Electrical characteristics
STM8S003K3 STM8S003F3
(1) C is approximately equivalent to 2 x crystal Cload.
(2) The oscillator selection can be optimized in terms of supply current using a high quality resonator with
small Rm value. Refer to crystal manufacturer for more details
(3) Data based on characterization results, not tested in production.
(4)
t
is the start-up time measured from the moment it is enabled (by software) to a stabilized 16
SU(HSE)
MHz oscillation is reached. This value is measured for a standard crystal resonator and it can vary
significantly with the crystal manufacturer.
Figure 18: HSE oscillator circuit diagram
R
m
f
to core
HSE
C
O
R
g
L
m
F
C
L1
C
m
OSCIN
m
Resonator
Consumption
control
Resonator
OSCOUT
C
L2
STM8
HSE oscillator critical g m equation
gmcrit= (2 × Π × fHSE)2 × Rm(2Co + C)2
Rm: Notional resistance (see crystal specification)
Lm: Notional inductance (see crystal specification)
Cm: Notional capacitance (see crystal specification)
Co: Shunt capacitance (see crystal specification)
CL1= CL2 = C: Grounded external capacitance
gm >> gmcrit
9.3.4
Internal clock sources and timing characteristics
Subject to general operating conditions for VDD and TA.
High speed internal RC oscillator (HSI)
Table 33: HSI oscillator characteristics
Symbol
Parameter
Conditions
Min
Typ
16
Max
Unit
fHSI
Frequency
MHz
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