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TMS320F2800157-Q1: Slew Rate

Shoo Saga
Expert 3171 points

Part Number: TMS320F2800157-Q1
Other Parts Discussed in Thread: LMR60406-Q1, LAUNCHXL-F2800157, TMDSCNCD2800157, LMR60406, C2000WARE

 

Hi team,

 

the slew rate in each rail is specified in the datasheet. However our WV covverter cannot meet the requirement since the requirement slew rate is fast. What is your recommneded buck covverter or PMIC device of this? and LMR60406-Q1 can be used here? (6ms,3.3V)

image.png

and how to create the XRSn signal? It looks PG of the Buckconverter cannot connect to the device directly.

Best,

Shoo

 

  • +1
    TI__Mastermind 20681 points

    Hi Shoo,

    We have had discussions of laxing the slew rate requirement since it is very fast, like you mentioned, and many converters are unable to reach the slew rate requirement. This spec is before we have the PMM power management module in the device which helps regulate the power during startup. I think you are safe to reference the TMDSCNCD2800157 or LAUNCHXL-F2800157 devices to reference the converter used. I think LMR60406 should also be sufficient based on the spec

    Regards,

    Peter

  • 0 in reply to Peter Luong
    TI__Expert 3171 points

    Hi Peter,

    How about connection of XRSn signal? Both user guide doesn't have schematic.

    Best,

    Shoo

  • 0 in reply to Shoo Saga
    TI__Mastermind 20681 points

    Hi Shoo,

    The schematic is available as a separate file from the user guide and is available on the product page or the C2000WARE SDK.

    The XRSn just requires a resistor between 2.2 kΩ and 10 kΩ should be placed between XRSn and VDDIO. You can optionally drive the XRSn signal from an external supervisory circuit like a supervisory IC or a reset button like we have done on the LAUNCHXL-F2800157

    Regards,

    Peter

  • 0 in reply to Peter Luong
    TI__Expert 3171 points

    Hi Peter,

    What I asked is power sequence requirement. I believe the device on the EVM board is not followed this power sequence requirement. 

    Is it Ok XRSn just pulled up to VDDIO?

    Best,

    Shoo

  • +1 in reply to Shoo Saga
    TI__Mastermind 20681 points

    Hi Shoo,

    The launchpad/controlcards rely on the internal PMM which assists in the power-up sequence. The VDDIO is provided by external LDO, note that supervisor circuit also has its own delay since it is derived from the same 3.3V as the LDO. It is fine to keep XRSn pull-up if you only rely on internal reset and do not need to have external reset

    Regards,

    Peter