Slightly OT: interest in a four-output, ultra-low jitter, synthesizer block?
After the recent discussion about Silicon Labs clock generators, I
looked at their Si5340A part and think it will be useful for a ham radio
project I'm working on. While it can do other things, for my use it
would use a 10 MHz input clock and generate 4 independent outputs in the
range of 100 kHz to 1028 MHz. Its jitter is <100fs, which translates to
"not bad" phase noise. Here's the data sheet if you're interested:
http://www.silabs.com/documents/public/data-sheets/Si5341-40-D-DataSheet.pdf
The challenge is that the chip is a 7x7 mm 44-QFN package and really
wants to be put on a six-layer circuit board. That's doable, but
challenging, for home assembly.
Rather than designing the chip into a larger circuit board, I'm thinking
of doing a small "carrier" board that would include just the chip and
critical bypass caps and have headers to plug into the main board.
Then, you could just drop the carrier into a project-specific board and
not have to worry about the complex layout and mounting. I have a
contract manufacturer who can build these up, if there's enough quantity
to justify the setup cost.
If you'd be interested acquiring in one or more of these, please drop me
a line off-list (jra at febo dot com). I don't think this will be a
TAPR project, but if there's enough interest to build 25 of these
carriers, I can probably make that happen. And remember -- this is just
the chip; you'll need to provide the rest of the circuit.
John
On Thu, Jan 25, 2018 at 7:32 AM, John Ackermann N8UR jra@febo.com wrote:
After the recent discussion about Silicon Labs clock generators, I looked
at their Si5340A part and think it will be useful for a ham radio project
I'm working on.
Have you considered the Si5340-EVB development board?
https://octopart.com/search?q=si5340-evb&start=0
It is about $150, relatively cheap for a development board, and there is
software to program it already.
73,
Mark
W7MLG
On Thu, 25 Jan 2018 09:32:56 -0500
John Ackermann N8UR jra@febo.com wrote:
http://www.silabs.com/documents/public/data-sheets/Si5341-40-D-DataSheet.pdf
The challenge is that the chip is a 7x7 mm 44-QFN package and really
wants to be put on a six-layer circuit board. That's doable, but
challenging, for home assembly.
Solderpaste stencil and a temp controlled frying pan helps :)
Rather than designing the chip into a larger circuit board, I'm thinking
of doing a small "carrier" board that would include just the chip and
critical bypass caps and have headers to plug into the main board.
Then, you could just drop the carrier into a project-specific board and
not have to worry about the complex layout and mounting. I have a
contract manufacturer who can build these up, if there's enough quantity
to justify the setup cost.
I'd be carefull with header pins at these frequencies. The slew-rate
of the chip is high enough that you get frequency components well into
the 10GHz range. I think a better idea would be just have castellation
at the PCB edge, with the right distances to meet impedance requriements,
and solder the PCB directly onto the main PCB without any connector inbetween.
Also be aware that these kind of chips are quite peculiar about
the quality of their power supply. You need to design it for the
internal VCO, such that it has good regulation well into the MHz range
and high quality blocking capacitors rated for GHz use. Using 3-terminal
pass through capacitors like the Murata EMIFIL[1] goes a long way
for these kind of applications (at only a slightly higher price than
normal capacitors).
Attila Kinali
[1] https://www.murata.com/en-global/products/emc/emifil/chip
--
<JaberWorky> The bad part of Zurich is where the degenerates
throw DARK chocolate at you.
Am 25.01.2018 um 15:32 schrieb John Ackermann N8UR:
The challenge is that the chip is a 7x7 mm 44-QFN package and really
wants to be put on a six-layer circuit board. That's doable, but
challenging, for home assembly.
Rather than designing the chip into a larger circuit board, I'm
thinking of doing a small "carrier" board that would include just the
chip and critical bypass caps and have headers to plug into the main
board. Then, you could just drop the carrier into a project-specific
board and not have to worry about the complex layout and mounting. I
have a contract manufacturer who can build these up, if there's enough
quantity to justify the setup cost.
Hi,
would this here be an acceptable solution?
No need for 6 layers.
Fanout of the chip to 100 mil wire wrap pins,
lives on 3.6 to 5V,
has regulators for the voltages needed:
LT3080 1V8 for digital core
LT3042 3V3 for analog core
LT3042 1V8 or 2V5 or 3V3 for IO voltage
Voltage for outputs can be selected per port between 1V8 core and IO
regulator
with a jumper wire.
There is a crystal and a CTS SMD oscillator.
Clock input 0: just 1:1
Clock input 1: differential with termination for PECL / LVDS
Clock input 2: onboard oscillator
Clock input 3: onboard crystal
Board size is abt. 1*2 inches, design rules 8mil/8mil, 1 signal layer +
1 GND layer.
You can cut away the left half if you definitely want only the fanout.
Via sizes are harmless enough for my DIY etch process, 0603 parts.
Altium Designer files are available, or Gerbers after review.
All parts available @ DigiKey.
I don't intend to push that much further :-)
73, Gerhard DK4XP
I hope the 2 .pngs are okay by size.
