TI card question - problem?...

[bacteria]

Sorry guys, I know some of you with think that this topic has "been covered", but I seem to have run into problems, and am not willing to risk my N64/GBA project frying because of the TI card.

I got a TI card, same one as per Harshboy's diagram (sticky), the PTH080000. I wired in a 100uf capacitor as per the diagram, tried a couple of transistors I had (1.8ohm and 2.2ohm) as per the diagram I had and got 0 volts. Without a resistor I got 0.9v from pin 6 (using pin 1 as the negative, ground); without a resistor and just the capacitor, measuring from pin 4, I get 2.89v. Pin 4 on the TI card is "inhibit".

Query is that the findings above are not as per other people's experiences, which makes me jittery. I don't know if the 2.89v from pin 4 is stable or if the voltage is likely to rise higher (and fry the N64 mobo), if it decreases from this (making the N64 mobo not work) and if it is wise to use this card at all. I had a bad experience with my first N64 board - fried because of this very issue - voltage spiked, I got smoke, and fried the mobo - I can't afford this to happen to my current project, it is too advanced now.

I don't know why I am getting different results from doing what is stated Harshboy's sticky. Issue is that I have discovered that I can only get the Jumper Pak working on my portable (I use a 3v car adapter), there isn't enough power to drive the Expansion Pack. In saying this, I am not prepared to try out the TI card to find it fries my system - not worth the risk. The Jumper Pak plays almost all titles after all and the car adapter seems perfectly stable. There is a good argument which states to stay with the Jumper Pak as it works fine, after all.

I need to know why I got different results from the expected norm - I am unhappy to experiment with the TI card if it is likely to give me problems; so I thought I would ask you guys for advice as to why my results are wrong; is it wise to just use a 100uf capacitor (do I need one at all?) and use pin 4 and ground (2.89v) and is this going to spike or lose voltage? I know 2.89v, if stable, is fine for the N64; but is the TI card stable and consistent under load?? I am sure you understand my concerns...

I have tried the TI card with a 7.4v battery pack and my PSone 7.5v mains adapter; same results.

I would be grateful for assistance and comments please. In a couple of days time, if I don't go the TI route, I will just stay with Jumper Pak and finish the top of my project and mount the PSone screen in place - then it will be too late to bother with the Expansion Pack; hence my query at this stage.

[superdeformed]

I wired in a 100uf capacitor as per the diagram, tried a couple of transistors I had (1.8ohm and 2.2ohm) as per the diagram I had and got 0 volts.

Do you mean a 1.8 ohm resistor or 1.8k ohm resistor? If you did use 1.8 (or 2.2) then that could be your problem. The output range of the PTH08000 is 0.9-5.5V, and using TI's formula a resistor value of 1.8 would set it to 5.79V (if it could actually go that high). With a resistor value that low between pin 5 and ground, the regulator is probably going into thermal shutdown. You need between 1.8k and 2.0k to get close to 3.3V on the output.

Without a resistor I got 0.9v from pin 6 (using pin 1 as the negative, ground);

According to the datasheet, this is what it should do as it's the default output voltage.

without a resistor and just the capacitor, measuring from pin 4, I get 2.89v. Pin 4 on the TI card is "inhibit".

Pin 4 is an input pin used to disable the regulator's output. It's internally referenced to about 3 volts, but it's not meant to provide any amount of current. There's no block diagram for the module in the datasheet so I can't say for sure, but trying to drive a load off of it would likely just force the regulator to shut down. (In short, you can't use it.)

[bacteria]

Thank you superdeformed for your reply, appreciated. I don't understand the datasheets (I did try). I didn't ask for this help out of lazyness but out of lack of knowledge, this type of electronics is something I can copycat but not create, if that makes sense.

I will try and get this component tomorrow and test it on Tuesday. If I can't get it to work; or I have damaged the TI board, I will ditch the idea and stay with the car adapter which I know works fine. I can't afford to screw up my project for this issue. I presume, if I get the magic figure of about 3v that I have rigged up the card right??

I knew I must have done something stupid as other people are using this card fine.

When you say "thermal shutdown", does that mean I have caused it permanent damage, or it just shut itself off before it got damaged?

[superdeformed]

The module has thermal protection that turns off the output if things start to get too hot, although I don't know if it does anything for the other pins. Hopefully nothing else blew, but if you still get 0.9V on pin 6 with no resistor attached that's a good indication that your regulator still works.

Once everything is hooked up correctly you should get the output voltage that you selected even without a load on the regulator. You can tell what the voltage should be based off of your resistor and TI's formula. The formula (simplified a bit) is:

R = 8910/(Vout - 0.9) - 1820, or rewritten, Vout = 8910 / (R + 1820) + 0.9, where Vout is the voltage output you want and R is the value of the resistor you should use.

To get as close as possible to 3.3V you would ideally want a 1.87k resistor, but either 1.8k or 2.0k will get you within 2-3% of that.

[timmeh87]

you said you were taking power from pin 4?

that pin is for shutting the regulator off. you shouldn't hook anything up to it, it cant supply power.

Have you come across this diagram yet? it may help.

http://i17.photobucket.com/albums/b64/H ... iagram.png

also, if its not being loaded it probably wont break regardless of how you set it.

[bacteria]

Thanks for the feedback guys, appreciated. We all have different skills here, that is the great thing with a forum, diversity of knowledge; there are always people to give a problem to and will assist with answers. Thanks. I will have an experiment!

Ok, tried it, I desoldered some transisters from a dead mobo I had from a telephone board I had, which looked right; I could only get 5.8v or 4v output from the required pins whatever I did on the TI board. Perhaps my TI board is defective. Oh well, I don't have much faith in this anymore, so I will stay with my car adapter; better the devil you know than the devil you don't, as the saying goes. I managed to get some TI free samples en-route, and can play with them at a later time when they arrive and I have finished my current project.