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TPSM8D6C24EVM-2PH: PMBUS behavior

Kazuki Itoh
Genius 9955 points
Part Number: TPSM8D6C24EVM-2PH
Other Parts Discussed in Thread: USB2ANY, , USB-TO-GPIO2, LM75B, TPSM8D6C24

Hi team,

 

Could you please address customer’s questions related to PMBus behavior of TPSM8D6C24EVM?

 

-------------------------------------

#1

The customer tried to test with the configuration below.

[PC/Fusion Digital Power Designer Ver7.7.9]ー[USB2ANY]ー[TPSM8D6C24EVM-2PH]

However, The Fusion Digital Power Designer showed up "No USB Adapter Found!" message.

Which one is the supported USB adapter (USB2ANY, USB-TO-GPIO2, USB-TO-GPIO)?

The customer is proceeding the debugging with USB2ANY Explorer as work around.

-------------------------------------

#2

Current monitoring read out (8Ch) READ_IOUT shows the negative current under no load.

Under no load,

              I2C: I2C internal address changed to 8C

              I2C  Read 0x0014   2 bytes  Data: 0x0000: 60 C5

was obtained. By calculating SLINEAR11, the current value is -2.625.

 

The customer checked the input voltage (88h)READ_VIN as well, but the output looks correct. When the input voltage is 12.2V,

              I2C: I2C internal address changed to 88

              I2C  Read 0x0014   2 bytes  Data: 0x0000: 09 D3

was obtained. SLINEAR11 calculation result is 12.140625, which matches the measurement. Could you please to address this error? Or, is the no load current accuracy is supposed to be this poor?

-------------------------------------

#3

About the PMBUS read format, referring to SLUA475, SM Bus Read Word (without PEC) on Fig 1 works (It should correspond to combination format in I2C).

 

Aside from that, when the customer tried the format which sends the stop condition after writing the target register address (CMD address) to the pointer register, then reading from the start condition, the ack was not returned and it was unable to read. (This format is just like Fig.4(C) and Fig. 10 in LM75B datasheet)

 

The difference is only one thing:

Prior case reads from the restart condition without issuing the stop condition after writing CMD address.

Prior case reads from the restart condition with issuing the stop condition after writing CMD address.

 

My customer would like to read the value with the later format.

Could you please check if there is the later case can be used to read from TPSM8D6C24?

 

-------------------------------------

 

Regards,

Itoh

  • +1
    TI__Guru 53305 points
    Kazuki Itoh said:

    The customer tried to test with the configuration below.

    [PC/Fusion Digital Power Designer Ver7.7.9]ー[USB2ANY]ー[TPSM8D6C24EVM-2PH]

    However, The Fusion Digital Power Designer showed up "No USB Adapter Found!" message.

    Which one is the supported USB adapter (USB2ANY, USB-TO-GPIO2, USB-TO-GPIO)?

    The customer is proceeding the debugging with USB2ANY Explorer as work around.

    FUSION Digital Power Designer software does not support the USB2ANY interface adapter because the USB2ANY interface adapter does not support the Block-Write / Block-Read Process call, which PMBus uses to read out the SMBALERT_MASK values.

    You will need to use the USB-TO-GPIO or USB-TO-GPIO2 adapter.

    The current version of the FUSION Digital Designer needs a separate DLL to work with the USB-TO-GPIO2 adapter (I will add it to this thread shortly)  An updated version of FUSION Digital Designer should be released next month with the DLL file included.

    Kazuki Itoh said:

    Current monitoring read out (8Ch) READ_IOUT shows the negative current under no load.

    Under no load,

                  I2C: I2C internal address changed to 8C

                  I2C  Read 0x0014   2 bytes  Data: 0x0000: 60 C5

    was obtained. By calculating SLINEAR11, the current value is -2.625.

    Yes, this is normal.  The TPSM8D6C24 module is able to read negative output currents and the -2.6A represents the sum of the currents measured from both converters.

    This represents about 4% of the rated current and 2% of full-scale measurement.

    Kazuki Itoh said:

    #3

    About the PMBUS read format, referring to SLUA475, SM Bus Read Word (without PEC) on Fig 1 works (It should correspond to combination format in I2C).

     

    Aside from that, when the customer tried the format which sends the stop condition after writing the target register address (CMD address) to the pointer register, then reading from the start condition, the ack was not returned and it was unable to read. (This format is just like Fig.4(C) and Fig. 10 in LM75B datasheet)

    The later is not a valid PMBus transaction, and does not work with the TPSM8D6C24 converter.  They will need to use the valid SMBus Read-Word transaction without a stop and with a repeated start.