STCC02-BD5 ® CONTROL CIRCUIT FOR HOME APPLIANCE MCU BASED APPLICATION APPLICATIONS Microwaves oven analog and power driver control Home Appliance digital control FEATURES Wide range input supply voltage operation: 7 to 27 V 5 V ± 10% full tolerance Voltage Regulator MCU reset circuit with activation delay timer and 45µs digital noise filter Highly immune and 30 µs filtered Zero Voltage Synchronization Door Closed detection adaptation One 100 mA fan relay coil driver with demagnetizing diode One 100 mA magnetron relay coil driver with demagnetizing diode including down lock circuit based on fan drive output state One 10 mA buzzer driver Ambient temperature: - 10 to 85 °C ■ ■ ■ ■ ■ DIP-16 ■ ■ ■ PIN-OUT CONNECTIONS ■ VIN 1 16 VDD DLC 2 15 /RST SYN 3 14 ZVS DS 4 13 CDD MAG2 5 12 IN1 FAN1 6 11 IN2 VCC 7 10 IN3 COM 8 9 ■ ■ BENEFITS Higher module compactness with reduced component count Drastic reduction of soldered pins on the board for faster module assembly time and lower use of lead High ESD robustness and transient burst immunity compliant with IEC61000-4 standards Enhanced functional reliability Accurate MCU supply for better Analog to Digital Conversion Enhanced circuit parametric quality Easy to design for short time to market ■ ■ ■ ■ ■ ■ BUZ3 ■ STCC02 BASED APPLICATION DIAGRAM Line VCC VIN MAINS CDD Neutral VIN CUP VCC JP DLC SYN RZV DOOR SWITCH VCC MAGNETRON RELAY FAN RELAY DS MAG2 FAN1 VDD 5V Regulator ZVS Zero volts sync. Door closed detection Magnetron driver Fan driver VCC COM /RST Reset with delay IN2 IN2 CDD IN1 IN2 IN3 Buzzer driver CDD VSS /RST NMI P04 P01 P02 P03 BUZ3 MCU BUZZER October 2003 - Ed: 1A 1/12 STCC02-BD5 CIRCUIT BLOCK DIAGRAM 5V Regulator VIN DLC VDD Reset with delay Zero volts sync. SYN DS ZVS Door closed detection MAG2 CDD IN2 Magnetron driver FAN1 /RST IN1 Fan driver VCC IN3 COM BUZ3 Buzzer driver FUNCTIONAL DESCRIPTION RSENSE VIN The STCC02 is a control circuit embedding most of the analog & power circuitry of a microwaves oven Over current control module. It interfaces the micro-controller limiter with the power and process sections of the oven. The voltage supply 1.25V The 5V voltage regulator supplies the Reference micro-controller MCU: especially functions such + as the timer, the Analog-Digital Converter ADC, and the low current outputs. Since all the R2 R1 high-current outputs sink their current from a different voltage supply, this regulator does not need to be oversized. Its average output current VDD can vary from 5 to 20 mA. Its output voltage accuracy, that contributes to the ADC accuracy of the MCU, is better than ± 10 % in the whole operating range of the temperature TAMB, the load current IDD and the input voltage VIN . The STCC02 input voltage range from 7 to 27 V; and its DC output current is less than 20 mA to keep the internal dissipation compatible with thermal package capability. The regulator includes also an over current limiter to prevent high current conditions during the power up inrush or the output short circuit. This limiter is made of a serial shunt resistance as current sensor and a circuit that regulates the input over current. ■ The reset circuit This circuit ensures a Low Voltage Detection (LVD) of the output voltage of the regulator. Most micro-controllers have an active RESET pin in the low state: so, the /RST pin will be active at low state. ■ VDD VDD VH = 4.25 V VL = 3.75 V VH PROGRAMMABLE DELAY VDD VL NOISE FILTER DLC /RST 500 Ω External Capacitor CUP If CUP = 47 nF, TUP = 6 ms 2/12 circuit output TUP = 6 ms CUP = 47 nF RST\ TDW ~ 40 µs internal latch output STCC02-BD5 The reset circuit senses the regulator voltage VDD. Its comparator with hysteresis achieves this task. The /RST pin is high when VDD is higher than the high threshold VH = 4.25 V; and is low when the VDD decreases below the low threshold VL = 3.75 V. The comparator output changes are filtered for a high immunity. When the reset is disabling (VDD >VH), the /RST signal rises after the delay time TUP . This delay is set by an external capacitor CUP connected to the DLC pin: TUP = 6 ms for CUP = 47 nF. When the reset is enabling (VDD <VL), the /RST signal is falling after a delay time TDW that is internally set at 40 µs when CUP= 47 nF. ■ The Zero Voltage Synchronization ZVS circuit VDD ZVS 20 µs Filter S1 RZV 25 kΩ SYN Q VCC AC LINE 500 kΩ S2 100 kΩ VTF COM The Zero Voltage Synchronization ZVS circuit generates a low frequency clock using the AC line cycles (20 ms on 50 Hz or 16.7 ms on 60 Hz). This clock allows the MCU to generate the cooking timings and to reduce the magnetron inrush current by powering it on at the AC line peak voltage. RZV = 10 kΩ; VCC = 15 V; ICC = 20 mA VZVS 50µs 115µs VTF 2V / div 40µs / div FALLING EDGE RISING EDGE The input pin SYN is an image of the mains voltage and is usually connected to the supply transformer through a resistor RZV. The circuit is protected against fast line transients because its state change will act on the whole MCU routines: a 30 µs filter is implemented giving a higher immunity to the MCU circuit. Since the ZVS pin is connected to the Non Maskable Interrupt NMI or INT\ of the MCU, its falling edge is the active counting event. The delay between the real Zero Crossing event and this ZVS falling edge depends on the internal filtering time, the resistance RZV, the transformer, the rectifier drop voltage VF, the VCC supply load and the temperature. The STCC02 contribution to this delay can be evaluated by measuring the delay between its input voltage VTF and its output voltage VZVS. When using VF = 0.8V, RZV = 10 kΩ, VCC = 15V, ICC = 20 mA, it is about 50 µs on rising voltage VTF and 115 µs on falling voltage VTF. 3/12 STCC02-BD5 ■ The Door closed detection circuit VDD VDD VCC DS 100 kΩ EMI Filter CDD 500 Ω Door Switch 50 kΩ The magnetron of the oven can be powered only if the door is closed in order to protect the oven user. This safety feature is ensured mechanically by putting the door switch in series with the magnetron relay coil supply. For redundancy purpose, the Door Closed Detection CDD signal is also transmitted to the MCU. Since the DS input detects the door state from an electromechanical switch, a spike suppressor is added to increase its robustness. Its EMI immunity in off state (open door) is increased thanks to a 50kΩ pull down resistor that maintains the DS signal in low state. ■ The magnetron relay coil driver DS Demagnetizing Diode VDD IN3 15 kΩ FAN1 MAG2 Relay Transistor This robust driver interfaces a DC relay coil and an MCU output. The relay coil power is rated up to 1.2 W for VCC = 12V. Its output stage is made of a transistor and a demagnetization diode. The transistor's reference is to the power ground COM and has a DC current rating of 100 mA. Its collector is connected to the outputs MAG2. The diode is connected between the output pin MAG2 and the Door Switch pin DS. To enhance safety rules and to prevent any unventilated operation of the magnetron, the relay coil magnetization is enabled by the fan conduction state that becomes a logic signal FAN1\. Furthermore, its demagnetization node is connected to the door switch pin DS: when the oven door is open, the coil of the magnetron relay is immediately disconnected from the relay supply VCC to switch off these heating loads. The boolean rule of the magnetron relay operation becomes: (Magnetron relay ON) = DS.IN2.FAN1\. 4/5 STCC02-BD5 VCC VCC Demagnetizing Diode 5 kΩ VDD IN3 50 kΩ VDD BUZ3 Buzzer Transistor IN1 15 kΩ FAN1 Relay Transistor Fan relay coil driver This robust driver interfaces a DC relay coil and an MCU output. The relay coil power is rated up to 1.2W for VCC = 12 V. Its output stage is made of a transistor and a demagnetization diode. The transistor is referred to the ground COM, has a DC current rating of 100 mA; and its collector is connected to the output FAN1. The diode is connected between the output pin FAN1 and the supply pin VCC. ■ Buzzer driver The MCU can drive a warning buzzer with a 50% PWM signal. The buzzer driver amplifies this signal in current and translates it from the 5V MCU output to the VCC supply to produce the right sound level from the buzzer. The output stage is made of a transistor and a 5 kΩ resistor. The transistor is referred to the power ground COM and is connected by its collector to the output BUZ3. It has a DC current rating of 10 mA and runs up to 5 kHz. Finally, the resistor is connected between the BUZ3 and VCC pins to discharge the capacitance of the buzzer at turn off and in off state. ■ 5/12 STCC02-BD5 ABSOLUTE RATINGS (limiting values) Symbol Pin Parameter name & conditions Value Unit VDD VDD Output supply voltage -0.3 to 6 V VIN VIN Input supply voltage -0.3 to 30 V DS, VCC SYN Door switch and power supply voltage AC input voltage, RZV = 10kΩ - 0.3 to 30 - 1 to 30 V V BUZ1, MAG2, FAN1 Output voltage -0.3 to 30 V VI IN1, IN2, IN3 Input logic voltage V VO ZVS, CDD, /RST Output logic voltage IM DS, VCC Maximum sourced current pulse, tp=10ms - 0.3 to VDD + 0.3V - 0.3 to VDD + 0.3V 120 mA MAG2, FAN1 Maximum sunk driver current pulse, tp=1ms Maximum DC sourced current 120 100 mA mA BUZ3 Maximum driver diode reverse current Maximum DC sourced current Maximum demagnetization diode reverse current 15 10 1 mA mA mA Maximum buzzer frequency Operating dissipation, DIL-16 package (1) Operating ambient temperature, DIL-16 Operating junction temperature 5 0.65 - 10 to 85 - 10 to 150 kHz W °C °C Storage junction temperature - 25 to 150 °C VDS, VCC VSYN VMO MAG2, FAN1 FMAX PDIS TAMB TJ IN3, BUZ3 All AII All V Note 1: Refer to the Application Recommendations for the calcultation of the functional dissipation. ELECTROMAGNETIC COMPATIBILITY RATINGS (TJ = 25°C, according to typical application diagram of page 1, unless otherwise specified) Symbol VESD Node All pins Parameter name & conditions Value Unit ESD protection, MIL-STD 883 method 3015, HBM model ±2 kV Value Unit 100 °C/W THERMAL RESISTANCE Symbol Rth (j-a) 6/12 Parameter DIL-16 thermal resistance junction to ambient Copper thickness = 35µm STCC02-BD5 TENTATIVE ELECTRICAL CHARACTERISTICS (TJ = 25°C, VCC = VIN = 12V, unless otherwise specified) Symbol Pin VDD VDD Output voltage supply VIN ISQ ISM VIN VIN VIN Input supply voltage Quiescent supply current Internal circuit current (IIN - IDS) IIN_SC VIN Limiting input current TUP VTH ISYN VDS H VDS L IDS SYN ZVS SYN SYN DS FAN1 On state output voltage IN2 VON MAG2 On state output voltage IIN3 FBUZ Off state output voltage IN3 5.5 V 1.25 1.9 27 2.5 3 V mA mA 45 90 mA 4.5 3.3 4.25 3.75 V V 0.3 0.5 V 1 6 ms ION = 100mA, VIN1 > 3.5V Off state output voltahe VIN1 < 1V, RL = 110Ω 0.9 VCC Magnetron relay coil driver Input activating current VIN2 = VDD, VFAN1 < 1.5V IIN2 VMAG2 H 5 Enabling reset daly time CUP = 47nF 45 Zero Voltage synchronization circuit Transition filtering time VTF = 0 to VCC rising and 10 30 falling step Transition threshold 0.4 0.6 Input activating current RZV = 10kΩ, VSYN = 24V 0.8 Door closed detection circuit Closed door detection 7 Open door detection Internal input current VDS = 27V 230 Door closed detection, zero voltage synchronization, reset circuits High level output voltage 0.8 VDD VON VFAN1 H 4.5 VDD = 0V Output in short circuit Reset circuit IIN1 VOL Typ. 7 CDD /RST Low level output voltage ZVS Fan relay coil driver IN1 Input activating current VIN1 = VDD VOH Min. VDD = 5V, IDD = 0 (open) VIN1 = VIN2 = VIN3 = VDD IDD = 20 mA /RST Threshold hysteresis Disabling reset delay time CUP = 47nF TDW TD Conditions Voltage supply IDD = 5 to 20mA Tamb = -10 to 85°C VIN = 7 to 27V CDD = 10µF Disabling reset threshold Enabling reset threshold VH VL VHYS Name ION = 100mA, VIN2 > 3.5V VFAN1 < 1.5V Input activating current VIN2 < 1V, RL = 110Ω Buzzer driver VIN3 = VDD Buzzer PWM frequency Duty cycle = 50% VBUZ3 H BUZ3 Off state output voltage VON On state output voltage RBUZ Buzzer resistance to VCC VIN1 ION = 10mA, VIN3 > 3.5V Max. Unit µs 70 µs 0.9 2 V mA 27 0.8 800 V V µA V 0.2 VDD V 300 800 µA 1 1.5 V VCC V 300 800 µA 1 1.5 V VDS V 0.9 VDS 60 200 2 0.9 VCC 1.2 4.7 µA kHz VCC V 1.8 V kΩ 7/12 STCC02-BD5 DC CHARACTERISTICS FIGURES Fig. 1 : Regulator characteristic with Tj = 25°C and VIN = 12V. 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0 Voltage regulation VDD (V) Current Limitation IDD (mA) 0 10 20 30 40 50 Fig. 2 : Regulator output voltage versus its junction temperature with VIN = 12V. 5.5 5.4 VDD (V) IDD=20mA IDD=5mA 5.3 5.2 5.1 5 4.9 4.8 4.7 4.6 Tj (°C) 4.5 -20 0 20 40 60 80 100 120 Fig. 3 : Regulator output voltage versus its input voltage with IDD = 5 and 20 mA and TJ = 25°C. 5.5 5.4 5.3 5.2 5.1 5 4.9 4.8 4.7 4.6 4.5 VDD (V) IDD=20mA VIN (V) 5 8/12 IDD=5mA 10 15 20 25 STCC02-BD5 APPLICATION RECOMMENDATIONS EVALUATION OF THE STCC02 DISSIPATION IN ITS APPLICATION In order to define accurately at which maximum input supply voltage the STCC02 can work safely, the dissipated power has to be evaluated. Indeed, the STCC02 device can withstand voltages up to 30V, as specified in the "ABSOLUTE RATINGS" section. However, when the VIN voltage is high, it will also increase the power dissipation PDIS and the junction temperature TJ of the whole circuit. For the evaluation of the maximum junction temperature, the following equation should be used to calculate dissipated power: ■ PDIS = (V IN − V DD ) × I DD + V IN ⋅ I Q + V ON × (I M @ FAN 1 + I M @ MAG 2 + I M @ BUZ 3 ) Indeed, the power dissipation is mainly due to the regulator and to the currents sunk by the three driver outputs FAN1, MAG2, and BUZ3. Furthermore, the input voltage VIN is linked to the relays conduction in most applications. When the relay coils are driven, the storage supply capacitor is discharged and VIN is no longer equal to the peak voltage of the transformer secondary winding. In this case, VIN should approach the average value of the secondary voltage. This value is then approximately 36% lower that in stand-by operation, as explained by the following equation: V IN (relays _ on ) ≈ 2 × V IN (relays _ off ) π When the relays are off, the dissipation losses formula is: PDIS = (V IN − V DD ) × I DD + V IN × I Q For instance if VIN = 27V, VDD = 5V, IQ = 2.5mA, IDD = 20mA, the dissipated power in the STCC02 is evaluated at 0.51W. When the relays are on, the full formula of the dissipation losses is applied. For instance in the same AC line conditions with the relays on, VIN drops down to 17.5V. Considering IM BUZ3 = 10mA, IM FAN1= IM MAG2 = 100mA and VON = 1.5V, the dissipated power in the STCC02 becomes 0.61W. The maximum junction temperature is given by: TJ max = TAMB max + Rth ( j − a ) × PDIS The maximum allowed input supply voltage is then chosen in order to keep the junction temperature below its maximum operating value 150°C. Since the maximum junction temperature is 150°C, the maximum ambient temperature TAMB is 85°C in this application, and the thermal resistance is 100°C/W, the maximum allowed dissipation becomes 0.65 W. The two dissipation cases described above are compatible with the package dissipation capability. Otherwise, the ambient temperature TAMB, the input voltage VIN or the load current IDD should limited by design to meet the circuit thermal requirements. 9/12 STCC02-BD5 ■ IMMUNITY IMPROVEMENT OF STCC02 AND ITS MICROCONTROLLER 2 DOOR SWITCH VCC VIN VIN 5v REG VDD VDD 3 5 4 DS 3 RST \ Reset RST \ 4 RELAY COIL Relay Drive MCU STCC02 VSS 1 COM 1 Some basic rules can be applied to improve the STCC02 immunity in its application: - The power grounds of VCC and DS should be split from the signal ground VSS. (1) - The STCC02 is placed as close as possible of the MCU;(2) - The supply capacitors would increase the system immunity by being placed closed to the blocks they feed;(3) - Wide supply copper plane should be avoided to reduce sensitivity to radiated interferences. More specifically with the STCC02 circuit, - A decoupling capacitor can be put on the STCC02 pins SYN and the MCU reset pin;(4) - Depending of the PCB layout quality, others capacitors may be put on sensitive pins such as the output regulator pin VDD, the synchronization circuit pin ZVS or the door switch pin DS. The power door switch is a well-identified electrical noise source for the electronic board. Its effect should be reduced as much as possible. For instance, its power wires should be twisted together and split from other wires. Its signal wires should be also twisted; and on the PCB, the VCC forward track and the DS signal reward track should be linked to reduce EMI on the signal DS.(5) ■ ELECTROMAGNETIC COMPATIBILITY TEST CIRCUIT Standards such IEC61000-4-X evaluate the electromagnetic compatibility of appliance systems. To test the immunity level of the STCC02 to the IEC61000-4-4 (transient bursts), a board representative of usual control unit for microwave oven has been developed, as shown on top of page 11. One characteristics of the IEC61000-4-4 test, is that no measurement equipment can be connected to the tested system, as it would corrupt the test results. That is why this board includes a remote monitoring circuit based on optic fibers. Thus, without any electrical link with an oscilloscope, it is possible to monitor the VDD voltage as well as the RESET or the ZVS outputs of the STCC02, during the IEC61000-4-4 test. This optical link detects parasitic commutations of outputs as short as 60ns. With this board, and the burst generator coupled to the mains as specified in the IEC61000-4-4 standard (see the above principle diagram), the STCC02 has been tested successfully at 4kV. MAINS 0.5 kV to 4 kV tr : 5 ns tp : 50 ns 10/12 BURST COUPLE STCC02-BD5 MAINS1 TR1 12V 1.5VA VCC D1 Vin 1N4002 C1 220uF D2~D5 1N4002 R1 10k C6 22nF VCC DOOR SWITCH ZVS CIRCUIT COMPATIBILITY WITH THE POWER SUPPLY RECTIFIER BRIDGE In some cases, the operation of the ZVS circuit may require a small capacitor CZV on the pin SYN in addition to the resistor RZV. The diodes of the full wave rectifier bridge may have a low speed and may switch off with recovery charges that create spikes on the pin SYN as shown on the waveforms below. With a10kΩ - 22nF RC circuit, the ZVS circuit becomes immune to such spikes. ■ VCC VIN 4ms/div VIN CUP 5V Regulator DLC SYN VZVS 2V/div VTF 5V/div VDD Reset with delay Zero volts sync. ZVS RZV CZV Door closed detection Magnetron driver Fan driver COM IN2 IN2 Buzzer driver OPEN DOOR SIGNAL IMMUNITY The door-closed signal is achieved by a high side switch connected between the VCC polarity and the DS pin. When the door switch is off and the magnetron relay coil is not supplied anymore, the low state signal is secured by the internal pull-down resistor of DS pin (50kΩ). In noisy environment with radiated interferences, the off state of the DS signal (open door) can be reinforced by adding a resistor from DS pin to the ground COM. Its resistance can be chosen from 50 kΩ to 22 kΩ. ■ VDD VDD VCC Door Switch DS RDS 100 kΩ EMI Filter CDD 500 Ω 50 kΩ 11/12 STCC02-BD5 PACKAGE MECHANICAL DATA DIP-16 DIMENSIONS REF. I L Inches Min. Typ. Max. Min. a1 0.51 0.020 B 0.77 1.65 0.030 Typ. Max. a1 b b1 e Z Millimeters B F e3 0.065 b 0.50 0.020 b1 0.25 0.001 D 20 0.787 E D 16 9 1 8 E 8.5 0.335 e 2.54 0.1 e3 17.78 0.7 F 7.1 0.280 I 5.1 0.201 L 3.3 Z 0.130 1.27 0.050 OTHER INFORMATION ■ Ordering code Marking Package Weight Base qty Delivery mode STCC02-BD5 STCC02-B DIP-16 1g 25 Tube Epoxy moulding resine meets UL 94,V0 Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. 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