Core Board
Hi, I suggest we at first should decide DAC chips we are going to make boards for, later decide exact voltages needed.
Primary list is current output type: AD1865, PCM1704, PCM63, TDA1541.
Those need only -15Va; -5Va; -5Vd; AGND; DGND; +5Va; +5Vd in general.
Earlier I had idea we need separate +12V or +15V for CCS of 2mA injection into TDA1541 outputs, but possibly CCS can run from +5Va input. Connecting CCS to +5V digital does not look correct.
Thanks
Saulius
Hi, I suggest we at first should decide DAC chips we are going to make boards for, later decide exact voltages needed.
Primary list is current output type: AD1865, PCM1704, PCM63, TDA1541.
Those need only -15Va; -5Va; -5Vd; AGND; DGND; +5Va; +5Vd in general.
Earlier I had idea we need separate +12V or +15V for CCS of 2mA injection into TDA1541 outputs, but possibly CCS can run from +5Va input. Connecting CCS to +5V digital does not look correct.
Thanks
Saulius
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Core Board
We are talking about separate board, compatible in digital signals and connectors and size with I2S-PCM board.
It should be designed for set of current type DAC chips to make stereo balanced conversion (actually four PCM channels in dual stereo, one power set per stereo).
In case of big mono DAC chips like PCM63 we are going to have two PCM channels only on core board - this can be stereo or mono balanced, it is up to solution of digital I/O (DL and DR or DL and DLn). In case of mono balanced way I guess power supply should not be dedicated to one DAC chip.
Saulius
We are talking about separate board, compatible in digital signals and connectors and size with I2S-PCM board.
It should be designed for set of current type DAC chips to make stereo balanced conversion (actually four PCM channels in dual stereo, one power set per stereo).
In case of big mono DAC chips like PCM63 we are going to have two PCM channels only on core board - this can be stereo or mono balanced, it is up to solution of digital I/O (DL and DR or DL and DLn). In case of mono balanced way I guess power supply should not be dedicated to one DAC chip.
Saulius
core board
Now I relized that AD1862 require only one pair of +/-12V because:
"The AD1862 operates with ±5 V to ±12 V supplies for the digital power supplies and ±12 V supplies for the analog supplies.
The digital and analog supplies can be separated for reduced
digital crosstalk. Separate analog and digital common pins are
also provided. The AD1862 typically dissipates less than
300 mW."
Now I relized that AD1862 require only one pair of +/-12V because:
"The AD1862 operates with ±5 V to ±12 V supplies for the digital power supplies and ±12 V supplies for the analog supplies.
The digital and analog supplies can be separated for reduced
digital crosstalk. Separate analog and digital common pins are
also provided. The AD1862 typically dissipates less than
300 mW."
Core Board
So we need to add AD1862 to the list:
Current list of DACs: AD1862, AD1865, PCM1704, PCM63, TDA1541.
Voltages: -15Va; -12Va; -5Va; -5Vd; AGND; DGND; +5Va; +5Vd; +12Va.
So we need to add AD1862 to the list:
Current list of DACs: AD1862, AD1865, PCM1704, PCM63, TDA1541.
Voltages: -15Va; -12Va; -5Va; -5Vd; AGND; DGND; +5Va; +5Vd; +12Va.
Core Board
Ian said: "I'll take care of the PCB design and prototyping."
Well, this excludes D20400a which would need +15a but I hardly believe anybody will make a core board for that.
I'm using Altium for schematics/pcb design.
Ian said: "I'll take care of the PCB design and prototyping."
Per our discussions with Ian from the I2S-PCM thread, AD1865 and TDA1541A will be the first, probably PCM1704 next.
Agree we should use separate pins for all voltages. This seems OK for me.
Well, this excludes D20400a which would need +15a but I hardly believe anybody will make a core board for that.
Agree,
One thing is very important: Analog and digital power supply should be separated from each other. As signal source of whole system, AGND and GDND should only be connected at one point on DAC.
By considering mostly we are gonna use good shunt or low noise power supply which has only one voltage output on each, I think we need following power supply options for connectors
+5V, GND (analog)
-5V, GND (analog)
-15V,GND (analog, for TDA1541A only)
+5V, GND (digital)
-5V, GND (digital)
So, at least, 10 pins in total is required for power supply connectors.
Core board works with high performance external IV for sure.
vzs could only decide the size and dimensions after power connectors are determined.
Type and P/N of power connectors and I/V output connectors should be take into consideration.
Ian
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Core Board
Few power connectors if somehow strange to use with one complex PSU - for example with Oliver's [dvb project] Salas shunt regulator board for TDA1541.
Anyway it is ok, just some of GND pins on core board will be unused.
Zsolt mentioned we should try to make output without current offset.
So I'm sure we need to have CCS of 2mA injection into outputs of TDA1541 on Core Board...
Few power connectors if somehow strange to use with one complex PSU - for example with Oliver's [dvb project] Salas shunt regulator board for TDA1541.
Anyway it is ok, just some of GND pins on core board will be unused.
Zsolt mentioned we should try to make output without current offset.
So I'm sure we need to have CCS of 2mA injection into outputs of TDA1541 on Core Board...
We should use separate 2pin connectors - so digital supply connectors can be placed away from analog ones - less crosstalk between ground return currents.
As Marek mentioned +/-12 is needed by AD1862. We can use the +/-5V connector (let's better call it +/-Va) for +/-12V in case of AD1862.
Regarding power supply connector: even four of these DACs consume less then 200mA per rail so I think a small sized one is well enough. I like the PH2.0 you're using for its small footprint.
For board output I don't see why we shouldn't use the same 2pin PH2.0
Do you have ideas for better connectors types for the output?
Thanks,
Zsolt
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Core Board
I'm not sure PH2.0 is best solution for power connector, because usable size of wire for it is up to AWG26 (0,4mm in diameter).
AWG26 wire will insert to power line copper resistance up to 13mOhm per 10cm. It is about half of Salas shunt regulator output impedance.
If possible, I would better use connector which can be wired up to AWG23-22 (up to 0,57 - 0,64 mm in diameter). This would reduce copper resistance at least twice.
On the other hand, if we are going to have 100 - 220 uF solid polymer type capacitors nearby DAC on each power lineon core board, such capacitor can have same range of ESR as shunt regulator's output impedance, so maybe here is no any problem at all, I dunno...
I'm not sure PH2.0 is best solution for power connector, because usable size of wire for it is up to AWG26 (0,4mm in diameter).
AWG26 wire will insert to power line copper resistance up to 13mOhm per 10cm. It is about half of Salas shunt regulator output impedance.
If possible, I would better use connector which can be wired up to AWG23-22 (up to 0,57 - 0,64 mm in diameter). This would reduce copper resistance at least twice.
On the other hand, if we are going to have 100 - 220 uF solid polymer type capacitors nearby DAC on each power lineon core board, such capacitor can have same range of ESR as shunt regulator's output impedance, so maybe here is no any problem at all, I dunno...
Core Board
AWG24 for power transmission can handle 0.577A - 3x more than the max. 0.18A (4xPCM1704) needed.
With AWG22 would be 5mH/10cm and about 5x more then max current.
Decoupling caps will take care of momentary power needs so I don't think we have to over-design too much.
JST PH (2mm pitch) can take up to AWG24, 8mH/10cm.
AWG24 for power transmission can handle 0.577A - 3x more than the max. 0.18A (4xPCM1704) needed.
With AWG22 would be 5mH/10cm and about 5x more then max current.
Decoupling caps will take care of momentary power needs so I don't think we have to over-design too much.
Capacitors will help at high frequency, but not much at low frequency, so I think a certain over-design in not a bad thing.
In general I think we shouldn't care about board dimensions: TDA1541, for example, needs some arrangements in its implementation, such as DEM, so the board size will be necessarily greater than the other DAC of the group.
I wouldn't forget PCM56, and maybe TDA1543 (some people seems are re-discovering this DAC).
Core Board
Agree,
and next issue is minimize cabling distances from I2S-PCM converter to our core board - because of high speed transmission any kind of cables should be as short as possible.
It completely depends on solutions we are going to put in this "standard" size core board.
Last time was mentioned FIFO board size - 70x80mm, but I'm not sure we can put here two TDA1541 with all, even SMD type, surroundings...
We can try another approach about size: agree about few different size core boards but with one fixed size side, preferably 80mm - the side where should be data lines from I2S-PCM board connected.
And mounting holes should be compatible to one of three sets:
1) I2S-PCM board (80x60mm);
2) FIFO board (80x70mm)
3) FIFO + clock board unbroken (80x132mm)
In that way we would have possibility to stack core board below or over different FIFO series board or boards (FIFO+clock).
Saulius
Agree,
and next issue is minimize cabling distances from I2S-PCM converter to our core board - because of high speed transmission any kind of cables should be as short as possible.
It completely depends on solutions we are going to put in this "standard" size core board.
Last time was mentioned FIFO board size - 70x80mm, but I'm not sure we can put here two TDA1541 with all, even SMD type, surroundings...
We can try another approach about size: agree about few different size core boards but with one fixed size side, preferably 80mm - the side where should be data lines from I2S-PCM board connected.
And mounting holes should be compatible to one of three sets:
1) I2S-PCM board (80x60mm);
2) FIFO board (80x70mm)
3) FIFO + clock board unbroken (80x132mm)
In that way we would have possibility to stack core board below or over different FIFO series board or boards (FIFO+clock).
Saulius
Ok, I got it.
I think UFL coaxial connectors used already by Ian with other devices are highly recommended.
Core Board
Regarding connectors, JST has a compact EH 2.5mm pitch series that allows up to AWG22 - for over design aficionados - we can use that.
To sum up what we have so far:
Power connectors: 5x2pin 2.5mm (JST EH series)
+Va, GND (analog)
-Va, GND (analog)
-15V,GND (analog, for TDA1541A only)
+5V, GND (digital)
-5V, GND (digital)
Input connectors: 1x10pin PH2.0, 8 x U-FL
Output connectors: 4x2pin PH2.0
Output will be current output only and without offset (some DACs may need offset nulling).
Size: Don't know exact size yet... to have a small size though we have to renounce for 4 PCM channels/board for large DACs.
Per board DACs:
- AD1865 - 2x - 4 PCM channels
- TDA1541A - 1x - 2 PCM channels. This one needs many additional components so most probably only one will fit. I think the best design I've seen so far is this: Setup TDA1541A DAC. We can take ideas regarding many TDA1541A related features
- PCM1704 - 4x - 4 PCM channels
...
Ian, when you have time please have a look at this: TDA1541A schematics. We don't need from here the PSU part and the 74HC175 reclocking but seems that DEM clocking needs a master clock (MCLKI) input. Do you think one of this beast will fit on an 80x60mm board?
Regards,
Zsolt
Regarding connectors, JST has a compact EH 2.5mm pitch series that allows up to AWG22 - for over design aficionados - we can use that.
To sum up what we have so far:
Power connectors: 5x2pin 2.5mm (JST EH series)
+Va, GND (analog)
-Va, GND (analog)
-15V,GND (analog, for TDA1541A only)
+5V, GND (digital)
-5V, GND (digital)
Input connectors: 1x10pin PH2.0, 8 x U-FL
Output connectors: 4x2pin PH2.0
Output will be current output only and without offset (some DACs may need offset nulling).
Size: Don't know exact size yet... to have a small size though we have to renounce for 4 PCM channels/board for large DACs.
Per board DACs:
- AD1865 - 2x - 4 PCM channels
- TDA1541A - 1x - 2 PCM channels. This one needs many additional components so most probably only one will fit. I think the best design I've seen so far is this: Setup TDA1541A DAC. We can take ideas regarding many TDA1541A related features
- PCM1704 - 4x - 4 PCM channels
...
Ian, when you have time please have a look at this: TDA1541A schematics. We don't need from here the PSU part and the 74HC175 reclocking but seems that DEM clocking needs a master clock (MCLKI) input. Do you think one of this beast will fit on an 80x60mm board?
Regards,
Zsolt
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