Datasheet

STM8L151x2, STM8L151x3 Electrical parameters
Doc ID 018780 Rev 4 67/112
LSE crystal/ceramic resonator oscillator
The LSE clock can be supplied with a 32.768 kHz crystal/ceramic resonator oscillator. All
the information given in this paragraph is based on characterization results with specified
typical external components. 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
(frequency, package, accuracy...).
Figure 17. LSE oscillator circuit diagram
Table 28. LSE oscillator characteristics
Symbol Parameter Conditions Min Typ Max Unit
f
LSE
Low speed external oscillator
frequency
32.768 kHz
R
F
Feedback resistor ΔV = 200 mV 1.2 MΩ
C
(1)
Recommended load capacitance
(2)
8pF
I
DD(LSE)
LSE oscillator power consumption
1.4
(3)
µA
V
DD
= 1.8 V 450
nAV
DD
= 3 V 600
V
DD
= 3.6 V 750
g
m
Oscillator transconductance 3
(3)
µA/V
t
SU(LSE)
(4)
Startup time V
DD
is stabilized 1 s
1. C= C
L1
= C
L2
is approximately equivalent to 2 x crystal C
LOAD
.
2. The oscillator selection can be optimized in terms of supply current using a high quality resonator with a small R
m
value.
Refer to crystal manufacturer for more details.
3. Data guaranteed by Design. Not tested in production.
4. t
SU(LSE)
is the startup time measured from the moment it is enabled (by software) to a stabilized 32.768 kHz oscillation.
This value is measured for a standard crystal resonator and it can vary significantly with the crystal manufacturer.
OSC_OUT
OSC_IN
f
LSE
C
L1
C
L2
R
F
STM8
Resonator
Consumption
control
g
m
R
m
C
m
L
m
C
O
Resonator