Q&A: What is EIM boot resistor value

Document created by Yixing Kong Employee on Sep 2, 2013
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Q:

Looking at the datasheet, why a 14.7KOhm pulldown and a 4.7KOhm pullup must be used?

When useing 4.7KOhm resistors in series from an MCU to control the boot pins, pull up is ok, but pull down is not. The EIM boot pins only see 4.7KOhm and not 14.7KOhm as recommended in the design guide. How did we determine those resistor values? at boot there is a pull-up of 100KOhm in the pad if I understand well, 4.7KOhm would do the job as well as 14.7K. right?

 

A:
4.7k will work fine for pull-up or pull-down. 10k pull-downs is to limit current drain while allowing use of simple SPST switches to configure boot-up. There are on-chip 100k pull resistors, so this limits max resistor size.

 

This document was generated from the following discussion: EIM boot resistor value

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