LM2674 3.3Volt - Do I run into any problems using this buck converter with low I_out?

Thread Starter

Alex009

Joined Jul 2, 2014
33
Hello everyone,

as the thread title (hopefully states):
Since I have no experience in circuit design with DC/DC converters and potential issues I would like to ask if you can use the
LM2674 in combination with a low output current by adapting the value of L and C_out?

The output current would be in the range of 150µA - 700µA [depending on the amount of devices connected].

DataSheet of the DC/DC-converter

DataSheet of the devices driven by the DC/DC-converter

Input Voltage: +15 Volt
Output Voltage: ~ +3.3 Volt [fixed voltage version of the above mentioned DC/DC]


A second question would be: do I have to consider anything special when chosing an inductor [besides of the correct value] - since there is no appropriate inductor in the Datasheet for such low currents.

Thank you.
BR
Alex
 

Papabravo

Joined Feb 24, 2006
21,159
There are many characteristics of an inductor that can cause you problems in a buck converter. I'm not familiar with that particular part, but most manufacturers of these parts have application notes on component selection that are published in addition to the datasheets. One recommendation is to do a preliminary PC board design or purchase an "evaluation" PC board. Trying to evaluate these parts on a traditional breadboard can quickly lead you astray.
 

OBW0549

Joined Mar 2, 2015
3,566
Since I have no experience in circuit design with DC/DC converters and potential issues I would like to ask if you can use the LM2674 in combination with a low output current by adapting the value of L and C_out? The output current would be in the range of 150µA - 700µA [depending on the amount of devices connected].
I've never used the LM2674, but from reading the data sheet it looks like you could.

However, I don't think there would be any advantage to using this part, because the efficiency would be terrible: from the data sheet, the LM2674's quiescent current (that is, the current it draws to power it's own internal circuitry) can be as high as 3.6 milliamps-- some five times the maximum load current you'll be asking it to supply.

At such low output currents, you usually get the highest efficiency (and the lowest cost and fewest headaches) from a micropower linear regulator. A lot of my designs have used the LP2951 because of its versatility, but there are many, many other similar products on the market.
 
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