Datasheet

Electrical characteristics STM32F100xC, STM32F100xD, STM32F100xE
50/105 DocID15081 Rev 8
Figure 12. 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 24 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 22. 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 22. HSE 4-24 MHz oscillator characteristics
(1)(2)
1. Resonator characteristics given by the crystal/ceramic resonator manufacturer.
2. Based on characterization, not tested in production.
Symbol Parameter Conditions Min Typ Max Unit
f
OSC_IN
Oscillator frequency 4 8 24 MHz
R
F
Feedback resistor 200 kΩ
C
L1
C
L2
(3)
3. It is recommended to use high-quality external ceramic capacitors in the 5 pF to 25 pF range (typ.),
designed for high-frequency applications, and selected to match the requirements of the crystal or
resonator. C
L1
and C
L2,
are usually the same size. The crystal manufacturer typically specifies a load
capacitance which is the series combination of C
L1
and C
L2
. PCB and MCU pin capacitance must be
included (10 pF can be used as a rough estimate of the combined pin and board capacitance) when sizing
C
L1
and C
L2
.
Recommended load capacitance
versus equivalent serial
resistance of the crystal (R
S
)
(4)
R
S
= 30 Ω 30 pF
i
2
HSE driving current
V
DD
= 3.3 V
V
IN
= V
SS
with 30 pF
load
1mA
g
m
Oscillator transconductance Startup 25 mA/V
t
SU(HSE)
(5)
Startup time V
DD
is stabilized 2 ms
ai14140c
OSC32_IN
External
STM32F10xxx
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