LM27341: Simulating inverting configuration

Matt Bruensteiner

Part Number: LM27341

I am attempting to simulate the inverting configuration of the LM27341 buck regulator.

My goal is +3.3 V input, -9 V, 100 mA output.

However I am having trouble getting this configuration to simulate in PSpice for TI.

Even if I take the provided reference design and simply rename the ground node to "O2" and connect the ground symbol to what was the output pin, I see no output voltage developed in a transient simulation.

(Notice the scale of the inductor current is picoamps and the scale of the output voltage is 10x10^-24 V)

I believe this indicates there is an internal connection to the global ground node in the simulation model subcircuit that is producing unrealistic behavior.

Is there a way to simulate this IC in inverting configuration?

Thanks,

Matt

over 3 years ago

0 Matt Bruensteiner over 3 years ago

Prodigy 10 points

Trying to attach my design file:

LM27341_TRANS.zip

Only the STARTUP design is modified from the provided reference design.

Matt

0 Lishuang Zhao over 3 years ago in reply to Matt Bruensteiner

TI__Expert 7500 points

Hi,

Amod is looking into this and will feedback to you soon.

Thanks,

Lishuang

0 Amod Vaze over 3 years ago in reply to Matt Bruensteiner

TI__Mastermind 23110 points

Matt,

Usually, if the spice model is not a dedicated inverting model, then it may not work as intended. This is because the internal circuits in the model may have been referenced to global ground node as you said. You can leave the ground connections as they were earlier. And, then connect the input voltage VIN between VIN and VOUT of the original buck converter. You will need to ensure you use the correct reference point for measuring voltages. I suggest using differential probe markers.

Hope this helps.

Thanks,
Amod

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LM27341: Simulating inverting configuration