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ADF4150HV Lock Detect Intermittent

Question asked by TimG on Dec 13, 2011
Latest reply on Dec 13, 2011 by Grzegorz.Wawrzola

I have an application using an ADF4150HV. I'm using the digital lock detect provided by the chip.  I find that the digital lock detect does not always go high, even though the VCO seems to be locked.

 

I am programming the following settings to the chip:

Register Writes:

     R0   0x001BEA90

     R1   0x0000F801

     R2   0x7800A2C2

     R3   0x0004025B

     R4   0x0080003C

     R5   0x10400005

 

Setting Breakdown:

(all numbers in decimal)

R0

INT                   55
FRAC               3410
R1
Prescaler          0
Phase              1
MOD                3840
R2
Low Noise/Low Spur        3
Muxout                           6
Reference Double            0
RDiv2                             0
10 Bit R Counter             2
Double Buffer                  1
Charge Pump Current  1
LDF                                0
LDP                                1
Power Down                    0
Charge Pump Tristate   0
Counter Reset                  0
R3
Boost Enable          1
CLK Div Mode         0
Clock Divider       75
R4
Feedback Select          1
Divider Select               0
Mute till lock detect  0
RF Ouptut Enable     1
Output Power            3
R5
AntiBacklash Pulse Width          0
Charge Cancellation Enable    0
Charge Pump Mode                    1
Lock Detect Pin Mode               1

I can write these settings back to back and after some writes the LD pin goes high, others it does not.  Am I doing something wrong?

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