Datasheet
Electrical characteristics STM32F030x4/x6/x8/xC
54/93 DS9773 Rev 4
For C
L1
and C
L2
, it is recommended to use high-quality external ceramic capacitors in the
5
pF to 20 pF range (Typ.), designed for high-frequency applications, and selected to match
the requirements of the crystal or resonator (see
Figure 17). 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
.
Note: For information on selecting the crystal, refer to the application note AN2867 “Oscillator
design guide for ST microcontrollers” available from the ST website www.st.com.
Figure 17. Typical application with an 8 MHz crystal
1. R
EXT
value depends on the crystal characteristics.
Low-speed external clock generated from a crystal resonator
The low-speed external (LSE) clock can be supplied with a 32.768 kHz crystal resonator
oscillator. All the information given in this paragraph are based on design simulation results
I
DD
HSE current consumption
During startup
(3)
--8.5
mA
V
DD
= 3.3 V,
Rm = 45 Ω,
CL = 10 pF@8 MHz
-0.5-
V
DD
= 3.3 V,
Rm = 30 Ω,
CL = 20 pF@32 MHz
-1.5-
g
m
Oscillator transconductance Startup 10 - - mA/V
t
SU(HSE)
(4)
Startup time V
DD
is stabilized - 2 - ms
1. Resonator characteristics given by the crystal/ceramic resonator manufacturer.
2. Guaranteed by design, not tested in production.
3. This consumption level occurs during the first 2/3 of the t
SU(HSE)
startup time
4. 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 measured for a standard crystal resonator and it can vary significantly
with the crystal manufacturer
Table 33. HSE oscillator characteristics
Symbol Parameter Conditions
(1)
Min
(2)
Typ Max
(2)
Unit
MS19876V1
(1)
OSC_IN
OSC_OUT
R
F
Bias
controlled
gain
f
HSE
R
EXT
8 MHz
resonator
Resonator with integrated
capacitors
C
L1
C
L2