ST STM8L - Hardware Requirements Summary; Power Supply; Power Supply Overview

Hardware requirements summary AN3029
6/42 DocID16139 Rev 5
1 Hardware requirements summary
To build an application around an STM8L or STM8AL device, the application board should
provide the following features:
• Power supply (mandatory)
• Clock management (optional)
• Reset management (optional)
• Debugging tool support: Single wire interface module (SWIM) connector (optional)
2 Power supply
2.1 Power supply overview
The STM8L or STM8AL can be supplied through a 1.65 V to 3.6 V external source (1.8 V to
3.6
V for STM8L05xxx). For medium density STM8L15xxx, medium density
STM8AL31xx/STM8AL3Lxx, and high density STM8L15xxx/STM8L162xx with BOR, the
power supply must be above 1.8 V at power-on and can go down to 1.65 V at power-down.
An on-chip power management system provides the constant digital supply to the core logic,
both in normal and low power modes. This guarantees that the logic consumes a constant
current over the voltage range. It is also capable of detecting voltage drops and generate
reset to avoid heratic behavior.
The STM8L and STM8AL devices provide:
• Depending on packages, one pair of pads (V
DD
/V
SS
), or several pairs of pads
(V
DDx
/V
SSx
) from 1.65 V or 1.8 V to 3.6 V.
All V
DDx
and V
SSx
must be at the same potential respectively. The V
DDx
pins must be
connected to V
DD
with external decoupling capacitors: one 100 nF Ceramic capacitor
for each V
DDx
pin and one single 1 µF Tantalum or Ceramic capacitor.
The STM8L15xxx, STM8AL31xx, and STM8L162xx devices also provide in some
packages:
• One pair of pads, V
DDA
/V
SSA
, dedicated to analog functions. V
DDA
and V
SSA
must be
at the same potential respectively as V
DD
and V
SS
. Refer to Section 3: Analog-to-digital
converter (ADC) for more details. The V
DDA
pin must be connected to two external
decoupling capacitors (one 100 nF Ceramic capacitor and one single 1 µF Tantalum or
Ceramic capacitor). Additional precautions can be taken to filter analog noise: V
DDA
can be connected to V
DD
through a ferrite bead.
STM8L152xx, STM8AL3Lxx and STM8L162xx devices manage the supply voltage needed
by the LCD in three different ways (see
Figure 1):
1. If the LCD feature is not used, connect the VLCD pin to V
DD
.
2. Apply to VLCD the voltage to be applied to the LCD.
3. Leave the STM8L152xx/STM8L162xx/STM8AL3Lxx to provide the correct voltage, via
its programmable LCD booster, by connecting the VLCD pin to a 1µF capacitor.