Datasheet

Functional description L6470
28/73 DocID16737 Rev 7
6.8.1 Internal oscillator
In this mode the internal oscillator is activated and OSCIN is unused. If the OSCOUT clock
source is enabled, the OSCOUT pin provides a 2, 4, 8 or 16-MHz clock signal (according to
OSC_SEL value); it is otherwise unused (see Figure 11).
6.8.2 External clock source
Two types of external clock source can be selected: crystal/ceramic resonator or direct clock
source. Four programmable clock frequencies are available for each external clock source:
8, 16, 24 and 32 MHz.
When an external crystal/resonator is selected, the OSCIN and OSCOUT pins are used to
drive the crystal/resonator (see Figure 11). The crystal/resonator and load capacitors (C
L
)
must be placed as close as possible to the pins. Refer to Tabl e 8 for the choice of load
capacitor values according to the external oscillator frequency.
If a direct clock source is used, it must be connected to the OSCIN pin and the OSCOUT pin
supplies the inverted OSCIN signal (see Figure 11).
Table 8. CL values according to external oscillator frequency
Crystal/resonator freq.
(1)
1. First harmonic resonance frequency.
C
L
(2)
2. Lower ESR value allows the driving of greater load capacitors.
8 MHz 25 pF (ESR
max
= 80 )
16 MHz 18 pF (ESR
max
= 50 )
24 MHz 15 pF (ESR
max
= 40 )
32 MHz 10 pF (ESR
max
= 40 )