Other Parts Discussed in Thread: CSD17483F4, TIDA-010014, OPA365
Tool/software: WEBENCH® Design Tools
I have been checking the Linear Led driver from your reference design TIDA-010014 that uses the TLV9062 and a CSD17483F4 MOSFET
In the first AC Small Signal Stability Simulation you obtain a Phase Margin of 88.92 at a cross frequency of 3.95MEG using the following circuit
I understand the compensation network and the fact that L1 and C2 are there for DC and AC analysis and will act as a short or as an open circuit,however, I wonder why the designer used a DC voltage of 70mV (V2 in the image) injected into the non inverting input (+) of the OpAmp?
For this kind of stability test we are supposed to tied to ground the non inverting input (+), am I right? adding this DC supply will change the behavior of the Open Loop Gain, 1/B and in general the Phase Margin of the circuit, and lead to a wrong stability analysis.
If we tied to ground the non inverting input (+) in the TINA SPICE file that you provided for this design we obtain totally different response with a very different Phase Margin for sure, as shown below:
In general, any other value smaller or larger than 70mV will completely change the response.
Am I getting lost somewhere ?
Any help will be appreciated.