Part Number: LMX2595
Other Parts Discussed in Thread: , USB2ANY
HI Ti,
We are working on LMX2595 PLL and we are generating 0.5GHz to 18 GHz frequency in steps of 1MHz.
We have mounted the LMX2595 in our card with FPGA in it. For changing frequency we are programming only 7 registers + R0 register which are mentioned below.
| R75 | CHDIV | ||||
| R46 | OUTB_MUX,Channel divider,VCO,SysRef | ||||
| R45 | OUTA_MUX,Channel divider,VCO,VCO2X | ||||
| R43 | PLL_NUM[15:0] | ||||
| R37 | PFD_DLY_SEL | ||||
| R36 | PLL_N | ||||
| R27 | VCO2X_EN | ||||
With this register we are getting lock at all frequencies without any issues.
But the issue is close by spurious. When I programm the LMX2595 using our FPGA we are getting more close by spurs at 125Khz, 250Khz and 500KHz away.( My test frequencies are 15001,15201,15199 MHz etc) spur level is -40dbc. I am using 50KHz Loop bandwidth
But when I programm the LMX2595 mounted on our card using Ticpro software( Here I am by passing the on board FPGA and I am taking the SPI from LMX2595EVM), I am not getting any spurs( spur level is -55dbc).
I checked the registers value of both methods, they are the same(charge pump current is also same). But only spurs are high when I programm through on board FPGA.
My doubt is, other than those 7 register and R0 registers, do we need write any other register. So that spurs will get reduced.
On board FPGA register map Tics pro register map 0x700000 0x700000 R112 0x6F0000 0x6F0000 R111 0x6E0000 0x6E0000 R110 0x6D0000 0x6D0000 R109 0x6C0000 0x6C0000 R108 0x6B0000 0x6B0000 R107 0x6A0000 0x6A0000 R106 0x690021 0x690021 R105 0x680000 0x680000 R104 0x670000 0x670000 R103 0x660000 0x660000 R102 0x650011 0x650011 R101 0x640000 0x640000 R100 0x630000 0x630000 R99 0x620000 0x620000 R98 0x610888 0x610888 R97 0x600000 0x600000 R96 0x5F0000 0x5F0000 R95 0x5E0000 0x5E0000 R94 0x5D0000 0x5D0000 R93 0x5C0000 0x5C0000 R92 0x5B0000 0x5B0000 R91 0x5A0000 0x5A0000 R90 0x590000 0x590000 R89 0x580000 0x580000 R88 0x570000 0x570000 R87 0x560000 0x560000 R86 0x550000 0x550000 R85 0x540000 0x540000 R84 0x530000 0x530000 R83 0x520000 0x520000 R82 0x510000 0x510000 R81 0x500000 0x500000 R80 0x4F0000 0x4F0000 R79 0x4E0003 0x4E0003 R78 0x4D0000 0x4D0000 R77 0x4C000C 0x4C000C R76 0x4B0940 0x4B0800 R75 0x4A0000 0x4A0000 R74 0x49003F 0x49003F R73 0x480001 0x480001 R72 0x470081 0x470081 R71 0x46C350 0x46C350 R70 0x450000 0x450000 R69 0x4403E8 0x4403E8 R68 0x430000 0x430000 R67 0x4201F4 0x4201F4 R66 0x410000 0x410000 R65 0x401388 0x401388 R64 0x3F0000 0x3F0000 R63 0x3E0322 0x3E0322 R62 0x3D00A8 0x3D00A8 R61 0x3C0000 0x3C0000 R60 0x3B0001 0x3B0001 R59 0x3A8001 0x3A8001 R58 0x390020 0x390020 R57 0x380000 0x380000 R56 0x370000 0x370000 R55 0x360000 0x360000 R54 0x350000 0x350000 R53 0x340820 0x340820 R52 0x330080 0x330080 R51 0x320000 0x320000 R50 0x314180 0x314180 R49 0x300300 0x300300 R48 0x2F0300 0x2F0300 R47 0x2E07FC 0x2E07FD R46 0x2DC0DF 0x2DD0DF R45 0x2C1FA3 0x2C1FA3 R44 0x2B0000 0x2B0000 R43 0x2A0000 0x2A0000 R42 0x290000 0x290000 R41 0x280000 0x280000 R40 0x27C350 0x27C350 R39 0x260000 0x260000 R38 0x250304 0x250304 R37 0x240028 0x24002D R36 0x230004 0x230004 R35 0x220000 0x220000 R34 0x211E21 0x211E21 R33 0x200393 0x200393 R32 0x1F43EC 0x1F43EC R31 0x1E318C 0x1E318C R30 0x1D318C 0x1D318C R29 0x1C0488 0x1C0488 R28 0x1B0002 0x1B0003 R27 0x1A0DB0 0x1A0DB0 R26 0x190C2B 0x190C2B R25 0x18071A 0x18071A R24 0x17007C 0x17007C R23 0x160001 0x160001 R22 0x150401 0x150401 R21 0x14E048 0x14E048 R20 0x1327B7 0x1327B7 R19 0x120064 0x120064 R18 0x11012C 0x11012C R17 0x100080 0x100080 R16 0x0F064F 0x0F064F R15 0x0E1E10 0x0E1E10 R14 0x0D4000 0x0D4000 R13 0x0C5001 0x0C5001 R12 0x0B0018 0x0B0018 R11 0x0A10D8 0x0A10D8 R10 0x091604 0x091604 R9 0x082000 0x082000 R8 0x0740B2 0x0740B2 R7 0x06C802 0x06C802 R6 0x0500C8 0x0500C8 R5 0x040A43 0x040A43 R4 0x030642 0x030642 R3 0x020500 0x020500 R2 0x010808 0x010808 R1 0x00251C 0x00251C R0
