STCC08 AC switch failure mode detector Features ■ 3.3 V and 5 V power supply compatible ■ ACS, ACST, TRIAC compatible ■ Gate driver output: 28 mA max sink current ■ Adjustable gate drive current ■ Sense the AC switch voltage in both AC line polarities ■ Diode mode failure detection for solid state AC switches ■ Short circuit failure detection for AC switches, relays, electromechanical switches ■ Home appliances ■ Open AC switch detection for AC switches, relays, electromechanical switches ■ ACS, ACST, TRIAC drive ■ AC switch failure modes detection ■ SO-8 SMD package ■ Zero voltage synchronization Benefits ■ Enable appliances to meet IEC 60335-1 and IEC 60730-1 standards ■ Enable appliances to meet IEC 61000-4-4 standard ■ Eliminates high DC current in inductive load, by detecting the diode mode failure ■ Improve system safety monitoring open switch failure with critical loads such as door locks ■ Enable MCU to sense all AC switch failure modes and protect the appliance ■ Less MCU pin allocated to AC failure detection multiple STCC08 designed with resistor dividers uses one I/O ■ Easy to drive with MCU directly connected or through an opto coupler ■ Highly compact with integrated solution in SMD version March 2008 SO-8 Applications Description The STCC08 is an AC switch failure mode detector and an AC power switch driver. It drives the AC switch and informs the MCU of switch failure. The MCU takes the appropriate actions to put the system in a secure state. Diode-mode, short circuit detection and open switch in both AC line polarities are detected. The STCC08 helps home appliances to meet the IEC 60335-1 safety standard. The STCC08 can be easily interfaced to an MCU with its CMOS input AC switch driver and CMOS compatible output for the failure mode detector. Rev 1 1/13 www.st.com 13 Characteristics 1 STCC08 Characteristics Figure 1. Circuit block diagram GATE DRIVER G IN + RIG VCC AVF AVF DRIVER AC POWER SWITCH SIGNAL SHAPING Table 1. Circuit pin descriptions Symbol Type IN SIGNAL Logic AC switch drive AVF SIGNAL Alternating voltage feedback: AC switch status output AC SIGNAL AC switch status sense input VCC POWER Positive power supply G SIGNAL AC switch gate driver output RIG SIGNAL AC switch gate current setting GND POWER Power supply reference Figure 2. Description Pin layout (top view) IN 2/13 GND GND AVF RIG N/C G AC VCC STCC08 Characteristics Table 2. Pin allocations Pin # Name 1 IN 2 AVF Alternating voltage feedback: AC switch status output 3 N/C Not connected 4 AC AC switch status sense input 5 VCC Positive power supply 6 G 7 RIG 8 GND Table 3. Description Logic AC switch drive AC switch gate driver output AC switch gate current setting Power supply reference Absolute ratings (Tamb = 25 °C unless otherwise stated, respect to GND) Symbol Pin Value Unit VCC VCC 0 to 6 V VIN IN Switch activation voltage -0.3V to VCC +0.3 V IG G Sunk driver current 30 mA IAC AC Input sense current peak 2.2 mA VAVF AVF Alternative feedback voltage -0.3 to VCC +0.3 V IAVF AVF Maximum feedback current 5 mA Junction temperature range -20 to 125 °C TJ All Storage junction temperature range -40 to 150 °C Table 4. Parameter name and conditions Power supply voltage Recommended operating conditions Symbol Pin VCC VCC IG G RIG RIG RAC AC RSHUNT - TAMB All TJ All Parameter name and conditions Value Unit 2.97 to 5.5 V Max. sunk driver gate current 28 mA Gate current setting resistor 30 Ω Detector resistance for AC line = 120 V 100 kΩ Detector resistance for AC line = 230 V 300 kΩ HV biasing resistance for AC line = 120 V 100 kΩ HV biasing resistance for AC line = 230 V 300 kΩ Operating ambient temperature range -20 to 85 °C Operating junction temperature range -20 to 125 °C Power supply voltage respect to GND 3/13 Characteristics STCC08 Table 5. Electrical characteristics Symbol Pin Name Conditions Min Typ Max Unit Switch drive (respect to GND, Tj=25 °C unless otherwise specified, RIG=30 Ω) IQUIESCENT VCC Quiescent current IN = GND VON IN On-state switch activation voltage VOFF IN Off-state switch release voltage IIN IN Input drive current Vin > Von IG G Gate drive current Vin > Von IAC AC Detection threshold 2 mA V 0.7*VCC 0.3*VCC V 50 µA 20 28 mA 82 236 µA Status output (respect to GND, Tj=25 °C unless otherwise specified) VOH AVF Minimum output voltage IAVF = 50 µA 0.7*VCC IAVF = 50 µA (CMOS Compatible) VOL Table 6. Table 7. Symbol 0.3*VCC V 1 V AVF Maximum drop voltage I AVF = 5 mA (Opto-transistor compatible) Thermal resistance Symbol RTH (j-a) V Parameter name and conditions SMD Thermal resistance Junction to Ambient Value Unit 140 °C/W System related electromagnetic compatibility ratings Node Pin VCC Parameter name and conditions Value Unit ±8 kV ±6 kV ±4 kV ESD protection, IEC 61000-4-2, per input, against air discharge Neutral VESD Line VESD G Gate through ACS; ESD protection, IEC 61000-4-2, pin to ground, against air discharge AC Alternating current through RAC = 300 kΩ; ESD protection, IEC 61000-4-2, pin to ground, against air discharge Neutral VCC ESD protection, IEC 61000-4-2, pin to ground, for contact discharge(1) VCC Total Peak Pulse Voltage Burst, IEC 61000-4-4(1) Neutral VPPB Line G Gate through ACS; Total Peak Pulse Voltage Burst, IEC 61000-4-4 (1) AC Alternating current through RAC; Total Peak Pulse Voltage Burst, IEC 61000-4-4(1) 1. System oriented test circuits - see Application note AN2716 4/13 STCC08 2 Functional description Functional description STCC08 functional description The STCC08 is a power circuit designed to drive up to 10 mA IGT AC switches and to detect AC switch failure modes through MCU diagnostic. It embeds a logic switch driver, an AC switch diode mode detection, a short circuit detection and an AC switch open detection. STCC08 can be powered by a 3.3 V or 5 V power supply voltage. Switch driver This driver is a logic level buffer (CMOS compatible) interfacing directly with the AC switch and the microcontroller. The AC switch must be driven in negative polarity: AC switch COM = A1 = VCC The drive Boolean rule is: Vin > Von: switch = ON Vin < Von: switch = OFF The AC switch can be driven in continuous, pulsed or angle phase modes. In insulated applications, the input can be driven through an opto-coupler powered with a non-insulated auxiliary power supply. RIG pin allows the AC switch gate current to be set. A resistor must be connected between this pin and the ground GND. This resistor is defined according to the miminmum ambient temperature and the AC switch IGT (see Figure 3). This optimizes the consumption of the application. Figure 3. Rig = f(Tamb_min) for 5/10 mA AC switches 130 RIG_Max(Ω ) 120 AC switch 10 mA @ 25 °C AC switch 5 mA @ 25 °C 110 100 90 80 70 60 50 40 30 20 10 0 -20 -15 -10 -5 0 5 10 15 20 25 30 Tamb_min (°C) 5/13 Functional description STCC08 Failure mode detection This function detects AC switch failure modes required by the IEC 60335 standard: ● The AC switch diode mode failure in both negative and positive AC line polarities This failure is simulated with a diode placed in parallel with the power switch according to the IEC 60335-1 standard. ● The AC switch short-circuit failure mode, any external shorting and any spurious power switch turn-on ● The open AC switch failure mode This function improves the system safety. A diode mode failure, a short circuit or an AC switch open can lead to dangerous situations for the system or the user. The AVF block monitors the state of the AC switch in both AC polarities. Its output AVF is transmitted to the MCU for failure detection. The MCU detects the failure according to the following truth table: Table 8. STCC08 status truth table with RSHUNT in parallel with the load IN (MCU generated) AVF MCU DIAGNOSTIC 0 Open collector AC switch OK 0 Open collector to 0 toggle Diode mode 0 0 Short AC switch 1 0 AC switch OK 1 Open collector Open AC switch For a diode mode, the AVF output toggles from open collector to GND each the half of the AC mains. Therefore, the AVF output is a pulsed signal during a diode mode failure. The MCU can put the system in a safe configuration, switching off the front end relay already existing in home appliance designs. Status reading The AVF output is an open collector, active at low level. It can either be connected to a MCU input, in pull up input configuration, or through an opto-coupler in insulated designs. For inductive loads, there is a phase shift between load current and AC line voltage. When the ACS control is removed: 6/13 ● The AC switch - latch structure - still conducts and the AVF is at low level until the next zero current crossing. ● The AVF is at low level until next zero current crossing. ● In the worst case, the load current crosses zero close to peak mains voltage. Then the AVF signal should be read at peak mains voltage. STCC08 Functional description Figure 4. Failure mode detection for inductive loads in DC control mode NORMAL MODE SHORT CIRCUIT DIODE MODE AC LINE LOAD CURRENT IN AVF SUGGESTED READING TIME NORMAL MODE SHORT CIRCUIT DIODE MODE The microcontroller can store the AC switch drive signal in a RAM register when it is driving the STCC08 input. Therefore it can save gate energy while determining conduction state from this RAM register and multiplexing this information with AVF signal. AC LINE: High voltage between AC line and neutral LOAD CURRENT: Current through the AC load IN: MCU output driving the STCC08 IN input. AVF: Alternating voltage feedback, output of the STCC08 7/13 Application information 3 STCC08 Application information Figure 5. Application example with an MCU direct drive + ACS 3.3V to 5V NEUTRAL VCC GATE DRIVER G IN + RIG RIG ACS VCC RSHUNT RAC VCC AVF DRIVER LOAD AVF AC SW POWER SWITCH SIGNAL SHAPING GND MCU LINE The placement of a 100 nF capacitor between VCC and GND close to the STCC08 is advised. SW is an electromechanical switch that is part of the application design, for example, the water sensor in a washing machine. 3.1 Recommendations The STCC08 is designed for 5 and 10 mA ACSs, ACSTs and TRIACs. STCC08 basic application The microcontroller reads the AC switch state from the AVF output of the STCC08. The microcontroller can power-off the application driving a front-end relay. Figure 6. Non-insulated application NEUTRAL 3.3V to 5V VCC GATE DRIVER G IN + RIG RIG ACS VCC RAC LOAD SW RSHUNT VCC AVF DRIVER AVF AC POWER SWITCH SIGNAL SHAPING GND MCU LINE FRONT END RELAY 8/13 SAFETY TURN OFF STCC08 Application information This function is effective whatever the drive and the nature of the load. Figure 7. ACS benefits VCC NEUTRAL G VMAX = V CL ACS RAC1 RAC2 AC The ACS clamping capability, from 800 V to 1100 V reduces the stress across RAC resistors during an AC line over-voltage. This provides a robust solution and allows setting high voltage resistors RAC to withstand the ACS clamping voltage instead of the AC line maximum over-voltage. STCC08 AVF alarms configuration Figure 8. Open load and Short circuit ACS discrimination 3.3V to 5V NEUTRAL VCC GATE DRIVER G IN + RIG RIG ACS VCC RAC LOAD SW RSHUNT VCC LINE AVF DRIVER AVF AC POWER SWITCH SIGNAL SHAPING GND MCU When RSHUNT is removed, the MCU cannot discriminate between an ACS short circuit and open load failure. See Table 9. 9/13 Application information Table 9. STCC08 STCC08 status truth table with RSHUNT removed IN (MCU generated) AVF MCU DIAGNOSTIC 0 Open collector AC switch OK 0 Open collector to 0 toggle Diode mode 0 0 Short circuit or open lead 1 0 AC switch OK 1 Open collector Open AC switch STCC08 ZVS application Figure 9. ZVS application schematic NEUTRAL 3.3V to 5V VCC GATE DRIVER G ACS IN + RIG - VCC VCC AVF DRIVER LINE RAC ZVS AC POWER SWITCH SIGNAL SHAPING GND MCU The gate driver drives an ACS while the failure detector is used independently for ZVS detection 10/13 STCC08 4 Package information Package information ● Epoxy meets UL94, V0 In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a lead-free second level interconnect. The category of second level interconnect is marked on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at www.st.com. Table 10. SO-8 dimensions Dimensions Ref. Min. Seating Plane C A2 h x 45° C A1 e b A Millimeters L k ppp C L1 Typ. A Inches Max. Min. Typ. 1.75 A1 0.1 A2 1.25 0.25 Max. 0.069 0.004 0.010 0.049 b 0.28 0.48 0.011 0.019 C 0.17 0.23 0.007 0.009 D 4.80 4.90 5.00 0.189 0.193 0.197 E 5.80 6.00 6.20 0.228 0.236 0.244 E1 3.80 3.90 4.00 0.150 0.154 0.157 D 8 5 E1 1 E e 4 1.27 h 0.25 0.50 0.010 0.020 L 0.40 1.27 0.016 0.050 8° 0° L1 k 1.04 0° ppp Figure 10. Footprint dimensions in mm(inches) 0.050 0.041 0.10 8° 0.004 Figure 11. Marking 6.8 (0.268) 0.6 (0.024) 4.2 (0.165) XXXXX : Marking ZZ : Manufacturing location Y : Year WW : week xxxxxx â z z y ww 1.27 (0.050) Pin 1 11/13 Ordering information 5 Ordering information Table 11. 6 Ordering information Order code Marking Weight Base Qty Delivery Mode STCC08 STCC08 0.08 g 100 Tube STCC08RL STCC08 0.08 g 2500 Tape and reel 13” Revision history Table 12. 12/13 STCC08 Document revision history Date Revision 20-Mar-2008 1 Changes Initial release. STCC08 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. 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