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Old 13 May 2010, 19:10   #21
Zetr0
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Bookmarked.
+1!!! thats damn handy!!!

thanks for the find'n share Anemos

Quote:
Originally Posted by kipper2k View Post
Thanks Anemos,

Thats a nice little tool. The IC typical current is 10 - 15ma so using that tool it says at 12v input, and 3.3v output with a typical current of 10ma, the divider should be 870 ohms/330 ohms. I'll play around later and see if theory holds true

thanks
erm.... not sure about them numbers my friend....

I just put in 12volts at 100ma (0.1amps) with an output of 3.3volts

the result was as follows - R1 = 87 Ohm & R2 = 33 ohm
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Old 13 May 2010, 20:38   #22
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+1!!! thats damn handy!!!

thanks for the find'n share Anemos



erm.... not sure about them numbers my friend....

I just put in 12volts at 100ma (0.1amps) with an output of 3.3volts

the result was as follows - R1 = 87 Ohm & R2 = 33 ohm

Hi Zetr0,

i re-read the specs and found out the ampss was 10ma and not 100, I think i initially had the same values as you and then when i ploughed in 10ma it came up with the ones i have listed now. I just got my parts today too, OMG! those chips are tiny, i am going to go blind soldering them in, i didnt realise just how tiny those buggers were.. I'll post a pic later.
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Old 13 May 2010, 21:02   #23
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Sweet!!!!

looking forward to them pics!
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Old 13 May 2010, 21:17   #24
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here ya go, i included a ballpoint of a pen and a vga adapter to illustrate the size of the chip, its gonna be fun lol.

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Old 13 May 2010, 21:39   #25
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oh man.. you need microscope to solder that.. :O
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Old 13 May 2010, 23:37   #26
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I thought some form of soldering iron would be required. Oh well, live and learn.
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Old 14 May 2010, 00:32   #27
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Hello,

@Kipper2K

You can run the op-amps off +/-5V, the power per-op-amp increases to 11mA though!

My preferred part for creating -5V is the Maxim MAX764, $6.10 each from Digikey. If you are interested in this part, I can dig out the partlist of the design I have used 3 times now.

Resistive dividers are fine for 1-2mA but the output varies with supply voltage and as the resistor heats up. For the 100mA you were looking for and using 87/33 ohm, you would dissipate 1.2W on a 12V supply.

Soldering those parts is not too bad, just use plenty of flux. To remove them, just blob solder over all the pins and pick it up with tweesers.

Today I was wire linking to pins on a part with the same 0.5mm pin spacing, had to lift the pin from the pad, solder a wire to the pad and an additional wire link to the pin that had been lifted. You need a microscope to do that job!

Looking at your PCB layout, can I make an improvement?

Move the crystals away from the video inputs on the first PCB. You have the crystal outputs running underneath the video inputs, with no guard traces or power plane. You are asking for noise problems.

Also if you are driving and AD724/AD725 and potentially the LT65501, how are you terminating the video?

I would recommend using 150 ohm resistors by the AD724/AD725 and by the LT65501, the resistors in parallel would give the 75 ohm termination required by video. You would need to track the RGB inputs as a matched T pair to reduce reflections.

Good luck, look forward to future updates.

Ian
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Old 14 May 2010, 14:50   #28
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You can run the op-amps off +/-5V, the power per-op-amp increases to 11mA though!

My preferred part for creating -5V is the Maxim MAX764, $6.10 each from Digikey. If you are interested in this part, I can dig out the partlist of the design I have used 3 times now.

Ian
Hi Ian,

thanks for the input, i'll reply to the other questions later, i jusrt want to run this part by you i found at Newark.com and digikey which looks like it will do the job using +5v and inverting it to -5v @100ma which should be fine

http://search.digikey.com/scripts/Dk...%23TRMPBFCT-ND
($4.69 each)

and...

http://www.newark.com/linear-technol...-ic/dp/25R3034
($2.60 if you buy 25, which i probably would)

They are both the same item. It looks like it just needs a couple of small caps for the external circuit. How does this looks for a suitable regulator ?

http://www.linear.com/pc/downloadDoc...33,P2152,D2135


edit. none in stock, lead time 34 days... minimum 100 order

Last edited by kipper2k; 14 May 2010 at 15:15.
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Old 14 May 2010, 15:30   #29
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I just found this adapter board for the LT6550/1 and for all MSOP 10 IC's.

http://canada.newark.com/roth-elektr...dCircuits_None

the price is... yo'ull see when you click on it.


So, this is what i am going to do, i am going to trace out some of these small adapter boards on a board and get Futurelec to make them, I will put on different types of adapter circuits on each board so that it will make it easy for people to use them for test boards etc. Depending on whether people want some of these boards made for different types of IC's then i will make them. The price of a 3" x 4" single sided board would be ~$7.00 each which would cover all my costs. this would be if i was to get 50 boards made. each board would have as many adapter circuits as i could squeeze on each board and with enough room between each little circuit on the board so they could be dremelled/cut into individual adapters.

If i get enough interest i will get them done. Let me know what IC adapters you would like to see on the board.. The idea is to get as many on a board as we possibly can.

ps.... you can fit about 11 of the msop adapters on a 4" x 3" board

just wondering if i should start a new thread with this ?

Last edited by kipper2k; 14 May 2010 at 15:49.
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Old 14 May 2010, 18:18   #30
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I thought some form of soldering iron would be required. Oh well, live and learn.
Brilliant humour
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Old 16 May 2010, 03:28   #31
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Hello,

@Kipper2K

You can run the op-amps off +/-5V, the power per-op-amp increases to 11mA though!

My preferred part for creating -5V is the Maxim MAX764, $6.10 each from Digikey. If you are interested in this part, I can dig out the partlist of the design I have used 3 times now.

Ian
I sent an email to Linear technology about the component diagram and asked if it definately required a -3.3v supply. They said the circuit should be good with +5v and -3v. The -3v @ 100ma can be provided by +5v input which will invert it to -3.3v (LTC-1983-3, cost $4.69), and uses just 3 small ceramic caps


Quote:
Originally Posted by Stedy View Post
Looking at your PCB layout, can I make an improvement?

Move the crystals away from the video inputs on the first PCB. You have the crystal outputs running underneath the video inputs, with no guard traces or power plane. You are asking for noise problems.
Ian
Here is a revised layout Ian, I rerouted the traces from underneath the crystals. I won't be putting a switch to control the active crystal on it, I'll just put a jumper block on the 6 pin header. Most people will only use one video mode anyway.




Quote:
Originally Posted by Stedy View Post
Also if you are driving and AD724/AD725 and potentially the LT65501, how are you terminating the video?
I am still going to use te Narmi Circuit (same as Amigamaniacs for the S-Video output using H + VSync)

The component portion of the circuit is right from the Datasheet of the LT6550, I will take the CSYNC from the Amiga (Pin 10), the same as Narmi in his Component Schematic and inject it into the Y output. I noticed he has a 680 ohm tied into the Y output. The LT6550 diagram makes no mention of inserting a resistor into the green component output. I added a pad for a zero ohm resistor in case i need to cut the trace and add a resistor if i need to.

Quote:
Originally Posted by Stedy View Post
I would recommend using 150 ohm resistors by the AD724/AD725 and by the LT65501, the resistors in parallel would give the 75 ohm termination required by video. You would need to track the RGB inputs as a matched T pair to reduce reflections.
I done a little bit of reading on impedence reflections and its over my head for the most part, i understand there is crosstalk in unbalanced circuits but not sure how to apply them here.

I think the board is done, i'll do some more checking before i commit, i'm still waiting for a couple more components so i have to wait for them to make sure i get the layout right.
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Old 17 May 2010, 19:27   #32
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Heres the board i am going to submit to Futurelec. It looks to be good, so i am going to get a few sample boards made up. I'll post the circuit for those people that want to take a look at it. Please don't assume its error free. The board is actually in 2 halves. the left half is the circuit i created that will accept Composite, S-Video and Component input (although i didn't put the composite header on as 99.9% of people will probably never use it at all). The Svideo part of the circuit is the same as mine and Amigamaniacs (using the AD724) so the Svideo should work fine, the Component portion is untested and is using 2 of the LT6550 triple video amp. The 23 pin header is not a standard 0.100" connector, the pins are actually 0.110" apart on the ones i have

The right side of the board contains Narmi's new component circuit that he has recently created using the LMH6722. He was having issues with the -ve voltage portion of the circuit, and i am not sure what his new workaround is. I have opted to use the LTC1983-3 inverter that hopefully will provide a stable -ve power.



Heres the PCB created with ExpressPCB...

http://www.kipper2k.com/amiga/dualboard.zip

Last edited by kipper2k; 17 May 2010 at 19:33.
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Old 17 May 2010, 22:38   #33
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Hi

@Kipper2K.

Hoopefully this illustrates the point on the impedance matching and track length matching for reflections:



The layout looks reasonable.

Can you add a copper fill to the underside of the board to increase the ground plane area?
This always helps to reduce noise on a double sided PCB.

HTH

Ian
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Old 18 May 2010, 15:27   #34
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Thanks for the input again Ian. I made changes (again). The boards now have a ground plane. This in fact allowed the removal of quite a few traces and allowed me to keep the traces further apart.

I sent the schematic away for manufacture last night, got up this morning, realised i made a few mistakes, had to send a "forgive me" email to Futurlec and "please use this one" instead.

I then had breakfast, took another look at the schematic, and said "oh F*%4" i had the -5 and +5 backwards. Soooo, another email "Forgive me, I'm stupid" was sent with version 3 telling them to junk the other 2 board schematices. I am not looking at the circuit again cos there aint any way i going to send em a "Forgive me, I have no idea what planet i musta been on" email, so i'll just save all my "Oh F*%$s" until i get the board and buy a roll of duct tape


So, hows your day going lol

PS... do not use the schematic i posted earlier... in fact i am going to kill the link.
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Old 18 May 2010, 15:43   #35
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ahh the wonders of a good nights sleep

thanks for the updates, hope this works out as planed
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Old 19 May 2010, 10:37   #36
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How many mA do you need? Two resistors make a voltage divider.
Much better to use zener. At least it provides some form of regulation.
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Old 27 May 2010, 23:08   #37
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Hi!

Kipper2k, i don't know if that will interest you, but i found some schematics for a a negative voltage regulator using zener diode

http://img215.imageshack.us/img215/9845/stab1118.jpg

Last edited by sanjyuubi; 27 May 2010 at 23:20.
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Old 28 May 2010, 02:33   #38
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Hi!

Kipper2k, i don't know if that will interest you, but i found some schematics for a a negative voltage regulator using zener diode

http://img215.imageshack.us/img215/9845/stab1118.jpg

Thanks for the schem Rafgc, unfortunately it looks like that needs a -10v input. I can't use the -ve voltage on the Amiga video output as its only rated at 10ma. I need at least 60ma so i had to go with a LTC 1983 inverter thats rated at 100ma using +5v input. Theres not a lot of cheap choices when trying to get a -ve from a +ve. Boards should be here next week hopefully
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Old 30 May 2010, 06:11   #39
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Heres a progrep on where i am at the moment on this project, i managed to shrink down the board size to about 1.6" squ. That means that it should fit inside this case shown below.

Component, Svideo, composite and stereo audio outputs







showing DB15 input that will allow all the useful inputs from devices that we output from, including the Amiga of course




Another shot of the 15 pin input and the power LED for those people that like the warm glow of a Blue LED (or other colours)





Another look, Case size btw is 2.6" square

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Old 30 May 2010, 13:34   #40
Anemos
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looks nice!, working already ?
can you upload some screen ?
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