This week, I finally was able to test J2111A in combination with an Omicron Lab Bode 100 Analyzer.
The target was to measure the stability (phase margin) of an 1.15V / 1A SPMS regulator in its application circuit where I don’t have access to the feedback path.
The regulator was connected to a 300mA resistive load to reach a normal operation point, all peripherals on the application board were disabled.
Unfortunately, the results are not quite useful, although I increased the Analyzer’s output power to its maximum, removed any input attenuation and reduced the receiver bandwidth to the minimum (see attached screenshot), the Q(Tg) measurement is way too noisy to calculate a proper phase margin result.
When checking the signals of the J2111A current Injector with an oscilloscope, I found that the current at the J2111A OUT port (measured with a current probe) does not match the I monitor voltage (measured with a high impedance passive probe in parallel to the Bode 100 Receiver 1 Input).
It looks like the output current cannot exceed the 24mA DC offset value (switch was set to +bias).
The J2111A MOD input signal (measured with a high impedance passive probe in parallel to the J2111A input) looks good, so, the Bode 100 output port seems to work fine.
As you can see on the Scope Screenshots, the 1.15V output voltage stays stable all the time.
The J2111A OUT+ line was connected to the 1.15V output voltage, the OUT- line was connected to the PCB’s GND.
Do you have any idea why the output current looks like this and could this be the reason why I do not get any useful readings from the Bode 100 Suite?