The datasheets for the MP5048 and the MP5048A have spec and performance data for varying Cout values ranging from 330/470uf (4A) to 1000uF (15A). What is the optimal method to determine the minimum size for Cout if you don’t know what the actual load capacitance will be? I’ll be using the MP5048 and setting the current limit to between 7 and 10 Amps. Noting that the MP5048 eval board uses 1000uF, but can be have up to 5 x 15A devices in parallel.
Hello,
The safest way to determine your optimal output capacitance when you don’t know the actual load capacitance is to assume the load capacitance is zero. It is recommended to begin your design following the datasheet recommendations and then you can alter Cout depending on your load requirements. If you have any other questions feel free to reach out.
Best,
Luke
Thanks Luke,
Does the eval board design also assume that the load capacitance is zero and thus your decision to employ 1000uF is also based on utilizing just one of the 5 available channels? Wherein if one used all 5 of the 15A channels they’d have to replace or add capacitance to the board (which there is provision for)? Given the difference in suggested Cout values between the 4A part and the 15A part there seems to be a) a relationship between the minimum Cout and the maximum current and b) that the relationship is not linear.
From a performance perspective, what would be the primary effect of under sizing Cout for those of use trying to design something with significant space constraints? I am working on a multichannel eFuse design and having to place several 50V 1000uF caps is becoming difficult to layout.
Hi Jason,
Output capacitance should be determined based on power constraints of whatever is downstream of the converter. The eval board uses Co that have been tested to guarantee the expected performance characteristics. The output capacitance’s effect on inrush current also has to be considered, as to keep the MOSFET’s within their SOA during startup. I_inr=Co*dVout/dt. The slew rate can be adjusted through Css. For your question regarding the relationship between Co and maximum output current: in steady state, output current is not a function of Co, but during startup Co does have an effect on inrush current.
Best,
Luke