This overvoltage protection circuit (OVP) protects sensitive electroni

The Datasheet Archive - 100 Million Datasheets from 7500 Manufacturers.

This overvoltage protection circuit (OVP) protects sensitive electroni

Datasheet Thumbnail

Top Searches for this datasheet

Overvoltage Crowbar Sensing Circuit
This overvoltage protection circuit (OVP) protects sensitive electronic circuitry from overvoltage transients regulator failures when used conjunction with external "crowbar" SCR. device senses overvoltage condition quickly "crowbars" short circuits supply, forcing supply into current limiting opening fuse circuit breaker. protection voltage threshold adjustable MC3423 programmed minimum duration overvoltage condition before tripping, thus supplying noise immunity. MC3423 essentially "two terminal" system, therefore used with either positive negative supplies.
MC3423
OVERVOLTAGE SENSING CIRCUIT
SEMICONDUCTOR TECHNICAL DATA
SUFFIX PLASTIC PACKAGE CASE
SUFFIX PLASTIC PACKAGE CASE (SOP-8)
MAXIMUM RATINGS
Rating Differential Power Supply Voltage Sense Voltage Sense Voltage Remote Activation Input Voltage Output Current Operating Ambient Temperature Range Operating Junction Temperature Storage Temperature Range Symbol VCC-VEE VSense1 VSense2 Vact Tstg Value +150 Unit Sense Current Source (Top View) Sense Drive Output Indicator Output Remote Activation
CONNECTIONS
ORDERING INFORMATION
Device Operating Temperature Range +70°C Package SO-8 Plastic
Simplified Application
Current Limited Power Supply Vout
MC3423D MC3423P1
Cout
MC3423
Semiconductor Components Industries, LLC, 2001
April, 2001 Rev.
Publication Order Number: MC3423/D
MC3423
ELECTRICAL CHARACTERISTICS (5.0 Tlow Thigh, unless otherwise noted.)
Characteristics Supply Voltage Range Output Voltage Indicator Output Voltage (IO(Ind) Sense Trip Voltage 25°C) Temperature Coefficient VSense1 (Figure Remote Activation Input Current (VIH (VIL Source Current Output Current Risetime 25°C) Propagation Delay Time 25°C) Supply Current
NOTES: Tlow Thigh +70°C
Symbol VCC-VEE VOL(Ind) VSense1, VSense2 TCVS1
VCC-2.2 2.45
VCC-1.8 0.06
2.75
Unit %/°C
ISource
-120
-180 mA/µs
ISource Vref 2.6V
Current Source
Sense
Output
Sense
Remote Activation
Indicator Output
Figure Representative Block Diagram
Switch Switch
MC3423
Switch VSense VSense Position Position
Switch Closed Open
Ramp until output goes high; this VSense threshold.
Figure Sense Voltage Test Circuit
http://onsemi.com
MC3423
Power Supply Sense Lead) MC3423 Sense Lead) *See text explanation. Load Vtrip Vref 2.6V minimum drift minimum value Figure
Figure Basic Circuit Configuration
Sense Lead)
10µF R1R2
Load
Vtrip Vref 2.6V 2N6504 equivalent 2N6505 equivalent 2N6506 equivalent 2N6507 equivalent 2N6508 equivalent 2N6509 equivalent
Power Supply
1N4740
MC3423 10µF
Sense Lead)
Figure Circuit Configuration Supply Voltage Above
Vtrip +VCC Power Supply Indication
Vref
MC3423
Vtrip
Vref 103] Isource
(See Figure
Figure Basic Configuration Programmable Duration Overvoltage Condition Before Trip
http://onsemi.com
MC3423
APPLICATION INFORMATION
Basic Circuit Configuration
basic circuit configuration MC3423 shown Figure supply voltages from Figure trip voltages above threshold trip voltage which MC3423 will trigger supply gate drive crowbar SCR, determined selection Their values determined equation given Figures graph shown Figure minimum value gate current limiting resistor, given Figure Using this value SCR, will receive greatest gate current possible without damaging MC3423. lower output currents required, increased value. switch, shown Figure used reset crowbar. Otherwise, power supply, across which connected, must shut down reset crowbar. current-limited supply used, fuse circuit breaker, should used protect and/or load. circuit configurations shown Figures will have typical propogation delay faster operation desired, connected with left floating. This will result decreasing propogation delay approximately expense slightly increased trip voltage value.
Configuration Programmable Minimum Duration Overvoltage Condition Before Tripping
Sense Lead) Power Supply Sense Lead) MC3423
Figure Configuration Programmable Duration Overvoltage Condition Before Trip/With Immediate Trip High Overvoltages
Additional Features
many instances, MC3423 will used noise environment. prevent false tripping circuit noise which would normally harm load, MC3423 programmable delay feature. implement this feature, circuit configuration Figure used. this configuration, capacitor connected from VEE. value this capacitor determines minimum duration overvoltage condition which necessary trip OVP. value found from Figure circuit operates following manner: When rises above trip point internal current source (Pin begins charging capacitor, connected overvoltage condition disappears before this occurs, capacitor discharged rate times faster than charging rate, resetting timing feature until next overvoltage condition occurs. Occasionally, desired that immediate crowbarring supply occur when high overvoltage condition occurs, while retaining false tripping immunity Figure this case, circuit Figure used. circuit will operate previously described small overvoltages, will immediately trip power supply voltage exceeds
Activation Indication Output additional output indicator activation provided MC3423. This output open collector transistor which saturates when activated. addition, used clock edge triggered flip-flop whose output inhibits shuts down power supply when trips. This reduces eliminates heatsinking requirements crowbar SCR. Remote Activation Input Another feature MC3423 remote activation input, voltage this CMOS/TTL compatible input held below MC3423 operates normally. However, raised voltage above output activated independent whether overvoltage condition present. should noted that internal pull-up current source. This feature used accomplish orderly sequenced shutdown system power supplies during system fault condition. addition, activation indication output MC3423 used activate another MC3423 single transistor inverter used interface former's indication output latter remote activation input, shown Figure this circuit, indication output (Pin MC3423 power supply used activate MC3423 associated with power supply small with adequate voltage rating.
http://onsemi.com
MC3423
Power Supply
RESISTANCE
Power Supply
1.0k
TRIP VOLTAGE
Figure versus Trip Voltage
Figure Circuit Configuration Activating MC3423 from Another
SUPPLY VOLTAGE
Note that both supplies have their negative output leads tied together (i.e., both positive supplies). their positive leads common (two negative supplies) emitter would moved positive lead supply would therefore have resized deliver appropriate drive
Crowbar Considerations
RG(min)
CAPACITANCE
Referring Figure seen that crowbar SCR, when activated, subject large current surge from output capacitance, Cout. This capacitance consists power supply output caps, load's decoupling caps, case Figure 11A, supply's input filter caps. This surge current illustrated Figure cause failure degradation three mechanisms: di/dt, absolute peak surge, I2t. interrelationship these failure methods breadth applications make specification semiconductor manufacturer difficult expensive. Therefore, designer must empirically determine circuit elements which result reliable effective operation. However, understanding factors which influence SCR's di/dt surge capabilities simplifies this task.
di/dt
GATE CURRENT LIMITING RESISTOR
Figure Minimum versus Supply Voltage
0.01
0.001
gate region driven area conduction takes finite amount time grow, starting very small region gradually spreading. Since anode current flows through this turned-on gate region, very high current densities occur gate region high anode currents appear quickly (di/dt). This result immediate destruction gradual degradation forward blocking voltage capabilities depending severity occasion.
0.0001 0.001
0.01
DELAY TIME (ms)
Figure Capacitance versus Minimum Overvoltage Duration
http://onsemi.com
MC3423
Power Supply Cout (11A) Sense Vout
Power Supply
(11B) Cout Sense
Vout
capability than corner-gate-fire type, heavily overdriving times IGT) gate with fast <1.0 rise time signal will maximize di/dt capability. typical maximum number phase control SCRs less than A(RMS) rating might A/µs, assuming gate current five times rise time. having done this, di/dt problem seen still exist, designer also decrease di/dt current waveform adding inductance series with SCR, shown Figure course, this reduces circuit's ability rapidly reduce voltage tradeoff must made between speedy voltage reduction di/dt.
Surge Current
*Needed supply current limited
Figure Typical Crowbar Circuit Configurations
Surge Output Capacitor Current Limited Supply Output
peak current and/or duration surge excessive, immediate destruction device overheating will result. surge capability directly proportional area. surge current cannot reduced adding series resistance Figure safe level which consistent with systems requirements speedy voltage reduction, designer must higher current SCR. This result average current capability exceeding steady state current requirements imposed power supply.
WORD ABOUT FUSING
Figure Crowbar Surge Current Waveform
RLead Output
LLead
MC3423 EMPIRICALLY DETERMINED!
Before leaving subject crowbar SCR, words about fuse protection order. Referring back Figure 11A, will seen that fuse necessary power supply protected output current limited. This fuse meant prevent failure rather prevent fire! order protect SCR, fuse would have possess rating less than that have high enough continuous current rating survive normal supply output currents. addition, must capable successfully clearing high short circuit currents from supply. Such fuse this quite expensive, even available.
CROWBAR SELECTION GUIDE
Figure Circuit Elements Affecting Surge di/dt
usual design compromise then garden variety fuse (3AG style) which cannot relied blow before thyristor does, trust that does fail, will fail short circuit. majority designs, this will case, though this difficult guarantee. course, sufficiently high surge will cause open. These comments also apply fuse Figure 11B. value di/dt that safely handle influenced construction characteristics gate drive signal. center-gate-fire more di/dt
selecting crowbar use, following selection guide presented.
Device 2N6400 Series 2N6504 Series 2N1842 Series 2N2573 Series 2N681 Series MCR3935-1 Series MCR81-5 Series IRMS IFSM 1000 Package TO-220 Plastic TO-220 Plastic Metal Stud Metal TO-3 Type Metal Stud Metal Stud Metal Stud
http://onsemi.com
MC3423
PACKAGE DIMENSIONS
SUFFIX PLASTIC PACKAGE CASE 626-05 ISSUE
NOTES: DIMENSION CENTER LEAD WHEN FORMED PARALLEL. PACKAGE CONTOUR OPTIONAL (ROUND SQUARE CORNERS). DIMENSIONING TOLERANCING ANSI Y14.5M, 1982. MILLIMETERS 9.40 10.16 6.10 6.60 3.94 4.45 0.38 0.51 1.02 1.78 2.54 0.76 1.27 0.20 0.30 2.92 3.43 7.62 -10_ 0.76 1.01 INCHES 0.370 0.400 0.240 0.260 0.155 0.175 0.015 0.020 0.040 0.070 0.100 0.030 0.050 0.008 0.012 0.115 0.135 0.300 -10_ 0.030 0.040
NOTE
SEATING PLANE
0.13 (0.005)
SUFFIX PLASTIC PACKAGE CASE 751-07 (SOP-8) ISSUE
NOTES: DIMENSIONING TOLERANCING ANSI Y14.5M, 1982. CONTROLLING DIMENSION: MILLIMETER. DIMENSION INCLUDE MOLD PROTRUSION. MAXIMUM MOLD PROTRUSION 0.15 (0.006) SIDE. DIMENSION DOES INCLUDE DAMBAR PROTRUSION. ALLOWABLE DAMBAR PROTRUSION SHALL 0.127 (0.005) TOTAL EXCESS DIMENSION MAXIMUM MATERIAL CONDITION. MILLIMETERS 4.80 5.00 3.80 4.00 1.35 1.75 0.33 0.51 1.27 0.10 0.25 0.19 0.25 0.40 1.27 0.25 0.50 5.80 6.20 INCHES 0.189 0.197 0.150 0.157 0.053 0.069 0.013 0.020 0.050 0.004 0.010 0.007 0.010 0.016 0.050 0.010 0.020 0.228 0.244
0.25 (0.010)
0.25 (0.010)
SEATING PLANE
0.10 (0.004)
http://onsemi.com
MC3423
Semiconductor trademarks Semiconductor Components Industries, (SCILLC). SCILLC reserves right make changes without further notice products herein. SCILLC makes warranty, representation guarantee regarding suitability products particular purpose, does SCILLC assume liability arising application product circuit, specifically disclaims liability, including without limitation special, consequential incidental damages. "Typical" parameters which provided SCILLC data sheets and/or specifications vary different applications actual performance vary over time. operating parameters, including "Typicals" must validated each customer application customer's technical experts. SCILLC does convey license under patent rights rights others. SCILLC products designed, intended, authorized components systems intended surgical implant into body, other applications intended support sustain life, other application which failure SCILLC product could create situation where personal injury death occur. Should Buyer purchase SCILLC products such unintended unauthorized application, Buyer shall indemnify hold SCILLC officers, employees, subsidiaries, affiliates, distributors harmless against claims, costs, damages, expenses, reasonable attorney fees arising directly indirectly, claim personal injury death associated with such unintended unauthorized use, even such claim alleges that SCILLC negligent regarding design manufacture part. SCILLC Equal Opportunity/Affirmative Action Employer.
PUBLICATION ORDERING INFORMATION
NORTH AMERICA Literature Fulfillment: Literature Distribution Center Semiconductor P.O. 5163, Denver, Colorado 80217 Phone: 303-675-2175 800-344-3860 Toll Free USA/Canada Fax: 303-675-2176 800-344-3867 Toll Free USA/Canada Email: ONlit@hibbertco.com Response Line: 303-675-2167 800-344-3810 Toll Free USA/Canada American Technical Support: 800-282-9855 Toll Free USA/Canada EUROPE: Semiconductor European Support German Phone: (+1) 303-308-7140 (Mon-Fri 2:30pm 7:00pm CET) Email: ONlit-german@hibbertco.com French Phone: (+1) 303-308-7141 (Mon-Fri 2:00pm 7:00pm CET) Email: ONlit-french@hibbertco.com English Phone: (+1) 303-308-7142 (Mon-Fri 12:00pm 5:00pm GMT) Email: ONlit@hibbertco.com EUROPEAN TOLL-FREE ACCESS*: 00-800-4422-3781 *Available from Germany, France, Italy, Ireland CENTRAL/SOUTH AMERICA: Spanish Phone: 303-308-7143 (Mon-Fri 8:00am 5:00pm MST) Email: ONlit-spanish@hibbertco.com Toll-Free from Mexico: Dial 01-800-288-2872 Access then Dial 866-297-9322 ASIA/PACIFIC: Semiconductor Asia Support Phone: 1-303-675-2121 (Tue-Fri 9:00am 1:00pm, Hong Kong Time) Toll Free from Hong Kong Singapore: 001-800-4422-3781 Email: ONlit-asia@hibbertco.com JAPAN: Semiconductor, Japan Customer Focus Center 4-32-1 Nishi-Gotanda, Shinagawa-ku, Tokyo, Japan 141-0031 Phone: 81-3-5740-2700 Email: r14525@onsemi.com Semiconductor Website: http://onsemi.com additional information, please contact your local Sales Representative.
http://onsemi.com
MC3423/D

This overvoltage protection circuit (OVP) protects sensitive electroni

Top Searches for this datasheet

Other recent searches