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PORZ signal level on ICE board

Per Nordstrom
Prodigy 50 points
Other Parts Discussed in Thread: TPS65910

Hi,

Looking at the ICE schematic:

http://www.ti.com/lit/zip/sprr170

The PORZ signal is driven from an AND gate. The AND gate is supplied by 1.8V. On the AM335X the PORZ input belongs to VDDSHV6. VDDSHV6 is connected to TPS65910 VAUX2  which defaults to 3.3V. According to AM335x datasheet the PORZ pin needs 2 Volts for a valid high level which the AND gate can't provide.

Isn't a levelshifter necessary for the PORZ signal in this design? 

Best regards,

Per

  • 0
    TI__Guru 62855 points

    We are in the process of changing the requirements for this input.  We are planning to make the following updates to the AM335x data sheet.

    Table 3-7 will have a new section added to provide the respective parameter values for; VIH min = TBD, VIL max = TBD, VHYS min = TBD, and II max = TBD.  We are in the process of determining the values for these parameters.

    The following note will be added to the new section of Table 3-7.

    "The input voltage thresholds for this input are always compatible with 1.8 volt LVCMOS logic levels and are not a function of VDDSHV6.  This makes this input 1.8 V compatible when VDDSHV6 = 3.3 V.  However, this input is not compatible to 3.3 V when VDDSHV6 = 1.8 V because the input voltage can not exceed VDDSHV6 by more than 0.3 volts."

    Regards,
    Paul

     

  • 0
    TI__Expert 5180 points

    Hi Per,

    One more note: There are two versions of the schematic on the ICE product website and you seem to look an older version of ICE. Please see the schematic related to Rev1.0A for the latest production version of ICE (or follow this link: http://www.ti.com/litv/zip/sprr176). There was a change on the PORZ circuit.

    Regards,

     Thomas