Build Thread for TPA BIII + Ian Async I2S FIFO + OPC NTD1 + Salas SSLV - Page 30 - diyAudio
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Old 27th November 2012, 11:04 PM   #291
qusp is offline qusp  Australia
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bigpandahk, mate I think you mistake my comment which was meant for someone else... sure this is a little familiar territory, but hey I admire your enthusiasm and patience (hmm interesting choice of words), Ian offered you the board freely, but yeah you gotta look both ways before crossing the road man, its what brings you down every time.

no attaching a sink to the top of the chip is extremely unlikely to help, youde be lucky to dissipate 10% out the top, due to the thermal impedance of the package. the powerpad is there for a reason, on that thing you used it has nothing to do with heatsinking, some use it for a voltage reference. you are after DGN20 POWERPAD, powerpad is part of the package name, not just a trademark, without that the thing will come close to frying itself even without a load, hell, maybe even quicker without a load...

you cant continue to play this loose mate, especially given in a few weeks you are going to be putting 100VDC across the output of your BIII with only a couple zeners and a hopefully short free board between them. that sort of currents and voltage can sizzle and pop components. you need to stop adding new stuff...now! so that the system is stable, known and all fully functional. otherwise you could easily see the dac and several hundred worth of resistors go up in smoke before you know it and to replace them wont be as cheap...

glad its got a hole Ian, that works quite well. the same technique I/we used for a DGN14 (LT3032) and lt1963A/1764A, but well its a lot smaller and has 2 holes in islands separated by 0.5mm one ground, one neg rail... the Ti should be a walk in the park. I hadnt spotted the holes, but my comments stand...for other reasons

Last edited by qusp; 27th November 2012 at 11:11 PM.
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Old 27th November 2012, 11:21 PM   #292
AR2 is offline AR2  United States
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I find this to do miracles sometimes. It is also right to say that, if not used properly could be a big nightmare. In this case where soldering needed to be done on the bottom flat surface of the chip it might do a really good job while trying to hand solder. Obviously if used with stencil and in reflow oven than that is what is meant for, but for hand work, one has to be careful. And it does not need to be this specific brand

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Old 27th November 2012, 11:23 PM   #293
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Quote:
Originally Posted by hochopeper View Post
I thought I had seen that hole when looking at the prototype pcbs when you posted photos. I'm still not sure about getting a normal soldering iron to the other pads of the chip and producing a neat or reliable job on them. Maybe I'm just looking for any excuse to buy a new soldering station??


I agree with you on the recommended loads there. For an isolated micro controller and LCD display (all isolated from the audio electronics) I don't think we should worry too much about noise performance An LM317 would do everything needed.

Chris
Yes, it needs a bit skill on soldering the QFN. I think the SMT rework station is a necessary though the thermal pad no problem for a normal iron.

This youtube may help:
How to Solder QFN MLF chips Using Hot Air without Solder Paste and Stencils - YouTube

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Old 27th November 2012, 11:33 PM   #294
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Quote:
Originally Posted by qusp View Post
you cant continue to play this loose mate, especially given in a few weeks you are going to be putting 100VDC across the output of your BIII with only a couple zeners and a hopefully short free board between them. that sort of currents and voltage can sizzle and pop components. you need to stop adding new stuff...now! so that the system is stable, known and all fully functional. otherwise you could easily see the dac and several hundred worth of resistors go up in smoke before you know it and to replace them wont be as cheap...
I agree.


bigpandahk, The calcs I did above were to show how easy it would have been to calculate the temps expected before just trying it and waiting to see what would happen.




Also, what were you planning to use as an input to these regs?
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Old 28th November 2012, 12:45 AM   #295
qusp is offline qusp  Australia
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obviously I meant DFN20 I was thinking of the DGN8/16 lol too many codes
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Old 28th November 2012, 01:33 AM   #296
syklab is online now syklab  Hong Kong
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Quote:
Originally Posted by iancanada View Post
Hi bigpandahk,

Don't use that adapter, it was not designed for a power supply. I'll send you a couple of my TPS7A4700 PCBs for a try.

Ian
Hi Ian,
I didn't mean to ask for anything free and never did in this DIY community, I am more than happy to pay for anyone's desgin work. Since this regulator pcb is not on the curent GB that's why I ask to see if it would be available, I like the size of your regulator PCB. I knew there is a EVM for only 20$ but it is bigger, 2.5" x 1.6". Anyhow, I will order a EVM kit to play with. No hard feelings and I enjoy your work very much.

Cheers

Last edited by syklab; 28th November 2012 at 01:59 AM.
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Old 28th November 2012, 02:23 AM   #297
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quap : "its what brings you down every time." - it's really true, I failed a lot and lost lot of money but still not learnt enough from experience

I will reconsider the whole power scheme for the project :
SSLV(1) for Buffalo, OTTO II
SSLV(2) for WaveIO, SideCar
7805 or LM317 for relays and battery management board
7812 for Arduino with LCD
TPS7A4700(1) for DSD - USB converter (with Ian's PCB)
TPS7A4700(2) for Teleporter

Batteries for i570, FIFO and SPDIF

The size of the casing will limit the quantity of transformer to be used. I have to combine them, may be one for the SSLV(s), one for the 78xx and the third one for the TPS. Including the two for NTD1, I hope there is enough space for 5 transformers.
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Old 28th November 2012, 02:33 AM   #298
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Quote:
Originally Posted by bigpandahk View Post
quap : "its what brings you down every time." - it's really true, I failed a lot and lost lot of money but still not learnt enough from experience

I will reconsider the whole power scheme for the project :
SSLV(1) for Buffalo, OTTO II
SSLV(2) for WaveIO, SideCar
7805 or LM317 for relays and battery management board
7812 for Arduino with LCD
TPS7A4700(1) for DSD - USB converter (with Ian's PCB)
TPS7A4700(2) for Teleporter

Batteries for i570, FIFO and SPDIF

The size of the casing will limit the quantity of transformer to be used. I have to combine them, may be one for the SSLV(s), one for the 78xx and the third one for the TPS. Including the two for NTD1, I hope there is enough space for 5 transformers.
bigpandahk,

Try this way to soldering the QFN, I believe you will make it .
How to Solder QFN MLF chips Using Hot Air without Solder Paste and Stencils - YouTube

Ian
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Old 28th November 2012, 02:40 AM   #299
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Originally Posted by iancanada View Post
bigpandahk,

Try this way to soldering the QFN, I believe you will make it .
How to Solder QFN MLF chips Using Hot Air without Solder Paste and Stencils - YouTube

Ian
Thanks Ian.
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Old 28th November 2012, 02:40 AM   #300
qusp is offline qusp  Australia
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hey man, no need for the bloody head, youre smart enough and from what ive seen skilled enough with the solder station, just not patient enough. I dont know if you do a lot of this stuff after long days at work/college etc? but many of the mistakes ive seen are mostly from rushing, or just thinking things will be OK, without KNOWING they will be ok. none of this is rocket-science, you can do it, but as above, you need to break it down into sub circuits, plan out what the voltage drop will be, trace out the ground connections, make each one of those sub-circuits work in isolation, then load tested with a suitable resistor to simulate what the regulator, or amplifier will see in use.

then and only then connect it to the real load, leave it connected, try and predict what the voltage drop should be based on the predicted load current, see how close that is to reality. THEN plan your next move, not immediately, chill on it, listen to some tunes and move on.

the above is a very good start, draw out the connections and what the expected input voltage, output voltage and difference between those is to give you the heat (not here, a simple flow chart type program will be) then you can use that to work out hoew much heat will need to be burned off, or if heat is not a concern, what the power/current budget is for that leg of the circuit etc etc

now i'm buggered,I gotta crash, you can do this, but youve gotta be smart about it, its not mechano

Last edited by qusp; 28th November 2012 at 02:43 AM.
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