W B 1 ® Accu-Guard SMD Thin-Film Fuse ® ACCU-GUARD TECHNOLOGY APPLICATIONS ® The Accu-Guard series of fuses is based on thin-film tech- • Cellular Telephones niques. This technology provides a level of control on the • Two-Way Radios component electrical and physical characteristics that is • Computers generally not possible with standard fuse technologies. This • Battery Chargers has allowed AVX to offer a series of devices which are designed for modern surface mount circuit boards which • Rechargeable Battery Packs require protection. • Hard Disk Drives • PDA’s FEATURES • LCD Screens • SCSI Interface • Accurate current rating • Digital Cameras • Fast acting • Video Cameras • Small-standard 0603, 0805, 1206 and 0612 chip sizes • Taped and reeled • Completely compatible with all soldering systems APPROVAL FILE NUMBERS used for SMT • UL, cUL: RCD#E143842 DIMENSIONS DIMENSIONS 0603, 0805 and 1206 0402 B T T W L B 2 L STANDARD SIZES: millimeters (inches) 0402 0603 0805 1206 0612 1.00±0.10 1.65±0.25 2.1±0.2 3.1±0.2 1.65±0.25 L (0.039±0.004) (0.065±0.010) (0.083±0.008) (0.122±0.008) (0.065±0.010) 0.55±0.07 0.80±0.15 1.27±0.1 1.6±0.1 3.1±0.2 W (0.022±0.003) (0.031±0.006) (0.050±0.004) (0.063±0.004) (0.122±0.008) 0.40±0.10 0.90±0.2 0.9±0.2 1.2±0.2 0.9±0.2 T (0.016±0.004) (0.035±0.008) (0.035±0.008) (0.047±0.008) (0.036±0.008) 0.20±0.10 0.35±0.15 0.3±0.15 0.43±0.25 0.35±0.15 B (0.008±0.004) (0.014±0.006) (0.012±0.006) (0.017±0.010) (0.014±0.006) HOW TO ORDER F 1206 A 0R20 F W TR Product Size Fuse Version Rated Current Fuse Speed Termination Packaging Fuse A=Accu-Guard® See table for Current expressed in F=Fast W=Nickel/solder TR=Tape and reel B=Accu-Guard® II standard sizes Amps. Letter R =coated C=Accu-Guard® II denotes decimal (Sn 63, Pb 37) 0603 point. e.g. D=Accu-Guard® II 0.20A=0R20 0612 1.75A=1R75 E=Accu-Guard® II 0402 2 ® Accu-Guard II SMD Thin-Film Fuse ® ® Accu-Guard II is a version of Accu-Guard fuses for a For F1206B and F0805B at -55°C is 107% of rating, at wider range of current and voltage ratings. Constructed on +25°C 100% of rating, at +85°C 93% of rating, at +125°C ® alumina substrates, Accu-Guard II fuses display superior 90% of rating. For F0805B 2.50A and 3.00A at +85°C 90% electrical, mechanical and environmental properties. of rating, at +125°C 90% of rating. ® Accu-Guard II dimensions are standard 0603, 0805, 1206 Interrupting rating: 50A. and 0612 chip sizes, see page 2. Insulation resistance: >20MΩ guaranteed (after fusing at rated voltage). ELECTRICAL SPECIFICATIONS For F0612D at -55°C 107% of rating, at +25°C 100% of Operating temperature: -55°C to +125°C rating, at +85°C 80% of rating, at +125°C 75% of rating. Current carrying capacity: For F0402E at -55°C 107% of rating, at -25°C 100% of rating, at +125°C 80% of rating. For F0603C at -55°C is 107% of rating, at +25°C 100% of rating, at +85°C 90% of rating, at +125°C 75% of rating. Current Resistance Voltage Drop Fusing Current Pre-Arc Rated 2 Size Part Number Rating 10% x I rated, 25°C @1 x I rated, 25°C (within 5 sec), 25°CI t @ 50A Voltage 2 A Ω (max.) mV (max.) A A -sec V F0402E0R25FWTR 0.25 650 220 0.625 0.00005 32 F0402E0R50FWTR 0.50 250 180 1.25 0.0003 32 0402 F0402E1R00FWTR 1.00 130 160 2.50 0.008 32 F0402E1R50FWTR 1.50 60 140 3.75 0.03 32 F0402E2R00FWTR 2.00 50 120 5.00 0.06 32 F0603C0R15FWTR 0.15* 1.75 (1.3 typ) 400 0.30 0.000004* 32 F0603C0R25FWTR 0.25 0.800 280 0.50 0.00003* 32 F0603C0R37FWTR 0.375 0.500 280 0.75 0.0001 32 F0603C0R50FWTR 0.50 0.320 280 1.00 0.0002 32 F0603C0R75FWTR 0.75 0.300 280 1.50 0.0015 32 0603 F0603C1R00FWTR 1.00 0.200 240 2.00 0.004 32 F0603C1R25FWTR 1.25 0.170 240 2.50 0.007 32 F0603C1R50FWTR 1.50 0.110 240 3.00 0.012 32 F0603C1R75FWTR 1.75 0.090 240 3.50 0.02 24 F0603C2R00FWTR 2.00 0.075 240 4.00 0.03 24 F0603C2R50FWTR 2.50 0.055 200 5.00 0.05 16 F0603C3R00FWTR 3.00 0.045 200 6.00 0.1 16 F0805B0R15FWTR 0.15* 1.75 (1.3 typ) 400 0.30 0.000004* 63 F0805B0R25FWTR 0.25 0.750 280 0.50 0.00003* 63 F0805B0R50FWTR 0.50 0.350 280 1.00 0.0002 63 F0805B0R75FWTR 0.75 0.270 280 1.50 0.001 63 0805 F0805B1R00FWTR 1.00 0.220 280 2.00 0.003 63 F0805B1R25FWTR 1.25 0.170 280 2.50 0.007 63 F0805B1R50FWTR 1.50 0.120 240 3.00 0.010 63 F0805B2R00FWTR 2.00 0.080 220 4.00 0.030 63 F0805B2R50FWTR 2.50 0.060 220 5.00 0.050 63 F0805B3R00FWTR 3.00 0.050 220 6.00 0.10 63 F1206B0R25FWTR 0.25 0.750 280 0.50 0.00003 63 F1206B0R50FWTR 0.50 0.350 280 1.00 0.0002 63 F1206B1R00FWTR 1.00 0.180 240 2.00 0.003 63 1206 F1206B1R50FWTR 1.50 0.120 240 3.00 0.010 63 F1206B2R00FWTR 2.00 0.080 220 4.00 0.030 63 F1206B3R00FWTR 3.00 0.050 220 6.00 0.10 63 F0612D4R00FWTR 4.00 0.040 260 10 0.10 32 0612 F0612D5R00FWTR 5.00 0.025 200 12.5 0.25 32 *Current is limited to less than 50A at 32V due to internal fuse resistance. 7 ® Accu-Guard II SMD Thin-Film Fuse ENVIRONMENTAL CHARACTERISTICS Test Conditions Requirement Solderability Components completely immersed in a Terminations to be well tinned solder bath at 235 ±5°C for 2 secs. No visible damage Leach Resistance Completely immersed in a solder bath Dissolution of termination at 260 ±5°C for 60 secs. ≤ 25% of area ∆R/R<10% Storage 12 months minimum with components Good solderability stored in “as received” packaging. Shear Components mounted to a substrate. No visible damage A force of 5N applied normal to the line joining the terminations and in a line parallel to the substrate. Rapid Change of Components mounted to a substrate. No visible damage Temperature 50 cycles -55°C to +125°C. ∆ R/R<10% Vibration Per Mil-Std-202F No visible damage Method 201A and ∆R/R<10% Method 204D Condition D. Bend Tested as shown in diagram No visible damage ∆R/R<10% 3 mm Deflection 45mm 45mm Load Life 25°C, rated current, 20,000 hrs. No visible damage F0805B, F1206B ∆R/R<10% 8 ® Accu-Guard II SMD Thin-Film Fuse FUSE TIME – CURRENT CHARACTERISTICS FOR SIZE 0402 (TYPICAL) 10 0.25A 1 0.50A 1.00A 1.50A 2.00A -1 10 -2 10 -3 10 -4 10 -5 10 -6 10 0.1 1 10 100 Current, Amp. 9 Pre-Arc Time, Seconds ® Accu-Guard II SMD Thin-Film Fuse FUSE PRE-ARC JOULE INTEGRALS VS CURRENT FOR SIZE 0402 (TYPICAL) 100 10 1 -1 10 -2 10 -3 10 -4 10 2.00A 1.50A -5 1.00A 10 0.50A 0.25A -6 10 0 10 20 30 40 50 60 Current, Amp 10 2 2 Pre-Arc I t, A sec ® Accu-Guard II SMD Thin-Film FUSE PRE-ARC JOULE INTEGRALS VS PRE-ARC TIME FOR SIZE 0402 (TYPICAL) 100 10 1 -1 10 -2 10 2.00A -3 10 1.50A 1.00A 0.50A -4 10 0.25A -5 10 -6 10 -7 -6 -5 -4 -3 -2 -1 10 10 10 10 10 10 10 1 10 Pre-Arc Time, Seconds 11 2 2 Pre-Arc I t, A sec ® Accu-Guard II SMD Thin-Film Fuse FUSE TIME - CURRENT CHARACTERISTICS FOR SIZE 0603 (TYPICAL) 10 0.15A 1 0.25A 0.375A 0.50A 0.75A 1.00A 1.25A -1 10 1.5A 1.75A 2.0A 2.5A 3.0A -2 10 -3 10 -4 10 -5 10 -6 10 0.1 1 10 100 Current, Amp. 12 Pre-Arc Time, Seconds ® Accu-Guard II SMD Thin-Film Fuse FUSE PRE-ARC JOULE INTEGRALS VS. CURRENT FOR SIZE 0603 (TYPICAL) 100 10 1 -1 10 -2 10 3.00A 2.50A 2.00A -3 10 1.75A 1.50A 1.25A -4 10 1.00A 0.75A 0.50A -5 0.375A 10 0.25A 0.15A -6 10 0 10 20 30 40 50 60 Current, Amp 13 2 2 Pre-Arc I t, A sec ® Accu-Guard II SMD Thin-Film Fuse FUSE PRE-ARC JOULE INTEGRALS VS. PRE-ARC TIME FOR SIZE 0603 (TYPICAL) 100 10 1 -1 10 -2 10 3.00A 2.50A 2.00A -3 10 1.75A 1.50A 1.25A -4 10 1.00A 0.75A 0.50A -5 10 0.375A 0.25A 0.15A -6 10 -7 -6 -5 -4 -3 -2 -1 10 10 10 10 10 10 10 110 Pre-Arc Time, Seconds 14 2 2 Pre-Arc I t, A sec ® Accu-Guard II SMD Thin-Film Fuse FUSE TIME - CURRENT CHARACTERISTICS FOR SIZES 0805 AND 1206 (TYPICAL) 10 0.15A 1 0.25A 0.50A 0.75A 1.00A 1.25A -1 1.5A 10 2.0A 2.5A 3.0A -2 10 -3 10 -4 10 -5 10 -6 10 0.1 1 10 100 Current, Amp. 15 Pre-Arc Time, Seconds ® Accu-Guard II SMD Thin-Film Fuse FUSE PRE-ARC JOULE INTEGRALS VS. CURRENT TIME FOR SIZES 0805 AND 1206 (TYPICAL) 100 10 1 -1 10 -2 10 3.00A 2.50A -3 10 2.00A 1.50A 1.25A -4 10 1.00A 0.75A 0.50A -5 10 0.25A 0.15A -6 10 0 10 20 30 40 50 60 Current, Amp 16 2 2 Pre-Arc I t, A sec ® Accu-Guard II SMD Thin-Film Fuse FUSE PRE-ARC JOULE INTEGRALS VS. PRE-ARC TIME FOR SIZES 0805 AND 1206 (TYPICAL) 100 10 1 -1 10 -2 10 3.00A 2.50A -3 10 2.00A 1.50A 1.25A -4 10 1.00A 0.75A 0.50A -5 10 0.25A 0.15A -6 10 -7 -6 -5 -4 -3 -2 -1 10 10 10 10 10 10 10 110 Pre-Arc Time, Seconds 17 2 2 Pre-Arc I t, A sec ® Accu-Guard II SMD Thin-Film Fuse FUSE TIME - CURRENT CHARACTERISTICS FOR SIZE 0612 (TYPICAL) 10 1 -1 10 -2 10 -3 10 5.0A 4.0A -4 10 -5 10 110 100 Current, Amp. 18 Pre-Arc Time, Seconds ® Accu-Guard II SMD Thin-Film Fuse FUSE PRE-ARC JOULE INTEGRALS VS. PRE-ARC TIME FOR SIZE 0612 (TYPICAL) 1000 100 10 1 5.00A -1 10 4.00A -2 10 -3 10 -4 10 -5 10 -6 -5 -4 -3 -2 -1 10 10 10 10 10 10 110 Pre-Arc Time, Seconds 19 2 2 Pre-Arc I t, A sec ® Accu-Guard II SMD Thin-Film Fuse FUSE PRE-ARC JOULE INTEGRALS VS. CURRENT FOR SIZE 0612 (TYPICAL) 1000 100 10 1 5.00A -1 10 4.00A -2 10 -3 10 -4 10 -5 10 0 10 20 30 40 50 60 Current, Amp 20 2 2 Pre-Arc i t, A sec ® Accu-Guard SMD Thin-Film Fuse QUALITY & RELIABILITY COMPONENT PAD DESIGN ® Accu-Guard series of fuses is based on established Component pads must be designed to achieve good joints thin-film technology and materials used in the semiconduc- and minimize component movement during soldering. tor industry. Pad designs are given below for both wave and reflow • In-line Process Control: This program forms an integral soldering. part of the production cycle and acts as a feedback sys- The basis of these designs are: tem to regulate and control production processes. The a. Pad width equal to component width. It is permissible to test procedures, which are integrated into the production decrease this to as low as 85% of component width but process, were developed after long research and are it is not advisable to go below this. based on the highly developed semiconductor industry b. Pad overlap 0.5mm. test procedures and equipment. These measures help AVX/Kyocera to produce a consistent and high yield line c. Pad extension 0.5mm for reflow. Pad extension about of products. 1.0mm for wave soldering. • Final Quality Inspection: Finished parts are tested for PREHEAT & SOLDERING standard electrical parameters and visual/mechanical The rate of preheat in production should not exceed characteristics. Each production lot is 100% evaluated for 4°C/second. It is recommended not to exceed 2°C/ electrical resistance. In addition, each production lot is second. evaluated on a sample basis for: Temperature differential from preheat to soldering should • Insulation resistance (post fusing) not exceed 150°C. • Blow time for 2 x rated current • Endurance test: 125°C, rated current, 4 hours For further specific application or process advice, please consult AVX. HANDLING AND SOLDERING HAND SOLDERING & REWORK SMD chips should be handled with care to avoid damage or contamination from perspiration and skin oils. The use Hand soldering is permissible. Preheat of the PCB to 100°C of plastic tipped tweezers or vacuum pick-ups is strongly is required. The most preferable technique is to use hot air recommended for individual components. Bulk handling soldering tools. Where a soldering iron is used, a tempera- should ensure that abrasion and mechanical shock are ture controlled model not exceeding 30 watts should be minimized. For automatic equipment, taped and reeled used and set to not more than 260°C. Maximum allowed product is the ideal medium for direct presentation to the time at temperature is 1 minute. placement machine. COOLING CIRCUIT BOARD TYPE After soldering, the assembly should preferably be allowed All flexible types of circuit boards may be used to cool naturally. In the event of assisted cooling, similar (e.g. FR-4, G-10). conditions to those recommended for preheating should be used. For other circuit board materials, please consult factory. REFLOW SOLDERING WAVE SOLDERING Dimensions: millimeters (inches) Dimensions: millimeters (inches) 0603 0805 0402 0603 0805 0402 0.85 0.8 0.6 1.0 (0.033) (0.031) (0.024) 1.25 (0.039) (0.049) 1.5 2.1 (0.083) (0.059) 0.5 2.3 0.6 1.7 3.0 (0.020) 0.5 (0.091) (0.068) (0.024) (0.118) (0.020) 1.0 3.1 0.6 4.0 (0.039) 0.8 (0.122) (0.024) (0.157) (0.031) 0.85 1.0 0.6 (0.033) (0.039) (0.024) 0.59 1.0 (0.023) 1.25 (0.039) (0.049) 0.59 0.8 (0.031) (0.023) 1.5 1.25 (0.049) (0.059) 0.8 (0.031) 1.25 (0.049) 1206 0612 1206 0612 0.85 1.25 1.0 (0.033) 1.5 (0.039) (0.059) (0.049) 2.3 0.6 (0.024) (0.091) 3.1 0.6 (0.024) 4.0 (0.122) 0.85 5.0 (0.157) (0.197) 2.0 (0.033) 2.0 (0.079) (0.079) 1.25 (0.049) 3.1 (0.122) 3.1 1.0 1.5 (0.039) (0.122) (0.059) 1.6 1.6 (0.063) (0.063) 21 ® Accu-Guard SMD Thin-Film Fuse RECOMMENDED SOLDERING PROFILES CLEANING RECOMMENDATIONS Care should be taken to ensure that the devices are thor- IR REFLOW oughly cleaned of flux residues, especially the space 220 beneath the device. Such residues may otherwise become Assembly exits heat– 210 no forced cooldown conductive and effectively offer a lousy bypass to the 200 190 device. Various recommended cleaning conditions (which 180 Additional soak time 186°C solder melting must be optimized for the flux system being used) are as 170 Assembly enters the to allow uniform temperature 45-60 sec. preheat zone heating of the 160 above solder substrate follows: melting point 150 140 Cleaning liquids . . . . . . .i-propanol, ethanol, acetylace- 130 tone, water, and other stan- 120 110 dard PCB cleaning liquids. 100 90 Ultrasonic conditions . . .power – 20w/liter max. fre- Soak time 80 1) Activates the flux 2) Allows center of board quency – 20kHz to 45kHz. 70 temperatures to catch up with 60 corners Temperature . . . . . . . . .80°C maximum (if not other- 50 40 wise limited by chosen solvent 30 system). 20 00.5 11.5 22.5 33.5 44.5 Time . . . . . . . . . . . . . . .5 minutes max. Time (mins) STORAGE CONDITIONS ® Recommended storage conditions for Accu-Guard prior to use are as follows: Temperature 15°C to 35°C WAVE SOLDERING Humidity ≤65% Air Pressure 860mbar to 1060mbar 3–5 seconds 260 240 220 200 100°C Natural 180 Cooling 160 140 120 100 Enter Wave 80 60 40 Time (seconds) 20 0 10 2030405060708090 100 110 120 Transfer from VAPOR PHASE preheat with min. delay & temp. loss Preheat Reflow 215°C 215°C 200 200 Duration varies Natural 180 180 with thermal mass Cooling of assembly 160 160 10–60 secs typical 140 140 120 120 Enter 100 100 Vapor 80 80 60 60 40 40 20 20 0 0 10 20 30 40 50 60 70 Time (minutes) Time (seconds) 22 TEMPERATURE °C TEMPERATURE °C COMPONENT LAND TEMP (DEG C) ® Accu-Guard SMD Thin-Film Fuse PACKAGING Automatic Insertion Packaging Tape & Reel: All tape and reel specifications are in compliance with EIA 481-1 — 8mm carrier — Reeled quantities: Reels of 3,000 or 10,000 pieces (for F0402: 5,000 or 20,000 pieces) G MAX. B* C A E D* FULL RADIUS F *DRIVE SPOKES OPTIONAL IF USED, ASTERISKED DIMENSIONS APPLY. REEL DIMENSIONS: millimeters (inches) A(1) B* C D* E F G 180 + 1.0 1.5 min. 13 ± 0.2 20.2 min. 50 min. 9.4 ± 1.5 14.4 max. (7.087 + 0.039) (0.059 min.) (0.512 ± 0.008) (0.795 min.) (1.969 min.) (0.370 ± 0.050) (0.567 max.) Metric dimensions will govern. Inch measurements rounded for reference only. (1) 330mm (13 inch) reels are available. 10 PITCHES CUMULATIVE E TOLERANCE ON TAPE ±0.2 D F C TOP TAPE W B A L P CENTER LINES DIRECTION OF FEED OF CAVITY P = 4mm except 0402 where P = 2mm CARRIER DIMENSIONS: millimeters (inches) AB C D E F +0.1 8.0 ± 0.3 3.5 ± 0.05 1.75 ± 0.1 2.0 ± 0.05 4.0 ± 0.1 1.5 -0.0 +0.004 (0.315 ± 0.012) (0.138 ± 0.002) (0.069 ± 0.004) (0.079 ± 0.002) (0.157 ± 0.004) (0.059 ) -0.000 Note: The nominal dimensions of the component compartment (W,L) are derived from the component size. Note: AVX reserves the right to change the information published herein without notice. 23 ® Accu-Guard SMD Thin-Film Fuse ® HOW TO CHOOSE THE CORRECT ACCU-GUARD FUSE FOR CIRCUIT PROTECTION ® Correct choice of an Accu-Guard fuse for a given applica- 5. Switch-on and Other Pulse Current 2 tion is fairly straightforward. The factor of pre-arc I t, howev- Many circuits generate a large current pulse when initially 2 er, requires clarification. The proper design for pre-arc I t is connected to power. There are also circuits which are sub- presented by way of example. ject to momentary current pulses due to external sources; telephone line cards which are subject to lightning-induced pulses are one example. These current pulses must be passed by the fuse without causing actuation. These puls- DESIGN PARAMETERS es may be so large that they are the determining factor for 1. Operating Temperature ® choosing the Accu-Guard current rating; not necessarily ® The Accu-Guard is specified for operation in the tempera- steady state current. ture range of -55°C to +125°C. Note, however, that fusing In order to design for current pulses, the concept of fuse current is sensitive to temperature. This means that the fuse 2 pre-arc Joule integral, I t, must be understood. Fuse current must be derated or uprated at circuit temperatures other rating is defined by the requirement that 2 x I will cause R than 25°C: actuation in <5 seconds. This rating does not indicate how ® Environmental Accu-Guard the fuse will react to very high currents of very short duration. Temperature Current Carrying Capacity* Rather, the fusing characteristic at very high currents is 2 2 F0805B, F1206A, F0805B 2.50A specified by I t-t curves (or I t-I). F0402E F0603C F0612D F1206B & 3.00A 2 I t expresses the amount of energy required to actuate the 2 -55°C to -11°C 1.07 x I 1.07 x I 1.07 x I 1.07 x I 1.07 x I fuse. Total I t expresses the total energy which will be R R R R R passed by the fuse until total cessation of current flow. -10°C to 60°CI I I I I R R R R R 2 Pre-arc I t expresses that energy required to cause large 61°C to 100°C 0.85 x I 0.93 x I 0.90 x I 0.90 x I 0.80 x I R R R R R 2 2 irreversible damage to the fuse element (Total I t = pre-arc I t 101°C to 125°C 0.80 x I 0.90 x I 0.90 x I 0.75 x I 0.75 x I 2 R R R R R + arc I t). If the Joule integral of the switch-on pulse is 2 *As a function of nominal rated current, I . larger than the fuse pre-arc I t, nuisance actuation will occur. R ® In order to choose the proper Accu-Guard current rating for 2. Circuit Voltage 2 a given application, it is necessary to calculate the I t Joule ® Maximum Voltage: Accu-Guard is specified for circuits of integral of the circuit switch-on and other current pulses and ® up to rated voltage. Accu-Guard will successfully break ® 2 compare them to the Accu-Guard I t-t curves. An Accu- currents at higher voltages as well, but over voltage may ® 2 Guard fuse must be chosen such that the pulse I t is no crack the fuse body. 2 more than 50% of the pre-arc I t of the prospective fuse. ® Minimum Voltage: Accu-Guard cannot be used in circuits 2 ® Pre-arc I t of the Accu-Guard fuses is well characterized; with voltage of about 0.5V and less. The internal resistance 2 2 I t-t and I t-I graphs are in this catalog. The problem is cal- of the fuse will limit the fault current to a value which will pre- 2 culating the I t of the circuit current pulses. This concept is vent reliable actuation of the fuse (<2 x rated current). not familiar to most engineers. Correct calculation of pulse ® Joule integral and subsequent choice of Accu-Guard 3. Maximum Fault Current current rating is illustrated by way of the attached examples. ® Accu-Guard is fully tested and specified for fault currents ® up to 50A. Accu-Guard will successfully break currents above 50A, but such over current may crack the fuse body or damage the fuse terminations. 4. Steady-State Current ® The Accu-Guard current rating is based on IEC Specifica- tion 127-3. In accordance with this international standard, ® Accu-Guard is specified to operate at least 4 hours at rated current without fusing (25°C). Engineering tests have shown ® that F0805B and F1206A/B Accu-Guard will in fact operate at least 20,000 hours at rated current without fusing (25°C). 24 ® Accu-Guard SMD Thin-Film Fuse 2. Triangular current pulse DESIGNING FOR CURRENT The Joule integral for triangular pulse is PULSE SITUATIONS 2 [(Imax.) x t]/3, 1. Sine wave current pulse see Fig. 2a. The Joule integral for sine wave pulse is 2 [(I ) x t]/2, max. l max. see Fig. 1a. l max. t Fig. 2a. Triangular pulse parameters for Joule t integral calculation, example #2. Fig. 1a. Sine wave pulse parameters for Joule integral calculation, example #1. Thus, for the current pulse in Figure 1b, the Joule integral is Thus, for the current pulse in Figure 2b, the Joule integral is 2 -6 -5 2 2 -3 -3 2 [(4.8A) x 7.7 x 10 sec]/2 = 8.9 x 10 A sec. [(1.5A) x 3 x 10 sec]/3 = 2.25 x 10 A sec. 2 msec/div 10 µsec/div 0.5A/div 1A/div Fig. 1b. Sine wave pulse, example #1. Fig. 2b. Triangular pulse, example #2. 2 The pulse duration is 7.7µsec. We must find a fuse that can The pulse duration is 3 msec. In the I t graph on page 6, pre- -5 -4 2 -3 2 absorb at least 8.9 x 10 X 2 = 1.8 x 10 A sec Joule inte- arcing Joule integral for 3 msec pulse is 4 x 10 A sec for the 2 -2 gral within 7.7 µsec without actuation. According to the I t 0.5A fuse (not enough) and 2 x 10 for the 0.75A fuse (more -4 2 graph on page 6, pre-arcing Joule integral is 2.3x10 A sec than enough). Therefore, 0.75A fuse should be chosen for for the 0.5A fuse, which is slightly more than needed. The this application, see Figure 2c. -5 2 next lower rating (0.375A), has only 6x10 A sec, which is not enough. Therefore, 0.5A fuse should be chosen for this FUSE PRE-ARCING JOULE INTEGRALS application, see Figure 1c. vs. PRE-ARCING TIME 2 2 PRE-ARCING TIME l t, A sec 100 FUSE PRE-ARCING JOULE INTEGRALS 10 vs. PRE-ARCING TIME 2 2 1 PRE-ARCING TIME l t, A sec 100 -1 10 0.75A 10 -2 10 x -3 1 10 -1 -4 10 10 -5 -2 10 10 -7 -6 -5 -4 -3 -2 -1 0.5A 10 10 10 10 10 10 10 110 -3 10 PRE-ARCING TIME, sec -4 10 x Fig. 2c. Choice of 0.75A fuse, example #2. -5 10 -7 -6 -5 -4 -3 -2 -1 10 10 10 10 10 10 10 110 2 Pre-arcing I t PRE-ARCING TIME, sec 2 Maximum I t design rule Fig. 1c. Choice of 0.5A fuse, example #1. 2 X I t for sample switch-on pulse 2 Pre-arcing I t 2 Maximum I t design rule 2 X I t for sample current pulse 25 ® Accu-Guard SMD Thin-Film Fuse DESIGNING FOR CURRENT PULSE SITUATIONS (CONT.) 3. Trapezoidal current pulse 4. Lightning strike The Joule integral for a trapezoidal pulse is A lightning strike pulse is shown in Figure 4a. After an initial 2 I I 2 (I ) + I x (I - I ) + ( - ) x t, max min linear rise, the current declines exponentially. [ ] min. min. max. min. 3 see Fig. 3a. l max. 0.51 max. l max. l min. t 0.5 Fig. 4a. Lightning pulse parameters for Joule t integral calculation, example #4. Fig. 3a. Trapezoidal pulse parameters for Joule Joule integral for the linear current rise is calculated as for a integral calculation, example #3. triangular pulse, see example #2. Thus, for current pulse in Figure 3b, the Joule integral is: The Joule integral for the exponential decline is 2 2 -3 -3 {(0.56A) +0.56A x (1A-0.56A)+ (1A-0.56A) } x 3 x 10 s = 1.9 x 10 A2sec. 2 [ ] I x t x (-1/2In 0.5) = 0.72I 2 x t max. 0.5 max. 0.5 3 Thus, for the sample lightning strike pulse in Figure 4b, the 0.5 msec/div total Joule integral is: 2 -6 2 -6 -3 2 (25A) x 2 x 10 sec/3+0.72 x (25A) x 10 x 10 sec = 4.92 x 10 A sec. 10 µsec/div 0.5A/div 5A/div Fig. 3b. Trapezoidal pulse, example #3. 2 According to the I t graph on page 6, the 0.5A fuse should Fig. 4b. Lightning strike pulse, example #4. be chosen for this application, see Figure 3c. For practical calculations, the duration of exponential decline may be assumed to be 3t , because within this time 98.5% 0.5 FUSE PRE-ARCING JOULE INTEGRALS of the pulse energy is released. Thus, the total pulse duration vs. PRE-ARCING TIME in this example is 30 µsec, and the 1.25A fuse should be 2 2 PRE-ARCING TIME l t, A sec 100 chosen for this application, see Figure 4c. 10 FUSE PRE-ARCING JOULE INTEGRALS 1 -1 vs. PRE-ARCING TIME 10 -2 2 2 10 PRE-ARCING TIME l t, A sec 100 x 0.50A -3 10 10 -4 10 1 -5 10 1.25A -7 -6 -5 -4 -3 -2 -1 -1 10 10 10 10 10 10 10 110 10 PRE-ARCING TIME, sec -2 10 x -3 Fig. 3c. Choice of 0.5A fuse, example #3. 10 -4 2 10 Pre-arcing I t -5 10 2 -7 -6 -5 -4 -3 -2 -1 Maximum I t design rule 10 10 10 10 10 10 10 110 PRE-ARCING TIME, sec 2 X I t for sample switch-on pulse Fig. 4c. Choice of 0.5A fuse, example #4. 2 Pre-arcing I t 2 Maximum I t design rule 2 X I t for sample switch-on pulse 26 ® Accu-Guard SMD Thin-Film Fuse DESIGNING FOR CURRENT PULSE SITUATIONS (CONT.) 5. Complex current pulse 6. Switch-on pulse and steady-state current If the pulse consists of several waveforms, all of them should In Figure 6a, the switch-on pulse is a triangle pulse with a -3 2 be evaluated separately, and then the total Joule integral 5.1 x 10 A sec Joule integral of 5 msec duration; the 0.75A should be calculated as well. fuse will meet this requirement, see Figure 6b. 200 µsec/div 2 msec/div 2A/div 0.5A/div Fig. 5a. Complex pulse, example #5. Fig. 6a. Switch-on pulse and steady-state current, example #6. In Figure 5a, the Joule integral for the first triangle is 2 -6 -3 [(4.67A) x 294 x 10 sec]/3=2.14 x 10 A2sec FUSE PRE-ARCING JOULE INTEGRALS and 0.75A fuse should meet this condition, see Figure 5b. vs. PRE-ARCING TIME 2 2 PRE-ARCING TIME l t, A sec 100 FUSE PRE-ARCING JOULE INTEGRALS 10 vs. PRE-ARCING TIME 1 2 2 PRE-ARCING TIME l t, A sec 100 -1 10 0.75A -2 10 10 x -3 1 10 -1 -4 10 10 0.75A -5 -2 10 10 x -7 -6 -5 -4 -3 -2 -1 10 10 10 10 10 10 10 110 x -3 10 PRE-ARCING TIME, sec -4 10 -5 10 Fig. 6b. Choice of 0.75A fuse, example #6. -7 -6 -5 -4 -3 -2 -1 10 10 10 10 10 10 10 110 2 Pre-arcing I t PRE-ARCING TIME, sec 2 Maximum I t design rule Fig. 5b. Choice of fuse, example #5. 2 X I t for sample switch-on pulse 2 Pre-arcing I t 2 Maximum I t design rule The steady-state current is 0.5A, and 1A fuse is typically rec- 2 I t for sample switch-on pulse X ommended to meet the steady-state condition. Based on steady-state current, the 1A fuse should be chosen for this application. The Joule integral for the second triangle is 2 -6 -3 2 [(5.33A) x 269 x 10 sec]/3 = 2.55 x 10 A sec, and 0.75A fuse is suitable for this case also, see Figure 5b. However, for the whole pulse, the Joule integral is -3 2 4.7 x 10 A sec, and the total duration is 563 µsec. For the -3 2 0.75A fuse, the Joule integral is only 8.6 x 10 A sec for this pulse duration, so the 1A fuse should be chosen for this application, see Figure 5b. 27