Preliminary
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3.9 Oscillators
3.9.1 LFXO
Table 3.8. LFXO
Symbol
Parameter
Condition
Min
Typ
Max
Unit
fLFXO
Supported nominal
crystal frequency
32.768
30
kHz
ESRLFXO
Supported crystal
equivalent series re-
sistance (ESR)
120 kOhm
25 pF
CLFXOL
Supported crystal
5
external load range
DCLFXO
ILFXO
Duty cycle
48
50
53.5
%
Current consump-
tion for core and
buffer after startup.
ESR=30 kOhm, CL=10 pF,
LFXOBOOST in CMU_CTRL is
1
190
nA
tLFXO
Start- up time.
ESR=30 kOhm, CL=10 pF,
40% - 60% duty cycle has
been reached, LFXOBOOST in
CMU_CTRL is 1
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
Parameter
Condition
Min
Typ
Max
Unit
fHFXO
Supported nominal
crystal Frequency
4
24 MHz
Supported crystal
equivalent series re-
sistance (ESR)
Crystal frequency 24 MHz
Crystal frequency 4 MHz
30
60 Ohm
ESRHFXO
400
1500 Ohm
gmHFXO
The transconduc-
tance of the HFXO
input transistor at
crystal startup
HFXOBOOST in CMU_CTRL
equals 0b11
20
mS
CHFXOL
Supported crystal
5
25 pF
external load range
DCHFXO
Duty cycle
46
50
85
54
%
4 MHz: ESR=400 Ohm,
CL=20 pF, HFXOBOOST in
CMU_CTRL equals 0b11
µA
Current consump-
tion for HFXO after
startup
IHFXO
24 MHz: ESR=30 Ohm,
CL=10 pF, HFXOBOOST in
CMU_CTRL equals 0b11
165
400
µA
µs
tHFXO
Startup time
24 MHz: ESR=30 Ohm,
CL=10 pF, HFXOBOOST in
CMU_CTRL equals 0b11
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2013-10-09 - EFM32ZG108FXX - d0063_Rev0.60
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