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LMX2595: Lock depends on OUTB_MUX

John Polak
Prodigy 151 points
Part Number: LMX2595
Other Parts Discussed in Thread: LMX2572

I am using LMX2595 with a reference frequency of 100MHz. I want to generate a 7.6GHz tone on output A. I get it working with these register values programmed:

R000: 0x6618 0x0808 0x0500 0x0642 0x0a43
R005: 0x00c8 0xc802 0x00b2 0x2000 0x0604
R010: 0x10d8 0x0018 0x5001 0x4000 0x1e70
R015: 0x064f 0x0080 0x012c 0x0064 0x27b7
R020: 0xa048 0x0401 0x0001 0x007c 0x071a
R025: 0x0c2b 0x0db0 0x0002 0x0488 0x318c
R030: 0x318c 0x03ec 0x0393 0x1e21 0x0000
R035: 0x0004 0x004c 0x0104 0x0000 0x0000
R040: 0x0000 0x0000 0x0000 0x0000 0x3c20
R045: 0xc8fc 0x07fd 0x0300 0x0300 0x4180
R050: 0x0000 0x0080 0x0820 0x0000 0x0000
R055: 0x0000 0x0000 0x0020 0x9201 0x0001
R060: 0x03e8 0x00a8 0x0322 0x0000 0x1388
R065: 0x0000 0x01f4 0x0000 0x03e8 0x0000
R070: 0xc350 0x0081 0x0000 0x003f 0x0000
R075: 0x0800 0x000c 0x0000 0x0003 0x0000
R080: 0x0000 0x0000 0x0000 0x0000 0x0000
R085: 0x0000 0x0000 0x0000 0x0000 0x0000
R090: 0x0000 0x0000 0x0000 0x0000 0x0000
R095: 0x0000 0x0000 0x0888 0x0000 0x0000
R100: 0x0000 0x0000 0x0000 0x0000 0x0000
R105: 0x0001 0x0000 0x8801 0x00f2 0x9d7d
R110: 0x0428 0x0093 0x011d

However, if I write R46 to 0x7ff (putting OUTB_MUX in high impedance mode) or to 0x7fc (setting channel divider) then the LMX2595 will report unlock. Why is this happening? When I am using OUTA_MUX set to channel divider, I am able to set OUTB_MUX to High impedance and still have lock. Is there some register that I need to change if I am not using one of the output muxes set to CH_DIV?

  • 0
    TI__Mastermind 29402 points

    Hi John, 
    I know for LMX2572, we cannot have one OUTX_MUX set to divider mode and the other OUTX_MUX to High-Z. We actually had to change it to reserved in the GUI. 
    LMX2572 & LMX259x are very similar and are even pin to pin compatible. Let me investigate to see if the same applies to LMX259x. 

    Regards, 

    Vicente