Hi,
Please see the oscilloscope shot. Can I ask you why the two scope shots are showing such a big different operation? The input current in second shot with the lower Cout keeps touching zero and increasing periodically in a closer look, which has an influence in output voltage waveform as well. What's the reason of this operating? May I get a wrong test setup?
CH1 : VOUT, CH4 : IIN
1) Cout 100uF, Load 500mA
2) Cout 4.7uF / Load 500mA
Thanks,
Hey Ella,
You mention that the current shown in the input current which is coming from the supply voltage, what is the input voltage look like during this event? I'm curious if the input voltage is dropping and forcing the LDO into dropout (reducing the LDO's load current) and then recovering allowing the LDO to provide more current and so you get this on/off behavior.
The other question I have is what type of load is this? Is the load coming from a resistor, a bench current source (electronic load), or does this scope shot show the the LDO powering an IC (if so what kind)? I ask because it doesn't look resistive, it looks like it suddenly turns (a resistive load would rise with Vout). If it is an Electronic Load one thing to watch out for is the fact the E-Loads have their own control loop and will change the resistance of the load based on the output voltage. Because the E-Load has it's own control loop there can be an interaction between the E-Load and any power source which doesn't properly mimic a real loads behavior and can cause over/undershoots like what you are showing.
