ST72141K2 datasheet(23/132 Pages) STMICROELECTRONICS

部品番号	ST72141K2

部品情報	8-BIT MCU WITH ELECTRIC-MOTOR CONTROL, ADC, 16-BIT TIMERS, SPI INTERFACE

PDF	132 Pages

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メーカー	STMICROELECTRONICS [STMicroelectronics]

ホームページ	http://www.st.com

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ST72141K

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3.3 LOW CONSUMPTION OSCILLATOR

The main clock of the ST7 can be generated by

two different sources:

an external source

a crystal or ceramic resonator oscillators

External Clock Source

In this mode, a square clock signal with ~50% duty

cycle has to drive the OSC2 pin while the OSC1

pin is tied to VSS (see Figure 15).

Figure 15. External Clock

Crystal/Ceramic Oscillators

This oscillator (based on constant current source)

is optimized in terms of consumption and has the

advantage of producing a very accurate rate on

the main clock of the ST7.

When using this oscillator, the resonator and the

load capacitances have to be connected as shown

in Figure 16 and have to be mounted as close as

possible to the oscillator pins in order to minimize

output distortion and start-up stabilization time.

This oscillator is not stopped during the RESET

phase to avoid losing time in the oscillator start-up

phase.

Figure 16. Crystal/Ceramic Resonator

OSC1

OSC2

EXTERNAL

ST7

SOURCE

OSC1

OSC2

LOAD

CAPACITANCES

ST7

CL1

CL0

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