Order this document by MC3425/D The MC3425 is a power supply supervisory circuit containing all the necessary functions required to monitor over and undervoltage fault conditions. These integrated circuits contain dedicated over and undervoltage sensing channels with independently programmable time delays. The overvoltage channel has a high current Drive Output for use in conjunction with an external SCR Crowbar for shutdown. The undervoltage channel input comparator has hysteresis which is externally programmable, and an open–collector output for fault indication. • Dedicated Over and Undervoltage Sensing • • • • • • POWER SUPPLY SUPERVISORY/ OVER AND UNDERVOLTAGE PROTECTION CIRCUIT SEMICONDUCTOR TECHNICAL DATA Programmable Hysteresis of Undervoltage Comparator Internal 2.5 V Reference 300 mA Overvoltage Drive Output 8 30 mA Undervoltage Indicator Output 1 Programmable Time Delays P1 SUFFIX PLASTIC PACKAGE CASE 626 4.5 V to 40 V Operation MAXIMUM RATINGS Symbol Value Unit Power Supply Voltage Rating VCC 40 Vdc Comparator Input Voltage Range (Note 1) VIR –0.3 to +40 Vdc IOS(DRV) Internally Limited mA Indicator Output Voltage VIND 0 to 40 Vdc Indicator Output Sink Current IIND 30 mA Power Dissipation and Thermal Characteristics Maximum Power Dissipation @ TA = 70°C Thermal Resistance, Junction–to–Air PD RθJA 1000 80 mW °C/W Drive Output Short Circuit Current Operating Junction Temperature TJ +150 °C Operating Ambient Temperature Range TA 0 to +70 °C Tstg –55 to +150 °C Storage Temperature Range NOTE: 1. The input signal voltage should not be allowed to go negative by more than 300 mV NOTE: 1. or positive by more than 40 V, independent of VCC, without device destruction. PIN CONNECTIONS O.V. DRV Output 1 8 VCC O.V. DLY 2 7 Gnd O.V. Sense 3 6 U.V. IND Output U.V. Sense 4 5 U.V. DLY Simplified Application (Top View) Overvoltage Crowbar Protection, Undervoltage Indication Vin Vout DC Power Supply + Cout MC3425 Undervoltage Indication ORDERING INFORMATION Device Operating Temperature Range Package MC3425P1 TA = 0° to +70°C Plastic DIP Motorola, Inc. 1996 MOTOROLA ANALOG IC DEVICE DATA Rev 2 1 MC3425 ELECTRICAL CHARACTERISTICS (4.5 V ≤ VCC ≤ 40 V; TA = Tlow to Thigh [Note 2], unless otherwise noted.) Characteristics Symbol Min Typ Max Unit REFERENCE SECTION Sense Trip Voltage (Referenced Voltage) VCC = 15 V TA= 25°C Tlow to Thigh (Note 2) VSense Line Regulation of VSense 4.5 V ≤ VCC ≤ 40 V; TJ = 25°C Power Supply Voltage Operating Range Power Supply Current VCC = 40 V; TA = 25°C; No Output Loads O.V. Sense (Pin 3) = 0 V; U.V. Sense (Pin 4) = VCC O.V. Sense (Pin 3) = VCC; U.V. Sense (Pin 4) = 0 V Vdc 2.4 2.33 2.5 2.5 2.6 2.63 Regline – 7.0 15 mV VCC 4.5 – 40 Vdc ICC(off) – 8.5 10 mA ICC(on) – 16.5 19 mA IIB – 1.0 2.0 µA INPUT SECTION Input Bias Current, O.V. and U.V. Sense Hysteresis Activation Voltage, U.V. Sense VCC = 15 V; TA = 25°C; IH = 10% IH = 90% VH(act) V – – 0.6 0.8 – – IH 9.0 12.5 16 VOL(DLY) VOH(DLY) – VCC–0.5 0.2 VCC–0.15 0.5 – Delay Pin Source Current VCC = 15 V; VDLY = 0 V IDLY(source) 140 200 260 µA Delay Pin Sink Current VCC = 15 V; VDLY = 2.5V IDLY(sink) 1.8 3.0 – mA Drive Output Peak Current (TA = 25°C) IDRV(peak) 200 300 – mA Drive Output Voltage IDRV = 100 mA; TA = 25° C VOH(DRV) VCC–2.5 VCC–2.0 – V Drive Output Leakage Current VDRV = 0 V IDRV(leak) – 15 200 nA Hysteresis Current, U.V. Sense VCC = 15 V; TA = 25°C; U.V. Sense (Pin 4) = 2.5 V Delay Pin Voltage (IDLY = 0 mA) Low State High State µA V OUTPUT SECTION Drive Output Current Slew Rate (TA = 25°C) di/dt – 2.0 – A/µs IDRV(trans) – 1.0 – mA (Peak) Indicator Output Saturation Voltage IIND = 30 mA; TA = 25°C VIND(sat) – 560 800 mV Indicator Output Leakage Current VOH(IND) = 40 V IIND(leak) – 25 200 nA Vth(OC) 2.33 2.5 2.63 V tPLH(IN/OUT) – 1.7 – µs tPLH(IN//DLY) – 700 – ns Drive Output VCC Transient Rejection VCC = 0 V to 15 V at dV/dt = 200 V µs; O.V. Sense (Pin 3) = 0 V; TA = 25°C Output Comparator Threshold Voltage (Note 3) Propagation Delay Time (VCC = 15 V; TA = 25°C) Input to Drive Output or Indicator Output 100 mV Overdrive, CDLY = 0 µF Input to Delay 2.5 V Overdrive (0 V to 5.0 V Step) NOTES: 2. Tlow to Thigh = 0° to +70°C 3. The Vth(OC) limits are approximately the VSense limits over the applicable temperature range. 2 MOTOROLA ANALOG IC DEVICE DATA 12 TA = 25°C 10 8.0 VCC = 40 V 6.0 VCC = 15 V 4.0 VCC = 5.0 V 2.0 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 VH(act), HYSTERESIS ACTIVATION VOLTAGE (V) 1.6 Figure 3. Hysteresis Current versus Temperature IH, HYSTERESIS CURRENT (µA) 15.0 U.V. Sense = 2.5 V 14.0 13.0 12.0 11.0 10.0 –55 –25 0 25 50 75 TA, AMBIENT TEMPERATURE (°C) 100 125 Figure 5. Output Delay Time versus Delay Capacitance t DLY , OUTPUT DELAY TIME (mS) 100 10 VCC = 15 V TA = 25°C 1.0 0.1 2.5 CDLY 200 µA tDLY = 0.01 0.001 0.0001 0.001 0.01 0.1 1.0 CDLY, DELAY PIN CAPACITANCE (µF) MOTOROLA ANALOG IC DEVICE DATA Figure 2. Hysteresis Activation Voltage versus Temperature 1.2 VH(act) = Voltage Level at which Hysteresis Current (IH) is 90% of full value. VCC = 5.0 V 1.0 0.8 VCC = 15 V VCC = 40 V 0.6 0.4 0.2 0 –55 –25 0 25 50 75 TA, AMBIENT TEMPERATURE (°C) 100 125 Figure 4. Sense Trip Voltage Change versus Temperature 0 VSense* = 2.400 V * = 2.500 V * = 2.600 V –10 –20 VCC = 15 V *VSense at TA = 25°C –30 –40 –50 –55 –25 0 25 50 75 100 125 TA, AMBIENT TEMPERATURE (°C) 10 IDLY(source), DELAY PIN SOURCE CURRENT ( µ A) IH, HYSTERESIS CURRENT (µA) 14 ∆ V Sense , SENSE TRIP VOLTAGE CHANGE (mW) Figure 1. Hysteresis Current versus Hysteresis Activation Voltage V H(act) , HYSTERESIS ACTIVATION VOLTAGE (V) MC3425 Figure 6. Delay Pin Source Current versus Temperature 260 240 VCC = 40 V 220 VCC = 15 V 200 VCC = 5.0 V 180 160 –55 –25 0 25 50 75 TA, AMBIENT TEMPERATURE (°C) 100 125 3 5.0 VCC = 15 V 1.0% Duty Cycle @ 300 Hz TA = 25°C 4.0 3.0 2.0 1.0 0 0 100 200 300 400 IDRV(peak), DRIVE OUTPUT PEAK CURRENT (mA) Figure 8. Indicator Output Saturation Voltage versus Output Sink Current 0.4 0.3 0.2 VCC = 15 V TA = 25°C 0.1 0 0 10 28 VCC = 15 V IDRV(peak) = 200 mA 1.0% Duty Cycle @ 300 Hz 2.420 2.380 2.340 2.300 –55 4 30 40 Figure 10. Power Supply Current versus Voltage 2.500 2.460 20 IIND, INDICATOR OUTPUT SINK CURRENT (mA) Figure 9. Drive Output Saturation Voltage versus Temperature I CC, POWER SUPPLY CURRENT (mA) V OH(DRV), DRIVE OUTPUT SATURATION VOTLAGE (V) V OH(DRV), DRIVE OUTPUT SATURATION VOLTAGE (V) Figure 7. Drive Output Saturation Voltage versus Output Peak Current V IND(sat) , INDICATOR OUTPUT SATURATION VOLTAGE (V) MC3425 Curve O.V. Sense U.V. Sense A VCC Gnd B Gnd VCC 24 20 A 16 12 B 8.0 4.0 TA = 25°C 0 –25 0 25 50 75 TA, AMBIENT TEMPERATURE (°C) 100 125 0 5.0 10 15 20 25 30 35 40 VCC, POWER SUPPLY VOLTAGE (V) MOTOROLA ANALOG IC DEVICE DATA MC3425 APPLICATIONS INFORMATION Figure 11. Overvoltage Protection and Undervoltage Fault Indication with Programmable Delay Figure 12. Overvoltage Protection of 5.0 V Supply with Line Loss Detector +VO R1A Vin VO = 5.0 V VO(trip) = 6.25 V +5.0V Power Supply 8 VCC 15k R1B 4 8 VCC + Power Supply 4.5V to 40V – 4 IH R2B CDLY CDLY U.V. Sense Pin 4 Gnd 1+ Figure 13. Overvoltage Audio Alarm Circuit +VO 2.5V OFF ON Figure 14. Programmable Frequency Switch Input Signal 12V 8 VCC 5.0µF 8 VCC 3 + 12V Power Supply Alarm On when: VO = 13.6 V O.V. Sense O.V. DRV I.V. p–p Output Pulse when: 1 f(input) < 25000 CDLY 10k 3 1 O.V. 1 DRV O.V. Sense 10k 2.7k 2.5V U.V. DLY Pin 5 U.V. IND Pin 6 R1A R2A tDLY = 12500 CDLY 12k 0.33µF 0.01µF R1B R2B , VO(trip) – 2.5 V R1B + R2B U.V. Hysteresis = IH U.V. O.V. DLY Gnd DLY 2 7 5 100 U.V. O.V. DLY Gnd DLY 2 7 5 O.V. 1 DRV O.V. Sense 10k O.V. 1 DRV O.V. Sense Line Loss Output MC3425 3 MC3425 3 R2A U.V. 6 IND U.V. Sense U.V. 6 IND U.V. Sense AC Line U.V. Fault Indicator 1.0k 1.0k MC3425 MC3425 4 82k 6.8k U.V. Sense 4 100Ω U.V. O.V. DLY DLY Gnd 5 2 7 U.V. Sense O.V. U.V. DLY Gnd DLY 5 7 2 0.1µF CDLY 0.1µF Gnd O.V. Sense Pin 3 2.5V O.V. DLY Pin 2 2.5V ON O.V. DRV Pin 1 MOTOROLA ANALOG IC DEVICE DATA OFF 5 MC3425 CIRCUIT DESCRIPTION source, IDLY(source), charging the external delay capacitor (CDLY) to 2.5 V. The MC3425 is a power supply supervisory circuit containing all the necessary functions required to monitor over and undervoltage fault conditions. The block diagram is shown below in Figure 15. The Overvoltage (O.V.) and Undervoltage (U.V.) Input Comparators are both referenced to an internal 2.5 V regulator. The U.V. Input Comparator has a feedback activated 12.5 µA current sink (IH) which is used for programming the input hysteresis voltage (VH). The source resistance feeding this input (RH) determines the amount of hysteresis voltage by VH = IHRH = 12.5 × 10–6 RH. Separate Delay pins (O.V. DLY, U.V. DLY.) are provided for each channel to independently delay the Drive and Indicator outputs, thus providing greater input noise immunity. The two Delay pins are essentially the outputs of the respective input comparators, and provide a constant current source, IDLY(source), of typically 200 µA when the noninverting input voltage is greater than the inverting input level. A capacitor connected from these Delay pins to ground, will establish a predictable delay time (tDLY) for the Drive and Indicator outputs. The Delay pins are internally connected to the noninverting inputs of the O.V. and U.V. Output Comparators, which are referenced to the internal 2.5 V regulator. Therefore, delay time (tDLY) is based on the constant current Vref CDLY 2.5 CDLY = 12500 CDLY tDLY = = IDLY(source) 200 µA Figure 5 provides CDLY values for a wide range of time delays. The Delay pins are pulled low when the respective input comparator’s noninverting input is less than the inverting input. The sink current, IDLY(sink), capability of the Delay pins is ≥ 1.8 mA and is much greater than the typical 200 µA source current, thus enabling a relatively fast delay capacitor discharge time. The Overvoltage Drive Output is a current–limited emitter–follower capable of sourcing 300 mA at a turn–on slew rate at 2.0 A/µs, ideal for driving “Crowbar” SCR’s. The Undervoltage Indicator Output is an open–collector, NPN transistor, capable of sinking 30 mA to provide sufficient drive for LED’s, small relays or shut–down circuitry. These current capabilities apply to both channels operating simultaneously, providing device power dissipation limits are not exceeded. The MC3425 has an internal 2.5 V bandgap reference regulator with an accuracy of ± 4.0% for the basic device. Figure 15. Representative Block Diagram VCC 8 + + O.V. Sense 200µA + Input Comparator – O.V. 3 + 200µA + Input Comparator – U.V. U.V. Sense + +Output Comparator – O.V. 4 – Output Comparator + U.V. + 1 O.V. DRV 6 U.V. IND 2.5V Reference Regulator IH 12.5µA Input Section 5 2 U.V. O.V. DLY DLY 7 Gnd Output Section Note: All voltages and currents are nominal. 6 MOTOROLA ANALOG IC DEVICE DATA MC3425 CROWBAR SCR CONSIDERATIONS Referring to Figure 16, it can be seen that the crowbar SCR, when activated, is subject to a large current surge from the output capacitance, Cout. This capacitance consists of the power supply output capacitors, the load’s decoupling capacitors, and in the case of Figure 16A, the supply’s input filter capacitors. This surge current is illustrated in Figure 17, and can cause SCR failure or degradation by any one of three mechanisms: di/dt, absolute peak surge, or I2t. The interrelationship of these failure methods and the breadth of the applications make specification of the SCR by the semiconductor manufacturer difficult and expensive. Therefore, the designer must empirically determine the SCR and circuit elements which result in reliable and effective OVP operation. However, an understanding of the factors which influence the SCR’s di/dt and surge capabilities simplifies this task. 1. di/dt As the gate region of the SCR is driven on, its area of conduction takes a finite amount of time to grow, starting as a very small region and gradually spreading. Since the anode current flows through this turned–on gate region, very high current densities can occur in the gate region if high anode currents appear quickly (di/dt). This can result in immediate destruction of the SCR or gradual degradation of its forward blocking voltage capabilities – depending on the severity of the occasion. The value of di/dt that an SCR can safely handle is influenced by its construction and the characteristics of the gate drive signal. A center–gate–fire SCR has more di/dt capability than a corner–gate–fire type, and heavily overdriving ( 3 to 5 times IGT) the SCR gate with a fast < 1.0 µs rise time signal will maximize its di/dt capability. A typical maximum number in phase control SCRs of less than 50 A(RMS) rating might be 200 A/µs, assuming a gate current of five times IGT and < 1.0 µs rise time. If having done this, a di/dt problem is seen to still exist, the designer can also decrease the di/dt of the current waveform by adding inductance in series with the SCR, as shown in Figure 18. Of course, this reduces the circuit’s ability to rapidly reduce the dc bus voltage and a tradeoff must be made between speedy voltage reduction and di/dt. Figure 16. Typical Crowbar Circuit Configurations (A) SCR Across Input of Regulator Series Regulator Vin Vout MC3425 + + Cin Cout (B) SCR Across Output of Regulator * Series Regulator Vin + Cin Vout Cout + MC3425 *Needed if supply is not current limited. MOTOROLA ANALOG IC DEVICE DATA 7 MC3425 Figure 17. Crowbar SCR Surge Current Waveform l lpk di dt Surge Due to Output Capacitor Current Limited Supply Output t 2. Surge Current If the peak current and/or the duration of the surge is excessive, immediate destruction due to device overheating will result. The surge capability of the SCR is directly proportional to its die area. If the surge current cannot be reduced (by adding series resistance – see Figure 18) to a safe level which is consistent with the system’s requirements for speedy bus voltage reduction, the designer must use a higher current SCR. This may result in the average current capability of the SCR exceeding the steady state current requirements imposed by the DC power supply. Figure 18. Circuit Elements Affecting SCR Surge & di/dt RLead LLead ESR ESL Output Cap R L A WORD ABOUT FUSING Before leaving the subject of the crowbar SCR, a few words about fuse protection are in order. Referring back to Figure 16A, it will be seen that a fuse is necessary if the power supply to be protected is not output current limited. This fuse is not meant to prevent SCR failure but rather to prevent a fire! In order to protect the SCR, the fuse would have to possess an I2t rating less than that of the SCR and yet have a high enough continuous current rating to survive normal supply output currents. In addition, it must be capable of successfully clearing the high short circuit currents from the supply. Such a fuse as this is quite expensive, and may not even be available. The usual design compromise then is to use a garden variety fuse (3AG or 3AB style) which cannot be relied on to blow before the thyristor does, and trust that if the SCR does fail, it will fail short circuit. In the majority of the designs, this will be the case, though this is difficult to guarantee. Of course, a sufficiently high surge will cause an open. These comments also apply to the fuse in Figure 16B. CROWBAR SCR SELECTION GUIDE As an aid in selecting an SCR for crowbar use, the following selection guide is presented. Device IRMS ITSM MCR310 Series MCR16 Series MCR25 Series 2N6501 Series MCR69 Series MCR264 Series MCR265 Series 10 A 16 A 25 A 25 A 25 A 40 A 55 A 100 A 150 A 300 A 300 A 750 A 400 A 550 A To MC3423 R & L EMPIRICALLY DETERMINED! UNDERVOLTAGE SENSING An undervoltage sense circuit designed, as shown in Figure equations: V CCU R1 12.5 with hysteresis may be 11, using the following * VCC1 + mA 2.5 R1 R2 + V CC1 * 2.5 where: VCCU is the designed upper trip point (output indicator goes off) VCC1 is the lower trip point (output indicator goes on) 8 MOTOROLA ANALOG IC DEVICE DATA MC3425 OUTLINE DIMENSIONS P1 SUFFIX PLASTIC PACKAGE CASE 626–05 ISSUE K 8 5 NOTES: 1. DIMENSION L TO CENTER OF LEAD WHEN FORMED PARALLEL. 2. PACKAGE CONTOUR OPTIONAL (ROUND OR SQUARE CORNERS). 3. DIMENSIONING AND TOLERANCING PER ANSI Y14.5M, 1982. –B– 1 4 F –A– NOTE 2 L C J –T– N SEATING PLANE D H M K DIM A B C D F G H J K L M N MILLIMETERS MIN MAX 9.40 10.16 6.10 6.60 3.94 4.45 0.38 0.51 1.02 1.78 2.54 BSC 0.76 1.27 0.20 0.30 2.92 3.43 7.62 BSC ––– 10_ 0.76 1.01 INCHES MIN MAX 0.370 0.400 0.240 0.260 0.155 0.175 0.015 0.020 0.040 0.070 0.100 BSC 0.030 0.050 0.008 0.012 0.115 0.135 0.300 BSC ––– 10_ 0.030 0.040 G 0.13 (0.005) M MOTOROLA ANALOG IC DEVICE DATA T A M B M 9 MC3425 NOTES 10 MOTOROLA ANALOG IC DEVICE DATA MC3425 NOTES MOTOROLA ANALOG IC DEVICE DATA 11 MC3425 Motorola reserves the right to make changes without further notice to any products herein. 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How to reach us: USA / EUROPE / Locations Not Listed: Motorola Literature Distribution; P.O. Box 20912; Phoenix, Arizona 85036. 1–800–441–2447 or 602–303–5454 JAPAN: Nippon Motorola Ltd.; Tatsumi–SPD–JLDC, 6F Seibu–Butsuryu–Center, 3–14–2 Tatsumi Koto–Ku, Tokyo 135, Japan. 03–81–3521–8315 MFAX: [email protected] – TOUCHTONE 602–244–6609 INTERNET: http://Design–NET.com ASIA/PACIFIC: Motorola Semiconductors H.K. Ltd.; 8B Tai Ping Industrial Park, 51 Ting Kok Road, Tai Po, N.T., Hong Kong. 852–26629298 12 ◊ *MC3425/D* MOTOROLA ANALOG IC DEVICE DATA M3425/D