EFM32GG380 Datasheet, PDF (22/70 Pages) List of Unclassifed Manufacturers – EFM32GG380 DATASHEET

3.9 Oscillators
3.9.1 LFXO
Table 3.9. LFXO
Preliminary
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Symbol
f_LFXO
ESR_LFXO
C_LFXOL
DC_LFXO
I_LFXO
t_LFXO
Parameter
Supported nominal crystal
frequency
Supported crystal equiv-
alent series resistance
(ESR)
Supported crystal external
load range
Duty cycle
Current consumption for
core and buffer after start-
up.
Start- up time.
Condition
Min
ESR=30 kOhm, C_L=10 pF,
LFXOBOOST in CMU_CTRL
is 1
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
48
50
190
25 pF
53.5 %
nA
400
ms
For safe startup of a given crystal, the load capacitance should be larger than the value indicated in
Figure 3.7 (p. 22) and in Table 3.10 (p. 23) for a given LFXOBOOST setting. The minimum
supported load capacitance depends on the crystal shunt capacitance, C₀, which is specified in crystal
vendors’ datasheet.
Figure 3.7. Minimum Load Capacitance (C_LFXOL) Requirement For Safe Crystal Startup
20
LFXOBOOST= 0,REDLFXOBOOST= 1
18
LFXOBOOST= 0,REDLFXOBOOST= 0
LFXOBOOST= 1,REDLFXOBOOST= 1
LFXOBOOST= 1,REDLFXOBOOST= 0
16
14
12
10
8
6
4
2
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
C0 [ pF]
2012-09-11 - EFM32GG380FXX - d0039_Rev1.00
22
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