Hello,
I am trying to simulate the Figure 84 – Positive and Negative Variable Supply from the LT8582 datasheet, using:
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LT8582 as dual boost / inverting converter
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LT3041 as positive LDO
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LT3099 as negative LDO
The goal is a bipolar supply, with a load mainly connected between VPOS and VNEG.
Target outputs:
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VPOS ≈ +8 V
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VNEG ≈ −6 V
I built the circuit in LTspice following Figure 84, including:
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Coupled inductors (K = 0.99)
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Schottky diodes (BAT54 / 1N5818)
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EN and SHDN pins tied high
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PGFB tied to IN (no fast-start required)
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Schottky clamps to prevent VPOS going below GND
However, the circuit does not start or regulate in simulation:
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out_positive ≈ 0 V -
out_negative ≈ 0 V -
SET pin currents in LT3041/LT3099 are essentially zero
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LDO input rails remain near 0 V
A .op analysis shows VIN = 12 V is present, but the switching converter does not appear to generate the intermediate rails for the LDOs. A transient simulation (.tran startup) also shows no regulation.
I would like to ask:
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Is Figure 84 expected to work directly in LTspice with the provided LT8582 / LT3041 / LT3099 models?
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Are there specific enable / sequencing requirements in simulation that are not obvious from the datasheet?
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Is a Schottky clamp or startup sequencing required for LT3041/LT3099 in LTspice?
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Are there known limitations or required initial conditions for LT8582 bipolar configurations in LTspice?
I have attached my LTspice schematic and screenshots of the simulation results.
Thank you very much for your help.
