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LTC6993-4 Rset

Category: Datasheet/Specs

Hello,

I see on the LTC6993-4  datasheet page 4, Rset value is 50k - 800k.

When I try to configure Rset = 121K, I lose output when Tdelay is below 1.2ms

When I try to connect Rset = GND, I get the output as I expected. Is this allowed Rset connected to GND?

Thank You.

Sabrina

6993-4.asc

  • Sabrina,

    First, you should not ground the SET pin. The model may work in simulation, but the part's performance will be very unreliable from part to part. Stay with the specified Rset values. Second, what is probably happening with your simulation is that the input pulse is being applied before the part has powered up and settled. This is described on page 15 of the data sheet. The LTSpice model does a reasonable job of simulating this. The "typical" time needed for power up initiation is about 1.21ms, Can you try running the same simulation with the input pulse delayed by 2ms? This should be safely past the power up initiation and should give expected performance then.