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AN2716
STCC08 application guidelines
purpose this document
Describe STCC08 device features Give technical recommendations Implement STCC08 appliance Achieve robust STCC08 design regarding tests (IEC 61000-4-4)
November 2008
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Contents
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Contents
STCC08 description
Main features STCC08 non-insulated insulated application diagram switch control switch failure mode detection signal reading synchronization
STCC08 consumption Recommended values detection application Electromagnetic compatibility (EMC) tests
Demonstration board description 61000-4-4 burst immunity test
Conclusion
Appendix Detection window width definition. Appendix Demonstration board component layout. Appendix Demonstration board schematic Appendix Demonstration board circuit layout view. Revision history
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STCC08 description
STCC08 description
Main features
STCC08 been designed improve safety home appliances. This device drive switches (TRIAC, ACST ACS) send back microcontroller (MCU) signal image voltage across controlled switch. STCC08 three functional blocks (see Figure Table
"gate driver" block used drive switch interface directly STCC08 with (CMOS compatible) "power switch signal shaping" block used measure switch voltage "AVF driver" block used give image switch voltage (digital information) STCC08 block diagram
Figure
Gate driver
STCC08
driver
SO-8 package
Power switch signal shaping
Table
STCC08 descriptions
Symbol SIGNAL POWER SIGNAL SIGNAL POWER Type SIGNAL SIGNAL switch drive Alternating voltage feedback: switch state output connected switch state sense input Positive power supply switch gate driver output switch gate current setting Power supply reference Description
Knowing STCC08 input state (used turn switch) voltage across controlled switch (given STCC08 output signal state), able identify switch failures (diode mode, short circuit, open circuit) take appropriate actions appliance secure state switching appliance front-end relay (see Section 1.4.3).
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STCC08 description
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STCC08 non-insulated insulated application diagram
STCC08 dedicated applications with MCU. Figure Figure show respectively STCC08 non-insolated insolated application diagrams. STCC08 compatible with power supplies. power supply must negative one. This means terminal connected neutral. voltage then (3.3 below neutral. Such connection mandatory drive most ACST TRIAC devices switches triggered only current taken from gate). Figure
Neutral
Un-insulated application diagram
3.3V
Gate driver
STCC08
RShunt
Load
driver
Power switch signal shaping
Line
Front relay
Figure
Insulated application diagram
insulatated Power supply Insulated Power supply VCC2
VCC1 Neutral
Gate driver
STCC08
driver
Power switch signal shaping
RShunt
OPTO1 VCC1 RAVF
VCC2
Load
Line Front relay OPTO2
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STCC08 description
switch control
STCC08 controls IGTTRIAC, ACST through "gate driver" block designed
Drive switch according control input state (CMOS compatible) switch turned switch turned
Regulate gate current switch thanks internal current controller
gate current value (Pin turn switch) defined external resistor value (resistor connected between STCC08 input ground). Figure gives maximum value this resistor (RIG_max) according minimum ambient temperature (Tamb_min) appliance switch values. Note that switch junction temperature increases when switch Tamb), gate current required turn switch decreases IGT). only minimum ambient temperature considered. Figure Resistor value according minimum ambient temperature switch
RIG_max
Switch:
10mA
Tamb_min (°C)
example, with switch minimum ambient temperature, maximum resistor used turn switch throughout whole appliance temperature range.
1.4.1
switch failure mode detection
STCC08 output configuration
STCC08 driver block used send switch state (see Section 1.4.2). STCC08 output open collector loaded with external resistor (RAVF) connected directly MCU, pull-up input configuration (see Figure
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STCC08 description Figure STCC08 output configuration
RAVF
driver
AN2716
STCC08
STCC08
driver
RPULL-UP
IAVF
output loaded with external resistor (RAVF)
output loaded with pull-up resistor (RPULL-UP)
IAVF current STCC08 must lower than (IAVF_max). Equation defines minimal RAVF pull-up resistor value use. example, with VCC_max RAVF RPULL-UP resistor value must higher than fulfill this condition.
Equation
_min PULL- _min _max
_max
signal toggles from according switch state line (see Section 1.4.2). RAVF RPULL-UP resistor values modify signal rise time (tR_AVF). This rise time increases with capacitance RAVF RPULL-UP resistors. limit influence this delay switch state detection (see Section 1.4.2) detection application (see Section maximum RAVF RPULL-UP resistor value recommended. With load capacitor maximum RAVF resistor, rise time typically about (see Figure Figure signal rising time measurement information
AVF= RAVF
driver
STCC08
VAVF
R_AVF
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STCC08 description
1.4.2
switch state detection principle
switch state detection achieved thanks STCC08 "power switch signal shaping" block. This block measures current (IAC) through STCC08 input, which image switch voltage (VT) during both line cycle (VLine). illustrated Figure three cases considered.
Case switch VLine), current, phase shift with line (see Section 1.5.1), flows through resistor both line polarities. this case, STCC08 output signal (VAVF) remains high level state (+VCC). Case switch current flows through resistor RAC. this case, output signal (VAVF) remains level state (GND). Case switch line voltage falls zero voltage, current flows through resistor RAC. this case, output signal (VAVF) goes zero level (GND).
Knowing STCC08 input state, then able determine switch state analyzing signal (see Section 1.4.3). Figure switch failure detection principle
ILoad
Neutral
STCC08
IACT -IACT VAVF switch switch
RShunt
VLine
Load
Power switch signal shaping
RAVF VAVF
Line
ILOAD
current follows waveform voltage across switch. signal toggles between zero level (GND) certain current value noted IACT (see Figure IACT electrical parameter dispersion shown Table Table IACT electrical parameter dispersion
Maximum (IACT_max) IACT Minimum (IACT_min)
peak current value (IAC-peak) must lower than (maximum current allowed through STCC08 input). Equation defines minimum resistor value (RAC_Min) limit this current worst case load fails short circuit). example, with VLine_rms_max 10%, resistor value must higher than
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STCC08 description
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Equation
Line rms_
peak
resistor RShunt used detect switch state whatever load state (connected disconnected). Without this resistor, STCC08 signal remains level (GND) whatever switch state when load disconnected (IAC detect switch state when load disconnected (with resistor RShunt), IAC-peak current remains higher than IACT_Max current (IAC current threshold ensure switch state detection Table Equation defines condition RShunt resistors ensure right switch states detection worst case load disconnected). example, with VLine_RMS_Min 10%, resistor value plus RShunt resistor value must lower than 1.24
Equation
Shunt_max
Line_ rms_ (236
limit power dissipation resistors RShunt lower than their influences load, minimum value recommended respectively under line. Equation Equation give power dissipation RShunt worst case.
Equation
(PRAC)
Line_ rms_
Equation
(PRShunt
Line_ rms_ Shunt
1.4.3
switch failures detection during normal operation
Knowing STCC08 input state, able determine switch state analyzing signal. Figure andTable give switch failure modes according signal state STCC08 signal state. case switch failure, appliance safe configuration switching appliance front-end relay.
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AN2716 Figure switch failure detection
STCC08 description
ILoad VCC/COM ILoad VLine switch Line Load RShunt STCC08 VAVF VAVF RAVF
VLine
switch state: failure) open circuit failure
ILoad VCC/COM ILoad VLine switch Line Load RShunt STCC08 VAVF VAVF RAVF VLine
switch state: failure) short circuit failure
ILoad VCC/COM ILoad VLine switch VAVF Line Load RShunt STCC08 VAVF RAVF VLine
switch state: positive diode mode failure
ILoad VCC/COM ILoad VLine switch Line Load RShunt STCC08 VAVF VAVF RAVF VLine
switch state: negative diode mode failure
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STCC08 description Table STCC08 status truth table
output state +VCC (Except each zero crossing line) Toggle from +VCC +VCC (Except each zero crossing line)
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control (IN)
switch state failure) Diode mode Short-circuit failure) Open-circuit
output must loaded with external resistor (RAVF) connected directly MCU, pull input configuration (see Section 1.4.1).
1.5.1
signal reading synchronization
Detection window width definition
When switch (not controlled failed open circuit), current flows through STCC08 input. value this current depends RShunt resistors, load impedance line voltage. signal toggles between zero level (GND) certain current value named IACT (see Figure This impact switch state detection. STCC08 controlled signal read when current lower than IACT (VAVF switch interpreted failed short circuit (see Figure andTable instead switch state failure). Figure Definition window width detect switch state
VLine IACT IACT
Detection
Note:
phase shift between line current when switch off. This phase shift very neglected most loads found home appliances (see Appendix
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AN2716
STCC08 description switch state detection must after before times each line cycle (see Figure values defined Appendix example, with RShunt VAC_Line minimum current phase shift load respectively equal respectively simplify switch detection, recommended that signal read around peak voltage line order avoid having wrong interpretation switch state.
1.5.2
switch state detection after signal removal
When signal removed turn switch), parasitic detection switch state exists next load current zero (see Figure inductive load case). signal remains low-level state when control removed (ILOAD switch interpreted switch short circuit failure. Figure Parasitic detection inductive load
VLine ILoad
IACT -IACT
Delay
Parasitic detection
ensure correct detection switch state, when control removed whatever load used, reading must carried according Equation example, with signal read after when control been removed.
Equation
Delay_min
Note:
Overall, recommended that signal read during several line cycles order avoid incorrect interpretation switch state.
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STCC08 consumption
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STCC08 consumption
Equation Figure Table define maximum STCC08 current consumption (IDC_max). current used only detect switch states. This current comes from line from STCC08 power supply. current gate current turn switch, defined according external resistor value (see Figure 12). current IQuiescent defines STCC08 quiescent current. maximum IQuiescent current specified maximum input current (IIN_Max) specified current, used polarize STCC08 output defined resistor RAVF pull resistor (see Equation
Equation
G_max
Quiesient
Figure STCC08 current consumption
Neutral STCC08 Quiescent RAVF
Line Load RShunt
Table
STCC08 consumption values
Definition switch gate current STCC08 current consumption collector current Maximum value Depends resistor. Figure Depends RAVF resistor (IAVF_max mA). Equation
Parameter IG_max IQuiescent IAVF
input current control switch)
Equation
_max _min
_max Pull-up_min
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STCC08 consumption Figure Maximum current (IG_max) versus resistor value
IG_max (mA)
RIG_min
example, with VCC_max RAVF maximum STCC08 current consumption about
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Recommended values
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Recommended values
Figure Table show application diagram recommended values implement STCC08 device appliance according line voltage. Figure Application diagram
3.3V Neutral
STCC08
RShunt
Load
Line
Front relay
Table
Recommended value
VLine RShunt RAVF
t1_max (see Appendix t2_min (see Appendix tDetection_min (see Appendix
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detection application
detection application
STCC08 "Power switch signal shaping" block used detect zero crossing line voltage. resistor must connected between input line shown Figure signal toggles between zero level each zero crossing line voltage. Figure detection
Neutral
Gate driver
STCC08
RShunt
Load Line
Power switch signal shaping driver
tAVF
Equation defines maximal signal level width (tAVF) each zero crossing line voltage according value resistor RAC.
Equation
Fmin
ACT_
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Electromagnetic compatibility (EMC) tests
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Electromagnetic compatibility (EMC) tests
Demonstration board description
STCC08 been tested using stand-alone demonstration board (see Appendix according 61000-4-4. Appendix Appendix give respectively electrical schematic layout demonstration board. This demonstration board work mains voltage. STCC08 board includes:
STCC08 ACS108-6S STLITE39 MCU. capacitive power supply (C15 In-dart connector load firmware Mechanical switches used simulate different switch failures (diode mode, short circuit open circuit) mechanical switch control STCC08 signal through LEDs used visualize detected failure modes. load: light bulb rms)
STLITE39 used turn ACS108-6S through STCC08 analyze signal power LEDs indicating switch states failures switch diode mode, short circuit open circuit). Regarding power supply, maximum average current absorbed board about capacitor been used ensure board works correctly (see Appendix
5.2.1
61000-4-4 burst immunity test
Test conditions
Ambient temperature: 25°C Relative humidity:
5.2.2
Demonstration board immunity test
line input capacitor used help avoid triggering switch (ACS108-6S). program reads signal each line peak voltage (see Figure 15). demonstration board validated signal remains same level during three consecutive line cycles.
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AN2716 Figure signal detection
Timer
Electromagnetic compatibility (EMC) tests
delay
delay
Read timer detection Timer
Read timer detection Timer
demonstration board mains wires placed above ground reference. mains wire shorter than Each operating cycle been tested (load on). demonstration board supports burst levels higher than without spurious triggering ST7Lite3 loss whatever coupling mode etc.).
5.2.3
Advice improve application immunity
improve application performance term EMC, software must oriented (for more information please refer application note AN1015):
Auto-recovery routine. each reset interrupt, program must check data stored scheduled not. reset occur without supply voltage having fallen below (data retention parameter). this case, full start-up necessary, program keep working with previous data. This helpful avoid missing load control switch status when reset occurs problem, example. checked registers expected, then complete initialization procedure launched. area adequate, then "smart reset" performed. Only registers that used store internal subroutine variables cleared. Only main registers keep their previous values switch status, switch control Using watchdog properly. Enable watchdog soon possible after reset never refresh watchdog interrupt routine. Secure unused program memory area. Fill unused memory locations with code that forces watchdog reset jumps known program location
want generate reset.
Input filtering. recommended that signal read during several line cycles.
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Conclusion
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Conclusion
This application note illustrates designers maximize STCC08 performance their appliances especially switch state detection robustness. This document describes STCC08 device gives technical recommendations about STCC08 implementation appliance.
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AN2716
Detection window width definition
Appendix
Detection window width definition
signal reading must after before each line cycle ensure detection switch failures (see Figure 16). Indeed, STCC08 controlled signal read when current lower than IACT (VAVF switch interpreted failed short circuit instead switch state (see Figure andTable Figure Detection window width switch state
VLine IACT IACT
Detection
Considering Figure current variation, when switch off, defined according Equation where IAC_peak peak current, line frequency, load characteristics, phase shift between current line voltage.
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Detection window width definition Figure load model definition
Neutral
AN2716
Line
switch Load
STCC08
Power switch signal shaping
RShunt
Equation
Considering Equation times given respectively Equation Equation worst case. minimal window width allowed (tDetection_min) detect switch state defined when maximum time minimum (see Equation 13).
Equation
Fmin
Peak_
Equation
Fmax Peak_
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AN2716
Detection window width definition
Equation
Detection
IAC_peak_min defines minimum peak current through STCC08 input ensure switch state detection. This current must higher than maximum specified IACT parameter (IACT_max) order detect switch state worst case (when load disconnected). Equation defines this condition. Indeed, when load disconnected, current limited RShunt resistors. example, with RShunt (see Equation Equation VLine_RMS_min 10%, IAC_Peak_min
Equation
Peak
Line Shunt
ACT_max (236
phase shift between line current when switch off. resistor RShunt value higher than most load impedances found home appliances, this phase shift depends only load characteristic resistor RAC. Figure gives Fresnel's diagram circuit Figure define phase shift. current phase shift equal respectively ILoad current (ILoad_RMS) Load phase shift load. current (IAC_RMS) phase shift depend value resistor load impedance. this case, according Fresnel's diagram, maximum phase shift defined Equation Equation
Equation
Line_
Load_ Load
Equation
AC_max
rms_max Load_max Load_ rms_min
example, worst case, minimum current (ILoad_min) maximum Load phase shift load respectively 90°, maximum phase shift about 1.26 This phase shift very neglected most loads have current higher than phase shift lower than 90°. With RShunt t1_max t2_min respectively Figure Fresnel's diagram
VLine_RMS
Load
AC_RMS
RAC).IAC_RMS
ILoad_RMS (RAC ILoad_RMS
simplify switch state detection, recommended that signal read around peak voltage avoid having incorrect interpretation switch state. Note: load resistor, disconnected, current phase with line
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Demonstration board component layout
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Appendix
Demonstration board component layout
Figure Demonstration board component layout
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AN2716
COM/VCC
Appendix
FUSE/1A Com/VCC 0.5W 2200uF/25V 100n/16V
Varistor 375V
2.2uF 1N4148
Mains
100n COM/VCC 1.2K COM/VCC IN_MCU OSCI/CLKIN OSC2 120n/16V 120n/16V IN_MCU
COM/VCC
100n/16V
COM/VCC
Gate
GATE
STCC08
INDART CONNECTOR HE10
10n/16V 10n/16V TP12 ON/OFF COM/VCC ST7LITE39
IN_MCU
PB0/AIN0 PB1/AIN1 PB2/AIN2 PB3/AIN3 PB4/AIN4 PB5/AIN5 PB6/RDI
PA0(HS) PA1(HS) PA2(HS) PA3(HS) PA4(HS) PA5(HS) PA6(HS) PA7/TDO
680k
10n/16V 100n/16V
Figure Demonstration board schematic
DIODE STCC08 CNTRL
OPEN
COM/VCC
1N4007
1N4007
Gate
Light Bulb
Demonstration board schematic
Demonstration board schematic
STCC08 CNTRL
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Demonstration board circuit layout view
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Appendix
Demonstration board circuit layout view
Figure layer view
Figure Bottom layer view
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Revision history
Revision history
Table
Date 26-Nov-2008
Document revision history
Revision Initial release. Changes
25/26
AN2716
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