Crystal input for ST25R3918

[TedA]

I want to use a MEMS oscillator driving the XTI pin instead of just a crystal between XTI and XTO.  What are the specifications on the input signal?  AC coupled? Amplitude? Drive impedance? Suggested circuit for a 0V to 3.3V output oscillator?

[AScha.3]

so use a standard oscillator. 3v3 supply, i always put 100 ohm in clock line, to avoid reflections.

just set HSE to bypass , in Cube.

[TedA]

AScha.3

Thanks!

Ted

[Brian TIDAL]

Hi,

this post is related to Crystal input for ST25R3918 NFC reader. Your answer is likely related to STM32 MCU...

Rgds

BT

[AScha.3]

Ooo, yes, my answer is related to STM32 MCU .

so for ST25R3918 it should be better to use just a standard crystal,

to ensure that the analogue circuits in the ST25R3918 are not disturbed.

[TedA · Accepted solution]

I don't have the option of using a standard crystal.  The chip will be used at temperatures below which crystals can be used. 

I thought that I might attenuate the oscillator output with a resistor divider and then, if necessary, capacitively couple the signal to the XTI input.

[AScha.3]

exactly, this i would try also :)

[TedA]

AScha, Brian,

Thanks for your input.

Ted