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Old 20th February 2013, 11:16 AM   #2451
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exactly

thanks
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Old 20th February 2013, 11:46 AM   #2452
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While we're talking about that TPS7A4700 reg.

I am wondering how much the X7R capacitor's non-linear capacitance wrt high frequencies impacts regulator performance, especially in the noise reduction LPF and the output. Is that HF noise mostly negated by local decoupling at the Si570? np0 caps are more linear wrt freq but aren't really available in the sizes we need on the output of this regulator. I'm also not keen on doing mix and match caps of different sizes to set up ringing and other dramas in the critical high freq area. I have tried looking for better alternative parts for the output caps or the CNR cap and other than different brand X7R or tant caps there isn't much around by the looks.

So from the above, I've come to the above that there isn't many places to gain a technical advantage from deviating from Ian's BOM. I guess that means Ian has thought through all of the above and come to the BOM selections for good reasons

I will probably do a few different versions with tant and panasonic spcap on the regulator input, just because I have a few boards to try.

Chris
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Old 20th February 2013, 12:54 PM   #2453
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How could these regs be used with the dual clock board ?
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Old 20th February 2013, 04:17 PM   #2454
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Quote:
Originally Posted by iancanada View Post
Do you have a oscilloscope? Can you find out what's wrong with the I2S signal?

In your normal playing, does dual xo clock board switching between 44.1K and 96K without problem?

Ian
I resolved by setting the "Default format" in "Control Panel \ Sound" to the limit that my Amanero can get. Now, this error still occur when play files with format 24bit/192khz. I updated Amanero with the latest firmware and drivers.

Van Duy.
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Last edited by nvduybom; 20th February 2013 at 04:24 PM.
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Old 21st February 2013, 03:31 AM   #2455
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Quote:
Originally Posted by hochopeper View Post
While we're talking about that TPS7A4700 reg.

I am wondering how much the X7R capacitor's non-linear capacitance wrt high frequencies impacts regulator performance, especially in the noise reduction LPF and the output. Is that HF noise mostly negated by local decoupling at the Si570? np0 caps are more linear wrt freq but aren't really available in the sizes we need on the output of this regulator. I'm also not keen on doing mix and match caps of different sizes to set up ringing and other dramas in the critical high freq area. I have tried looking for better alternative parts for the output caps or the CNR cap and other than different brand X7R or tant caps there isn't much around by the looks.

So from the above, I've come to the above that there isn't many places to gain a technical advantage from deviating from Ian's BOM. I guess that means Ian has thought through all of the above and come to the BOM selections for good reasons

I will probably do a few different versions with tant and panasonic spcap on the regulator input, just because I have a few boards to try.

Chris
The MLCC capacitors are very interesting.

They have good high frequency performance comparing with tan and others. But the temperature characteristic are poor. You can do a test:
Measure the capacitance at room temperature by a capacitor mater. Then, use a hot gun heat the MLCC to around 100 degree C. Measure the capacitance again.

X7R +10% to 20%
X5R -10% to 20%
Y5V -50% to 70%

NP0 or C0G are best, but the capacitance too small.

MLCC from different brand sound slightly different. Similar to changing the audio interconnection cable.

Ian
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Old 21st February 2013, 04:40 AM   #2456
qusp is offline qusp  Australia
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remember the point of a regulator is to have a completely stable voltage at the output and particularly when powering clocks or references, I cant see the voltage coefficient would cause any problems on the output, as any voltage driven distortion is usually dynamic in nature.

on my TPS PCB i'm allowing for 0201 size for the noise reduction and output bypass on the underside (for low voltage/lowest noise application). I will be trying the thin film AVX caps here, they now go up to 10nf, but I will probably just stick to c0g with polystyrene film (relcap) option

my board is a bipolar reg, primarily for analogue, higher voltage applications
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Old 21st February 2013, 04:48 AM   #2457
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I guess my comment about HF capacitance was bought on after seeing this graph in wikipedia article on ceramic caps.



I haven't been able to find a similar graph in TDK/murata datasheets for their caps though so I've had some difficulty rationalising it. I would expect the HF performance to be also a function of the size of the capacitor so I was looking to see if a capacitor array may be used to improve HF performance of X7R for example. In the mean time I'll use X7R caps and keep hunting for other alternatives.


Chris
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Old 21st February 2013, 01:00 PM   #2458
marce is offline marce  United Kingdom
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I do power supplies for high rel and X7R are acceptable and often better tan most, also for local decoupling X7R's are better than COG. Anything less than an X7R shouldn't be used unless you want small package high value reservoir capacitors scattered around digital designs and need the space.
The only exception to this is on oscillators it is worth having a very low value (and thus small case size 0603 at least) COG for ultimate decoupling.
X7R are the best decoulers going, you get the smallest case size for a given value (and that is critical) and when using different values you get less resonant peaks than you would do with other capacitors. COG are not the best cap for decoupling digital designs, and once you get above about 20MHz the caps are basicvly not a lot of use. The actual decoupling is on die capacitance first, power plane capacitance second, small decouplers near the pins with the lowest inductance possible 3rd (that means small size) then reservoir capacitors and finaly power supply.
I often use this tool on complex designs to calculate and optimise the power delivery system for high rel complex designs:
http://www.algozen.com/DS_CADSTAR_LT...2011_10_05.pdf

This is on designs that often have to work at -40/+85 DEG C, life critical applications, that are tested to the nth degree at all temp ranges.

Last edited by marce; 21st February 2013 at 01:05 PM.
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Old 21st February 2013, 01:05 PM   #2459
qusp is offline qusp  Australia
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and also remember the board and part was specified with ceramic caps, so the performance you see in the datasheet is with them
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Old 21st February 2013, 01:08 PM   #2460
qusp is offline qusp  Australia
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yep, I got some x7r as well for the 1uf bypass at the input side (0402), but I really want to try out those silly expensive thin films =) as my only real wank value part on the board, I cant help myself . as well as providing space for the larger film (not a huge aerial, just 5mm) because for here low noise is preferable and I want to try a couple different things out.

other people will be getting the boards too, so I figure its good to leave a couple options to satisfy different peoples cap fetishes as long as it doesnt compromise the layout.

Last edited by qusp; 21st February 2013 at 01:13 PM.
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