IFR configuration

AN4494

4.6

Expected results

The measured value must be compensated in order to consider the variations of the power

supply, temperature and the crystal tolerance:

XTAL_startup = XTAL_startup(measured)*1.2*1.1*1.2 = 1.584* XTAL_startup (measured)

The first coefficient (1.2) can be omitted if the test is performed at the minimum operative

voltage.

Finally, to find the HS_STARTUP_TIME value that must be set up in the IFR, use this

formula:

HS_STARTUP_TIME = 110 µs + MAX {XTAL_startup, (0.56*XTAL_startup+304)}

4.7

Note

Examples:

XTAL_startup = 300 µs → HS_STARTUP_TIME = 680 µs

XTAL_startup = 700 µs → HS_STARTUP_TIME = 1219 µs

4.8

Other

N/A.

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