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DS13105 Rev 4 91/135
STM32WLE5J8/JB/JC Electrical characteristics
127
the resonator and the load capacitors have to be placed as close as possible to the
oscillator pins to minimize output distortion and startup stabilization time.
Refer to the crystal resonator manufacturer for more details on the resonator characteristics
(frequency, package, accuracy).
For more information on the crystal selection, refer to application note Oscillator design
guide for STM8AF/AL/S and STM32 microcontrollers (AN2867).
Figure 14. Typical application with a 32.768 kHz crystal
Note: No external resistors are required between OSC32_IN and OSC32_OUT, and it is forbidden
to add one.
In bypass mode, the LSE oscillator is switched off and the input pin is a standard GPIO.
The external clock signal has to respect the I/O characteristics detailed in Section 5.3.16:
I/O port characteristics.The recommend clock input waveform is shown in the figure below.
Table 54. Low-speed external user clock characteristics
(1)
Symbol Parameter Conditions Min Typ Max Unit
I
DD(LSE)
LSE current
consumption
LSEDRV[1:0] = 00 - Low drive capability - 250 -
nA
LSEDRV[1:0] = 01 - Medium-low drive capability - 315 -
LSEDRV[1:0] = 10 - Medium-high drive capability - 500 -
LSEDRV[1:0] = 11 - High drive capability - 630 -
G
mcritmax
Maximum
critical crystal
g
m
LSEDRV[1:0] = 00 - Low drive capability - - 0.50
µA/V
LSEDRV[1:0] = 01 - Medium-low drive capability - - 0.75
LSEDRV[1:0] = 10 - Medium-high drive capability - - 1.70
LSEDRV[1:0] = 11 - High drive capability - - 2.70
t
SU(LSE)
(2)
Startup time V
DD
stabilized - 2 - s
1. Guaranteed by design.
2. t
SU(LSE)
is the startup time measured from the moment it is enabled (by software) until a stable 32 MHz oscillation is
reached. This value is measured for a standard crystal and it can vary significantly with the crystal manufacturer.
MS30253V2
OSC32_IN
OSC32_OUT
Drive
programmable
amplifier
f
LSE
32.768 kHz
resonator
Resonator with integrated
capacitors
C
L1
C
L2