Rainbow-electronics MAXQ3120 Manual de usuario descargar pdf (Pagina 21)

MAXQ3120

High-Precision ADC

Mixed-Signal Microcontroller

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System Timing

The MAXQ3120 generates its internal system clock

from an external high-frequency crystal. Because the

MAXQ3120 includes internal capacitors for this pur-

pose, no external capacitors are required to use the

high-frequency crystal. The MAXQ3120 should not be

driven directly by an external clock source.

A crystal warmup counter enhances operational relia-

bility. Each time the external crystal oscillation must

restart, such as after exiting stop mode, the device initi-

ates a crystal warmup period of 65,536 oscillations.

This allows time for the crystal amplitude and frequency

to stabilize before using it as a clock source.

Power Management

Advanced power-management features minimize power

consumption by dynamically matching the processing

speed of the device to the required performance level.

This means device operation can be slowed and power

consumption minimized during periods of reduced

activity. When more processing power is required, the

microcontroller can increase its operating frequency.

Software-selectable clock-divide operations allow flexi-

bility, selecting whether a system clock cycle is 1, 2, 4,

or 8 oscillator cycles. By performing this function in soft-

ware, a lower power state can be entered without the

cost of additional hardware.

For extremely power-sensitive applications, two addi-

tional low-power modes are available.

• Divide-by-256 power-management mode (PMM)

(PMME = 1, CD1:0 = 00b)

• Stop mode (STOP = 1)

In PMM, one system clock is 256 oscillator cycles, signifi-

cantly reducing power consumption while the microcon-

troller functions at reduced speed. The optional

switchback feature allows enabled interrupt sources,

such as the external interrupts and USARTs, to cause the

processor to quickly exit PMM mode and return to a

faster internal clock rate.

Figure 2. Clock Sources

MAXQ3120

GLITCH-FREE

MUX

DIV 1

DIV 2

DIV 4

DIV 8

PWM

CLOCK

DIVIDER

SELECTOR

DEFAULT

WATCHDOG

TIMER

RESET DOG

RWT

RESET

POWER-ON

RESET

STOP

POWER-ON

RESET

SWB

INTERRUPT/SERIAL PORT

RESET

STOP

POWER MONITOR

REAL-TIME CLOCK

LCD CONTROLLER

WATCHDOG RESET

CLOCK

GENERATION

SYSTEM CLOCK

ENABLE

WATCHDOG INTERRUPT

32kHz

CRYSTAL

MONITOR

ENABLE

INPUT

CRYSTAL

CRYSTAL KILL

XDOG

STARTUP

TIMER

CLK INPUT

RESET

XDOG COUNT

XDOG DONE

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 32 33

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Rainbow-electronics MAXQ3120 Manual de usuario Pagina 21

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