Hello,I made a PCM1794 DAC,but now I want to power it from USB.I know that if the DC-DC converter isn't done properly,it will sacrifice performance.I can make it with buck-boost MC34063,but I doubt about it's noise qualities.Can you recommend me a schematic?I need at least +/- 9V for I/V and LPF.
Thanks!
Thanks!
Not sure how much current you need but these convertors are excellent and would allow regs to be fitted.
IZ0512S - XP POWER - CONVERTER, DC/DC, 3W, +/-12V | Farnell United Kingdom
IZ0512S - XP POWER - CONVERTER, DC/DC, 3W, +/-12V | Farnell United Kingdom
Hmm how much capacitance can I place on the output?
500 mA for 2.0,I need about 150
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If that is the output needed current than may i remind you that +/-12V @150mA it's about 3,6W, witch ignoring any looses, at 5V it would require more than 700mA? I doubt veery much u can make it work cus u ask to much from it...
The data sheets for a specific reg may give a value but remember the ripple is at high frequency and so the caps can be small. Values around 47 to 100uf would probably be typical.
Well,I hope it won't introduce noise in the audio band.
OK,USB outputs 500mA or 2,5W.
I will power the DAC(VCC and VDD) direclty from USB,that's 45+45 mA or 450mW.VDD is powered with a 3.3V regulator,which will dissipate around 100mW.The output section requires 30 mA,I will power it with +/- 9 V,which makes 540mW,considering 75% efficiency,let's make it 750 mW.So far we have 450 + 100 + 750 = 1,3W.The rest will go for the XMOS(which requires around 500 mW).We still have some reserve,so I think it will work fine.I'll order a +/- 9 V 1W module tomorrow.
Thanks!
OK,USB outputs 500mA or 2,5W.
I will power the DAC(VCC and VDD) direclty from USB,that's 45+45 mA or 450mW.VDD is powered with a 3.3V regulator,which will dissipate around 100mW.The output section requires 30 mA,I will power it with +/- 9 V,which makes 540mW,considering 75% efficiency,let's make it 750 mW.So far we have 450 + 100 + 750 = 1,3W.The rest will go for the XMOS(which requires around 500 mW).We still have some reserve,so I think it will work fine.I'll order a +/- 9 V 1W module tomorrow.
Thanks!
I'm wondering now...
1. Murata 0509DC 1W,7-15 mV ripple on output,110 kHz.Total power:1,8W.
2. Murata 0512DC 2W,150-200 mV ripple(!),90 kHz + 78/7909 regs
78xx have about 60 dB PSRR,so it can make it ripple 200uV.
I think I'll be going with the second option.But here we have 30mA for the opamps,20mA for the regs,and power some dissipation for them,so (0.03*18)+(0.02*24)+(3*0.03) = 1,1W.Plus 0.6W for DAC and 0.5W for XMOS,we're walking on the edge with 2.2W total power.
1. Murata 0509DC 1W,7-15 mV ripple on output,110 kHz.Total power:1,8W.
2. Murata 0512DC 2W,150-200 mV ripple(!),90 kHz + 78/7909 regs
78xx have about 60 dB PSRR,so it can make it ripple 200uV.
I think I'll be going with the second option.But here we have 30mA for the opamps,20mA for the regs,and power some dissipation for them,so (0.03*18)+(0.02*24)+(3*0.03) = 1,1W.Plus 0.6W for DAC and 0.5W for XMOS,we're walking on the edge with 2.2W total power.
have a traco tma0512D, w/o load gives +-21v ; low drop regs recomended
loading both sides with 220r gives +-11,6v (2*0,5w)
takes 5v 0,3a
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I was just looking at the Traco module.It allows up to 330uF capacitance,which is good.
Bad thing is that I just measured 60mA for analog part at +/-12 V.
Analog stage is 2xLM4562 for I/V and AD8599 for LPF.I think that I've missed that LM4562 takes 10mA per channel.AD8599,on the other hand,takes 5mA per channel.Some current is dissipated from resistors,too.So the best thing to do is changing LM4562s with AD8599s or OPA1612s.It will save 20mA.
Here's a summary then:
From USB :
PCM1794 VCC : +5V , 37mA = 185 mW
PCM1794 VDD : +3.3V , 45mA = 148 mW
+3.3V LDO : +5V,10mA constant current = 50 mW
+3.3V LDO dissipation : 1.7V , 45mA = 76 mW
XMOS(datasheet) : 500mW(probably much lower,i use the new DXIO pro)
Total : 959 mW
From power module :
7809 : +12V,6mA constant current = 72mW
7809 dissipation : 3V,40mA = 120 mW
7909 : +12V,6mA constant current = 72mW
7909 dissipation : 3V,40mA = 120 mW
Analog part : +/-9V,40mA = 720 mW
Some resistors = 50 mW
Power module efficiency : 79%
Total : 1450 mW
Total total : 2450 mW
Barely.Wow.Hopefully,it will be a tad lower,because this is power for fs = 192 kHz.At 44.1 kHz,the DAC uses much lower current.Still,no headroom at all.
How do they make it,anyway?There's E-MU 0202 USB,AudioTrak Dr. Dac 2,and these things even have headphone amps and analog inputs!
Bad thing is that I just measured 60mA for analog part at +/-12 V.
Analog stage is 2xLM4562 for I/V and AD8599 for LPF.I think that I've missed that LM4562 takes 10mA per channel.AD8599,on the other hand,takes 5mA per channel.Some current is dissipated from resistors,too.So the best thing to do is changing LM4562s with AD8599s or OPA1612s.It will save 20mA.
Here's a summary then:
From USB :
PCM1794 VCC : +5V , 37mA = 185 mW
PCM1794 VDD : +3.3V , 45mA = 148 mW
+3.3V LDO : +5V,10mA constant current = 50 mW
+3.3V LDO dissipation : 1.7V , 45mA = 76 mW
XMOS(datasheet) : 500mW(probably much lower,i use the new DXIO pro)
Total : 959 mW
From power module :
7809 : +12V,6mA constant current = 72mW
7809 dissipation : 3V,40mA = 120 mW
7909 : +12V,6mA constant current = 72mW
7909 dissipation : 3V,40mA = 120 mW
Analog part : +/-9V,40mA = 720 mW
Some resistors = 50 mW
Power module efficiency : 79%
Total : 1450 mW
Total total : 2450 mW
Barely.Wow.Hopefully,it will be a tad lower,because this is power for fs = 192 kHz.At 44.1 kHz,the DAC uses much lower current.Still,no headroom at all.
How do they make it,anyway?There's E-MU 0202 USB,AudioTrak Dr. Dac 2,and these things even have headphone amps and analog inputs!
Oh...can I?I thought that specs were 500mA for the whole system...ok then.Thanks!Phew!
http://www.tracopower.com/products/dc-dc-converters/
batteries are cheap, lithium also. Why not add it to project? (i presume you want it portable)
if not, its not shame to have wall adapter
usb ports have often ptc protection, that does mean laptops and desktops will behave diferently to hi loads
batteries are cheap, lithium also. Why not add it to project? (i presume you want it portable)
if not, its not shame to have wall adapter
usb ports have often ptc protection, that does mean laptops and desktops will behave diferently to hi loads
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