[McHUG] Re: Si570 board question

[Peter Morton]

Rich-

Don't put anything at the R3 and R4 positions.  These positions are tied to 
ground at one end and to the SI570 outputs on the opposite end.  These parts 
are no longer used and are no longer on the schematic.

For the SI570 output connection to the SMA connectors:

If you are using the LVDS version of the SI570, I recommend you use the 0.1 
uF capacitors supplied at C6 and C7.  The capacitors will provide isolation 
at the board outputs from the DC voltage present at the SI570 outputs. If 
you decide to use an LVDS receiver at the receiving end, short the C6 and C7 
positions.  The LVDS outputs only swing about 0.35 volts and ride at a 
nominal 1.25 volt common-mode DC level.

If you are using the CMOS version of the SI570, how the output is configured 
depends on what you are driving on the receiving end.  If  you are driving 
3.3 volt logic, then use the 49.9 ohm resistors in place of C6 and C7 or 
short out the C6 and C7 positions.  The resistors provide short-circuit 
protection and some protection from inadvertent mis-connections.  The CMOS 
SI570 puts out a square-wave swinging from 0 to 3.3 volts.  If you drive 
something other than 3.3 volt devices, you may have to use a different 
output configuration.

Headers:

Header H1 and R5 are for the Vc pin of the SI571.  The SI570 does not use 
this pin.  Nothing needs to be done at H1 and R5.

H3  is for the OE (output enable) pin of the SI570.  I put a wire jumper 
between pins 1 (VDD) and 2 of the header H3 to pull this input high.  I 
subsequently learned that the part has an internal pull-up resistor on this 
input so no jumper is required (but I haven't tried it without the jumper).

Good luck.

-Pete


----- Original Message ----- 
From: "Rich Mitchell" <geobra at att.net>
To: "Peter Morton" <mortonph at comcast.net>
Sent: Saturday, March 22, 2008 12:05 PM
Subject: Re: Si570 board question


> Pete and Steve,
>
> Thanks all, I guess the bevel is in the detail.
>
> Followup questions for Si570 board.  Now I have R3, R4 and R5 empty.  I 
> assume R3 and R4 are where you would put either the  49.9 resistors or 
> wire if you wanted DC connection.  R5 at 0 should be a wire?? Or just 
> leave it out and ignore H4, whatever that was for.  H3 is a 3 way header. 
> What is that used for?  I would guess set it on 1 - 2 to program the Si570 
> and 2 - 3 once a frequency is chosen.  If you are going to be frequency 
> agile you just leave it on 1 - 2??
>
> Thanks
> Rich
>
> --
> McHUG - Physical Computing ;)
> MicroController Ham User Group
>  -------------- Original message from "Peter Morton" 
> <mortonph at comcast.net>: --------------
>
>
>> Rich-
>>
>> The rounded pin (as viewed from the bottom) of the SI570 is pin 1.  The
>> package should be oriented so this pin is next to the dot on the board.
>>
>> The GTL2002 has a beveled edge along the long dimension on top of the
>> package.  This edge is on the same side as pins 1 through 4.  I couldn't
>> figure it out either until I downloaded the data sheet.
>>
>> -Pete
>>
>> ----- Original Message ----- 
>> From: "Rich Mitchell"
>> To: "Peter Morton" ; "Steve Beckman" ;
>> "Steve Beckman"
>> Sent: Saturday, March 22, 2008 9:21 AM
>> Subject: Si570 board question
>>
>>
>> > Steve and Pete,
>> > Been up early trying to build the Si570 board.  Just want to confirm 
>> > the
>> > orientation of U2 and U3.  I figure on U2, the Si570, the rounded pin 
>> > on
>> > the bottom of the chip corresponds with the hex shaped mark on the 
>> > board.
>> > So the printing on the chip is upside down compared to the "U2" on the
>> > board.  I haven't found the pin 1 indicator on U3.  So is the printing 
>> > on
>> > the chip upside down or right side up compared to the printing on the 
>> > rest
>> > of the board?
>> >
>> > Steve, most excellent box of parts!!!!  By the way, Chuck Coffee 
>> > describes
>> > himself as a "AVR nut".  Sounds like one of us.
>> >
>> > Rich
>> >
>> > --
>> > McHUG - Physical Computing ;)
>> > MicroController Ham User Group
>>