arahman137
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Hi, this is my first post and I have got a strange problem.
I have been trying to design a 3rd order Switched cap filter and I got it to work in Cadence 5 with an FDA that I designed. Now when I converted to Cadence 6 I made sure that my FDA was exactly as the same as the one I had in Cadence 5.
However, now the 3rd order Sw Cap circuit shows oscillation (in Cadence 6). I went ahead and reduced it to a 1st order circuit and then replaced the switched caps with resistors and no problem. But as soon as I start putting switches in there (and I have used both MOS switches and ideal switches) the FDAs go into oscillation. I am still running transient analysis - and I am not sure where everything's going wrong.
My dead time generator is 16 Mhz and the Oscillation frequency is about 800 MHz. My FDA had a DC gain of 65 dB with a 110 MHz UGB with 10 pF load. Does anyone have any idea?
I have been trying to design a 3rd order Switched cap filter and I got it to work in Cadence 5 with an FDA that I designed. Now when I converted to Cadence 6 I made sure that my FDA was exactly as the same as the one I had in Cadence 5.
However, now the 3rd order Sw Cap circuit shows oscillation (in Cadence 6). I went ahead and reduced it to a 1st order circuit and then replaced the switched caps with resistors and no problem. But as soon as I start putting switches in there (and I have used both MOS switches and ideal switches) the FDAs go into oscillation. I am still running transient analysis - and I am not sure where everything's going wrong.
My dead time generator is 16 Mhz and the Oscillation frequency is about 800 MHz. My FDA had a DC gain of 65 dB with a 110 MHz UGB with 10 pF load. Does anyone have any idea?
