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Simulators >> Circuit Simulators >> dc non-convergence in reference circuit
https://designers-guide.org/forum/YaBB.pl?num=1354713881

Message started by lhlbluesky_lhl on Dec 5^th, 2012, 5:24am

Title: dc non-convergence in reference circuit
Post by lhlbluesky_lhl on Dec 5^th, 2012, 5:24am

as the picture shows, the first reference circuit generates a global 1.5v voltage for the whole chip, then in ir receiver module, there is another reference circuit using 1.5v to generate the voltage of ir module (1.45v, 1.2v, 0.75v, 05v, 0.1v), and at every node, there is a 1pF mos cap. when simulating the first reference with bandgap seperately, it works well; when simulating the ir module with the second reference circuit (with ideal voltage source vdc=1.5v at second reference input), the ir module works well too; but when i simulate the whole circuit as the picture shows (first 1.5v reference + second reference + ir module), the dc operating point is of non-convergence, and the 1.5v voltage becomes to 2.1v (vdd=3v) for 3v/ss/-40deg corner, becomes to 1.04v for 2.7v/ss/-40deg, and other undesired value for other corner. very strange, i wonder why. what is the possible reason? thanks.

Title: Re: dc non-convergence in reference circuit
Post by Lex on Dec 5^th, 2012, 6:27am

Try a transient simulation for those conditions to confirm the DC level.