Any one using LM2577(voltage regulator)

Hi Michael,

Suggest you make sure the input current "Is" meets this device's specs.

If it does, suggest you contact Texas Instruments to resolve this issue.

Best regards,

Mel

Hello Michael,

You might want to check the value of the capacitor across the input of the regulator.  TI says 0.1uF, but other diagrams like the test circuit say a 220uF capacitor should be used.  The ripple current may be causing problems with the 5V input circuit.  As Mel says, contact TI to check.

Thanks

David

I had similar problem with control circuit TPS40210.

What is nominal current of choke coil 100uH? Have you used 0.1uF on input and 680uF on output?

Hi,

I have connected the exact same circuit as I have seen from the data sheet.

I have not measured the Inom, however as I am using a DC power source in lab, I think it shouldn't be a problem for the source to supply enough current.

What could be the other factor ?

Thank you very much for your kind reply =)

Hi,

May I know what what do you mean by ripple current may be causing a problem?

I have tried several capacitor value and the same thing happen - voltage drops as soon as I connect it to a load like dc fan / dc motor/ LED.

Thank you very much for your kind reply. =)

Hi,

not ripple current but maximum allowed coil current can cause problem. Do you have specifications of choke coil?

Sometimes also big internal resistance of capacitors can cause problems. Do you have specifications of capacitors or information on manufacturer/type?

Hi,

I use this circuit in 2 projects. I had a problems with transitions between high load and low or no load. I had also problems with circuit startup with AC adapter and laboratory power source. Behavior of this circuit was always different. Sometimes DC/DC was very "noisy" or in some undefined state. Solution was in compensation network. I changed capacitor in comp. network and everything was ok. In my situation was value of capacitor quite far from calculated values. From my previous experiences with switching power converters I often use paralel combination of ESR electrolyth capacitor and small ceramic or 1uF tantalum capacitor on inputs and outputs.