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ADS1191 crystal

Nissim Zur
Prodigy 220 points
Other Parts Discussed in Thread: ADS1191

It is not clare what external crystal to attached to ADS1191. 512 KHz or 2.048 MHz ?

It seem near impossible to find crystal at 512 KHz. and Data sheet state that there is "Internal oscillator clock frequency", may be no need crystal at all. 

Thank you. 

-Nissim

  • 0
    TI__Mastermind 38745 points

    Hello Nasim,

    There are a few options for providing a master clock to the ADS1191. The device does contain an internal 512 kHz oscillator which may be utilized when the CLKSEL pin is held high. In this case, no external oscillator is required. The status of the CLK pin will depend on the CLK_EN bit of the CONFIG2 register. If that bit is cleared, the CLK pin will be in a high impedance state. If the bit is set, the CLK pin outputs the 512 kHz internal oscillator signal which may be useful to synchronize daisy-chained devices. 

    If you wish to use an external oscillator, hold the CLKSEL pin low. In that case, the CLK pin is configured as an input. There are two options for external clock frequencies: 512 kHz or 2.048 MHz. If the 512 kHz external frequency is used, you must be sure to clear the CLK_DIV bit in the LOFF_STAT register. If the 2.048 MHz external frequency is used, the CLK_DIV bit in the LOFF_STAT register must be set (the bit is cleared by default). That bit must be configured correctly so that the internal clock divider generates a 128 kHz modulator clock frequency no matter what external clock frequency is provided. 

    For more information regarding the clock options, please refer to page 24 of the ADS1191 datasheet. Also, a description of the device register map begins on page 36 of the ADS1191 datasheet. 

    Regards,

    Brian