ST10F272M-4Q3 STMICROELECTRONICS [STMicroelectronics], ST10F272M-4Q3 Datasheet - Page 147

• Manufacturer Part Number: ST10F272M-4Q3
• Description: 16-bit MCU with 256 Kbyte Flash memory and 20 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST10F272M
24.8.10
Note:
Figure 46. ST10F272M PLL jitter
PLL lock / unlock
During normal operation, if the PLL gets unlocked for any reason, an interrupt request to the
CPU is generated, and the reference clock (oscillator) is automatically disconnected from
the PLL input: in this way, the PLL goes into free-running mode, providing the system with a
backup clock signal (free running frequency f
failure occurrence without risking to go into an undefined configuration: The system is
provided with a clock allowing the execution of the PLL unlock interrupt routine in a safe
mode.
The path between reference clock and PLL input can be restored only by a hardware reset,
or by a bidirectional software or watchdog reset event that forces the RSTIN pin low.
The external RC circuit on RSTIN pin must be properly sized in order to extend the duration
of the low pulse to lock the PLL before the level at RSTIN pin is recognized high: A
bidirectional reset internally drives the RSTIN pin low for just 1024 TCL (definitly not
sufficient to lock the PLL starting from free-running mode).
Table 63.
1. Not 100% tested, guaranteed by design characterization
Symbol
t
t
PSUP
LOCK
T
f
free
JIT
PLL Start-up time
PLL Lock-in time
Single Period Jitter
(cycle to cycle = 2 TCL)
PLL free running frequency
T
±5
±4
±3
±2
±1
JIT
0
PLL characteristics (V
0
Parameter
200
(1)
(1)
16MHz
400
24MHz
Stable V
Stable V
starting from free-running mode
6 sigma time period variation
(peak to peak)
Multiplication factors: 3, 4
Multiplication factors: 5, 8, 10, 16
DD
N (CPU clock periods)
= 5V ± 10%, V
600
32MHz
DD
DD
free
Conditions
and reference clock
and reference clock,
). This feature allows recovery from a crystal
40MHz
800
SS
= 0V, T
1000
A
Electrical characteristics
= -40 to +125°C)
1200
-500
64MHz
Min
250
500
–
–
Value
1400
+500
2000
4000
Max
300
250
147/176
Unit
kHz
µs
µs
ps