RM46L450
RM46L850
SPNS184 –SEPTEMBER 2012
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4.6.1.2 Low Power Oscillator
The Low Power Oscillator (LPO) is comprised of two oscillators — HF LPO and LF LPO, in a single
macro.
4.6.1.2.1 Features
The main features of the LPO are:
•
•
•
Supplies a clock at extremely low power for power-saving modes. This is connected as clock source #
4 of the Global Clock Module.
Supplies a high-frequency clock for non-timing-critical systems. This is connected as clock source # 5
of the Global Clock Module.
Provides a comparison clock for the crystal oscillator failure detection circuit.
BIAS_EN
LFEN
LFLPO
LF_TRIM
Low
Power
Oscillator
HFEN
HFLPO
HF_TRIM
HFLPO_VALID
nPORRST
Figure 4-5. LPO Block Diagram
Figure 4-5 shows a block diagram of the internal reference oscillator. This is a low power oscillator (LPO)
and provides two clock sources: one nominally 80KHz and one nominally 10MHz.
Table 4-10. LPO Specifications
Parameter
MIN
Typical
MAX
Unit
Clock Detection
oscillator fail frequency - lower threshold, using
untrimmed LPO output
1.375
2.4
4.875
MHz
oscillator fail frequency - higher threshold, using
untrimmed LPO output
22
38.4
9.6
78
MHz
LPO - HF oscillator
untrimmed frequency
5.5
19.5
10
MHz
µs
startup time from STANDBY (LPO BIAS_EN High for
at least 900µs)
cold startup time
900
180
100
µs
kHz
µs
LPO - LF oscillator
untrimmed frequency
36
85
startup time from STANDBY (LPO BIAS_EN High for
at least 900µs)
cold startup time
2000
µs
64
System Information and Electrical Specifications
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