[time-nuts] Si570 question

[Jim Lux]

I'm sure someone here has fooled with the Si570.
I just got a few of them (CMOS output), and am about to deadbug one of
them to fool with it (unless there's some convenient protoboard out
there available.. I didn't look too long and hard, but some casual
googling didn't find one).
Looking at AN334 from SiLabs:
It looks like you just need a 10nF bypass on the Vcc, a pull down on the
OE (1k), 1k pullups to 3.3V on SDA/SCL (which is going to be driven by a
3.3V teensy 3.0/3.1 microcontroller)
150 ohm loads to ground, followed by a 0.1 uF DC block?

I'm going to be running it at less than 50 MHz (although the parts I got
are preset to 100 MHz)

Any traps for the unwary?
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[paul swed]

I just picked up the si5351a and the thing that jumps out at mee is the 228
registers to program.
Granted it lets you create just about any frequency and there is a good
program that tells you what to set the registers to. But 228 registers is a
lot.
The traditional I2C is indeed simple. Make sure you watch the LSB order and
setup times.
I see there are various ebay class boards to connect to usb for a few $ and
also boards that let you program in Windows studio as an example.
Or as you want to do straight out of a micro.
Regards
Paul

Post by Jim Lux
I'm sure someone here has fooled with the Si570.
I just got a few of them (CMOS output), and am about to deadbug one of
them to fool with it (unless there's some convenient protoboard out there
available.. I didn't look too long and hard, but some casual googling
didn't find one).
It looks like you just need a 10nF bypass on the Vcc, a pull down on the
OE (1k), 1k pullups to 3.3V on SDA/SCL (which is going to be driven by a
3.3V teensy 3.0/3.1 microcontroller)
150 ohm loads to ground, followed by a 0.1 uF DC block?
I'm going to be running it at less than 50 MHz (although the parts I got
are preset to 100 MHz)
Any traps for the unwary?
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[Jim Lux]

Post by paul swed
I just picked up the si5351a and the thing that jumps out at mee is the 228
registers to program.
Granted it lets you create just about any frequency and there is a good
program that tells you what to set the registers to. But 228 registers is a
lot.
The traditional I2C is indeed simple. Make sure you watch the LSB order and
setup times.
I see there are various ebay class boards to connect to usb for a few $ and
also boards that let you program in Windows studio as an example.
Or as you want to do straight out of a micro.

yes, there are a lot of registers, but there is some code out there to
manage them, which I haven't actually looked at.

The micro I'm using does I2C quite nicely, and I've used it for a
variety of devices.

I was wondering more about RF aspects.. How much Power supply rejection
do these things have (yeah, the ap note shows a single bypass cap, but
that may be "good enough to demonstrate function")... and how much
harmonic output content is there.


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[paul swed]

Clue-less.
As to the good code I have only found maybe 1 site. I thought there would
be more. I think it was hackaday.
Regards

Post by Jim Lux

Post by paul swed
I just picked up the si5351a and the thing that jumps out at mee is the 228
registers to program.
Granted it lets you create just about any frequency and there is a good
program that tells you what to set the registers to. But 228 registers is a
lot.
The traditional I2C is indeed simple. Make sure you watch the LSB order and
setup times.
I see there are various ebay class boards to connect to usb for a few $ and
also boards that let you program in Windows studio as an example.
Or as you want to do straight out of a micro.

yes, there are a lot of registers, but there is some code out there to
manage them, which I haven't actually looked at.
The micro I'm using does I2C quite nicely, and I've used it for a variety
of devices.
I was wondering more about RF aspects.. How much Power supply rejection do
these things have (yeah, the ap note shows a single bypass cap, but that
may be "good enough to demonstrate function")... and how much harmonic
output content is there.
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[Götz Romahn]

Jim,
thre is some info at:
http://www.box73.de/product_info.php?products_id=1869
it's all in German. If you can read that, goto "Zusaztinformationen"
(additional informations) where you will find a comprehensive articel
(pdf-document) also in German language (no I have not played with it).
enjoy Götz

Post by Jim Lux
I'm sure someone here has fooled with the Si570.
I just got a few of them (CMOS output), and am about to deadbug one of
them to fool with it (unless there's some convenient protoboard out
there available.. I didn't look too long and hard, but some casual
googling didn't find one).
It looks like you just need a 10nF bypass on the Vcc, a pull down on the
OE (1k), 1k pullups to 3.3V on SDA/SCL (which is going to be driven by a
3.3V teensy 3.0/3.1 microcontroller)
150 ohm loads to ground, followed by a 0.1 uF DC block?
I'm going to be running it at less than 50 MHz (although the parts I got
are preset to 100 MHz)
Any traps for the unwary?
_______________________________________________
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[Jim Lux]

Post by Götz Romahn
Jim,
http://www.box73.de/product_info.php?products_id=1869
it's all in German. If you can read that, goto "Zusaztinformationen"
(additional informations) where you will find a comprehensive articel
(pdf-document) also in German language (no I have not played with it).
enjoy Götz

that was quite informative (and not totally beyond my limited German
vocabulary)

Looks like they just send the output out through a couple of DC blocks,
with no load resistors.


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[Orin Eman]

I have one of these: http://sdr-kits.net/PA0KLT_Description.html

built with the CML output Si570 that goes to 1417 MHz (!)

There is a schematic in the assembly manual that's linked to from that
page. They use 100n and 1n capacitors in parallel on Vdd and 4K7 pullups
on SCL/SDA. They have 100n DC blocks directly on the output pins.

Into a 50 ohm load, the CML outputs produce about 4dBm as I recall.
Obviously, the CMOS output will be different.

There is a review of a different Si570 kit on the Clifton Labs site:

http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm

I got similar results comparing my kit against an HP 8640B. The Si570
beats the 8640B close in just as shown on the Clifton Labs site.

Some Softrock SDR radios also use the Si570. They use a single 10n
capacitor on Vdd and 2K2 pullups...:

http://www.wb5rvz.org/ensemble_rxtx/03_lo

I have the Softrock Ensemble RXTX. It works fine on RX, but unfortunately
I have not been able to get satisfactory image rejection on TX. I suspect
the FST3253.

So, it looks like decoupling isn't that critical - 10n or 100n||1n in these
examples. 1K pullups on SDA/SCL seem to be overkill and anything
reasonable <= 4K7 should work.

Orin.

Post by Jim Lux
I'm sure someone here has fooled with the Si570.
I just got a few of them (CMOS output), and am about to deadbug one of
them to fool with it (unless there's some convenient protoboard out there
available.. I didn't look too long and hard, but some casual googling
didn't find one).
It looks like you just need a 10nF bypass on the Vcc, a pull down on the
OE (1k), 1k pullups to 3.3V on SDA/SCL (which is going to be driven by a
3.3V teensy 3.0/3.1 microcontroller)
150 ohm loads to ground, followed by a 0.1 uF DC block?
I'm going to be running it at less than 50 MHz (although the parts I got
are preset to 100 MHz)
Any traps for the unwary?
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.

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[Jim Lux]

Post by Orin Eman
I have one of these: http://sdr-kits.net/PA0KLT_Description.html
built with the CML output Si570 that goes to 1417 MHz (!)
There is a schematic in the assembly manual that's linked to from that
page. They use 100n and 1n capacitors in parallel on Vdd and 4K7 pullups
on SCL/SDA. They have 100n DC blocks directly on the output pins.
Into a 50 ohm load, the CML outputs produce about 4dBm as I recall.
Obviously, the CMOS output will be different.
http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm
I got similar results comparing my kit against an HP 8640B. The Si570
beats the 8640B close in just as shown on the Clifton Labs site.
Some Softrock SDR radios also use the Si570. They use a single 10n
http://www.wb5rvz.org/ensemble_rxtx/03_lo
I have the Softrock Ensemble RXTX. It works fine on RX, but unfortunately
I have not been able to get satisfactory image rejection on TX. I suspect
the FST3253.
So, it looks like decoupling isn't that critical - 10n or 100n||1n in these
examples. 1K pullups on SDA/SCL seem to be overkill and anything
reasonable <= 4K7 should work.
Orin.

thanks... looks like it's time to stop analyzing and go find a piece of
copper clad to stick this thing down on. I see a lunchtime project
coming up,


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[Neil Schroeder]

Jim-

Do you need to tune it? The 571 is the VCXO - but if you're feeling
adventuresome you could drive the 570 as an NCO (numerical) via its i2c
interface.

NS

Post by Orin Eman
I have one of these: http://sdr-kits.net/PA0KLT_Description.html
built with the CML output Si570 that goes to 1417 MHz (!)
There is a schematic in the assembly manual that's linked to from that
page. They use 100n and 1n capacitors in parallel on Vdd and 4K7 pullups
on SCL/SDA. They have 100n DC blocks directly on the output pins.
Into a 50 ohm load, the CML outputs produce about 4dBm as I recall.
Obviously, the CMOS output will be different.
http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm
I got similar results comparing my kit against an HP 8640B. The Si570
beats the 8640B close in just as shown on the Clifton Labs site.
Some Softrock SDR radios also use the Si570. They use a single 10n
http://www.wb5rvz.org/ensemble_rxtx/03_lo
I have the Softrock Ensemble RXTX. It works fine on RX, but unfortunately
I have not been able to get satisfactory image rejection on TX. I suspect
the FST3253.
So, it looks like decoupling isn't that critical - 10n or 100n||1n in these
examples. 1K pullups on SDA/SCL seem to be overkill and anything
reasonable <= 4K7 should work.
Orin.
thanks... looks like it's time to stop analyzing and go find a piece of

copper clad to stick this thing down on. I see a lunchtime project coming
up,
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[Brooke Clarke]

Hi Jim:

A number of hams have built VFOs using this chip, for example here's some data:
http://www.cliftonlaboratories.com/si570_kit_from_k5bcq.htm#Frequency_Spectrum
Mail_Attachment --
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html

Post by Jim Lux
I'm sure someone here has fooled with the Si570.
I just got a few of them (CMOS output), and am about to deadbug one of them to fool with it (unless there's some
convenient protoboard out there available.. I didn't look too long and hard, but some casual googling didn't find one).
It looks like you just need a 10nF bypass on the Vcc, a pull down on the OE (1k), 1k pullups to 3.3V on SDA/SCL (which
is going to be driven by a 3.3V teensy 3.0/3.1 microcontroller)
150 ohm loads to ground, followed by a 0.1 uF DC block?
I'm going to be running it at less than 50 MHz (although the parts I got are preset to 100 MHz)
Any traps for the unwary?
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

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