PCM1702 PCM1704 PCM63 (PCM 63 1702 1704) sensitive to >>5V on one of the supply rails
PCM1702 PCM1704 PCM63 (PCM 63 1702 1704) sensitive to undervoltage on one of the supply rails ?
I have heard from some guys, that it is very important, that both pos. and neg. voltage values while start up phase must increase with absolutely identical speed, because with different values in the pos. and neg. rail can trigger a defect or a non-resettable internal error.
The same also applies after switching off, so that even the zero value comes about at the same time.
Is that really true ??
If yes, an appropriate switch-on delay unit in the 5V rails is necessary - this would have to be provided in any case to ensure that exactly 5V is present at exact the same time on the positive rail and the negative rail (maybe with help of solid state relay).
OTOH - such an unit I haven't discover until now in any D/A converter device on the marked equipped with one of the in the headline mentioned IC's.
Thank you very much for an information.
PCM1702 PCM1704 PCM63 (PCM 63 1702 1704) sensitive to undervoltage on one of the supply rails ?
I have heard from some guys, that it is very important, that both pos. and neg. voltage values while start up phase must increase with absolutely identical speed, because with different values in the pos. and neg. rail can trigger a defect or a non-resettable internal error.
The same also applies after switching off, so that even the zero value comes about at the same time.
Is that really true ??
If yes, an appropriate switch-on delay unit in the 5V rails is necessary - this would have to be provided in any case to ensure that exactly 5V is present at exact the same time on the positive rail and the negative rail (maybe with help of solid state relay).
OTOH - such an unit I haven't discover until now in any D/A converter device on the marked equipped with one of the in the headline mentioned IC's.
Thank you very much for an information.
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I played with dual differential 1704's and spent years trying to get the best sound out of them - mostly a very low noise power supplies, regulators, power rails' decoupling, improving the ground scheme, isolating other digital switching IC's (microcontrollers, digital filters...) from infiltrating DAC IC's Vcc/Vee & polluting the ground, and I/V stage of course (using AD811's🙂). I have never faced the issue you are referring to; I did not have to use any special means to sequentially power anything up, or down.
This issue existed with CS8412 and was easily solved by placing 2 antiparallel diodes between analog en digital power supplies. That simple trick will also work for other ICs. If one of the supply lines is "faster" it will also power on the other supply pin till that "slower" voltage turns up.
Old stuff really, it is maybe more worthwhile to invest time in recent stuff.
Old stuff really, it is maybe more worthwhile to invest time in recent stuff.
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Yes, actually you are right as long it's for a new project - e. g. with this DAC-IC:
AK4499EQ - Best DAC ever
But I didn't ask the question in post 1 because I want to build a DAC with this old stuff, rather it is about repairing an existing DAC that is around 25-30 years old and before replacing the IC it is to find out the reason, why this IC became faulty. Here is the thread with some images and schematics:
One of German's most ultimate DAC: Horch "STEPS 1" - Schematic wanted
If one were to use the AK4499 and its updated circuit board instead of replacing the PCM1702, the same question arises with the approach implemented with the large capacitors.
AK4499EQ - Best DAC ever
But I didn't ask the question in post 1 because I want to build a DAC with this old stuff, rather it is about repairing an existing DAC that is around 25-30 years old and before replacing the IC it is to find out the reason, why this IC became faulty. Here is the thread with some images and schematics:
One of German's most ultimate DAC: Horch "STEPS 1" - Schematic wanted
If one were to use the AK4499 and its updated circuit board instead of replacing the PCM1702, the same question arises with the approach implemented with the large capacitors.
The diode trick wil prevent this. You could use Schottky diodes for even lower difference. I won't read up on the old DAC thread as I am tired of troubleshooting old DACs. For some reason people sell everything but they keep their DACs 30 years. Then they also expect optimal performance when connecting a high res streamer. Or they keep this outdated and jittery stuff just to be able to say that their analog stuff like their turntable is beter or something.
If one of the rails comes up faster than the other the diodes will work. If too large capacitors are used, well make em smaller. And get used to it, R2R DAC chips do fail after so many years. You can do a root cause analysis but you could also just call it a day by stating it is old and worn out.
If one of the rails comes up faster than the other the diodes will work. If too large capacitors are used, well make em smaller. And get used to it, R2R DAC chips do fail after so many years. You can do a root cause analysis but you could also just call it a day by stating it is old and worn out.
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As jean stated, PCM1704 are mentioned, digital and analog supplies must be in 0.1V difference even during power on and off transition, in an application note ANJ1092. This application note is written by an employee of BB Japan at the time, and there is no English version. But, ANJ1082 of PCM1702 written by the same person, are separating digital and analog supply by a ripple filter, not sure it is OK...
Thank you, good advice. The only thing that has been done in the dac mentioned in previous post, is to insert an inductor between A-GND and D-GND (analog ground and digital ground).
I will do the introduce of the diodes both between the pos. rails (+Vcc/Vdd) and the neg. rails (-Vcc/Vdd).
Maybe it makes sense even to replace the inductor between A-GND and D-GND with such diodes.
The application notes are to find under
http://30.pro.tok2.com/~easyaudiokit/kit-room2/datasheet/ANJ_1082.pdf
and
https://www.ti.com/jp/lit/an/jaja00...60993&ref_url=https%3A%2F%2Fwww.google.com%2F
but unfortunately I don't find it anywhere in English.
I will do the introduce of the diodes both between the pos. rails (+Vcc/Vdd) and the neg. rails (-Vcc/Vdd).
Maybe it makes sense even to replace the inductor between A-GND and D-GND with such diodes.
The application notes are to find under
http://30.pro.tok2.com/~easyaudiokit/kit-room2/datasheet/ANJ_1082.pdf
and
https://www.ti.com/jp/lit/an/jaja00...60993&ref_url=https%3A%2F%2Fwww.google.com%2F
but unfortunately I don't find it anywhere in English.
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Please leave the inductor where it is. In the past this issue with symmetric PSU's and sometimes asymmetric startup behavior and also 2 positive or negative supply voltages coming up in a sequence was more known as I think bipolar IC's were more prone to be sensitive to this. I think we called it "latch up" or something like that.
In practice the most chosen solution was to simple tie Vcc and Vdd (and also -Vcc and Vdd) together so the issue would not occur so easy 🙂 The technically (datasheet!) and audiophile approved way was to have separate PSU's with the antiparallel diodes. Even with everything equal one device could have latch up while another device never exhibited the phenomenon. The diodes solved it.
You can make a german solution for the till now unknown maximum 0.1V difference in supply voltages AND the possibility that voltages don't come up at the same time: first make sure all supply voltages are within a close limit of eachother. If not then adjust so all voltages are equal with max. 0.1V difference. Then keep Vcc and Vdd shorted at startup with relay contacts and do the same for - Vcc and Vdd. After 1 or 2 seconds delay the contacts open and the pins will have their own separate supply. The simplest muting circuit is OK for this when a 4 pole relay is chosen. Only do so if coils or resistors are used in the PSU lines to avoid large surge currents (or simply measure currents and just short both supply lines to eachother as 0.1V max. will likely not cause bad things).
In practice the most chosen solution was to simple tie Vcc and Vdd (and also -Vcc and Vdd) together so the issue would not occur so easy 🙂 The technically (datasheet!) and audiophile approved way was to have separate PSU's with the antiparallel diodes. Even with everything equal one device could have latch up while another device never exhibited the phenomenon. The diodes solved it.
You can make a german solution for the till now unknown maximum 0.1V difference in supply voltages AND the possibility that voltages don't come up at the same time: first make sure all supply voltages are within a close limit of eachother. If not then adjust so all voltages are equal with max. 0.1V difference. Then keep Vcc and Vdd shorted at startup with relay contacts and do the same for - Vcc and Vdd. After 1 or 2 seconds delay the contacts open and the pins will have their own separate supply. The simplest muting circuit is OK for this when a 4 pole relay is chosen. Only do so if coils or resistors are used in the PSU lines to avoid large surge currents (or simply measure currents and just short both supply lines to eachother as 0.1V max. will likely not cause bad things).
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I note, here it is pointed out that the voltage difference between ± Vcc and ± Vdd must remain very small. This is by the DAC-PCB absolutely guaranteed, because there are no different rails for ± Vcc and ± Vdd present - go to post #54 under
https://www.diyaudio.com/forums/dig...ac-horch-steps-1-schematic-6.html#post6417501
First Image shows the neg. rails to PIN5 and PIN16 of PCM1702 and one positive rail to PIN 9 (component side) and second/third image the second positive rail to PIN3 of PCM1702.
The question whether the difference in the values of the voltage between + Vcc resp. +Vdd and -Vcc resp. -Vdd even should only remain very small during the start-up phase and during discharge process after switched off is still unanswered.
I guess, this doesn't matter (otherwise the DAC-IC in cd player devices would always fail if one of the positive and negative voltages wasn't present due to a fault in the associated power supply), however, I don't know exactly.
We inadvertently destroyed one of a pair of PCM1704s when the negative rail was not connected during power up. The second piece survived.