Teccor® brand Thyristors Explanation of Maximum Ratings and Characteristics for Thyristors Introduction Data sheets for SCRs and Triacs give vital information regarding maximum ratings and characteristics of Thyristors. If the maximum ratings of the Thyristors are surpassed, possible irreversible damage may occur. The characteristics describe various pertinent device parameters which are guaranteed as either minimums or maximums. Some of these characteristics relate to the ratings but are not ratings in themselves. The characteristic does not define what the circuit must provide or be restricted to, but defines the device characteristic. For FYBNQMFBNJOJNVNWBMVFJTJOEJDBUFEGPSUIFEWEU because this value depicts the guaranteed worst-case limit GPSBMMEFWJDFTPGUIFTQFDJmDUZQF5IJTNJOJNVNEWEU value represents the maximum limit that the circuit should allow. Maximum Ratings VRRM: Peak Repetitive Reverse Voltage -- SCR The peak repetitive reverse voltage rating is the maximum peak reverse voltage that may be continuously applied to the main terminals (anode, cathode) of an SCR. (Figure AN1008.1) An open-gate condition and gate resistance termination is designated for this rating. An increased reverse leakage can result due to a positive gate bias during the reverse voltage exposure time of the SCR. The repetitive peak reverse voltage rating relates to case temperatures up to the maximum rated junction temperature. (anode, cathode) of an SCR. This rating represents the maximum voltage the SCR should be required to block in the forward direction. The SCR may or may not go into conduction at voltages above the VDRM rating. This rating is specified for an open-gate condition and gate resistance termination. A positive gate bias should be avoided since it will reduce the forward-voltage blocking capability. The peak repetitive forward (off-state) voltage rating applies for case temperatures up to the maximum rated junction temperature. Triac The peak repetitive off-state voltage rating should not be surpassed on a typical, non-transient, working basis. (Figure AN1008.2) VDRM should not be exceeded even instantaneously. This rating applies for either positive or negative bias on main terminal 2 at the rated junction temperature. This voltage is less than the minimum breakover voltage so that breakover will not occur during operation. Leakage current is controlled at this voltage so that the temperature rise due to leakage power does not contribute significantly to the total temperature rise at rated current. +I Voltage Drop (vT) at Specified Current (iT) Latching Current (IL) Minimum Holding Current (IH) -V +V +I Specified Minimum Off-state Blocking Voltage (VDRM) Voltage Drop (vT) at Specified Current (iT) Reverse Leakage Current - (IRRM) at Specified VRRM Off-state Leakage Current – (IDRM) at Specified VDRM Latching Current (IL) -I Off - State Leakage Current - (IDRM) at Specified VDRM Minimum Holding Current (IH) Figure AN1008.2 -V Breakover Voltage V-I Characteristics of Triac Device +V IT: Current Rating Specified Minimum Off - State Blocking Voltage (VDRM) Specified Minimum Reverse Blocking Voltage (VRRM) Reverse Breakdown Voltage Figure AN1008.1 -I Forward Breakover Voltage V-I Characteristics of SCR Device VDRM: Peak Repetitive Forward (Off-state) Voltage SCR The peak repetitive forward (off-state) voltage rating (Figure AN1008.1) refers to the maximum peak forward voltage which may be applied continuously to the main terminals ©2008 Littelfuse, Inc. Specifications are subject to change without notice. Please refer to http://www.littelfuse.com for current information. SCR For RMS and average currents, the restricting factor is usually confined so that the power dissipated during the on state and as a result of the junction-to-case thermal resistance will not produce a junction temperature in excess of the maximum junction temperature rating. Power dissipation is changed to RMS and average current ratings for a 60 Hz sine wave with a 180º conduction angle. The average current for conduction angles less than 180º is derated because of the higher RMS current connected with high peak currents. The DC current rating is higher than the average value for 180º conduction since no RMS component is present. Explanation of Maximum Ratings and Characteristics for Thyristors AN1008 AN1008 Teccor® brand Thyristors AN1008 PD = TJ(MAX)–TC RRJC where TJ(max) is the maximum rated junction temperature (at zero rated current), TC is the actual operating case temperature, and RRJC is the published junction-to-case thermal resistance. Transient thermal resistance curves are required for short interval pulses. Triac The limiting factor for RMS current is determined by multiplying power dissipation by thermal resistance. The resulting current value will ensure an operating junction temperature within maximum value. For convenience, dissipation is converted to RMS current at a 360º conduction angle. The same RMS current can be used at a conduction angle of less than 360º. For information on non-sinusoidal waveshapes and a discussion of dissipation, refer to the preceding description of SCR current rating. ITSM: Peak Surge (Non-repetitive) On-state Current -SCR and Triac The peak surge current is the maximum peak current that may be applied to the device for one full cycle of conduction without device degradation. The maximum peak current is usually specified as sinusoidal at 50 Hz or 60 Hz. This rating applies when the device is conducting rated current before the surge and, thus, with the junction temperature at rated values before the surge. The junction temperature will surpass the rated operating temperature during the surge, and the blocking capacity may be decreased until the device reverts to thermal equilibrium. The surge-current curve in Figure AN1008.3 illustrates the peak current that may be applied as a function of surge duration. This surge curve is not intended to depict an exponential current decay as a function of applied overload. Instead, the peak current shown for a given number of cycles is the maximum peak surge permitted for that time period. The current must be derated so that the peak junction temperature during the surge overload does not exceed maximum rated junction temperature if blocking is to be retained after a surge. SUPPLY FREQUENCY: 60 Hz Sinusoidal LOAD: Resistive RMS ON-STATE CURRENT [ I T(RMS)]: Maximum Rated Value at Specified Case Temperature 1000 Peak Surge (Non-repetitive) On-state Current (I TSM ) – Amps The dissipation for non-sinusoidal waveshapes can be determined in several ways. Graphically plotting instantaneous dissipation as a function of time is one method. The total maximum allowable power dissipation (PD) may be determined using the following equation for temperature rise: 400 300 250 40 A TO - 2 18 150 120 100 80 25 A T0-2 Notes: 1) Gate control may be lost during and immediately following surge current interval. 2) Overload may not be repeated until junction temperature has returned to steady-state rated value. 20 60 50 40 15 A TO 30 -220 20 10 1 10 100 1000 Surge Current Duration – Full Cycles Figure AN1008.3 Peak Surge Current versus Surge Current Duration ITM: Peak Repetitive On-state Current – SCR and Triac The ITM rating specifies the maximum peak current that may be applied to the device during brief pulses. When the device operates under these circumstances, blocking capability is maintained. The minimum pulse duration BOETIBQFBSFEFmOFEBOEDPOUSPMUIFBQQMJFEEJEU5IF operating voltage, the duty factor, the case temperature, and the gate waveform are also defined. This rating must be followed when high repetitive peak currents are employed, such as in pulse modulators, capacitivedischarge circuits, and other applications where snubbers are required. di/dt: Rate-of-change of On-state Current – SCR and Triac 5IFEJEUSBUJOHTQFDJmFTUIFNBYJNVNSBUFPGSJTFPG current through a Thyristor device during turn-on. The value of principal voltage prior to turn-on and the magnitude and rise time of the gate trigger waveform during turn-on are among the conditions under which the rating applies. If UIFSBUFPGDIBOHFPGDVSSFOUEJEU FYDFFETUIJTNBYJNVN WBMVFPSJGUVSOPOXJUIIJHIEJEUEVSJOHNJOJNVNHBUF ESJWFPDDVSTTVDIBTEWEUPSPWFSWPMUBHFFWFOUT UIFO localized heating may cause device degradation. During the first few microseconds of initial turn-on, the FGGFDUPGEJEUJTNPSFQSPOPVODFE5IFEJEUDBQBCJMJUZPG the Thyristor is greatly increased as soon as the total area of the pellet is in full conduction. 5IFEJEUFGGFDUTUIBUDBOPDDVSBTBSFTVMUPGWPMUBHF or transient turn-on (non-gated) is not related to this SBUJOH5IFEJEUSBUJOHJTTQFDJmFEGPSNBYJNVNKVODUJPO temperature. "TTIPXOJO'JHVSF"/UIFEJEUPGBTVSHFDVSSFOU can be calculated by means of the following equation. di ITM ---- = ----dt 2t1 Explanation of Maximum Ratings and Characteristics for Thyristors ©2008 Littelfuse, Inc. Specifications are subject to change without notice. Please refer to http://www.littelfuse.com for current information. Teccor® brand Thyristors VDM = Off-state voltage prior to switching di = ITM dt 2 t1 50% IDRM: Peak Repetitive Off-state (Blocking) Current 10% 0 t t1 Time Figure AN1008.4 Relationship of Maximum Current Rating to Time I2t Rating -- SCR and Triac The I2t rating gives an indication of the energy-absorbing capability of the Thyristor device during surge-overload conditions. The rating is the product of the square of the RMS current (IRMS)2 that flows through the device and the time during which the current is present and is expressed in A2s. This rating is given for fuse selection purposes. It is important that the I2t rating of the fuse is less than that of the Thyristor device. Without proper fuse or current limit, overload or surge current will permanently damage the device due to excessive junction heating. PG: Gate Power Dissipation -- SCR and Triac Gate power dissipation ratings define both the peak power (PGM) forward or reverse and the average power (PG(AV) ) that may be applied to the gate. Damage to the gate can occur if these ratings are not observed. The width of the applied gate pulses must be considered in calculating the voltage and current allowed since the peak power allowed is a function of time. The peak power that results from a given signal source relies on the gate characteristics of the specific unit. The average power resulting from high peak powers must not exceed the average-power rating. TS, TJ: Temperature Range -- SCR and Triac The maximum storage temperature (TS) is greater than the maximum operating temperature (actually maximum junction temperature). Maximum storage temperature is restricted by material limits defined not so much by the silicon but by peripheral materials such as solders VTFEPOUIFDIJQEJFBOEMFBEBUUBDINFOUTBTXFMMBTUIF encapsulating epoxy. The forward and off-state blocking capability of the device determines the maximum junction (TJ) temperature. Maximum blocking voltage and leakage current ratings are established at elevated temperatures near maximum junction temperature; therefore, operation in excess of these limits may result in unreliable operation of the Thyristor. Characteristics VBO: Instantaneous Breakover Voltage -- SCR and Triac Breakover voltage is the voltage at which a device turns on (switches to on state by voltage breakover). (Figure AN1008.1) This value applies for open-gate or gate©2008 Littelfuse, Inc. Specifications are subject to change without notice. Please refer to http://www.littelfuse.com for current information. SCR IDRM is the maximum leakage current permitted through the SCR when the device is forward biased with rated positive voltage on the anode (DC or instantaneous) at rated junction temperature and with the gate open or gate resistance termination. A 1000 Ω resistor connected between gate and cathode is required on all sensitive SCRs. Leakage current decreases with decreasing junction temperatures. Effects of the off-state leakage currents on the load and other circuitry must be considered for each circuit application. Leakage currents can usually be ignored in applications that control high power. Triac 5IFEFTDSJQUJPOPGQFBLPGGTUBUFCMPDLJOHMFBLBHF DVSSFOU for the Triac is the same as for the SCR except that it applies with either positive or negative bias on main terminal 2.(Figure AN1008.2) IRRM: Peak Repetitive Reverse Current – SCR This characteristic is essentially the same as the peak GPSXBSEPGGTUBUFCMPDLJOHMFBLBHF DVSSFOUFYDFQUOFHBUJWF voltage is applied to the anode (reverse biased). VTM: Peak On-State Voltage -- SCR and Triac The instantaneous on-state voltage (forward drop) is the principal voltage at a specified instantaneous current and case temperature when the Thyristor is in the conducting state. To prevent heating of the junction, this characteristic is measured with a short current pulse. The current pulse should be at least 100 μs duration to ensure the device is in full conduction. The forward-drop characteristic determines the on-state dissipation. See Figure AN1008.5, and refer to “IT: Current Rating” on page AN1008-2. Positive or Negative Instantaneous On-state Current (iT) – Amps Current ITM resistance termination. Positive gate bias lowers the breakover voltage. Breakover is temperature sensitive and will occur at a higher voltage if the junction temperature is kept below maximum TJ value. If SCRs and Triacs are turned on as a result of an excess of breakover voltage, instantaneous power dissipations may be produced that can damage the chip or die. 90 80 TC = 25 °C 70 40 A TO-218 60 50 40 30 20 10 Figure AN1008.5 0 15 and 25 A TO-220 0 0.6 0.8 1.0 1.2 1.4 1.6 1.8 Positive or Negative Instantaneous On-state Voltage (vT) – Volts On-state Current versus On-state Voltage (Typical) Explanation of Maximum Ratings and Characteristics for Thyristors AN1008 AN1008 Teccor® brand Thyristors AN1008 IGT: DC Gate Trigger Current VGT: DC Gate Trigger Voltage SCR SCR IGT is the minimum DC gate current required to cause the Thyristor to switch from the non-conducting to the conducting state for a specified load voltage and current as well as case temperature. The characteristic curve illustrated in Figure AN1008.6 shows that trigger current is temperature dependent. The Thyristor becomes less sensitive (requires more gate current) with decreasing junction temperatures. The gate current should be increased by a factor of two to five times the minimum threshold DC trigger current for best operation. Where GBTUUVSOPOJTEFNBOEFEBOEIJHIEJEUJTQSFTFOUPSMPX temperatures are expected, the gate pulse may be 10 times the minimum IGT, plus it must be fast-rising and of sufficient duration in order to properly turn on the Thyristor. VGT is the DC gate-cathode voltage that is present just prior to triggering when the gate current equals the DC trigger current. As shown in the characteristic curve in Figure AN1008.8, the gate trigger voltage is higher at lower temperatures. The gate-cathode voltage drop can be higher than the DC trigger level if the gate is driven by a current higher than the trigger current. Triac The difference in VGT for the SCR and the Triac is that the Triac can be fired in four possible modes. The threshold trigger voltage can be slightly different, depending on which of the four operating modes is actually used. 2.0 V GT V GT (T J = 25 °C) 3.0 1.5 1.0 Ratio of I GT Ratio of I GT (T J = 25 °C) 4.0 2.0 .5 0 1.0 -65 -40 -15 +25 +65 +125 Junction Temperature (T J) – °C Figure AN1008.8 0 -65 -15 +25 +65 Junction Temperature (T J) – °C -40 Figure AN1008.6 +125 IL: Latching Current Normalized DC Gate Trigger Current for All Quadrants versus Case Temperature Triac The description for the SCR applies as well to the Triac with the addition that the Triac can be fired in four possible modes (Figure AN1008.7): Quadrant I (main terminal 2 positive, gate positive) Quadrant II (main terminal 2 positive, gate negative) Quadrant III (main terminal 2 negative, gate negative) Quadrant IV (main terminal 2 negative, gate positive) ALL POLARITIES ARE REFERENCED TO MT1 MT2 (-) MT2 POSITIVE (Positive Half Cycle) + IGT GATE (+) IGT (-) MT1 IGT GATE (+) MT1 REF - + IGT MT2 IGT GATE MT2 NEGATIVE (Negative Half Cycle) MT1 REF NOTE: Alternistors will not operate in Q IV Figure AN1008.7 SCR Latching current is the DC anode current above which the gate signal can be withdrawn and the device stays on. It is related to, has the same temperature dependence as, and is somewhat greater than the DC gate trigger current. (Figure AN1008.1 and Figure AN1008.2) Latching current is at least equal to or much greater than the holding current, depending on the Thyristor type. Latching current is greater for fast-rise-time anode currents TJODFOPUBMMPGUIFDIJQEJFJTJODPOEVDUJPO*UJTUIJT dynamic latching current that determines whether a device will stay on when the gate signal is replaced with very short gate pulses. The dynamic latching current varies with the magnitude of the gate drive current and pulse duration. In some circuits, the anode current may oscillate and drop back below the holding level or may even go negative; hence, the unit may turn off and not latch if the gate signal is removed too quickly. REF QII QI QIII QIV MT2 MT2 IGT GATE MT1 REF Normalized DC Gate Trigger Voltage for All Quadrants versus Case Temperature Definition of Operating Quadrants Explanation of Maximum Ratings and Characteristics for Thyristors Triac The description of this characteristic for the Triac is the same as for the SCR, with the addition that the Triac can be latched on in four possible modes (quadrants). Also, the required latching is significantly different depending on which gating quadrants are used. Figure AN1008.9 illustrates typical latching current requirements for the four possible quadrants of operation. ©2008 Littelfuse, Inc. Specifications are subject to change without notice. Please refer to http://www.littelfuse.com for current information. Teccor® brand Thyristors This value will be reduced by a positive gate signal. This characteristic is temperature-dependent and is lowest at the maximum-rated junction temperature. Therefore, the characteristic is determined at rated junction temperature and at rated forward off-state voltage which is also a worstcase situation. Line or other transients which might be applied to the Thyristor in the off state must be reduced, so that neither the rate-of-rise nor the peak voltage are above specifications if false firing is to be prevented. Turn-on BTSFTVMUPGEWEUJTOPOEFTUSVDUJWFBTMPOHBTUIFGPMMPX current remains within current ratings of the device being used. 14 12 I L — mA 10 II 8 6 IV 4 I III 2 0 1.0 2.0 3.0 4.0 5.0 6.0 I GT — mA Figure AN1008.9 Critical dv/dt Typical Triac Latching (IL) Requirements for Four Quadrants versus Gate Current (IGT) IH: Holding Current -- SCR and Triac The holding current is the DC principal on-state current CFMPXXIJDIUIFEFWJDFXJMMOPUTUBZJOSFHFOFSBUJPOPO state after latching and gate signal is removed. This current is equal to or lower in value than the latching current (Figure AN1008.1 and Figure AN1008.2) and is related to and has the same temperature dependence as the DC gate trigger current shown in Figure AN1008.10. Both minimum and maximum holding current may be important. If the device is to stay in conduction at low-anode currents, the maximum holding current of a device for a given circuit must be considered. The minimum holding current of a device must be considered if the device is expected to turn off at a low DC anode current. Note that the low DC principal current condition is a DC turn-off mode, and that an initial on-state current (latching current) is required to ensure that the Thyristor has been fully turned on prior to a holding current measurement. Ratio of IH I H (T J = 25 °C) 4.0 INITIAL ON-STATE CURRENT = 400 mA dc 3.0 2.0 1.0 0 -65 -40 -15 +25 +65 +125 Junction Temperature (TJ) – °C Figure AN1008.10 Normalized DC Holding Current versus Case Temperature dv/dt, Static: Critical Rate-of-rise of Off-state Voltage — SCR and Triac 4UBUJDEWEUJTUIFNJOJNVNSBUFPGSJTFPGPGGTUBUFWPMUBHF that a device will hold off, with gate open, without turning on. Figure AN1008.11 illustrates the exponential definition. ©2008 Littelfuse, Inc. Specifications are subject to change without notice. Please refer to http://www.littelfuse.com for current information. VD 63% of V D 0 t VD dv = 0.63 dt t t = RC Figure AN1008.11 Exponential Rate-of-rise of Off-state Voltage %FmOJOHEWEU dv/dt, Commutating: Critical Rate-of-rise of Commutation Voltage -- Triac $PNNVUBUJOHEWEUJTUIFSBUFPGSJTFPGWPMUBHFBDSPTT the main terminals that a Triac can support (block without switching back on) when commutating from the on state in one half cycle to the off state in the opposite half cycle. This parameter is specified at maximum rated case temperature (equal to TJ) since it is temperature-dependent. *UJTBMTPEFQFOEFOUPODVSSFOUDPNNVUBUJOHEJEU BOE peak reapplied voltage (line voltage) and is specified at rated current and voltage. All devices are guaranteed to commutate rated current with a resistive load at 50 Hz to 60 Hz. Commutation of rated current is not guaranteed at higher frequencies, and no direct relationship can be NBEFXJUISFHBSEUPDVSSFOUUFNQFSBUVSFEFSBUJOHGPS higher-frequency operation. With inductive loading, when the voltage is out of phase with the load current, a voltage TUSFTTEWEU PDDVSTBDSPTTUIFNBJOUFSNJOBMTPGUIF Triac during the zero-current crossing. (Figure AN1008.12) A snubber (series RC across the Triac) should be used XJUIJOEVDUJWFMPBETUPEFDSFBTFUIFBQQMJFEEWEUUPBO amount below the minimum value which the Triac can be guaranteed to commutate off each half cycle. $PNNVUBUJOHEWEUJTTQFDJmFEGPSBIBMGTJOFXBWF DVSSFOUBU)[XIJDImYFTUIFEJEUPGUIFDPNNVUBUJOH DVSSFOU5IFDPNNVUBUJOHEJEUGPS)[JTBQQSPYJNBUFMZ 20% lower while IRMS rating remains the same. (Figure AN1008.4) Explanation of Maximum Ratings and Characteristics for Thyristors AN1008 AN1008 Teccor® brand Thyristors AN1008 EM ESOURCE TIME IG di/dt ITRM be reapplied. (Figure AN1008.14) Turn-off time is a function of many parameters and very dependent on temperature and gate bias during the turn-off interval. Turn-off time is lengthened for higher temperature so a high junction temperature is specified. The gate is open during the turnoff interval. Positive bias on the gate will lengthen the turnoff time; negative bias on the gate will shorten it. IT (di/dt)C ITM Voltage across Triac 10% 50% ITM 63% VDRM (dv/dt) C 'JHVSF"/ 50% IRM 8BWFTIBQFTPG$PNNVUBUJOHEWEUBOE Associated Conditions The tgt is the time interval between the application of a gate pulse and the on-state current reaching 90% of its steady-state value. (Figure AN1008.13) As would be expected, turn-on time is a function of gate drive. Shorter turn-on times occur for increased gate drives. This turn-on time is actually only valid for resistive loading. For example, inductive loading would restrict the rate-of-rise of anode current. For this reason, this parameter does not indicate the time that must be allowed for the device to stay on if the gate signal is removed. (Refer to the description of “IL: Latching Current” on page AN1008-4.) However, if the load was resistive and equal to the rated load current value, the device definitely would be operating at a current above the dynamic latching current in the turn-on time interval since current through the device is at 90% of its peak value during this interval. 90% Off-state Voltage 10% 90% 10% Delay Time Gate Trigger Pulse Turn-on Time Rise Time 50% 50% 10% ID Off-State Leakage iR Reverse Current trr VD tq Off-State Voltage dv/dt VT tgt: Gate-controlled Turn-on Time -- SCR and Triac On-state Current di/dt t1 Figure AN1008.14 Waveshapes of tq Rating Test and Associated Conditions RθJC, RθJA: Thermal Resistance (Junction-to-case, Junction-to-ambient) -- SCR and Triac The thermal-resistance characteristic defines the steadystate temperature difference between two points at a given rate of heat-energy transfer (dissipation) between the points. The thermal-resistance system is an analog to an electrical circuit where thermal resistance is equivalent to electrical resistance, temperature difference is equivalent to voltage difference, and rate of heatenergy transfer (dissipation) is equivalent to current. Dissipation is represented by a constant current generator since generated heat must flow (steady-state) no matter what the resistance in its path. Junction-to-case thermal resistance establishes the maximum case temperature at maximum rated steady-state current. The case temperature must be held to the maximum at maximum ambient temperature when the device is operating at rated current. Junction-to-ambient thermal resistance is established at a lower steady-state current, where the device is in free air with only the external heat sinking offered by the device package itself. For RRJA, power dissipation is limited by what the device package can dissipate in free air without any additional heat sink: Gate Pulse Width Figure AN1008.13 Waveshapes for Turn-on Time and Associated Conditions RRJC = tq: Circuit-commutated Turn-off Time -- SCR The circuit-commutated turn-off time of the device is the time during which the circuit provides reverse bias to the device (negative anode) to commutate it off. The turn-off time occurs between the time when the anode current goes negative and when the anode positive voltage may Explanation of Maximum Ratings and Characteristics for Thyristors RRJA = TJ–TC P(AV) TJ–TA P(AV) ©2008 Littelfuse, Inc. Specifications are subject to change without notice. Please refer to http://www.littelfuse.com for current information.