Hi everyone,
I'm embarking on learning more about microcontrollers, ICs, etc and I have a small project that I'm working on that will use a PGA2311. I've done stuff like this before, I'm a decent programmer, and I understand a lot about the EE side of things, but my degrees are in music, so I have some holes I probably need to plug.
One of these gaps in my knowledge is that on the spec sheets, it specifies +5V for the digital side, and +5V and -5V on the analog side. Does this mean the digital side is DC and the analog side is AC ? If not, how does one get both the positive and negative DC voltages ? I always thought of DC as being just... well... DC.
Any reading materials that anyone can recommend, or resources to go learn would be appreciated.
best,
matt
I'm embarking on learning more about microcontrollers, ICs, etc and I have a small project that I'm working on that will use a PGA2311. I've done stuff like this before, I'm a decent programmer, and I understand a lot about the EE side of things, but my degrees are in music, so I have some holes I probably need to plug.
One of these gaps in my knowledge is that on the spec sheets, it specifies +5V for the digital side, and +5V and -5V on the analog side. Does this mean the digital side is DC and the analog side is AC ? If not, how does one get both the positive and negative DC voltages ? I always thought of DC as being just... well... DC.
Any reading materials that anyone can recommend, or resources to go learn would be appreciated.
best,
matt
Welcome to diyAudio 🙂
It is all DC. The plus 5 and minus 5 (written as -/+5 volts) would be typical for any audio stage and often is in the -/+15 or -/+18 volt region.
The logic works on 5 volts and its common to keep digital and analogue supplies separate to maintain and improve noise figures. Often even the grounds are separate to help minimise noise.
The -/+ part is to allow a DC coupled audio stage to be able to swing both above and below the notional zero point. The majority of audio gear and also power amps use these dual or split supplies. The alternative is a single rail supply and AC coupling with the circuitry biased to keep the output at around one half the single rail voltage.
Reading up on 'opamps' and their theory and practice would probably help your understanding.
It is all DC. The plus 5 and minus 5 (written as -/+5 volts) would be typical for any audio stage and often is in the -/+15 or -/+18 volt region.
The logic works on 5 volts and its common to keep digital and analogue supplies separate to maintain and improve noise figures. Often even the grounds are separate to help minimise noise.
The -/+ part is to allow a DC coupled audio stage to be able to swing both above and below the notional zero point. The majority of audio gear and also power amps use these dual or split supplies. The alternative is a single rail supply and AC coupling with the circuitry biased to keep the output at around one half the single rail voltage.
Reading up on 'opamps' and their theory and practice would probably help your understanding.
re the diagrams in the PGA2311 datasheet:
Digital Ground = the 0V of the digital power supply.
Analogue Ground = the 0V of the Analogue power supply.
The digital and analogue grounds are connected together at one point only on the PCB to avoid noise.
So you need a power supply with -5V / 0 / +5V for the analogue supply and a second of 0 / 5V for the digital supply.
If using a transformer then you want separate windings for the analogue and digital or you will not meet the 'grounds connected at one point only' rule.
This will probably mean using two transformers unless you wind an additional secondary yourself.
Digital Ground = the 0V of the digital power supply.
Analogue Ground = the 0V of the Analogue power supply.
The digital and analogue grounds are connected together at one point only on the PCB to avoid noise.
So you need a power supply with -5V / 0 / +5V for the analogue supply and a second of 0 / 5V for the digital supply.
If using a transformer then you want separate windings for the analogue and digital or you will not meet the 'grounds connected at one point only' rule.
This will probably mean using two transformers unless you wind an additional secondary yourself.
You should skim read this to start. Don't get bogged down on anything, just keep soaking in the vocabulary, the schematics, and the warnings from history...
https://sound-au.com/articles/power-supplies2.htm
https://sound-au.com/articles/index.htm#psud
https://sound-au.com/articles/power-supplies2.htm
https://sound-au.com/articles/index.htm#psud
Thanks to those who replied so far! I'm making progress and learning a lot. SPI is working and I have a much better understanding of decoupling caps and power supplies now. I haven't yet blown anything up so that's a good sign 🙂
@teletype1 Something like this below, I have used the schematics from and Elektor project ( if you want value ) It is using LM317 and LM337,
This is for Analog +/- 5Volts
and for Digital +5 its a simple 7805 regulator.
J3 to J6 are Spade connectors for the Secondry to connect on the PCB
This is for Analog +/- 5Volts
and for Digital +5 its a simple 7805 regulator.
J3 to J6 are Spade connectors for the Secondry to connect on the PCB
Personally, I would not connect + and - supply grounds at the power supply. I would connect them together at the load instead. Also would not use a center-tapped transformer winding. Otherwise you get common-impedance coupling between the power supplies due to both return ground currents being shared on one line. Okay for low performance designs, but I wouldn't allow that type of coupling for high performance.
HI Mark,
please expand on this, I would like some more may be a drawing.
Also in my amp the transformer secondry for PGA VA is with 0-12 and 0-12 for the dual supply .
Hi aditya,
Please let me say a little more about how I sometimes like to design power supplies at the macro level. I often like to use positive regulators only, even for negative voltage rails.
For example, here is a power supply board with two isolated positive regulators:
https://www.ebay.com/itm/134903077968?itmmeta=01HW6D1Q6N5T6QXVX06B60A50K&hash=item1f68d99c50:g:zYgAAOSwvW5iC2Dr&itmprp=enc:AQAJAAAA4Gvoxwz/+2wiUV+l62y/OytZSsma3Ckf19u1/X/wlyXnljXE0ERY4LKRbrQ1ScnbRH4wdoNvbjxTpY9SGibTspEB472YUliGeMdIJLUXeA235Xf2Yi88xzwMJ+Pu4oFNvjT5/hTxvzK/qJqQ0TEPiy9AQIjxXXtR5rsD3fRZQXBmgpiP4Bt50NWtTLHMRG0NjFwfHuEKhfVxmw+TfXLjAtsTBGv1y2dR4g1+iHG6N1Lmnw2nnQqjIWeW2a6i/Jy4Hhw0rtuTvP/Y7ljoLJ3ITxwWxtxJ/VNHvTQmwSOBKQzw|tkp:BFBMwPOGzeFj
If I use an isolated, dedicated transformer winding to power each regulator then there is no shared ground between them anywhere. Also, each regulator has a + and a - output terminal. I only want to define which terminal will be connected to ground (or circuit common) at the load. Say, maybe, at a dac board for the output stage. For the positive opamp rail, I connect one power supply - terminal to PCB ground and the + terminal to the + opamp rail. For the negative opamp rail I tie the + terminal of the other regulator to PCB ground and the - terminal to the negative opamp rail.
This can have some advantages. First since I am using identical regulators for both rails, then I expect things like output impedance verse frequency to be the same for both rails. Some people think that having power rails with the same measured properties tends to give better sound from the audio circuit being powered. The second reason is that ground return currents for each supply are separate. Common impedance coupling happens in situations where multiple currents flow through the same resistance/impedance. Each of the currents creates its own voltage drop across the conductor, and those voltage drops all ad up. Well. having the ground voltage move up and down due to shared ground currents is just as bad has having the rail voltage moving up and down. Its the difference in voltage between ground and the rail that matters for some things.
Hopefully that clears things up a little. If any questions, please feel free to ask.
Please let me say a little more about how I sometimes like to design power supplies at the macro level. I often like to use positive regulators only, even for negative voltage rails.
For example, here is a power supply board with two isolated positive regulators:
https://www.ebay.com/itm/134903077968?itmmeta=01HW6D1Q6N5T6QXVX06B60A50K&hash=item1f68d99c50:g:zYgAAOSwvW5iC2Dr&itmprp=enc:AQAJAAAA4Gvoxwz/+2wiUV+l62y/OytZSsma3Ckf19u1/X/wlyXnljXE0ERY4LKRbrQ1ScnbRH4wdoNvbjxTpY9SGibTspEB472YUliGeMdIJLUXeA235Xf2Yi88xzwMJ+Pu4oFNvjT5/hTxvzK/qJqQ0TEPiy9AQIjxXXtR5rsD3fRZQXBmgpiP4Bt50NWtTLHMRG0NjFwfHuEKhfVxmw+TfXLjAtsTBGv1y2dR4g1+iHG6N1Lmnw2nnQqjIWeW2a6i/Jy4Hhw0rtuTvP/Y7ljoLJ3ITxwWxtxJ/VNHvTQmwSOBKQzw|tkp:BFBMwPOGzeFj
If I use an isolated, dedicated transformer winding to power each regulator then there is no shared ground between them anywhere. Also, each regulator has a + and a - output terminal. I only want to define which terminal will be connected to ground (or circuit common) at the load. Say, maybe, at a dac board for the output stage. For the positive opamp rail, I connect one power supply - terminal to PCB ground and the + terminal to the + opamp rail. For the negative opamp rail I tie the + terminal of the other regulator to PCB ground and the - terminal to the negative opamp rail.
This can have some advantages. First since I am using identical regulators for both rails, then I expect things like output impedance verse frequency to be the same for both rails. Some people think that having power rails with the same measured properties tends to give better sound from the audio circuit being powered. The second reason is that ground return currents for each supply are separate. Common impedance coupling happens in situations where multiple currents flow through the same resistance/impedance. Each of the currents creates its own voltage drop across the conductor, and those voltage drops all ad up. Well. having the ground voltage move up and down due to shared ground currents is just as bad has having the rail voltage moving up and down. Its the difference in voltage between ground and the rail that matters for some things.
Hopefully that clears things up a little. If any questions, please feel free to ask.