LPC812 - on board power availability

Question about power
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olzeke51
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LPC812 - on board power availability

Post by olzeke51 » Fri Jun 06, 2014 3:21 pm

I was evaluating the 812 tssop20
5v from the usb dongle is zener'd (I assume - there is a diode on the pcb)
down to approx 3.1v.

I connected an LED VSS to VDD and the voltage dropped about 150mv or so
The LED was drawing approx 3.6ma (per my Harbor Freight/Centec DMM)

what power is available - considering the size of the traces and SMT diode ??

I want to connect a 1K pot, some I2C resisters, and a 3 terminal temp sensor to it.
an LED possibly - (definitely for troubleshooting)



basicchip
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Re: LPC812 - on board power availability

Post by basicchip » Fri Jun 06, 2014 6:45 pm

Love those Harbor Freight Centec meters, it is part of my recommendations for a lab.

Yes there is a 2V Zener diode on the board that drops the 5V to a nominal 3V. It takes advantage of the wide power supply range of the LPC812.

I wouldn't try to power a whole lot of stuff, but the diode is rated at 150mW so that is 75 mA at 2V, and the LPC812 takes less than 5mA. And by using a diode you can always have an external 3.3V regulator to power the chip and system.

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