Datasheet

Electrical characteristics STM32F21xxx
88/175 DocID17050 Rev 9
Figure 28. High-speed external clock source AC timing diagram
Figure 29. Low-speed external clock source AC timing diagram
High-speed external clock generated from a crystal/ceramic resonator
The high-speed external (HSE) clock can be supplied with a 4 to 26 MHz crystal/ceramic
resonator oscillator. All the information given in this paragraph are based on
characterization results obtained with typical external components specified in Table 29. In
the application, the resonator and the load capacitors have to be placed as close as
possible to the oscillator pins in order to minimize output distortion and startup stabilization
time. Refer to the crystal resonator manufacturer for more details on the resonator
characteristics (frequency, package, accuracy).
ai17528
OS C _I N
External
STM32F
clock source
V
HSEH
t
f(HSE)
t
W(HSE)
I
L
90 %
10
%
T
HSE
t
t
r(HSE)
t
W(HSE)
f
HSE_ext
V
HSEL
ai17529
OSC32_IN
External
STM32F
clock source
V
LSEH
t
f(LSE)
t
W(LSE)
I
L
90%
10%
T
LSE
t
t
r(LSE)
t
W(LSE)
f
LSE_ext
V
LSEL