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TS5A3160 application

Kevin Kreger
Expert 1020 points
Other Parts Discussed in Thread: TS5A3160, TS5A3159

Hi,

I'm using (or ~probably~ misusing :) a TS5A3160 to switch a 0 to 1.5V voltage to the base of two transistors:

I change the value on the 0-1.5V input and then switch the 3160. This is done at a 1kHz rate. I'm not always getting clean switching as there is glitching between the two values meant for the separate transistor bases. BTW, I do not have a scope but the device let's me plot the transistor currents.

Please note that PE2 is a direct output from a Stellaris MCU. This output can be configured a number of ways, pullup, pulldown and differing drive currents.

I am wondering if my very simple implementation needs some type of discrete Rs or Cs to get it to function properly.

As well, please comment on whether this is better handled with a few discrete FETs as it is a very slow circuit, 1kHz.

Thanks in advance for your help!

Kind regards,

Kevin Kreger

  • 0
    TI__Expert 6395 points

    Hello Kevin,

    The TS5A3160 is specified as Make-Before-Break which could be causing the glitching you are seing if there is a momentary connection between the base of the two transistors.  The TS5A3159 is the same switch but specified as Break-Before-Make and could solve your issues.

    Could you also provide a little more detail on your logic levels at PE2?

    Regards,

    Andrew Mason

  • 0 in reply to Andrew_Mason
    Expert 1020 points

    Hi Andrew,

    Thanks for the prompt reply. You may have nailed it with the make before break observation.

    PE2 is the ouput from a Stellaris LM3S5P56 with a 3.3V power supply.

    PE2 has multiple driver currents and pull-up configurations that it can be set to that are internal to the chip.  The output current strength can be 2mA, 4mA, 8mA, or 8mA with slew-rate control. The output can be configured as standard push-pull, or with weak pull up, or with weak pull down.

    The power to the TS5A3160 is 3.0V. The level of PE2 V out high minimum is 2.4V, and V out low minimum is 0.4V. They don't give nominal values, but I believe they should be ~3.3V high and ~0.0V low (I can measure if this is important).

    I have set the PE2 to two different configurations to try to fix this. I've kept the current at 2mA and tried both Weak Pull Up and Weak Pull Down.
    I tried some other changes in my code to reduce the glitching (setting the 0-1.5V input to zero between pulses), so I cannot say which setting (if either) works better but I currently have it set to 2mA, weak pull down.

    Sorry for the lengthy explanation, but I just wanted to make sure I have it correct.

    Thank again.

    Kind regards,

    Kevin

  • 0 in reply to Kevin Kreger
    TI__Expert 6395 points

    Hello Kevin,

    Your logic levels look fine from what you described as long as they are above/below datasheet specified thresholds.  I would recommend trying the TS5A3159 to see if the Break-Before-Make solves your problems.

    Regards,

    Andrew

  • 0 in reply to Andrew_Mason
    Expert 1020 points

    Thanks Andrew! I will try it per your advice.

    Best,

    Kevin