ST72521R6 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
ST72521R6
STMicroelectronics
ST72521R6 Datasheet PDF : 199 Pages
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ST72521M/R/AR
6 SUPPLY, RESET AND CLOCK MANAGEMENT
The device includes a range of utility features for
securing the application in critical situations (for
example in case of a power brown-out), and re-
ducing the number of external components. An
overview is shown in Figure 10.
For more details, refer to dedicated parametric
section.
Main features
s Optional PLL for multiplying the frequency by 2
(not to be used with internal RC oscillator)
s Reset Sequence Manager (RSM)
s Multi-Oscillator Clock Management (MO)
– 5 Crystal/Ceramic resonator oscillators
– 1 External RC oscillator
– 1 Internal RC oscillator
s System Integrity Management (SI)
– Main supply Low voltage detection (LVD)
– Auxiliary Voltage detector (AVD) with interrupt
capability for monitoring the main supply or
the EVD pin
– Clock Security System (CSS) with Clock Filter
and Backup Safe Oscillator (enabled by op-
tion byte)
6.1 PHASE LOCKED LOOP
If the clock frequency input to the PLL is in the
range 2 to 4 MHz, the PLL can be used to multiply
the frequency by two to obtain an fOSC2 of 4 to 8
MHz. The PLL is enabled by option byte. If the PLL
is disabled, then fOSC2 = fOSC/2.
Caution: The PLL is not recommended for appli-
cations where timing accuracy is required. See
“PLL Characteristics” on page 168.
Figure 9. PLL Block Diagram
fOSC
PLL x 2
/2
0
fOSC2
1
PLL OPTION BIT
Figure 10. Clock, Reset and Supply Block Diagram
SYSTEM INTEGRITY MANAGEMENT
OSC2
OSC1
MULTI-
OSCILLATOR
(MO)
fOSC
fOSC2
PLL
(option)
CLOCK SECURITY SYSTEM
(CSS)
CLOCK
FILTER
SAFE
OSC
fOSC2
MAIN CLOCK
CONTROLLER
WITH REALTIME
fCPU
CLOCK (MCC/RTC)
RESET
VSS
VDD
EVD
RESET SEQUENCE
MANAGER
(RSM)
AVD Interrupt Request
SICSR
AVD AVD AVD LVD
S IE F RF
0
CSS CSS WDG
IE D RF
WATCHDOG
TIMER (WDG)
CSS Interrupt Request
LOW VOLTAGE
DETECTOR
(LVD)
0
AUXILIARY VOLTAGE
DETECTOR
1
(AVD)
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