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ADRF 6850 unable lock PLL

Question asked by bruno_20 on Jun 19, 2017
Latest reply on Jul 28, 2017 by gyaliniz



I am using ADRF 6850, however when starts aquisiton of pll don't lock and when i whacth LOMON outputs i have  a lobe with 12 MHz in my desired frequency. If i change the LO frequency i continue with lobe of 12MHz.


I am using a 13.5MHZ oscilator




the value of registers

const char cr0_val = 0x00; //FRAC word 4 bit[7:0]; LSB, last register to be updated
const char cr1_val = 0x00; //FRAC word 3 bit[15:8];
const char cr2_val = 0x00; //FRAC word 2 bit[23:16]
const char cr3_val = 0x00; //FRAC word 1 bi1[24] MSB
const char cr4_val = 0x01; //RESERVED
const char cr5_val = 0x00; //5-bit division enable, bit[4]=1
const char cr6_val = 0x3C; //INT less significant bit[7:0] FREQ=810MHz
const char cr7_val = 0x00; 
const char cr8_val = 0x00; //RESERVED
const char cr9_val = 0x60; //set charge pump current bit[7:4],bit[3:0]=0
const char cr10_val = 0x21; //5-bit ratio bit[4:0]=00001 , divide-by-2 bit[6]=0, doubler bit[5]=1
const char cr11_val = 0x00; //RESERVED
const char cr12_val = 0x18; //pll power up bit[2]=0,
const char cr13_val = 0x08; //RESERVED
const char cr14_val = 0x00; //LDET[7]=0,
const char cr15_val = 0x00; //RESERVED
const char cr16_val = 0x00; //RESERVED
const char cr17_val = 0x00; //RESERVED
const char cr18_val = 0x60; //RESERVED
const char cr19_val = 0x00; //RESERVED
const char cr20_val = 0x00; //RESERVED
const char cr21_val = 0x00; //RESERVED
const char cr22_val = 0x00; //RESERVED
const char cr23_val = 0x70; //LDCount0 bit[3]=1, lock detector enable bit[4]=1,, bit[6:5]=1
const char cr24_val = 0x38; //Autocalibration enable bit[0]=0, bit[4:3]=1
const char cr25_val = 0x70; //Autocalibration timer 100us
const char cr26_val = 0x00; //RESERVED
const char cr27_val = 0x00; //LOMON output bit[1:0]=1 -6dBm, power up LOMON bit[2]=1
const char cr28_val = 0x08; //RFDIV bit[2:0]=000, bit[3]=1
const char cr29_val = 0x41; //power up modulator bit[0]=1, bit[7]=1, bit[6]=0 vcom, bit[3]=0 narrow band
const char cr30_val = 0x00; //VGA bit[0]=1 60 dBm 


I write the registers from cr30 to cr0, being the register cr0 last register written. After this, I write
cr27 = 0x07, where i power up LOMON outputs.


I follow the power-up sequence of data sheet, however i can't see where is my mistake.