AN1709 datasheet(17/38 Pages) STMICROELECTRONICS

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EMC DESIGN GUIDE FOR ST MICROCONTROLLERS

3 ST MCU DESIGN STRATEGY & EMC SPECIFIC FEATURE

At the initial specification of a new product, EMC dedicated features are implemented after an

identification of EMC constraints imposed by the MCU target applications. You should refer to

the specific product datasheet to know which of these feature described here are embedded.

Figure 10. Overview of specific features embedded in ST Microcontrollers

3.1 SUSCEPTIBILITY

3.1.1 Low Voltage Detector (LVD)

The purpose of the LVD is to ensure that the Microcontroller will always work in its safe oper-

ating area (see Figure 12.). In terms of EMS, the presence of the LVD makes the MCU more

robust, ensuring that if any outside disturbance affects the power supply, the application can

recover safely.

When VDD is below the « Min Working VDD » the behaviour of the Microcontroller is no longer

guaranteed. There is not enough power to decode/execute the instructions and/or read the

memory. When VDD is below the LVD level the Microcontroller enters in reset state (internal

reset High) in order to prevent unpredictable behaviour. There are 2 levels with 250mV hys-

teresis in order to avoid oscillating when the micro restarts. When a LVD reset occurs, a bit is

set by HW. This bit can be used to recover an application.

The Low Voltage Detector function generates a static reset when the VDD supply voltage is

below a VIT- reference value. This means that it secures the power-up as well as the power-

down keeping the Microcontroller in reset.

ST Microcontrollers

for EMC in

Low Power Oscillator

I/O Protection

Watchdog

LVD/AVD

Internal PLL

Internal Voltage Regulators

(For MCUs with low power core)

Multi Oscillator

Embedded features

Controlled Slope

(Firmware Management

refer to AN 1015)

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