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TPS62090: 1.1Vout does't start with load connected

Part Number: TPS62090
Other Parts Discussed in Thread: TPS62813M, TPS62813-Q1
I implemented on a board a circuitry for the 5V->1.1V conversion using the IC tps62090 following the example of figure 37 on component datasheet with the only difference of Rlow=158k and Rup=59k.

i encountered the following problem:
If I turn on the 5V with the load connected, the output does not go to 1.1V but makes attempts to turn on as if it were going into protection.
If I turn on the 5V with the load disconnected the converter reaches 1.1V and this power supply remains stable even when I connect the load.

I find more or less the same behavior certainly less accentuated by simulating the circuit. However, on the board the 1.1V does not even start on a 0.5Ohm resistive load.
 

could you help me?
what could be the problem?
  • Hi Albert,

    Output voltage normally drop if device doesn't have enough input current supply during external load. Could you check it on your circuitry? 

    For simulation, can you share the model ? I didn't see input capacitor on simulation profile and would like to check the model why it is not working properly.

    Did you try to use Webench model to check simulation model? 

    Link: https://webench.ti.com/power-designer/switching-regulator/simulate/550 

    Best regards,

    Tanvee

  • Thank you.

    My circuit has enough input current.

    I think that input capacitor is useless in my simulation, anyway i put it. I add  also a capacitive load of 100uF that represents fpga decoupling capacitor on my board. The behavior in simulation reflects what happens in the real circuit.

     

    here the result from webench

  • Hi Albert,

    You are triggering the two-level short circuit protection, described in the D/S section 7.3.4. 

    Check if your real, actual system load behaves like the one in your lab and in your simulation.  In some cases, the real load will not draw significant current during start-up until the supply voltage reaches some minimum voltage.

    As well, you should use the newer, smaller, more efficient, fixed frequency TPS62813-Q1 family for future designs which require -Q1.  We also have the TPS62813M devices, if you need to startup/operate down to -55 C.

    Thanks,

    Chris