[Clutz]

Hey guys,

RE: AD1896: Why did you choose togo with a 3.3V PSU for both VDD_CORE and VDD_IO, instead of 3.3V for VDD_CORE and 5.0V for VDD_IO? Was it just to simply the power supply situation?

 

[00940]

I couldn't find anything in the datasheet suggesting better performances for a 5V supply. This bit "The AD1896 is a 3.3 V, 5 V input tolerant part .... The AD1896 is 5 V input-tolerant only when the VDD_IO supply pin is supplied with 5 V" seems to suggest that a VDD_IO of 5VDC is only useful for higher inputs.

So, yes, we went with what was easiest (and cheaper) to lay out.

 

[Clutz]

I'm thinking of going with the following

PCM2707 (requires 3.3V supply, in addition to the 5.0Vbus provided by USB) -> AD1896 (3.3V and 5.0V), Df1706 (3.3V part), AD1862 (+/-12V for the analog side, and +/- 5 to 12V for the digital side).


a) The 3.3V PSU for the digital poarts (PCM2707, AD1896, DF1706) would be derived from the +12V PSU for the digital portion of the AD1862, and then a separate +/-12V for the analog portion of the AD1862/I/V stage

OR

b) I could go with a single 3.3V supply to power the PCM2707, AD1896, and DF1706, and have a 5.0V PSU for the AD1896 and the digital side of the AD1862, and then a +/-12V PSU for the analog side of the AD1896.

c) I could go with a 3.3V PSU for the PCM2707, DF1706, and AD1896, plus a 5.0V PSU also for the AD1896, derived from the +/-12V PSU for the AD1862 (ultimately 3.3V derived from the 5.0V, derived from the +12V) for the digital portion; and a separate +/-12V PSU in the for the analog portion.

So for a) I could create a +3.3V PSU from the +/- 5-12V PSU required for the AD1862 (e.g. one transformer), and one +/-12V PSU for the analog side of the AD1862 and the I/V stage (which will be an opamp - probably ths4631).

or for b) I could create a +3.3V needed for the PCM2707, AD1896, and DF1706 from the +/-5V PSU required for the digital portion of the portion of the AD1862; and then a single +/-12V power supply for the analog portion of the AD1862 and the ths4631 opamps used for i/v conversion.

What do you think?

 

[Clutz]

IC6: USBUFxx? Where did you get the Eagle library for this particular part?

Thanks,
Clutz

 

[00940]

Bleot made the part I think.

Quote:

or for b) I could create a +3.3V needed for the PCM2707, AD1896, and DF1706 from the +/-5V PSU required for the digital portion of the portion of the AD1862; and then a single +/-12V power supply for the analog portion of the AD1862 and the ths4631 opamps used for i/v conversion.

I'd go that way, with some RLC networks to isolate the channels.

 

[ble0t]

Yea...that was a custom part. I've gotten fairly good at those in EAGLE

Remember...datasheets are your friends

 

[Clutz]

My analog power supply will consist of two: 20VA 20VAC with center tapped secondaries. The first will be for the digital portion, and the second will be for the digital portion. One power supply for digital, one for analog. Each of the power supplies will be identical


Mains :115VAC -> Center Tapped Transformer 14VAC -> RCLCAC -> SoftRecovery Diodes (or Diode Bridge) + snubbers -> Voltage Regulators

Digital Power Supplies

12V PSU's:
Voltage Regulator (LM7812, 12V OUT): 12V PSU for the DIGITAL AD1862
Voltage Regulators(LM7912): -12V PSU for the DIGITAL AD1862

5V and 3V PSUs
Voltage Regulator (LT1763, 5V OUT): 5V PSU for the AD1896
Voltage Regulator (LT1763, 3.3V OUT): 3.3V PSU for the PCM2707, AD1896, DF1706

Analog Power Supply:

Separate Transformer: Center Tapped Transformer: 14VAC-> RCLCRC -> Bridge + snubbers> LM7812/LM7912

I'd actually make this on two separate boards.

How does that seem?

 

[Clutz]

On the updated BOM:
Re: R7, R10, R17, R19. I cannot find any 600R resistors anywhere - is 560 close enough? Additionally, Idon't know what KK1, and KK2 are supposed to be - and I can't find anything for the part L1.

There seems to be a large number of parts that need to be ordered from Mouesr. Is thjere any reason to use parts from mouser (e.g. vishay dale) over equivalent parts from Digikey (e.g. Panasonic, Yageo), simply so I can simplify any resulting order?

Thanks,
Clutz

 

[Pars]

Quote:

Originally Posted by Clutz On the updated BOM: Re: R7, R10, R17, R19. I cannot find any 600R resistors anywhere - is 560 close enough? Additionally, Idon't know what KK1, and KK2 are supposed to be - and I can't find anything for the part L1.

Would 604 ohms be close enough? Or 590? Check PPC604YCT-ND at Digikey... all kinds of BC and PPC (basically the same) there. I like the BC resistors (SRC25 IIRC). 1% 0.4W metal film.

 

[ezkcdude]

I second the vote (if that was a vote) for going with digikey parts. The only resistors I like better at Mouser, because digikey doesn't carry them, are the Vishay 0.1% VTF.

 

[ble0t]

L1 was in the Mouser BOM:

434-01-101JFastron High Reliability Radial RF Chokes

As for those other resistors, I think I missed those (oops), so I guess just try and get as close as you can

EDIT: The reason I went with Mouser for most of the resistors and capacitors is because they don't force an order in multiples or 5 or 10, thus saving some $$$ which is always a good thing

 

[Clutz]

ble0t: That's what I figured. I'll have to decided if it's worth waiting 2 weeks for a USPS shipping to Canada, or find out if the FedEx brokerage fees are ridiculous. I've got most of the BOM for this figured out for Digikey - just gotta figure out a BOM for Mouser, or convert it to digikey - and then add on some parts for other projects. Could be the single largest order yet.

I can't seem to figure out how to make new parts in Eagle..

Do I just draw the outline as I want it to appear in the schematic first and THEN layout the pads? Any advice?

 

[steinchen]

While populating the board I realized that I'm short of one reg101ua-5, Mouser is out of stock, may someone hook me up on his digikey order ?

Quote:

Originally Posted by Clutz I can't seem to figure out how to make new parts in Eagle.. Do I just draw the outline as I want it to appear in the schematic first and THEN layout the pads? Any advice?

The easiest way is to copy existing devices / packages and alter them. The device editor is all but intuitive to me too, when creating new parts I always hold the manual in my left hand :X

 

[MASantos]

Quote:

Originally Posted by steinchen While populating the board I realized that I'm short of one reg101ua-5, Mouser is out of stock, may someone hook me up on his digikey order ?

You need the 5volt fixed one right?

I have two of those I don't need. Send me a Pm with your adress, I'll ship them tomorrow.

 

[ble0t]

Here's a pretty basic overview of how to add a new part to the library. The basic premise is that you need to design a symbol (schematic) and a package (layout/board) and then combine those into a device so that when you add a part to your schematic/board, it has an equivalent symbol/package to add to the other.

http://myhome.spu.edu/bolding/EE4211/EagleTutorial4.htm

I hope that helps a bit...