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Powering an Arduino and PGA2311 from LCDPS? (and Opus and SPDIF...)
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Joined: 2/23/2014(UTC) Posts: 3 
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Hi,
I've been planning to get one of the kits with Opus DAC, SPDIF transceiver and LCDPS module.
I understand the LCDPS can power both the analog and digital side of the Opus DAC, as well as the digital (only side) of the SPDIF transceiver. My plan is to add a fourth custom module with a PGA2311 and an Arduino to control output volume and a source select relay to create a complete dac/preamp box.
Both the Arduino and PGA2311 needs a digital +5V supply wich I assume a can take from the same +7,5 V that powers the SPDIF and digital part of Opus.
PGA2311 is a digitally controlled volume attenuator and opamp (http://www.ti.com/lit/ds/sbos218a/sbos218a.pdf).
The PGA2311 then needs an additional +5 and -5V for its built in opamp.
My questions are:
1. Is it ok to parallell power from the digital side of LCDPS to Arduino and PGA2311 with regulation(7,5>5V) in between?
2. How can I source +-5V from LCDPS for the analog (opamp) side of the PGA2311? If I understand things correctly (I probably dont..) the LCDPS outputs two lines of +7,5V and two lines of GND(0V)? I can regulate +7,5V down to +5V, but how do I get -5V?
I have a DC/DC transformer which outputs 2x +-9V and 2x +-15V, but I'd prefer to use the LCDPS as my only power module.
PS. I'm a newbie. I really just want things to work and not interrested in hassling around too much. I chose the Opus kit because it seems reliabale, with good enough SQ, and relatively easy to implement.
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Rank: Member
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Joined: 8/22/2010(UTC) Posts: 38  Thanks: 14 times
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Quote:Both the Arduino and PGA2311 needs a digital +5V supply wich I assume a can take from the same +7,5 V that powers the SPDIF and digital part of Opus. 7.5VDC != 5VDC. You would need extra DC-to-DC with it's own power and voltage requirements. Quote:1. Is it ok to parallell power from the digital side of LCDPS to Arduino and PGA2311 with regulation(7,5>5V) in between? Yes, and you need to calculated the total power consumptions and make sure the current from LCDPS is sufficient. Quote:2. How can I source +-5V from LCDPS for the analog (opamp) side of the PGA2311? If I understand things correctly (I probably dont..) the LCDPS outputs two lines of +7,5V and two lines of GND(0V)?
You can not. LCDPS is basically two independent PSUs on a single board providing 2 positive voltages only. LC BPS or similar is required. Quote:I can regulate +7,5V down to +5V, but how do I get -5V? LC BPS or similar is required. Quote:PS. I'm a newbie. I really just want things to work and not interrested in hassling around too much. I chose the Opus kit because it seems reliabale, with good enough SQ, and relatively easy to implement. The default set works great. If you design in extra features, you probably need to understand what needs to be done. Edited by user Monday, February 24, 2014 2:55:14 AM(UTC)
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Originally Posted by: johanwahlberg  Hi,
I've been planning to get one of the kits with Opus DAC, SPDIF transceiver and LCDPS module.
I understand the LCDPS can power both the analog and digital side of the Opus DAC, as well as the digital (only side) of the SPDIF transceiver. My plan is to add a fourth custom module with a PGA2311 and an Arduino to control output volume and a source select relay to create a complete dac/preamp box.
Both the Arduino and PGA2311 needs a digital +5V supply wich I assume a can take from the same +7,5 V that powers the SPDIF and digital part of Opus.
PGA2311 is a digitally controlled volume attenuator and opamp (http://www.ti.com/lit/ds/sbos218a/sbos218a.pdf).
The PGA2311 then needs an additional +5 and -5V for its built in opamp.
My questions are:
1. Is it ok to parallell power from the digital side of LCDPS to Arduino and PGA2311 with regulation(7,5>5V) in between?
2. How can I source +-5V from LCDPS for the analog (opamp) side of the PGA2311? If I understand things correctly (I probably dont..) the LCDPS outputs two lines of +7,5V and two lines of GND(0V)? I can regulate +7,5V down to +5V, but how do I get -5V?
I have a DC/DC transformer which outputs 2x +-9V and 2x +-15V, but I'd prefer to use the LCDPS as my only power module.
PS. I'm a newbie. I really just want things to work and not interrested in hassling around too much. I chose the Opus kit because it seems reliabale, with good enough SQ, and relatively easy to implement. The Arduino Mega I used recommended a higher voltage than 5V, I'd check you may be able to run 7.5V straight into it.
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Rank: Member
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Joined: 2/23/2014(UTC) Posts: 3
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Thank you. Arduino wants 5V which is easily regulated.
The issue is the +-5V to the PGA2311. Do you have any suggestions on a simple approach to this? Sounds to me the easiest way is to add a LCBPS. If so, can I parallell wire it from the transformer with the LCDPS?
The transformer outputs 2x +-9V at 0.8A each and 2x +-15V at 0.5A each.
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Rank: Administration
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Originally Posted by: johanwahlberg Thank you. Arduino wants 5V which is easily regulated.
The issue is the +-5V to the PGA2311. Do you have any suggestions on a simple approach to this? Sounds to me the easiest way is to add a LCBPS. Yes. Quote: If so, can I parallell wire it from the transformer with the LCDPS?
The transformer outputs 2x +-9V at 0.8A each and 2x +-15V at 0.5A each.
No. That will result in a short. You need a second transformer.
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Rank: Member
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Joined: 2/23/2014(UTC) Posts: 3
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Okay, not even with its second secondary? Two (+9,-0 and -9,+0) are used by LCDPS. I still have +15,-0 and -15,+0 available from the transformer.
OR
Can I use just the LCBPS with all three modules?
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 2,868
Location: Massachusetts, USA
Thanks: 2 times
Was thanked: 141 time(s) in 134 post(s)
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Originally Posted by: johanwahlberg Okay, not even with its second secondary? Two (+9,-0 and -9,+0) are used by LCDPS. I still have +15,-0 and -15,+0 available from the transformer.
OR
Can I use just the LCBPS with all three modules? Ah, I missed that. You can use the 15V taps for the bipolar supply. Note, however, that the current rating is a little low, and may lead to other problems.
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