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IVC 102

Ravaner Max
Prodigy 40 points
Other Parts Discussed in Thread: IVC102

Hello. I'm going to use an IVC102 in a mass spectrometer application. I need to know what will happen if  for swtch1 I use a 250 ns width and 60 µs period strobe. I've read several times the datasheet and it's always set the use of a 10 µs width signal ... What happens with shorter strobes ?

  • 0
    TI__Prodigy 130 points

    Max,

    I am not sure that I have enough information regarding your application to answer this confidently.  What value of capacitor are you using,  and what is your specific timing to Switch one and switch two?   With that information I can better understand what you are asking.  

    The reason that the Capacitor value makes a difference is because the reset switch has an on resistance of a 1-2 Kohms. So the discharge time may be an issue depending on the amount of charge that has to be discharged off of the capacitor.   If you look at figure 1b in the data sheet you can see that when the reset switch (S2) is closed there is some finite discharge time that is dependent on the reset on resistance and the integration cap.  First order sanity check should be 2Kohms X integration Cap for one time constant.  If you are using the 100pf internal cap,  one time constant would be about  1uS.  You probably want to wait a minimum of 5 time constants.   The 10 uS delay shown is a conservative 10+ time constants.

    Bubba

  • 0 in reply to Bubba
    Prodigy 40 points

    HI,

    Thanks for your answer. I think I must be more clear.

    1) Reset duration has no contraints it can be as long as necessary.

    2) The question is relative to switch #1. This switch must be on to establish communication between outside sensor and the integrator. The integration is accomplished by many (lets say thousands ... )  switch  on of S1. This switch is closed every 60 µs (for example) and for a short duration (250ns) this makes that charges are injected in integrator, many times but each time for a short duration.

    My question  : is this short closing time compatible with the S1 switch ? For information, I realized that switch with discrete components (2N4117 for S1) and it works. My project is to use IVC 102 instead of  FET transistors in order to gain place.

     

  • 0 in reply to Ravaner Max
    TI__Prodigy 130 points

    Max,

    I can't answer this one.  My sense on this is that 250nS is pushing the envelope.  If this worked with the discrete FET switch well maybe,... but I think this is one that your just going to have to try to find out if it works.  I would be concerned with S1's on resistance and the ability to suficiently transfer the charge in that short time.  You are going where no man has gone before...;-)   I would like to hear back if it works.

    Good Luck!
    Bubba

  • 0 in reply to Bubba
    Prodigy 40 points

    Hi Bubbe,

     I just received yesterday component IVC102 from USA. I tested it and VERY VERY good news ... It works perfectly with a 250 ns switch 1 on strobe. Steps are clearly visible on out ramp. My project can progress now. Thanks for your replies.