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TPS2596: Thermal shutdown down time

Michiaki Tanii
Expert 4610 points
Part Number: TPS2596
Other Parts Discussed in Thread: TPS25924,

Hi

How can we estimate the thermal shutdown time ?
In the case of configured that RLIM is 200mA, if Rdson = 150mohm, PD would be around 6mW.

If the current was inputted over the RLIM, how customer can estimate the thermal shutdown time in the above case ?

Thank you and best regards,

Michiaki

  • 0
    TI__Guru** 105361 points

    Hi Michiaki,

    6mW would be the PD before entering into current limit mode of operation.

    In current limit mode, the device maintains constant current value which was set at Rilim. The power dissipation across the device is (VIN-VOUT)*I_limit. As VOUT value depends on amount of overload, the power dissipation and hence the duration the device operates before thermal shutdown depends on amount of overload.

    For example, for TPS25924 device... (in the same way, you can calculate for TPS2596)

    With Vin=5V and current limit value is 2A. When the output is loaded with 1ohm, it is an overload event and output voltage VOUT becomes 2A*1ohm=2V. The power dissipation across the device is (5-2)*2=6W. The device operates for 400ms at 25deg before thermal shutdown.

    For example Vin=12V and current limit value is 3.5A. when output is shorted VOUT=0, the power dissipation is (12V-0)*3.5A = 42W. The device should operate for 2ms at 25deg before thermal shutdown.

    BR, Rakesh

  • 0
    TI__Guru 57737 points

    HI Michiaki,

    Thermal shutdown time of TPS2596 depends on the the power dissipation in the IC and the Junction to Ambient thermal resistance (RQJA)  of the IC. RQJA is a function of board layout.

    Table 7.4 in the datasheet provides you RQJA value of TPS2596 on a Standard JEDEC board with and without the thermal PAD soldered on the board. The RQJA value on your board can be different than the value in the datasheet and has to be measured.

    When the eFuse is operating in steady state (without any fault condition) the power loss in the IC would be (I^2 * Rdson) as you mentioned. When there is any fault condition like over current and if the IC is in current limiting mode, the power loss will be = (Vin-Vout) * Ilim.