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Original question:

TPS546D24SEVM-2PH: Voltage drop and Iout not supported more than 5A TPS546D24SEVM-2PH

TPS546D24SEVM-2PH: TPS546D24SEVM-2PH

sal hash
Prodigy 65 points
Part Number: TPS546D24SEVM-2PH

Tool/software:

Hi,

How we could change the Vout on the evaluation board? Is it possible or i have to manually change the resistor? if yes which resistor?

Also for our design do we always need to relay on the divider resistor at VSEL? I thought by default it will be the divider resistors and afterwords we could change the voltage out as per our desire using PMBUS?

The IC gives the temperature value using PMBUS is the value given is self heating or its the total ambient+self heating temperature? how to calculate it?

Where to find the relationship between frequency and self-heating of the IC? i want to see the trade off of frequency vs Temperature as my applications ambient temperature is 100°C in average

Thanks

Sal

  • 0
    TI__Genius 11396 points

    Hi Sal,

    sal hash said:
    How we could change the Vout on the evaluation board? Is it possible or i have to manually change the resistor? if yes which resistor?

    You can change the Vout by adjusting the resistor divider at the VSEL pin, or you can modify it via software using PMBus communication with the TI FUSION GUI.

    sal hash said:
    Also for our design do we always need to relay on the divider resistor at VSEL? I thought by default it will be the divider resistors and afterwords we could change the voltage out as per our desire using PMBUS?

    The factory default for the PIN_DETECT_OVERRIDE register is set to 0x1F2F, which means the device resets to the pin-detected value at power-on. However, you can configure it to reset to a stored NVM value.

    sal hash said:
    The IC gives the temperature value using PMBUS is the value given is self heating or its the total ambient+self heating temperature? how to calculate it?

    The reported value is the internal die temperature (Tj) with an accuracy of ±3°C. For example, if the ambient temperature is 25°C and the IC dissipates 1W, then Tj = 25°C + (8.1°C/W * 1W) = 33.1°C. Thermal resistance can vary based on PCB layout and heat sinking.

    sal hash said:
    Where to find the relationship between frequency and self-heating of the IC? i want to see the trade off of frequency vs Temperature as my applications ambient temperature is 100°C in average

    The Safe Operating Area charts (https://www.ti.com/lit/ds/symlink/tps546d24s.pdf#page=15) show the current limits based on ambient temperature and airflow. You can also use our WEBENCH designer for power calculations and junction temperature estimates at different frequencies.

    Thank you,
    Tomoya

  • +1 in reply to Tomoya Ide
    Prodigy 65 points

    You can change the Vout by adjusting the resistor divider at the VSEL pin, or you can modify it via software using PMBus communication with the TI FUSION GUI.

    Yes i have tried to over write but it dosent work, it shows on the GUI that i have changed but when you go to monitoring+in reality it dosent work?
    how to figure out this problem?

    Maybe i am using the wrong steps?

  • +1 in reply to sal hash
    TI__Genius 11396 points

    Hi Sal,

    Based on the screenshot you've shared, you've only changed the VOUT_MAX, which is the command to set the upper limit on the output voltage. 

    The commands you want to use to change the output voltage would be VOUT_COMMAND and VOUT_SCALE_LOOP (if necessary), which is the section I highlighted below:

    You can also access these registers in the tab "All Config." You can also set VOUT_MIN and VOUT_MAX to set the lower and upper limits on the output voltage to prevent the user from accidentally setting the output voltage outside the range. 

    Once you change the setting, click "Write to Hardware," and Vout will change.

    If you need to, please reach out directly, and I can go through the steps with you via call. 

    Thank you,
    Tomoya

  • 0 in reply to Tomoya Ide
    Prodigy 65 points

    Thanks , just one last thing the maximum Vout is 1.5v why is that? or i have to change some other parameteres?

    I am using the same chip using our design and we managed to go for more Voltages

  • +1 in reply to sal hash
    TI__Genius 11396 points

    Hi Sal,

    The VOUT_MIN and VOUT_MAX values are set to 0.5V and 1.5V, respectively. This is due to the VSEL pin strap resistors on the EVM, which are connected to AGND with a 14.7 kOhm resistor with no top resistor in the resistor divider (Resistor Divider = none).

    If you want to increase VOUT_MAX (for example, to 6V), you need to write the new value to VOUT_MAX. To store this value in non-volatile memory (NVM), either write "STORE_USER_ALL" or click the "Store Config to NVM" button in the TI FUSION GUI.

    Thank you,
    Tomoya

  • 0 in reply to Tomoya Ide
    Prodigy 65 points

    Got it Thanks