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AM2632: AM2632 pin pulse voltage and current stress.

Srinath S
Prodigy 45 points
Part Number: AM2632

We are using AM2632 Arm micro-controller.

We ran simulations to determine the stress on each uC pin for ISO pulses, and the schematic and results are shown below.

ISO Pulses

Limit Voltage

Limit Current

Applied Voltage

Applied  Current

Comments

ISO Pulse 1

+3.3V to -0.5V

+/-100mA

-0.566V @1ms

-300nA @4ms

This negative voltage is again based on the clamping diode Vf. Used clamping diode for simulation is BAW100C

ISO Pulse 2a

+3.3V to -0.5V

+/-100mA

2.95V @14ms

20nA@2ms

 

ISO Pulse 3a

+3.3V to -0.5V

+/-100mA

1.2276V 

3.8nA

 

ISO Pulse 3b

+3.3V to -0.5V

+/-100mA

1.2292V

5.4nA

 

 

Please let us know whether these stresses are acceptable.

If somethings missing , please highlight.

  • 0
    TI__Mastermind 22685 points

    Hi Srinath,

    Please note that the AM263x device does not have failsafe IOs.  You should ensure that you stay within the recommended operating conditions of the pins as listed in the AM263x datasheet at all times to ensure normal operation of the device and within the absolute maximum values at all times to prevent physical damage to the device.

    We do have some ppt slides on solutions external solutions since the AM263x does not include failsafe IOs.  Hopefully these slides will be helpful to you.

    Thanks,
    Mike

    AM263x_Overvoltage_Failsafe_IO_rev3.pptx

  • 0 in reply to Mike Pridgen
    Prodigy 45 points

    Hello ,

    Good Day !

    Thanks for presentation.

    I see here injection current limit is 2mA  from presentation .

    Also as per datasheet voltage limit range was –0.5V to 4.0V.

    As per our Simulation below are stress levels , and i see there are way well within limit.

    ISO Pulses

    Limit Voltage

    Limit Current

    Applied Voltage

    Applied  Current

    Comments

    ISO Pulse 1

    +4 to -0.5V

    +/-100mA

    -0.566V @1ms

    -300nA @4ms

    This negative voltage is again based on the clamping diode Vf. Used clamping diode for simulation is BAW100C

    ISO Pulse 2a

    +4V to -0.5V

    +/-100mA

    2.95V @14ms

    20nA@2ms

     

    ISO Pulse 3a

    +4V to -0.5V

    +/-100mA

    1.2276V 

    3.8nA

     

    ISO Pulse 3b

    +4V to -0.5V

    +/-100mA

    1.2292V

    5.4nA

     

    Please let us know whether these stresses are acceptable.

  • 0 in reply to Srinath S
    TI__Mastermind 22685 points

    Hi Srinath,

    Just an FYI, the voltage limit range of -0.5V to 4.0V is for the VDDS33 power rail itself, not the IO pins.  So if the injection is only applied to a VDDS33 pin, then the only concern is ISO Pulse 1 having an applied voltage of -0.566V, which is outside of the -0.5 to 4.0V allowable range on VDDS33.

    The IO pins have different specifications, which for transient voltages is -0.3V to 1.2*VDDS33 for up to 20% of the signal period.  VDDS33 here is represented by the actual voltage on VDDS33.  Assuming your pulses are fast enough to fall within the 20% period portion of the spec, you are allowed a 20% overshoot above VDDS33, which if VDDS33 is exactly 3.300V, sets the maximum pulse voltage at 3.960V.  However, the minimum pulse voltage is still -0.3V.  This means ISO Pulse 1 is still falling outside of the allowable range.

    Thanks,
    Mike

  • 0 in reply to Mike Pridgen
    Prodigy 45 points

    Hello Mike , 

    Thanks for feedback.

    We are using ADC port V15.

    As per datasheet , IO Voltage is can be applied 3.3V.

    According to this we could apply voltage till -0.5V to 4V.

    If we are wrong , please correct us.

    Also is it possible to provide model for internal clamping diodes so that .

    So that we could perform simulate with right model.

  • 0 in reply to Srinath S
    TI__Mastermind 22685 points

    Hi Srinath,

    Where are you seeing in the AM263 datasheet that you can apply voltage range from -0.5V to 4V to an analog input pin?

    I had discussions with some folks on the analog design team, and the allowable range for an analog input pin should be -0.3V to VDDA33 + 0.3V.  So again, that -0.566V falls outside of this range and is a concern.

    Thanks,
    Mike