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TMS570LC4357: HF LPO frequency after trimming

Katharina Gilles
Prodigy 145 points
Part Number: TMS570LC4357
Other Parts Discussed in Thread: HALCOGEN

Hi,

I have a question regarding the frequency of HF LPO.
In HalCoGen, the default configuration for HF LPO is 10MHz.
In the datasheet, the typical value for HF LPO is 9MHz (without trimming) and 9.6MHz (with trimmming).

During startup, the trim value is written from OTP memory to LPOMONCTL register.

Which is the typical frequency after trimming? 9.6MHz or 10MHz?

Thanks, Katharina

  • 0
    TI__Mastermind 21425 points
    Hello,
    During device test, a trim value is written into the one-time programmable section of the flash memory (OTP), address 0xF008_01B4. Bits 31:16 of this OTP word contain a 16 bit value that may be programmed into LPOMONCTL(15:0) in order to initialize the trim for both HF LPO and LF LPO.
    In Datasheet is stated that trimmed frequency is typically 9.6MHz.
    You could change this by unchecking Set Trim from OTP in HALCoGen. If it is checked value from OTP is loaded. You can follow the changes in system.c that halcogen generates.

    Best regards,
    Miro
  • 0 in reply to Miro
    Prodigy 145 points

    This trim value from OTP is written during my system initialization, in HalCoGen the checkbox "Set Trim from OTP" is checked (and this is what I want).

    However, also in HalCoGen, the value for HF LPO is 10Mhz (default configuration).

    In HL_system.h, I find the define

    #define LPO_HF_FREQ  10.000F

    generated by HalCoGen.

    So what is true now? 9.6MHz as the datasheet states, or 10MHz as HalCoGen suggests?

    Or are these values irrelevant, because I can only rely on the frequency being somewhere between 8MHz and 11MHz?

    Regards, Katharina

  • 0 in reply to Katharina Gilles
    TI__Mastermind 49120 points
    Hi Katharina,

    The untrimmed value for the HF LPO ranges from 5.5MHz to 19.5MHz. The trim procedure generated by HALCoGen tries to configure the HF LPO frequency to be as close to 10MHz as possible, but never over 10MHz. The trim values are configured using a 5-bit register field, so there are a discrete set of trim values that can be applied. This is the reason for the HF LPO being 9.6MHz instead of 10MHz using the trim procedure generated by HALCoGen. You can also write your own procedure to get closer to 10MHz (may be a bit over) if you wish.

    Nevertheless, the main oscillator is expected to be the most accurate timing source in the system. The internal clock monitor provides a gross frequency check on the oscillator frequency.

    Regards,
    Sunil