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TPS22950-Q1: Clarification regarding RLIM calculation

Srujan L
Prodigy 50 points
Part Number: TPS22950-Q1

Tool/software:

Dear Team TI,

from the TPS22950CQDDCRQ1 Datasheet, a snapshot of 9.2.2 Detailed Design Procedure section is below. Here if we calculate for RLIM, considering ILIM=500mA, we end up getting 2.22 ohm and not 2.21 kilo ohm from the given equation (2). Can you please confirm whether should the calculation result be considered in kilo ohm or it is a typo in the datasheet.

Even in section 6.5 electrical characteristics for Output current Limit, the RLIM values are matching for the given ILIM's typical values without kilo ohms in resistor units after calculating for RLIM for their respective ILIM's using equation (2) from the section 9.2.2 Detailed Design Procedure.

Can you please clarify whether kilo ohms should be considered with the unit ohms?

Thank you. I'm anticipating for a quick response.

Best Regards,

Srujan L

  • 0
    TI__Mastermind 32021 points

    Hello Srujan,

    If you take RILIM 2.21 you will get 0.5A which is 500mA.

    RILIM unit is KoHms and ILIM is in amps.

    So, in formula put 2.21 in place of RILIM.

    Thanks

    Amrit 

  • 0 in reply to Amrit Jit
    Prodigy 50 points

    Dear Amrit,

    So I understood that I have to use 2.21 Kohm resistor in my design to limit a current of 500mA.

    Also I have another query for you.

    After reading the data sheet, I understood that the fault pin goes low only if the temperature of the switch reaches thermal shutdown point. The same can be understood by the graph below from the datasheet

    Can you please confirm whether,

    1. the fault goes low only when the devices reaches thermal shutdown point ?

    2. What temperature is the thermal shutdown point?

    3. does the fault will be pulled low when the output current through the switch reaches ILIM set value and when this ILIM current is constantly maintained?

    Requirement:

    I was looking for a switch which meets the below parameters:

    1. which gives fault indication once the output current through the switches exceeds the set limit and with current limit function.

    2. ACE-Q Qualified/ Automotive grade

    3. Non-China/ Taiwan origin.

    Can you please answer my query and if possible suggest a switch with the above requirements.

    Thank you.

    Best Regards,

    Srujan L

  • 0 in reply to Srujan L
    TI__Mastermind 32021 points

    Hello Srujan,

    1. Check Table 8-1. table which shows the FLT state.

    2.  TSD is 170 degC. Check EC table.

    3.Yes, after some time device goes into TSD and shuts down because of power dissipation and FLT will be low.

    TPS22950-Q1 is a good fit.