RM44L920: TCXO module on OSCIN

Matthew Steinberg

Part Number: RM44L920

Hi,

Can the oscillator input of the RM44Lx20 safety CPU's (OSCIN) be driven direct from a clipped sine TCXO module with a 0.8V rms (minimum) amplitude? Specifically, we're thinking of using the IQD part (#IQXT-220-1) at 19.2 MHz. The RM44 datasheet and Technical Reference Manual are slightly ambiguous on this - they only suggest use of a standard non-TC crystal in a classic config with Kelvin ground and OSCOUT capacitors, or alternatively direct drive with a logic level clock of 0v to 3V3. The internal oscillator input circuitry in the RM44Lx looks as though it should function with a TCXO, but would like confirmation if possible.

Thanks for any advice you can offer.

Matthew

over 7 years ago

0 QJ Wang over 7 years ago

TI__Guru**** 196756 points

Hi Mathew,

The external oscillator can be used by connecting the the clock to OSCIN pin. The clock signal should be toggling between 0V and 3.3V.

0 Matthew Steinberg over 7 years ago in reply to QJ Wang

Prodigy 90 points

Hi QJ,

Thanks for your reply. Is it possible to drive OSCIN directly with a clipped sinewave signal of minimum amplitude 0.8 V rms at 19.2 MHz? The clipped sine would be AC coupled through e.g. a 10nF capacitor.

Best regards,

Matthew

0 QJ Wang over 7 years ago in reply to Matthew Steinberg

TI__Guru**** 196756 points

Hi Matthew,

I think that it works. The maximum input clock is 20MHz.

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RM44L920: TCXO module on OSCIN