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PLL interface - RF Cafe Forums
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lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
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Test & Measurement
Post subject: PLL interface Posted: Wed Dec 28, 2005 9:15
Who can give advice for PLL interface:
if PLL divders and
powerdown setting are programmable through a three-wire serial interface,
for a fixed frequency operating, can I use a simple three-wire series
EEPROM instead of microcontroller for PLL interface.
Your kind help
will be greatly appreciated
Posted: Thu Dec 29, 2005 2:07 am
Mon Jun 27, 2005 2:02 pm
Yes you can use EEPROM for that. The PLL chip doesn´t
really care about the way the programming command is being provieded,
as long as it provided in the right sequence, timing and logic levels.
Post subject: PLLPosted: Thu Dec 29, 2005 8:12 am
Most if not all EEPROMs are not system controllers. A "system controller"
is capable of generating control signals. That means that most if not
all EEPROMs cannot be used to generate the control signals needed by
the PLL. You'll need a microcontroller or PLD to do that.
merely respond to "read" and "write" commands generated elsewhere.
Post subject: Posted:
Thu Dec 29, 2005 5:47 pm
Thanks for guest and IR. Does it mean I
should use microcontroller such
as ATMEL ATtiny22, not use a simple
three-wire serial EEPROM such AT93C86?
Post subject: Posted: Thu Dec 29, 2005 6:05 pm
Sorry, another question: if PLL frequency is fixed, does it still need
any microcontroller or EEPROM? May it can be programmed outside from
Post subject: Posted:
Thu Dec 29, 2005 6:43 pm
Hello again RFGuy,
The EEPROM is
needed to program your PLL to hope from one known fixed frequency to
another. In case that your frequency is constant and doesn´t vary at
all, you can program your PLL without any EEPROM or any other PLD or
Posted: Thu Dec 29, 2005 7:20 pm
Thank you. Guest. You are so kind.
It means even I don't need to put any EEPROM or uP in the RF board.
Post subject: Posted: Fri Dec 30,
2005 1:14 am
Joined: Mon Jun 27, 2005
is true. If you use only a single constant frequency then you can deliver
your signals directly to the PLL without any additional components.
Post subject: PLLPosted: Fri Dec 30, 2005 1:43 am
IR & RFguy,
It depends on the specific PLL chip. Those that
have a 3-wire interface such as I2C (Philips) or SPI (Motorola/Freescale)
and including many by National, must have some circuitry to provide
serial data and clock. IR is correct, IF and ONLY IF you have a parallel
interface PLL chip, or one of the very rare ones with on-board EEPROM.
So be careful - just because you need only one frequency does not mean
that you don't have to get the correct divisor(s) into the chip.
Post subject: Posted:
Fri Dec 30, 2005 2:11 pm
Guest and IR,
Thank your help. How about
Silicon Lab Si3133 or Si4136? it has 3 -wire serial interface. No need
Happy New Year
Post subject: PLLPosted: Sat Dec 31, 2005 8:01 pm
I think you require
external parts with the SiLabs Si4136. According to the data sheet:
The Si4136 is programmed serially with 22-bit words
18-bit data fields and 4-bit address fields.
When the serial interface
is enabled (i.e., when SEN is
low) data and address bits on the SDATA
clocked into an internal shift register on the rising edge
of SCLK. Data in the shift register is then transferred on
edge of SEN into the internal data register
addressed in the address
field. The serial interface is
disabled when SEN is high.
Which sounds to me like there are no dependable default values loaded
IR, do you read it the same way?
Post subject: Posted: Sat Dec 31, 2005
Thank guest. You helped me many times. Before that, I did
PLL design only for loop filter and VCO, the frequency is not fixed,
so always used microcontroller , but no direct design with control function.
so I am not good at PLL interface. if frequency is fixed, Si4136 need
microcontroller or not? welcome more advices from PLL expert
Post subject: Need to pay attention to sink/source
currentsPosted: Sun Jan 01, 2006 9:24 am
Regardless of what you
use for a controller, you will need to check the sink/source current
requirements for the PLL control lines. I found out about this minor,
but important, detail the hard way in one of my former designs.
Post subject: Posted: Sun Jan 01, 2006 10:14
Joined: Mon Jun 27, 2005 2:02 pm
Hello RFguy and guest,
you will need control over the timing of writing to the Si4136.
the designs I have been involved with, it was done through a CPLD.
The function of the CPLD is to assure the right timing of the writing
sequence to the PLL device.
Also using CPLD makes it easier for
you to debug the circuit in case of problems. Most often it happens
that bits are sent in a wrong order because of misunderstanding the
sequence mentioned in the data sheet.
Then while getting a strange
output frequency or none at all, one can´t really understand if the
problem is programming-related or RF-related. By using a CPLD or similar
programmable device it is easier to eliminate and tackle problems.
Post subject: Posted: Sun Jan 01, 2006 11:47 am
Thank IR and guest again. Have a wonderful new year!