STM32WB55xx STM32WB35xx
Electrical characteristics
6.3.10 External clock source characteristics
High-speed external user clock generated from an external source
The high-speed external (HSE) clock is supplied with a 32 MHz crystal oscillator or a sine
wave.
The devices include internal programmable capacitances that can be used to tune the
crystal frequency in order to compensate the PCB parasitic one.
The characteristics in Table 54 and Table 55 are measured over recommended operating
conditions, unless otherwise specified. Typical values are referred to TA = 25 °C and ï€
VDD = 3.0 V.
Table 54. HSE crystal requirements(1)
Symbol
Parameter
Conditions
Min Typ Max Unit
fNOM Oscillator frequency
fTOL Frequency tolerance
-
-
32
- MHz
Includes initial accuracy, stability over
temperature, aging and frequency pulling
-
due to incorrect load capacitance.
-
(2) ppm
CL Load capacitance
-
ESR Equivalent series resistance
-
6
-
8 pF
-
- 100 Ω
1. 32 MHz XTAL is specified for two specific references: NX2016SA and NX1612SA.
2. Refer to the standard specification: 50 ppm for BLE, 40 ppm for 802.15.4 and when both BLE and 802.15.4 are used.
Table 55. HSE clock source requirements(1)
Symbol
Parameter
Conditions
Min Typ Max Unit
fHSE_ext User external clock source frequency
-
fTOL
Frequency tolerance
Includes initial accuracy, stability
over temperature and aging.
-
VHSE Clock input voltage limits
Sine wave, AC-coupled(3)
0.4
DuCy(HSE) Duty cycle
-
45
Offset = 10 kHz
-
φn(HSE) Phase noise for 32 MHz
Offset = 100 kHz
-
Offset = 1 MHz
-
32 - MHz
-
(2) ppm
- 1.6 VPP
50 55
%
- -127
- -135 dBc/Hz
- -138
1. Guaranteed by design.
2. Refer to the standard specification: 50 ppm for BLE, 40 ppm for 802.15.4 and when both BLE and 802.15.4 are used.
3. Only AC coupled is supported (capacitor 470 pF to 100 nF).
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