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TS12A12511 problems switching and all within data sheet specification

derek koonce
Prodigy 160 points
Other Parts Discussed in Thread: TS12A12511

I have a circuit that operates all within the specification of the analog switch. Upon power up, the switch is activated and the signals are passed through without a problem. At a point in time, the switch is deactivated and it still operates well. However, after several cycles, when the switch is activated again, it does not switch back immediately. The switch starts to have a delay and eventually stops switching back. If the power is removed from the circuit and re-applied, the switch works fine until the deactivation/reactivation cycle.

I have an immediate need to get this resolved due to a looming November 10th deadline to fix the PCB design. Any help is greatly appreciated. I have call the Ap support phone and the guys there have done so much and have been awaiting a response from the designers. I have a board that I can ship overnight to show them the problem. I have provided schematics and scope waveforms - but they seem to have stalled in the support.

I look forward to this community to help find the solution.

Below is what I have sent thus far to the App group.

=========================

Device: TS12A12511

Schematic:

 

Devices of concern: U8 and U14

Supply voltage 7.5Vdc

 

Before switching:

Green is input (pin 6)

Blue (U8) and red (U14) are outputs of two different analog switches.

After switching back:

Why are the switches not going back to the left side of the first picture?

 

I replaced the parts and things seem to work better. However after a few cycles I get the following waveform.

Why the long delay in switching over? Note: Time base is stretched out.

 

  • 0
    Prodigy 160 points

    After some further deep thought and reading of other manufacturer's analog switch datasheets, I am seeing that the test condition of the switch operating is with 10 ma of current. I started to suspect that a minimum current is required to operate the switch - which seems somewhat improbable. However, after moving the R39 resistor to the connection of U9-8, and lowering the value of R39 and R38 such that there is more current flowing through the switch, it appears to start to work when switched to the NO side. However, the NC still seems to always function - with a low voltage applied, 60mV, the current is very low. Thus I am now questioning as to what minimum current is required to flow through the NO switch in order for this device to operate; there is nothing in the data sheet that would indicate this need.

  • 0 in reply to derek koonce
    Prodigy 160 points

    It would be nice to know how TI built this switch - circuit-wise. What is the structure of the MOSFET switch? Configuration? Anyone know?

  • 0 in reply to derek koonce
    Prodigy 160 points

    Lots of views. But no additional help? Surely I thought TI would be all over this if there was a potential flaw in the IC. I do have a board to offer for evaluation.

  • 0 in reply to derek koonce
    Prodigy 160 points

    Coming up to 3 months since this issue was flagged. One would figure some result would have come out from the design side of TI. As far as I know, the apps head has pinged the design group with no response over the last 1.5+ months.

  • 0 in reply to derek koonce
    TI__Mastermind 46480 points

    Send this to Dick Stacey via Email,  dick_stacey@ti.com I beleive these are still his parts.  He may not be watching this particular forum.