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TMS570LS3137-EP: How to operate LM4132 Enable pin by using GPIO of TMS570LS3137-EP.

Venugopal B
Prodigy 70 points
Part Number: TMS570LS3137-EP
Other Parts Discussed in Thread: TMS570LS3137, LM4132, HALCOGEN

HI TI team,

We are planning to operate (ON/OFF) LM4132-2.5V Reference IC by using GPIO port B of TMS570LS3137.

LM4132 input voltage is 5V and EN pin is pulled up with VIN for 2uA asper datasheet specification. So if I left floating for EN pin and measure the voltage it will be 5V.   

TMS570 GPIO port B has the option of open drain output, and it can be configured using HalcoGen. So no needs to use external transistor.

We are planning to use Open drain configure to pull down EN pin of LM4132 to turn ON and OFF the Reference voltage.

TMS570 recommended Maximum voltage applied to GPIO is 3.3V.. My Query is that if I connect as described above it will create any issue with Microcontroller.

Please kindly share the feedback.

Thanks and Regards,

Venugopal

  • 0
    TI__Guru**** 172286 points

    Hi,

      I think that should be fine. Please see below description from LM4132.

    7.3 Feature Description The LM4132 can be remotely operated by applying an EN voltage between 65% of VIN, and VIN. The LM4312 can be remotely disabled by applying an EN voltage between 0 V to 35% of VIN. The EN pin can also be strapped to VIN, so VREF is active when VIN is applied.

  • 0 in reply to Charles Tsai
    Prodigy 70 points

    Hi, 

    Thank you for your positive feedback. i am clear about  LM4132 operation.

    My confusion is that, LM4132 will have defiantly 5V due to internal pull up (Current limited to 2uA).

    If i connect the 5V directly to GPIO of controller (my VCCIO is 3.3V) in Open drain output configuration, what will be the impact in controller? Whether it will damage the IC?

    What is the Power-ON Reset state of GPIO bank B of TMS570?. I am unable to find the right data on datasheet.

    Please kindly share your feedback on signal interface.  

    Thanks,

    Venugopal B.

  • 0 in reply to Venugopal B
    TI__Guru**** 172286 points

    Hi,

      I was thinking for a different device that is 5V tolerant when I answered the question. For this device which is not 5V tolerant, I will suggest you go through a level shifter or a voltage divider. 

      The reset state of GPIOB is pulldown. 

  • 0 in reply to Charles Tsai
    Prodigy 70 points

    Hi,

    Thank you for your feedback, I have not found the Table number 4-23 for GIO, in TMS5703137CGWTQEP datasheet table 4-3 reffers the GIO.

    I am sharing the Snapshot of available datasheet. Please kindly share the additional data if you have.

    As you said reset state is Pull down and also after reset I will use as Open drain O/P configuration, and also LM4132 has weak Pull up. So when controller is in power ON reset 5V will be pulled down and after reset completes GIO will configured as Open Drain so external 5V pull up is not an issue for MOSFET.

    I needs to know the IO direction when the Power ON reset, its Input or Output?.

    Thanks and regards,

    Venugopal B.

  • 0 in reply to Venugopal B
    TI__Guru**** 172286 points

    Hi,

      During Power on reset, the pin is input. 

  • 0 in reply to Charles Tsai
    Prodigy 70 points

    Hi,

    Thank you for sharing the information.

    So as mentioned above can I connect LM4132 of EN pin to Open Drain Output of TMS570?

    Thanks and regards,

    Venugopal B

  • +1 in reply to Venugopal B
    TI__Guru**** 172286 points

    Hi,

     I think it should be fine but you need to ensure the sizing of your pullup resistor to 5V such that it meets the input clamping current (3.5mA) requirement of TMS570 I/O. See below and the datasheet. 

  • 0 in reply to Charles Tsai
    Prodigy 70 points

    Hi,

    Thank you for your feedback and support.