STM CircleOS forum / Primer2 expansion board

FR4 · 2009-01-27 11:14:48

A question to the hardware developers:

How much current can VCC2V8 on Pin1 JP2 drive?

Francis · 2009-01-27 12:53:47

If we look at the datasheet of U9 (the 2.8V regulator), it could drive up to 800mA (max output current), but the implementation is not so good and I expect that 100mA would be good (check that your primer2 has been corrected as specified at: http://www.stm32circle.com/resources/known.php ). I believe that we could encounter an overheating with higher currents.
The typical current (digital parts of the board except RLink) from U9 is around 40mA. Therefore I consider that U9 could drive typically 50mA for the additional devices on the extension board.
Anyway, I will make some measurements on one primer and I will report the results.

FR4 · 2009-01-27 14:14:45

I think overheating is not the issue a that point. Maximum current is depending on the ratings of U9 and on the ratings of the coil L2. How much is the maximum current for L2? And at what current is L2 saturated?
Maybe you can give me the datasheet for L2?

Francis · 2009-01-28 09:22:42

We will publish the datasheet of L2 in the 'resources' section.
BTW, I made some measurements with a potentiometer as load on the extension board.
Up to 150mA (current consumed on the extra load) the voltage is still stable (2.84V). It falls down between 150mA and 200mA. The internal consumption could be also increased by a very active application (but probably less than 25mA).
Conclusion: let's consider 100mA as a good nominal value.

# 1 2009-01-27 11:14:48 Primer2 expansion board

Primer2 expansion board

# 2 2009-01-27 12:53:47 Primer2 expansion board

Re: Primer2 expansion board

# 3 2009-01-27 14:14:45 Primer2 expansion board

Re: Primer2 expansion board

# 4 2009-01-28 09:22:42 Primer2 expansion board

Re: Primer2 expansion board

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