EMRFD Message Archive 12519

Message Date From Subject
12519 2016-03-18 15:42:29 Rod KM6SN SI570s
Hi All,

I use SI570 from Digikey. I use software similar to Farhan's Minima

All I do is measure the startup frequency (before any I2C commands have been
sent to the SI570), and then correct the software for the exact startup
Works well.

12520 2016-03-19 09:21:56 aa0zz Re: SI570s
DigiKey has two versions of the Si570 in stock: part numbers 570CAC000121DG and 570CAC000141DG.
570CAC000121DG has a start-up frequency of 100 MHz and 570CAC000141DG has a start-up frequency of 56.32 MHz.
As previously mentioned, software can read the default frequency and act accordingly; however, some software packages don't do this so you have to be careful.  The 56.32 MHz start-up was very popular, at least at first, because the popular divide-by-4 mechanisms (to get I and Q) put it in the 20M band (14.080 MHz).  My favorite start-up frequency is 10 MHz so it can immediately be heard upon power-up with a ham receiver. 
One more note.  The "A" in the "CAC" portion of the part number indicates these parts have a total stability (temperature etc) of 61.5ppm.  There are two other Si570 varieties (available from Silicon Labs direct) which guarantee even less drift.  The type "B" gives 31.5ppm and the latest (my favorite) is type "C" which gives 20ppm.  Beware that the "C" requires the software to use different Si570 registers for the parameters and some software may not handle this.  Software auto-detect for distinguishing between A or B vs C is not quite as straight-forward as might be expected but can be done.

-Craig, AA0ZZ
12521 2016-03-19 09:28:16 Ashhar Farhan Re: SI570s
i have used all types (including the LVDS) version with the same libraries. it worked everytime.

- f