Mbed VOUT current

Development Boards MicroMod
1

Could someone please tell me what is the maximum current that can be drawn from the VOUT pin of the LPC1768 based Mbed board? I tried looking for this information in the datasheet, but couldn’t find it. Maybe I’m not looking at the right place.

I’m trying to connect the sparkfun Nokia LCD board, and the JPEG camera with the mbed, and I’m wondering if I can draw 484mA (324mA for the backlight, 100mA for the LCD and 60mA for the JPEG camera) from the VOUT pin directly. That would save me the trouble of using another 3.3v supply.

Thanks in advance!

-D

2

With that sort of load I’d use a separate regulated supply. It’s far more than the regulator on the mbed can deliver.

3

@leon: Thanks! That does make sense.

Could someone also point me to the electrical specifications of the mbed? I am somehow unable to find detailed specifications anywhere, which is kind of surprising for an NXP product.

4

http://mbed.org/nxp/lpc1768/technical-reference/

5

@rmteo1: Thanks. I had already seen that link, it doesn’t exactly specify how much current load the VOUT pin can bear.

Anyhow, for anybody interested in the future, I went through the schematics of the mbed, it has two LD1117S33 regulators, one for powering the internal 3.3v used by the board and one for VOUT. The regulator has a maximum load of 800mA.

The schematic can be found here: http://mbed.org/projects/handbook/svn/M … -005.1.pdf

6

This is what I see on that page:

Power

  • Powered by USB or 4.5v - 9.0v appiled to VIN

  • <200mA (~100mA with Ethernet disabled)

  • Real-time clock battery backup input VB

  • 1.8v - 3.3v Keeps Real-time clock running

  • Requires 27uA, can be supplied by a coin cell

  • 3.3v regulated output on VOUT to power peripherals

  • 5.0v from USB avialable on VU (only avilable when USB is connected!)

  • Current limited to 500mA

  • Digital IO pins are 3.3v, 40mA each, 400mA max total

7

That 800 mA is probably for the TO-220 package with a large heat sink.