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problems with LM5069-1

Rosa Torru
Prodigy 10 points
Other Parts Discussed in Thread: TPS2490, LM5069, TPS2590, LM5066

Hello, My name is Rosa and we want to use the LM5069-1 for design a circuit. We want to control the limit current and the under/over voltaje and the reverse input voltaje block, We dont want to use the power limit, in the pin 7, the circuit has 1Moh.

Limit curretnt is 20A Under voltaje 21 Vcc and over 31 Vcc.

 In this moment all are working but if we switch on with load for 1, 2, or 20A the circuit doesnt work. If we swicth on the circuit without load we can measure la voltage out and after we put load the circuit is working perfectly.

We have designed a circuit using TPS2490, we switch on for 10A load and one Works perfectly. We think that there is a error with the LM5069-1. Could you help us ?]

  • 0
    TI__Mastermind 42795 points

    Hi Rosa,

    Turning on into a loaded output can be complicated, especially if the load is an electronic lab bench load. E-loads have an active loop that can interfere with the regulation loop of the LM5069. Can you try starting into a simple resistive type load?

    Also, with a power limiting hotswap there is a "minimum" load resistance for reliable start up. Meaning, that if the load resistor is lower than the minimum then the output cannot start. There is an explanation in the TPS2590 datasheet starting on page 10. The load resistor should be larger than R=Vin^2/(4 x PowerLimit).

    Lastly, the LM5069 will require a minimum sense voltage (or minimum power limit for the application) for start up. The LM5069 datasheet does not mention this but you can refer to the LM5066 datasheet for an explanation (see LM5066 DS, page 22 as highlighted below). 

    LM5066 DS, pg 22:

     

     

    LM5069 DS, pg 15

     

    LM5069 should have an additional term such as “-0.0025 x Vin/Rs” after EQ 2 to account for the offset at Vout=0V. Target start up offset voltage should be greater than 5mV (LM5066 uses 3mV in the ppg above). So, for this case it sets a minimum power limit which would then yield the minimum Rpwr for a given Rs and Vin.

    Good luck.