• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 100 subscribers
  • Views 447 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

66AK2H12: IO pins voltage levels issues

Radoslaw Rak
Prodigy 30 points

Part Number: 66AK2H12
Other Parts Discussed in Thread: 66AK2H14

Hello team,

I've got a question about voltage level on reset pins.

RESET, POR, and RESETFULL voltage is about to 1V. Why is that if voltage translator are powered with 1V8? It is similar situation with some other pins like bootmode pins. We use the same voltage translator: TXS0108EPWR like in schematics K2H_K2EVM-HK_SCH_A104_Rev4_0.

Few months ago we apply another TI DSP processor ( TMS32C6670 ) and we used the same voltage translators. Everything works correctly and voltages of some IO pins are also about to 1V.

Kind Regards,

Radek

  • 0
    TI__Mastermind 46460 points

    Radek,

    The K2H_K2EVM-HK_SCH_A104_Rev4_0 schematic does not drive any reset signals through a TXS0108EPWR device.  The reset signals to the 66AK2H14 device are sourced from a GPIO expander.  The TXS0108EPWR devices are used with JTAG and and with some of the SPI and GPIO control signals which specifically have only high impedance loads.  I assume then that you are referring to boards that you developed which drive the reset signals through a TXS0108EPWR.  That is not a good device for unidirectional signals like reset.  You should instead use something like the SN74AVC4T245PW which we have on many of our test boards for buffering and level translation of the reset signals.

    The TXS0108EPWR is a bidirectional buffer with a pass-gate and pull-up resistors.  It does not have the ability to drive a high level with any significant current.  When the output is high, it is held in that state by a weak 4K pull-up resistor.  Do you have any pull-down resistors on these nets?  If so, this is why you are seeing improper logic voltages.

    Tom

  • 0 in reply to Tom Johnson 16214
    Prodigy 30 points

    Tom,

    We changed value of pull-down resistor for POR to 33k and removed pull-down resistor for RESET and RESETFULL. We also removed voltage spikes on LMZ power modules output.

    It seems that processor is working. Is answering by transition RESETSTAT to high level. Thank You for your help. Now we are going to check DSP processor with JTAG.

    Best regards

    Radek Rak