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TPS709: Current limit at Vin=24V

Yusuke Mukuno
Expert 7395 points
Part Number: TPS709

Hi Expert,

Could you please let me know about the following figure at Vin=24V?

Can we estimate it will be linear increasing to 24V?

Do you have the figure that is showing to 24V?

Current limit spec

Test condition is note (4).

Can you estimate the current limit value at Vin=24V and Vout=3.3V?

Thanks

Muk

  • 0
    TI__Genius 12345 points

    Hi Mukuno-San, 

    Unfortunately, we do not have any data for Vin>8.5, however, we do not expect the current limit go beyond the maximum value of 500mA as specified in our EC table. 

    I can go ahead and take a bench measurement with the given conditions. Please allow 1-2 days so I can take the measurement. 

    Best,

    Edgar Acosta

  • 0 in reply to Edgar Acosta1
    TI__Expert 7395 points

    Edgar-san

    Thank you for your supporting.

    My understanding,

    It might be difficult to checking on the Bench test, because drop voltage (Vin - Vout) of customer condition is higher.

    Vin=24V, Vout=3.3V

    If current limit is 500mA, Ploss= (24V-3.3V)x 0.5A = around 10W. I think, Thermal shutdown is applied faster than current limit.

    So the figures in the datasheet cannot show the data at Vin>8V.

    Can you estimate the design value from electrical internal circuit? 

    Thanks

    Muk 

  • 0 in reply to Yusuke Mukuno
    TI__Genius 12345 points

    Hi Mukuno-San,

    It is true that taking a measurement with 10W of power dissipation is hard and Thermal Shutdown would probably kick in, however, during a current limit event, the device will limit the current first and then the Thermal Shutdown protection will act to cool off the device. 

    Having said that, it is possible to take the measurement. One way to do it is performing a Load Transient as shown below:

    I have set Vin=24V. Vout=3.3V and a resistive load of 5.6Ohms.

    We can observe that the maximum current value is 566mA which is close to the expected 589mA from the I = 3.3V/5.6Ohms. After this notice that the current is limited to ~333mA, and the typical value for this device is 320mA. Therefore, the current limit is still within the specified range of values provided in our DS. 

    Keep in mind that the load transient pulse is close to 64us, if this where to be increased, then we would trigger the thermal shutdown feature. 

    Best, 

    Edgar Acosta