Line Regulation for MP9488

DC-DC Power Converters
1

Hello Team,
we have received one evalution board for MPS9488 for our requirement testing. our requirement is 12V to 154V input voltage range and 5V output with ±5% tolerence having 250mA maximum load. we tested the evaluation board by modifying Resistor R1 with 4.7k for 5V rest of the components are same as it is. we found out during the line regulation for our maximum load of 250mA when the voltage goes below 17V the regulation is not good it start decreasing 200mV/1V for 14.4V we are geeting 4V output.

as per the IC its mention that the input voltage will be of 7.5V to 450V but we are having issue with the 17V below. are we missing something ?

2

Hello Team,

Also there is one observation that at low input voltage with full load regulation ic is not working as expecting as of i have requirement of input voltage 14.4V, Output Voltage 5V with 250mA Load but i am getting 4V at the output with desired Load of 250mA this is nearly 20% Tolerence which is not accepted. may i know the reason for this behaviour ?

3

probably a minimum off time issue imposing in effect a maximum duty cycle. try doubling the inductor value ( like use two in series) and see what happens.

4

Hello Mr.jshannon,
yes your correct for the minimum off time limitation issue ,
any update on the regulation issue i have below observation
when there is full load the regulation is 4.7V
when there is dummy load + External light load around 10mA it gives 5V regulated
and when there is no load that means only dummy load it gives 5.3V
this tolerence scenario is happning with all the cases either you choose 15V output or 3.3V or 3V output.
is this the regulation provided by this IC or we have scope to improve it ?

5

Hello,

I noticed the following things about this issue that seem to be significant parts of your issue:

  • The output dropping off from 14.4V to 4V at a 250mA load is concerning.
  • Light load stabilizes at 5V, which is indicative of regulation issues at heavy load in this application where 4.7V under full load struggles to maintain regulation.
  • The impact of doubling the inductance helps with energy storage but doesn’t fully resolve the root cause if he minimum off time is a limiting factor.

Perhaps adjusting your feedback network would add stability to your system. If for some reason this doesn’t work and regulation is still problematic, here is another part that would perhaps be more well suited for your application:

Hopefully this helps,
Krishan