Datasheet

STM32F405xx, STM32F407xx Electrical characteristics
Doc ID 022152 Rev 2 85/167
Figure 27. High-speed external clock source AC timing diagram
Figure 28. 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 Ta bl e 2 8 . 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
OSC_IN
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