Objective Development Forums

Diodes in place of 3.3V LDR?

2008-11-06T19:41:26+02:00

I'm still pretty new to electronics, so I had not known about the forward voltage on diodes. Thank you for the explanation. Very helpful

Statistics: Posted by morrog — Thu Nov 06, 2008 7:41 pm

Re: Diodes in place of 3.3V LDR?

2008-11-06T11:54:57+02:00

morrog wrote:...two diodes in place of a 5V to 3.3V regulator. I can't image how two diodes are supposed to drop the voltage down from 5V to 3.3V.

A silicon diode has a forward voltage (Flussspannung) of about 0.7 V. Two diodes will drop the 5V down to 5V - (2* 0.7V) = 3.6V, which is sufficient low voltage for the USB lines. An extra advantage is that diodes have no quiescent current, therefore, standard conform USB sleep mode (less than 500 µA current) is easiest with these two diodes.

Statistics: Posted by henni — Thu Nov 06, 2008 11:54 am

Diodes in place of 3.3V LDR?

2008-11-06T08:24:08+02:00

On the homepage for AVR USB, the schematic shows two diodes in place of a 5V to 3.3V regulator. Would that really work? I can't image how two diodes are supposed to drop the voltage down from 5V to 3.3V.

Thank you.

Statistics: Posted by morrog — Thu Nov 06, 2008 8:24 am