Datasheet

Electrical characteristics STM32F427xx STM32F429xx
120/239 DocID024030 Rev 10
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 Table 39. 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).
Table 39. HSE 4-26 MHz oscillator characteristics
(1)
1. Guaranteed by design.
Symbol Parameter Conditions Min Typ Max Unit
f
OSC_IN
Oscillator frequency 4 - 26 MHz
R
F
Feedback resistor - 200 - kΩ
I
DD
HSE current consumption
V
DD
=3.3 V,
ESR= 30 Ω,
C
L
=5 pF@25 MHz
- 450 -
µA
V
DD
=3.3 V,
ESR= 30 Ω,
C
L
=10 pF@25 MHz
- 530 -
ACC
HSE
(2)
2. This parameter depends on the crystal used in the application. The minimum and maximum values must
be respected to comply with USB standard specifications.
HSE accuracy − 500 - 500 ppm
G
m
_crit_max Maximum critical crystal g
m
Startup - - 1 mA/V
t
SU(HSE
(3)
3. t
SU(HSE)
is the startup time measured from the moment it is enabled (by software) to a stabilized 8 MHz
oscillation is reached. This value is based on characterization and not tested in production. It is measured
for a standard crystal resonator and it can vary significantly with the crystal manufacturer.
Startup time V
DD
is stabilized - 2 - ms
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