VRM spec sheets usually mention the maximum current, but don't seem to say anything about cooling, other then maximum temperature. Do they expect it to be cooled sufficiently, or will they not meet the maximum operating temperature under maximal load? If, for example, I had an LM2596 step down converter, could I use more then the specified 3A maximum by putting a heatsink and fan on the IC?
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1\$\begingroup\$ 1) what's a VRM ? I know you mean a voltage regulator but VRM is not a commonly used acronym. 2) An LM2596 is a step down converter. 3) look at the datasheet of the IC to see if you can use it at a higher current. If it is specified ofr 3 A why load it with more ? Why not get a 5 A regulator instead. Sufficient cooling is always needed. \$\endgroup\$– BimpelrekkieCommented Feb 1, 2017 at 22:03
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\$\begingroup\$ Even if a regulator can work at a higher current, even with sufficient cooling, it might fail sooner than expected. \$\endgroup\$– BimpelrekkieCommented Feb 1, 2017 at 22:22
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\$\begingroup\$ Matthew, I'm guessing VRM means Voltage Regulator Module - is that what you mean? As already commented, it's not a common term or at least not common in my experience. \$\endgroup\$– TonyMCommented Feb 1, 2017 at 22:37
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\$\begingroup\$ I thought VRM was a popular term for either a step up or down converter. I guess not. @FakeMoustache Sorry, that was a typo. It is step down. \$\endgroup\$– MatthewCommented Feb 1, 2017 at 22:44
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\$\begingroup\$ VRM is a term peculiar to PC mainboard industry of about 20 years old, from the era of first VID-controlled power supplies for PC CPU. In early days they were designed in a form of vertical add-on board, and later become incorporated on-boards, where the M part (module) has lost its meaning. Power characteristics of the core power supply for Intel processors were entitled as "VRM specifications". \$\endgroup\$– Ale..chenskiCommented Feb 1, 2017 at 23:22
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Look more closely at the data sheets (LM2596 data sheet) - they will invariably give information such as the maximum junction temperature and the thermal resistance. In the case of the LM2596 the 3A rating is at 25 deg junction temperature. There is also a section on thermal considerations (p33) showing how to calculate the operating temperature and recommended heat sinking approaches.
The maximum current is often limited by the circuitry to protect the device in case of short circuit this is in addition to any thermal aspects.
Frequently you will find it is very difficult to meet the maximum ratings as it will be difficult to keep the device cool enough.
answered Feb 1, 2017 at 22:05