ST STEVAL-IHM020V1 Manuale utente

November 2008 Rev 1 1/23

UM0583

User manual

STEVAL-IHM020V1 demonstration board based on the

STCC08 AC switch failure mode detector

Introduction

The STEVAL-IHM020V1 demonstration board (see Figure 1) provides a means to evaluate

the performance of the STCC08, which is an AC switch failure mode detector and an AC

power switch driver. The device is dedicated to driving up to 10 mA IGT AC switches (ACS,

ACST and TRIACs), and detecting any switch failures. This solution embeds a switch driver

and an AC switch state detector. It contributes to system safety by monitoring AC switches

driving sensitive loads such as drain pumps, door locks, heaters, cooling fans, and

compressors.

Figure 1. STEVAL-IHM020V1, STCC08 demonstration board

This user manual provides all information needed to set up and operate the demonstration

board. With this demonstration board, you can:

■Evaluate the full ST solution (microcontroller + STCC08)

■Test and analyze the AC switch failure detection features of the STCC08 device

AM01336v1

www.st.com

Contents UM0583

2/23

Contents

1 Demonstration board introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.1 Package contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2 Board presentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 STCC08 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.1 Block diagram description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2 Gate driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3 ACS failure detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.1 ST7LITE39F2 microcontroller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.2 DC capacitive power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4 Using the demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.1 Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.2 Measurement points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.3 Getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

4.3.1 Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5 IEC 61000-4-4 Burst immunity test . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.1 Test conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.2 Demonstration board immunity test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

5.3 Recommendations for improving application immunity . . . . . . . . . . . . . . 16

6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Appendix A STCC08 demonstration board schematic . . . . . . . . . . . . . . . . . . . . 19

Appendix B Bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

UM0583 List of figures

3/23

List of figures

Figure 1. STEVAL-IHM020V1, STCC08 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Figure 2. Main components used (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 3. Main components used (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Figure 4. STCC08 block diagram description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 5. Application diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Figure 6. AC switch failure-detection principle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 7. Measurement points (top layer view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Figure 8. STCC08 demonstration board (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Figure 9. Short-circuit detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 10. Diode mode detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 11. Open circuit detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Figure 12. AVF signal detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Figure 13. STEVAL-IHM020V1 demonstration board schematic diagram. . . . . . . . . . . . . . . . . . . . . . 19

Demonstration board introduction UM0583

4/23

1 Demonstration board introduction

1.1 Package contents

The following items are supplied in this package:

●Demonstration board featuring the STCC08 AC switch failure mode detector

●DVD containing user manual, product presentation and datasheets.

1.2 Board presentation

Figures 2and 3show the board and the main components used.

Figure 2. Main components used (top view)

Figure 3. Main components used (top view)

AM01337v1

AC switch state

visualization

15 W AC load

STCC08

Capacitive

power

supply

AC switch failuressimulation

MCU ST7FLITE39

STCC08

control

ACS108-6S

AM01338v1

SW2 SW3SW1 SW4 SW5

U3D6

UM0583 Demonstration board introduction

5/23

Components on the demonstration board include:

●the STCC08 device (U1)

●the STLITE39F2 MCU (U2). The 8-bit MCU drives the AC switch through the STCC08,

analyzes the STCC08 AVF signals and powers LEDs to indicate AC switch failures

●the ACS108-6S (U3), transient voltage protected AC switch

●A capacitive DC power supply

●An ICC (in-circuit connector) (J3) to load the firmware in the MCU.

Warning: Before the board is connected to a computer through the ICC

connector, ensure that the AC line is connected to the board

through an insulated plug. This is essential to avoid electrical

shock.

●A switch to simulate an AC load failure in open circuit (SW1)

●2 switches (SW2, SW3) to simulate a diode mode failure in both polarities of the AC line

and a short-circuit of the AC switch (when SW2 and SW3 are in the “YES” position at

the same time)

●A switch to simulate an AC switch failure in open circuit (SW4)

●An STCC08 CNTRL switch (SW5). This switch is used to turn the AC switch (ACS) on

or off through the MCU and the STCC08

●An STCC08 CNTRL LED (D5), used to see whether or not the AC switch has been

controlled by the user

●LEDs to define the ACS state

– A “DIODE” LED (D6) to visualize an ACS failure in diode mode in both AC line

cycles. The LED is on if the AC switch fails in diode mode.

– An “OPEN” LED (D7) to indicate an ACS failure in open circuit. This LED is on if

the AC switch is damaged in open circuit

– A “CC” LED (D8) to show an ACS failure in short-circuit on both polarities of the

AC line. This LED is on if the AC switch is damaged in short-circuit

– An “ON” LED (D9) to indicate that the AC switch is on

●Test points to allow the connection of voltage probes:

– L (TP2) and N (TP1): line and neutral of the AC line

– VCC (TP3): positive power supply

– GND (TP4): power supply reference

– ZVS (TP5): zero crossing of the AC line voltage

– OUT (TP6): anode of the ACS

– AC (TP7): ACS status sense input

– AVF (TP8): alternating voltage feedback. ACS status output

– ON/OFF (TP12): “STCC08 CNTRL” switch state, used to turn on or off the ACS

through the MCU and the STCC08

– IN (TP9): STCC08 IN input used to control the ACS

●An AC line connector (J1)

●An AC load: light bulb (15 W at 230 VRMS).

For more detailed information, please refer to the schematic diagram in Appendix A.

STCC08 description UM0583

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2 STCC08 description

2.1 Block diagram description

Figure 4 shows the block diagram of the STCC08. It includes a “gate driver” block to control

the AC switch, a “power switch signal shaping” block used to read the AC switch state and a

buffer able to send the AC switch state to the MCU (AVF DRIVER). This signal should be

analyzed by the MCU, which can power-off the application in hazardous situations (for

example, to open a relay (SW) placed in the front-end of the application - see Figure 5).

Table 1 provides the pin definitions of the STCC08.

Figure 4. STCC08 block diagram description

Figure 5. Application diagram

Note: The STCC08 AVF driver block is used to send the AC switch state to the MCU. The AVF

output is an open collector and should be loaded with an external resistor or connected

directly to the MCU, in pull-up input configuration.

AM01339v1

AVF

GND

POWER SWITCH

SIGNAL SHAPING

AVF DRIVER

GATE DRIVER

AVF

GND

STCC08

AVF

IN GND

SO-8

AM01340v1

AVF

GND

POWER SWITCH

SIGNAL SHAPING

GATE DRIVER

MCU

AVF

GND

LOAD

NEUTRAL

STCC08

RShunt

RAC

LINE

FRONT END RELAY

AVF

GND

POWER SWITCH

SIGNAL SHAPING

AVF DRIVER

GATE DRIVER

MCU

= 3.3V to 5 V

AVF

GND

LOAD

NEUTRAL

ACS

STCC08

RShunt

RAC

LINE

FRONT END RELAY

UM0583 STCC08 description

7/23

2.2 Gate driver

The STCC08 can control up to 10mA IGT TRIACs, ACST and ACS through a “GATE

DRIVER” block designed:

●to drive the AC switch according to the IN control input state:

– For IN = “1” = VCC: AC switch turn on

– For IN = “0” = GND: AC switch turn off

●to regulate the gate current of the AC switch, thanks to the internal current controller

2.3 ACS failure detection

External resistors (R1, R2, R3 and R4) sense the voltage across the ACS. Using these

resistors, the STCC08 constantly monitors the ACS state. Knowing the STCC08 IN input

state, the ACS state can be deduced by analyzing the AVF signal. Figure 6 gives the ACS

state according to the AVF signal state and the IN signal state.

Table 1. STCC08 pin definition

Pin Symbol Type Description

1 IN Signal AC switch drive

2 AVF Signal Alternating voltage feedback: AC switch state output

3 NC Not connected

4 AC Signal AC switch state sense input

5 VCC Power Positive power supply

6 G Signal AC switch gate driver output

7 RIG Signal AC switch gate current setting

8 GND Power Power supply reference

STCC08 description UM0583

8/23

Figure 6. AC switch failure-detection principle

AM01341v1

ACSstate: OFF if IN=0 (GND) or failed in open circuit if IN=1 (VCC)

ACSstate: ON if IN=1 (VCC) or failed in short circuit if IN=0 (GND)

ACSstate: failed in positive diode mode circuit if IN=0 (GND)

ACSstate: failed in negative diode mode if IN=0 (GND)

VCC

AVF

VCC

AVF

STCC08

AVF

Load

VCC/COM

RAC

AC switch

Load

Line

Load

RShunt

VCC

AVF

VCC

AVF

STCC08

AVF

Load

VCC/COM

RAC

AC switch

Load

Line

Load

RShunt

VCC

AVF

Load

VCC/COM

RAC

Load

Line

Load

RShunt

AC switch

VCC

AVF

STCC08

AVF

VCC

AVF

Load

VCC/COM

RAC

Load

Line

Load

RShunt

AC switch

VCC

AVF

STCC08

AVF

VCC

AVF

ILoad

VCC/COM

RAC

Load

Line

ILoad

RShunt

AC switch

VCC

AVF

STCC08

AVF

VCC

AVF

ILoad

VCC/COM

RAC

Load

Line

ILoad

RShunt

AC switch

VCC

AVF

STCC08

AVF

VAC

VCC

AVF

Load

VCC/COM

RAC

Load

Line

Load

RShunt

AC switch

VCC

AVF

STCC08

AVF

VCC

AVF

Load

VCC/COM

RAC

Load

Line

Load

RShunt

AC switch

VCC

AVF

STCC08

AVF

UM0583 STCC08 description

9/23

Table 2 gives the AC switch state according to the AVF signal and the MCU control (IN).

Knowing the IN signal state, the MCU is able to define the AC switch state by analyzing the

AVF signal. According to the failure mode, the MCU can place the system in a safe

configuration by switching off the home appliance front-end relay.

Note: “If the AC switch is damaged in short-circuit: the ‘CC’ LED is ON (D8)”

“f the AC switch is damaged only in one direction (diode mode): the ‘DIODE’ LED is ON

(D6)”

Table 2. AVF output definition

STCC08 control (IN) AVF signal AC switch states

0+V

CC (except at each zero crossing of the AC line) OFF (no failure)

0 Toggle from +VCC to 0 Diode mode

0 0 Short-circuit

1 0 ON (no failure)

1+V

CC (except at each zero crossing of the AC line) Open circuit

Features UM0583

10/23

3 Features

3.1 ST7LITE39F2 microcontroller

The 8-bit MCU used in this board is the ST7LITE39F2. It belongs to the ST7 family of

microcontrollers, and offers a large number of features at minimum cost.

●The peripheral hardware requirements are reduced to a minimum:

– No quartz or external resonator is used. Instead, an internal RC-oscillator in the

ST7LITE3 is used to generate the clock

– No external RESET circuit is used

●In the MCU firmware, four options must be set:

– Software watchdog activation

– RC oscillator selection

– PLL disabled

– Low voltage detection selection

Note: The MCU firmware has been developed only to evaluate the STCC08 device and is not

compliant with the class B (IEC60335-1 Ed4) requirements.

3.2 DC capacitive power supply

A DC capacitive power supply is used on the board. One peculiarity of this DC power supply

is that it is “negative”. The VCC terminal is connected to neutral. This means that the GND

voltage is 5 V below neutral. Such a connection is mandatory to drive the ACS. Indeed, the

ACS can only be triggered by a negative current (i.e. sourced from the gate). The maximum

average current absorbed by the board is about 44 mA (see Table 3). In this case, a 2.2 µF

C16 capacitor value has been used to ensure that the board works correctly in the worst

application conditions (230 V/110 VRMS line voltage ± 10% and VCC ± 10%).

Note that a 43.2 ΩRIG resistor (R23) value is used. In this case, the minimum ambient

temperature must be 0 °C in order to work correctly the board. For lower ambient

Table 3. Maximum average current sunk by the board

Device Average

current

consumption Comments

MCU 2.5 mA Maximum supply current in run mode. FCPU=1 MHz and VCC=5.5 V

LEDs (two LEDs maximum

can be ON at the same time) 15 mA LED STCC08 controlled

LEDs visualizing the ACS failure

R19=R20= R21= R22=475 Ω ± 1%

Maximum current consumed

by STCC08 (include the gate

current of the ACS) 26 mA VCC_MAX=5.5 V, temperature = 0° C

RIG = 43.2 ± 1% (R23)

Others (mechanical switch) 0.5 mA VCC_Max=5.5 V

Total 44 mA

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