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LM25141-Q1: Optional Synchronization to an External Clock

tateo yamashiro
Guru 10890 points
Part Number: LM25141-Q1
Other Parts Discussed in Thread: LM25141

Hi,

We got a question from the customer about LM25141-Q1.
Could you help us?

[Question]
They found the below description from datasheet. What does "optional" mean? They need the Sync function. What order number should they select? Does LM25141QRGERQ1 have Sync function?

Best Regards,
tateo

  • 0
    TI__Prodigy 700 points
    Hi Tateo san,


    Optional means the listed functions can be activated over control pins on the LM25141. If a particular function is not wanted then it can be disabled over these pins as well.
    Yes, the LM25141QRGERQ1 has all these options via control pins and the Sync function over the DEMB pin.

    1. Optional Frequency shift:
    The switching frequency is selected by the OSC pin to 2.2MHz or 440kHz. The frequency can be shifted with the RT pin from 1.8 MHz to 2.53 MHz or 300 kHz to 500 kHz depends on the OSC selection. The Frequency shift can be done at the RT pin with a RT resistor to GND or by applying an external analog voltage to the RT pin. Please refer to section "7.3.3 Oscillator" in the datasheet to find more details.

    2. External Synchronization:
    To synchronize the LM25141-Q1 to an external source, apply a logic level clock signal to the DEMB pin. The synchronization range is 350 kHz to 550 kHz when the internal oscillator OSC pin is set to 440 kHz. When the internal oscillator OSC pin is set to 2.2 MHz, the synchronization range is 1.8 MHz to 2.6 MHz. Please refer to section "7.3.4 Synchronization" in the datasheet for more information.

    3. Optional Spread Spectrum
    The LM25141-Q1 provides a frequency dithering option that can be enabled by connecting a capacitor from the DITH pin to AGND. If the DITH pin is connected to VDDA or GND then Spread spectrum is disabled. Please refer to section "7.3.5 Frequency Dithering (Spread Spectrum)" in the datasheet with more details.

    Best Regards,
    Robert Loke