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How to build a 10MOhm Resistor on chip for 32.768KHz XTAL

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walkingsun

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The Xtal osc circuit needs a huge shunt resistor.

How to make it on chip?

thank you!
 

Re: How to build a 10MOhm Resistor on chip for 32.768KHz XTA

not seen before,
anyone has good idea???
 

Re: How to build a 10MOhm Resistor on chip for 32.768KHz XTA

1> high-res poly resistor(comfortable);
2> large trans-gate (be careful in low supply voltage);
3> a voltage buffer, and it's band-width should smaller than 32K;
 

Re: How to build a 10MOhm Resistor on chip for 32.768KHz XTA

usually long length CMOS cell operated in triode region are cascaded to form such large resistors.
 

I once designed a 32.768K with only 500k internal resistor. Maybe you need not such large resistor. Try reduce it and check the simulation first.
 

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