EFM32ZG222 Datasheet, PDF (25/66 Pages) Silicon image – Energy, gas, water and smart metering

3.9 Oscillators
Preliminary
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3.9.1 LFXO
Table 3.8. LFXO
Symbol
f_LFXO
ESR_LFXO
C_LFXOL
DC_LFXO
I_LFXO
t_LFXO
Parameter
Condition
Min
Supported nominal
crystal frequency
Supported crystal
equivalent series re-
sistance (ESR)
Supported crystal
external load range
Duty cycle
Current consump-
tion for core and
buffer after startup.
ESR=30 kOhm, C_L=10 pF,
LFXOBOOST in CMU_CTRL is
1
Start- up time.
ESR=30 kOhm, C_L=10 pF,
40% - 60% duty cycle has
been reached, LFXOBOOST in
CMU_CTRL is 1
Typ
Max
Unit
32.768
kHz
30
120 kOhm
5
25 pF
48
50
53.5 %
190
nA
400
ms
For safe startup of a given crystal, the energyAware Designer in Simplicity Studio contains a tool to help
users configure both load capacitance and software settings for using the LFXO. For details regarding
the crystal configuration, the reader is referred to application note "AN0016 EFM32 Oscillator Design
Consideration".
3.9.2 HFXO
Table 3.9. HFXO
Symbol
f_HFXO
ESR_HFXO
g_mHFXO
C_HFXOL
DC_HFXO
I_HFXO
t_HFXO
Parameter
Condition
Min
Supported nominal
crystal Frequency
Supported crystal Crystal frequency 24 MHz
equivalent series re-
sistance (ESR)
Crystal frequency 4 MHz
The transconduc-
tance of the HFXO
input transistor at
crystal startup
HFXOBOOST in CMU_CTRL
equals 0b11
Supported crystal
external load range
Duty cycle
Current consump-
tion for HFXO after
startup
4 MHz: ESR=400 Ohm,
C_L=20 pF, HFXOBOOST in
CMU_CTRL equals 0b11
24 MHz: ESR=30 Ohm,
C_L=10 pF, HFXOBOOST in
CMU_CTRL equals 0b11
Startup time
24 MHz: ESR=30 Ohm,
C_L=10 pF, HFXOBOOST in
CMU_CTRL equals 0b11
Typ
4
20
5
46
Max
Unit
24 MHz
30
60 Ohm
400
1500 Ohm
mS
25 pF
50
54 %
85
µA
165
µA
400
µs
2013-10-09 - EFM32ZG222FXX - d0066_Rev0.60
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