HMC830 Frequency Hopping - Direct LUT ?

The LUT is device specific. From page 4 in the app-note:

If you generate the LUT with one device and use it on another the switch capacitor selection might not be optimum over temperature and time.  I believe you want to use the "Direct LUT" method as described in the app-note.   This method associates each desired frequency with a switch capacitor selection.

Hello dyoung1,

You are right. I missed that part.

So, I have to include in microcontroller code a routine to generate the LUT and store in EEPROM.

Thank you for your help.

Hello,

I have a doubt regarding the table with the values of the switch capacitors.

I set the HMC830 without auto-calibration.

Then I printed the registry values "Reg 10h VCO Tune Register" to various frequencies with a step of 10KHz in order to see that frequency changes occur Reg10 value. (see attached below)

As shown in the table, there are some "jumps" in the Reg10 values.

I have seen that there are 6 jumps and are always 32 to 5 on the previous value (see column "changes").

My questions are:

Will they always be 6 jumps?

Is the jump occurs in the same registry value?

Thank you very much for your help.

-------------------------------------

-------------------------------------

Autocal will pick the best VCO and switch capacitor setting for a given frequency.  The actual location of the "jumps" vary depending on the VCO.  

You can decode Reg 0x10 as follows:

Reg 0x10[7:6] VCO selection, 11b= lowest frequency)

Reg 0x10[5] don't care, may by high or low

Reg 0x10[4:0] switch capacitor setting (11111b=lowest frequency)

As you see the cause of the large jumps is the don't care bit 5.  If you create a new 7 bit number by concatenating [7:6] with [4:0] you will get a steady decrease in this number as you perform the same measurement.  But for any given frequency the number will vary from part to part.

Thank you very much for your help. It has been very useful.

Sorry, I get the values of the table with self-calibration function activated (do not explain well in my previous comment).

Best regards.

Hello again,

We have another question: Which sequence needs to be sent in manual mode? We configure the PLL registers in the following order in manual mode:

1 Reg 0A (bit 11 = 1 , Bypass VCO Tuning)

2 VCO_Reg 02h K (K>1 or K=1, depending on the frequency required)

3 Reg 05h 00 (Recommended in Datasheet)

4 Reg 03h Integer Part

5 Reg 04h Fractional Part

6 VCO_Reg 00h Tuning (LUT Table data)

Each time a frequency is set we need to program Reg 0A to remain in Manual mode.

If we program Reg 03 (Nint) and Reg 04 (Nfrac) before VCO_Reg 02h, then the sequence does not work.

Please, could you help us?, thank you very much.

Once autocal is turned off (Reg 0x0A[11]=1) it should stay off unless you perform a soft reset ( Reg 0x00[5]=1).  Can you read Reg 0x0A[11] during the manual tuning procedure to see if it has changed from "1" to "0"?

Manual tuning should work when Nint and Nfrac are set before the output divider (VCO_Reg 02h).  You do not need step #3 (Reg 05h 00) since autocal is off.