# general questions regarding electric design

Discussion in 'Electronic Basics' started by Stijn Goris, Apr 1, 2004.

1. ### Stijn GorisGuest

hi all,

I m designing a (virtual) product for my university. I don' have a lot of
electronic knowledge.
here are some questions:
- I want to split an incomming electric wire (inside a product eg
microwave). Go from 2 electric wires to 4. Does someone know what I have to
use for this?
- I use some chips on my PCB (CPU, flash memory component, RTC). Does a chip
always needs its own klockpulsgenerator or can I use one on the PCB and
connect all the componets to it. Someone knows a website where I can find
info regarding klokpuls generators?
- I m looking for a powerfeed. Has to convert 110 or 220-230 AC to -> 3.3 DC
.. Someone knows where I ca nfind such a device.

I hope my questions are clear enough.

kind regard
Stijn

2. ### Amnon PomerantsGuest

Hi
When you come to distribute clocks over your PCB I recommend two major
points:
1. Use point to point only, and not daisy chain
2. Separate the clock sources for different functionalities.
Meaning don't use same oscilator to drive both the CPU block and for example
your Telecom block, even if both need same frequency.

Point to point will be achieved by connecting a clocks distributor chip to
Use for that a special chip and not a regular buffer.
Look at IDT/ PRECOM/ CYPRESS/ TI for such chips

For the AC--> DC converter , many vendors provide it,
a small search in Google will show you.
I myself have used HiTron, ASTEC, LUCENT

Amnon

3. ### Seth KosterGuest

- I m looking for a powerfeed. Has to convert 110 or 220-230 AC to -> 3.3 DC
Normal AC can be rectified with three basic circuits, the half
wave
rectifier, the full wave rectifier and the bridge rectifier. The
circuit above is a half wave rectifier.
The half wave just puts a diode in the circuit, allowing only one
half the AC waveform to flow while the negative half is cut off. The
full wave uses two diodes and the center tap of a transformer to
convert both halfwaves from each end of the transformer to positive
while completing the path to the center tap (ground). The bridge
uses four diodes to rectify without using a center tap. In any of
these cases you'll get pulsating DC and will want to filter it using
capacitance and/or inductance.
Check out a google search on any of these and you should find a
schematic (all very easy).
Polyphase AC uses other rectification configurations, so check your
appliance out.
To limit a DC voltage one could use a zener diode in parallel with
the limited circuit (rail to rail if full DC circuit needs to be
limited). Check the requirements of the zener to be sure it can
handle the output of the ps. Another possibility is a voltage
regulator.