Datasheet

BIAS_EN
Low-Power
Oscillator
LFEN
LF_TRIM
HFEN
HF_TRIM
LFLPO
HFLPO
HFLPO_VALID
nPORRST
77
RM57L843
www.ti.com SPNS215C –FEBRUARY 2014–REVISED JUNE 2016
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System Information and Electrical SpecificationsCopyright © 2014–2016, Texas Instruments Incorporated
6.6.1.2 Low-Power Oscillator
The Low-Power Oscillator (LPO) is comprised of two oscillators — HF LPO and LF LPO, in a single
macro.
6.6.1.2.1 Features
The main features of the LPO are:
• Supplies a clock at extremely low power to reduce power consumption. This is connected as clock
source 4 of the Global Clock Module (GCM).
• Supplies a high-frequency clock for nontiming-critical systems. This is connected as clock source 5 of
the GCM.
• Provides a comparison clock for the crystal oscillator failure detection circuit.
Figure 6-4. LPO Block Diagram
Figure 6-4 shows a block diagram of the internal reference oscillator. This is a low-power oscillator (LPO)
and provides two clock sources: one nominally 80 kHz and one nominally 10 MHz.
6.6.1.2.2 LPO Electrical and Timing Specifications
Table 6-13. LPO Specifications
PARAMETER MIN TYP 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 78 MHz
LPO - HF oscillator
Untrimmed frequency 5.5 9 19.5 MHz
Trimmed frequency 8.0 9.6 11.0 MHz
Start-up time from STANDBY (LPO BIAS_EN high for at least
900 µs)
10 µs
Cold start-up time 900 µs
LPO - LF oscillator
Untrimmed frequency 36 85 180 kHz
Start-up time from STANDBY (LPO BIAS_EN high for at least
900 µs)
100 µs
Cold start-up time 2000 µs