Datasheet

use a crystal inferior to 12.5pF load capacitance without external capacitors as shown in the following

figure.

Table 42-6. Maximum ESR Recommendation for 32.768kHz Crystal

Crystal C

(pF) Max ESR [kΩ]

12.5 313

Note: Maximum ESR is typical value based on characterization. These values are not covered by test

limits in production.

Figure 42-7. External Real Time Oscillator without Load Capacitor

XOUT32

XIN32

32.768kHz

However, to improve crystal accuracy and safety factor, the data sheet recommends adding external

capacitors as shown in the next figure.

To find suitable load capacitance for a 32.768kHz crystal, consult the crystal datasheet.

Figure 42-8. External Real Time Oscillator with Load Capacitor

XOUT32

XIN32

32.768kHz

22pF

Table 42-7. External Real Time Oscillator Checklist

Signal Name Recommended Pin Connection Description

XIN32 Load capacitor 22pF

(1)(2)

Timer oscillator input

XOUT32 Load capacitor 22pF

(1)(2)

Timer oscillator output

1. These values are given only as typical examples.

2. Decoupling capacitor should be placed close to the device for each supply pin pair in the signal

group.

Note: In order to minimize the cycle-to-cycle jitter of the external oscillator, keep the neighboring pins as

steady as possible. For neighboring pin details, refer to the Oscillator Pinout section.