Voltage regulator for a noisy power supply

Dear All:

I need a low noise power supply. I bought an SMPS, but it has lot of noise and transient spikes. To regulate the voltage and contain these spikes, I am thinking of building a voltage regulator, my requirements are 3.3 V - 5 V, and 1.5 A.

1. Which one would be more appropriate for me..LM317 based regulator or LM2596 based

2. For this current, do I need to worry about heating

3. Do I need to place an additional LC circuit to contain the ripples

Shilpa

jw0752 over 11 years ago

Hi Shilpa,

1. The LM317 is a linear voltage regulator which means that it will regulate to your chosen voltage by creating an internal resistance to dissipate the unused input voltage as heat. The LM317 is capable of the 1.5 amps that you mention. The peripheral components needed to hookup the LM317 are simpler than for the LM2596 and the TO-220 type case is able to be mounted on a heat sink and in fact must be at 1.5 amps. The output of the LM317 will likely have less ripple and spikes than the LM2596. The LM2696 is a switching type regulator and will require more external components. It is also a surface mount device and might be a little more difficult to mount and heat sink. Since it is a switcher it may also have some ripple and spikes though these will be minimal if it is properly engineered into the support circuit. In its favor is the fact that it can handle 3 amps.

2. Yes at 1.5 amps heat will be a consideration particularly for the LM 317.

3. This depends on how bad your primary supply is and how much load you put on the circuit. I would guess that there would be less problem with the LM317.

I have included Links to the Data Sheets for each part so you can see for yourself.

http://datasheet.octopart.com/LM317T-STMicroelectronics-datasheet-10835884.pdf

http://www.ti.com/lit/ds/symlink/lm2596.pdf

John
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