11.5.7 CMU_HFXOSTEADYSTATECTRL - HFXO Steady State Control
Offset
Bit Position
0x030
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
0
0x3
0x168
0xA
0x07
Access
R
W
R
W
R
W
R
W
R
W
R
W
Name
Bit
Name
Reset
Access Description
31:28
REGISHUPPER
0xA
RW
Set Regulator Output Current Level (shunt Regulator). Ish = 120uA
+ REGISHUPPER X 120uA
Set to steady state value of 3.
27
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
26
PEAKDETEN
0
RW
Enables Oscillator Peak Detectors
Direct control allowed when PEAKDETSHUNTOPTMODE=MANUAL and HFXO is ready.
25:24
REGSELILOW
0x3
RW
Controls Regulator Minimum Shunt Current Detection Relative to
Nominal
Steady state used during HFXO FSM. Direct control allowed when PEAKDETSHUNTOPTMODE=MANUAL and HFXO is
ready.
23:20
Reserved
To ensure compatibility with future devices, always write bits to 0. More information in
19:11
CTUNE
0x168
RW
Sets Oscillator Tuning Capacitance
This CTUNE value is applied during the steady state phase of the HFXO (as well as during the peak detection and shunt
current optimization algorithms). 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).
10:7
REGISH
0xA
RW
Sets the Steady State Regulator Output Current Level (shunt Reg-
ulator)
This REGISH value is applied during the steady state phase of the HFXO. Direct control allowed when PEAKDETSHUN-
TOPTMODE=MANUAL and HFXO is ready. Ish = 120uA + REGISH X 120uA.
6:0
IBTRIMXOCORE
0x07
RW
Sets the Steady State Oscillator Core Bias Current.
This IBTRIMXOCORE value is applied during the steady state phase of the HFXO. It is also used as the initial value during
the peak detection algorithm. Direct control allowed when PEAKDETSHUNTOPTMODE=MANUAL and HFXO is ready.
Current (uA) = IBTRIMXOCORE x 40uA. Bits 6 and 5 may only be high in the crystal oscillator startup phase..
Reference Manual
CMU - Clock Management Unit
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