10.5.7 CMU_HFXOSTARTUPCTRL - HFXO Startup Control
Offset
Bit Position
0x02C
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Reset
0xA
0x09
0x0A0
0x60
Access
R
W
R
W
R
W
R
W
Name
Bit
Name
Reset
Access Description
31:28
RESERVED1
0xA
RW
Sets the regulator output current level (shunt regulator).
Ish=120uA+reg_ish x 120uA
This REGISH value is applied during the keep warm phase of the HFXO
27:21
RESERVED0
0x09
RW
Sets the oscillator core bias current. Current (uA) = ib_xo_core x
40uA. Bits 6 and 5 may only be high in the crystal oscillator start-
up phase
This IBTRIMXOCORE value is applied during the keep warm phase of the HFXO
20
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
19:11
CTUNE
0x0A0
RW
Sets oscillator tuning capacitance. Capacitance on HFXTAL_N and
HFXTAL_P (pF) = Ctune = Cpar + CTUNE<8:0> x 40fF. Max Ctune
25pF (CLmax ~12.5pF). CL(DNLmax)=50fF ~ 0.6ppm (12.5ppm/pF)
This CTUNE value is applied during the startup phase of the HFXO
10:7
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
6:0
IBTRIMXOCORE
0x60
RW
Sets the startup oscillator core bias current. Current (uA) = IB-
TRIMXOCORE x 40uA. Bits 6 and 5 may only be high in the crystal
oscillator startup phase
This IBTRIMXOCORE value is applied during the startup phase of the HFXO
EFM32JG1 Reference Manual
CMU - Clock Management Unit
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