DV330PW, and observed strange behavior. This TI part is listed as a direct replacement for the NXP part on Digi-key.

My problem with the NXP (hopefully not the TI part) is that although the RDON is supposed to be 10 Ohms, the voltage difference between input/output is 1V. I input a 5V pulse and observe a 4V pulse at the output with a scope. the load is an OP-Amp. (high impedance).

We want to use the chip to switch TTL or RS422 pulses, and also some analog signals in other applications.

The pules are about 100uS, the frequency up to 200Hz.

We power the IC with 5V, and the signals trough the input/outputs are up to 5V.

we do not toggle the switch during operation, we select with a jumper which switch to use (S1 or S2).

Thanks,

Victor

  • Victor,

    Seeing a 1V drop of an RS422 signal across this type of signal switch does seem strange. I could think that if you have 100mA through the 10 ohm Ron switch you could have 1V drop (1V= (10ohm)(100mA)) or if the NX5DV330 switch was only a single NMOS switch and the Vt<Vgs is turning off the FET before your signal can get to 5V.

    When you try the TI TS5V330C part can send scope shots with labels on which signals are going into which pins? Do you have a schematic or drawing of your circuit as well?

    Thank you,
    Adam
  • Hi Adam,

    Thanks for the reply! Yes, I ordered the TS5V330C and will be testing it next week.

    So, based on my usage description (non-video application), you believe the TS5V330C is a viable option?

    Below is a simplified schematic of what we are doing.

    Thanks,

    Victor

  • Victor,

    The TS5V330C like all of the TS5XXXX devices are passive FET switches.  When the gate of the FET is biased they will conduct any signal through the drain and the source as long as the signal is within the recommended bandwidth, voltages, and current specified in the datasheet.  The Frequently Asked Questions page on the switches and multiplexers forum has some more explanation how these FET switches operate as well as the first 10 pages of this application note.

    We will wait for your scope shots for further debug. 

    Thank you,

    Adam

  • Hi Adam,

    Thanks for the information.

    From the application note, what category does the TS5V330C fall in? Single FET, parallel FET, charge pump? I could not find that info from the datasheet. I guess it does not have a charge pump? that said, what would be the maximum voltage I can expect at the switch terminals if I power the chip with 5V?

    I repeated the tests with the NXP switch and observed the output follows the input from 1 to 4V. 4V is the max output voltage, when powering with 5V.

    Victor

  • Victor,

    Great question on what category the switch is.  This was the first question I asked myself when I saw your post but it has taken me several days to track down the documentation through the archives of this older device.  Today I finally discovered the TS5V300C is a single FET switch.  I predict that you will have the same issue that you are having with the NXP device since the single FET will clip the signal when Vgs < Vt as the signal on the source (I/O pin) approaches the gate voltage (Vcc pin).

    I see how it can be hard to tell that the TS5V330C switch will have this behavior because the datasheet information is sparse.  I have tagged this datasheet for an improvement project. 

    I have found a 4-channel 2:1 device that has a charge pump so that you will not see the Vgs < Vt issue because the charge pump will boost the gate voltage higher than Vcc.  The SN74CB3Q3257 comes in a 16 PW package and is p2p compatible with the TS5V330C.

    Thank you,

    Adam

     

  • Hi Adam,

    thanks! I looked into the device (SN74CB3Q3257) and it only can be powered up to 3.6V. I would have to retrofit a regulator.

    I also looked at the SN74CBT3257C and SN74CBT3257, which go up to 5V, but they don't mention the charge pump, so I guess they are also single FET.

    Any other suggestions? Perhaps a strictly digital switch?

    Thanks,

    Victor

  • Victor,

    I'm sorry I didn't recognize your 5V supply requirement when I did my search on TI.com for 4-channel 2:1 switches.  What about using TS5N412?  

    Also I'm not sure what the you mean by digital switch.  As far as passive FET switches are concerned, a digital signal is a analog signal with many harmonics causing fast rising and falling edges.   If you can explain the difference I can try and help you find one.  

    Adam

  • Adam,

    thanks for recommending the TS5N412! I looked at the datasheet and it looks like it will work well for me. I will order it and try it out.

    As for digital, I was referring to a digital-only mux/demux.

    I was also looking into the CD74HCT4066. The application note you showed me mentions it has the input/output characteristics I need; but that is not mentioned in the datasheet?

    Seems many information is left out on the datasheets in general?

    Thanks,

    Victor

  • Victor,

    I'm glad to hear the TS5N412 looks promising. 

    Many of our older devices are not documented as well as we would like but please expect much better datasheets from us so that we can incorporate what you would like to see for our newer families MUX36XXX and TMUX1XXXX devices. 

    Thank you,

    Adam