Osc_Out - ST STM32F103x6 Manual

STM32F103xx
High-speed external clock
The high-speed external (HSE) clock can be supplied with a 4 to 16 MHz crystal/ceramic
resonator oscillator. All the information given in this paragraph are based on characterization
results obtained with typical external components specified in
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 17.
Symbol
f
OSC_IN
R
F
C
L1
(2)
C
L2
i
2
g
m
(4)
t
SU(HSE)
1. Resonator characteristics given by the crystal/ceramic resonator manufacturer.
2. For C
L1
designed for high-frequency applications, and selected to match the requirements of the crystal or
resonator. C
capacitance which is the series combination of C
included when sizing C
capacitance).
3. The relatively low value of the RF resistor offers a good protection against issues resulting from use in a
humid environment, due to the induced leakage and the bias condition change. However, it is
recommended to take this point into account if the MCU is used in tough humidity conditions.
4. t
SU(HSE)
oscillation is reached. This value is measured for a standard crystal resonator and it can vary significantly
with the crystal manufacturer
Figure 13. Typical application with a 8-MHz crystal
1. R value depends on the crystal characteristics. Typical value is in the range of 5 to 6R
EXT
HSE 4-16 MHz oscillator characteristics
Parameter
Oscillator frequency
Feedback resistor
Recommended load capacitance
versus equivalent serial
resistance of the crystal (R
HSE driving current
Oscillator Transconductance
startup time
and C it is recommended to use high-quality ceramic capacitors in the 5 pF to 25pF range (typ.),
L2
and C are usually the same size. The crystal manufacturer typically specifies a load
L1 L2,
and C (10 pF can be used as a rough estimate of the combined pin and board
L1 L2
is the startup time measured from the moment it is enabled (by software) to a stabilized 8 MHz
Resonator with
integrated capacitors
C L1
8 MH z
resonator
R EXT (1)
C L2
(1)
Conditions
= 30 Ω
R
S
(3)
)
S
V = 3.3 V
DD
V =V with 30 pF
IN SS
load
Startup
V is stabilized
SS
and C . PCB and MCU pin capacitance must be
L1 L2
OSC_IN
Bias
controlled
R F
gain
OSC_OU T
Electrical characteristics
Table 17. In the application,
Min Typ Max
4 8 16
200
30
1
25
2
f HSE
STM32F103xx
ai14145
.
S
Unit
MHz
kΩ
pF
mA
mA/V
ms
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