L9803 STMicroelectronics, L9803 Datasheet - Page 18

• Manufacturer Part Number: L9803
• Description: Super Smart Power Motor Driver With 8-bit Mcu, Ram, Eeprom, Adc, Wdg, Timers, Pwm And H-bridge Driver
• Manufacturer: STMicroelectronics

Clocks, Reset, Interrupts & Power saving modes
3
3.1
3.1.1
Note:
18/126
Clocks, Reset, Interrupts & Power saving modes
Clock system
General Description
The MCU accepts either a Crystal or Ceramic resonator, or an external clock signal to drive
the internal oscillator. The internal clock (f
frequency (f
factor of 2, 4, 8, or 16 can be applied, in Slow Mode, to reduce the frequency of the f
this clock signal is also routed to the on-chip peripherals (except the CAN). The CPU clock
signal consists of a square wave with a duty cycle of 50%.
The internal oscillator is designed to operate with an AT-cut parallel resonant quartz crystal
resonator in the frequency range specified for f
recommended when using a crystal, and
feedback resistance values. The crystal and associated components should be mounted as
close as possible to the input pins in order to minimize output distortion and start-up
stabilisation time.
Use of an external CMOS oscillator is recommended when crystals outside the specified
frequency ranges are to be used.
Table 2.
R
C
includes the external capacitance tied to the pin plus the parasitic capacitance of the board
and of the device).
Rp: External shunt resistance. Recommended value for oscillator stability is 1M
Figure 5.
SMAX
OSCIN
C
is the equivalent serial resistor of the crystal (see crystal specification).
,C
C
R
OSCOUT
OSCIN
OSCOUT
SMAX
R
P
OSC
Recommended Values for 16 MHz Crystal Resonator
External Clock Source Connections
)
.
: Maximum total capacitances on pins OSCIN and OSCOUT (the value
The external Oscillator clock is first divided by 2, and an additional division
1-10 MΩ
56pF
56pF
40 Ω
EXTERNAL
CLOCK
OSC
Table 2
CPU
in
) is derived from the external oscillator
osc
lists the recommended capacitance and
. The circuit shown in
OSC
NC
1-10 MΩ
out
47pF
47pF
60 Ω
Figure 6
1-10 MΩ
150 Ω
22pF
22pF
Ω
is
.
CPU
L9803
;