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LMX2592: TICSPRO Default Configuration vs Datasheet

Saverio Mercurio
Prodigy 70 points
Part Number: LMX2592

When selecting the "Default Configuration" menu item are the register values that are loaded supposed to be recommended values as a starting point, or are they supposed to match what the datasheet indicates as default values? We are seeing discrepancies with some of the values and it's not clear whether this is an error or intentional. Specifically:

Reg0, CAL_CLK_DIV: Datasheet says 3 is the default, but TICSPRO uses 0

Reg13, CP_ICOARSE: Datasheet says 1 is the default, but TICSPRO uses 0

Reg35, CHDIV_SEG1_EN: Datasheet says 0 is the default, but TICSPRO uses 1

Reg47, OUTB_POW: Datasheet says 0 is the default, but TICSPRO uses 15

Reg64, FJUMP_SIZE: Datasheet says 15 is the default, but TICSPRO uses 7

We are using rev F of the datasheet and v1.7.5.7 of TICSPRO

  • 0
    TI__Guru* 81400 points

    Hi Saverio,

    The default value as shown in the datasheet register maps section refer to the silicon default value after a power-up cycle or a software RESET.

    Silicon default value may not be the appropriated value for normal operation. 

    After a power-up cycle or a software RESET, we need to program all the registers. Non-configurable bits (fixed value 1's or 0's) need to be identical to the register table in Figure 7.-5. 

  • 0 in reply to Noel Fung
    Prodigy 70 points

    I understand that the default values in the datasheet may not be appropriate for "normal" operation. I'm also aware of the non-configurable bits. However, the "default" values that TICSPRO uses for the parameters I've identified seem ... arbitrary. For example, OUTB_POW is set to a larger value than the power-up value. Why? It's the secondary output buffer which is less likely to be used, and the default even has OUTB disabled. Why would TICSPRO increase the power setting from the default of 0? TICSPRO's default value for CP_ICOARSE of 0 sort of makes sense, given that the datasheet even says 

    For optimal accuracy of the lock detect circuit over temperature, it is recommended that only set this register to either 0 or 2.

    yet the default power-up value is 1.

    CAL_CLK_DIV is set to 0, which sets the calibration clock to be the same as OSCin. This seems to be solely trying to reduce lock time by default. Why? 

    It seems that the "Default configuration" in TICSPRO isn't the same as the "Default configuration" of the datasheet. This is confusing.

  • +1 in reply to Saverio Mercurio
    TI__Guru* 81400 points

    Hi Saverio,

    Except for the silicon default values, there is no default configuration in the datasheet, most of the configurable register bits are application dependent, we must put something meaningful and valid values according to the application need. For example, a power setting of 0 is not a normal operation setting unless you really need very small output power. CAL_CLK_DIV should also be set to match with the actual OSCin frequency. 

    Default TICS Pro configuration matches with the hardware configuration of the EVM, although this may not be the configuration you required in your system.

  • 0 in reply to Noel Fung
    Prodigy 70 points

    "Default TICS Pro configuration matches with the hardware configuration of the EVM, although this may not be the configuration you required in your system."

    I think this, more than anything else, really explains why there's a difference. The datasheet provides default values for all fields that are not fixed-values, and as I indicated, some of these are not the same as the default values in TICSPRO. The fact that TICSPRO is targeting the EVM helps to explain why these are different. 

    Thank you for your responses.