Hello,
I am having trouble with a PDS I am designing using LRM64010 (and other switching DC/DC's). I've attached a webench design report which is pretty close to what I am using. I purchased the LMR64010 demo board and replaced the following components:
D1 -> MBR0530T1G
C1-> 10uF MLCC
CF - > 82pF C0G MLCC
C2 -> 10uF MLCC
R1 -> 246k Resistor
Vin: 12V, Vout: 24, Io = .030A
I load the output of the circuit with a resistor of approximately 800ohms for .030A of output current. Using a bench supply and the loaded circuit standalone I see an input current of .07A. There are other loads on my 12V input rail totaling around 331mA. Adding in the load from the 24V rail I should have about 401mA of load current. My 12V rail has a max current limit of .5A, I use a bench supply for this at the moment but in the final design this is a seperate DC/DC.
What I see when I attempt to power up the entire PDS is that if my current limit is set to .5A I OC the supply. While the supply is in OC protection I can probe each of my voltage rails and all are fine except for the LMR64010 rail which is pulled down. If I set the current limit on my supply to around 1.1A or above the entire PDS powers up fine with a current draw of around 400mA.
What I suspect is happening is the inrush current from the network of DC/DC's is exceeding the .5A limit and preventing the LMR64010 from powering up properly. The problem I am having is trying to figure out what inrush current too expect, and how to properly size my 12V rail. I am trying to determine if there is a way to control the inrush current of the LMR64010. I am using other DC/DC's in the PDS such as TPS62112-EP and TPS62111-EP but their datasheet mention that they limit inrush current and they do not seem to be what is driving the overcurrent.