Selection Process 1. that the circuit parameters do not exceed these ratings. Determine the following circuit operating parameters: 4. Verify that the ambient operating temperature within close proximity to the device is within its normal operating range. Thermally derate IHOLD and IMAX as necessary. See equation below. • Normal operating current – IHOLD • Maximum circuit voltage – VMAX • Maximum interrupt current – IMAX • Ambient operating temperature 2. Select the suitable form factor. 3. Compare the PTC data sheet ratings on littelfuse.com for VMAX and IMAX to ensure IHOLD = IMAX 5. Check that the trip time protects the circuit. 6. Verify that the post trip resistance (R1MAX) of the device is taken into account in the circuit design. 7. Independently test and evaluate the suitability and performance of the PTC in the actual application. Thermal derating factor SURFACE MOUNT 0805L 1206L 1210L RADIAL LEADED 1812L 2016L 2920L USBR 30R International Sales, Distribution and Engineering Facilities: Photos Chip Size 0805 (2012) 1206 (3216) 1210 (3225) 1812 (4532) 2016 (5041) 2920 (7351) Hold Current (IHOLD) 0.10-1.00A 0.125-2.00A 0.05-1.75A 0.10-2.60A 0.3-2.00A 0.30-3.00A 0.75-2.5A 0.9-9.00A Max voltage (VMAX) 15V 30V 30V 60V 60V 60V 16V 30V Max fault current (IMAX) 40A 100A 100A 100A 40A 40A 40A 40A -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C Agency approval cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV RoHS Compliant Yes Yes Yes Yes Yes Yes Yes Yes Lead-Free Yes Yes Yes Yes Yes Yes Yes Yes Operating Temperature Range COMPETITOR CROSS Tyco/Raychem Series nano SMD micro SMD mini SMD mid SMD SMD RUSB RUE Amp Rating NA 0.500-1.50A 0.050-1.50A 0.140-2.60A 0.300-2.00A 0.300-3.00A 0.750-2.50A 0.900-9.00A Max voltage NA 6V 6-30V 6-60V 6-60V 6-60V 16V 30V MF-NSMF MF-USMD MF-MSMD MF-SMDF MF-SM Bourns Series MF-R Amp Rating NA 0.12-2.00 0.05-1.50A 0.05-1.50A 0.55-2.00A 0.300-2.5A NA 0.90-9.0A Max voltage NA 6-30V 6-30V 6-30V 10-60V 6-60V NA 30V PTC Selection Table (cont.) BATTERY STRAP (AXIAL LEADED) 60R North America • Birmingham, Michigan USA Des Plaines, Illinois USA and Irving, Texas USA Technical Assistance Phone: 800 999 9445 847 824 1188 Fax: 847 391 0459 Europe • Dünsen, Germany Phone: +49 4244 8190 Fax: +49 4244 819 139 • Munich, Germany Phone: +49 8955 27660 Fax: +49 8955 276 699 • Utrecht, The Netherlands Phone: +31 30 299 9900 Fax: +31 30 299 9800 NO = Not offered Series Name World Headquarters Littelfuse, Inc. 800 E. Northwest Highway Des Plaines, IL 60016 USA www.littelfuse.com PTC Selection Table Series Name POLYFUSE® PTC SELECTION GUIDE 250R 600R ST LT LR VT VL • Swindon, England Phone: +44 1793 720770 Fax: +44 1793 720771 Photos 0.1-3.75A 0.08-0.18A 0.15-0.16A 1.2-4.2A 0.7-3.4A 1.9-10.00A 1.7-2.4A Max voltage (VMAX) 60V 60/250V 60/600V 15/24V 15/24V 15/20V 16V 12V Max fault current (IMAX) 40A 3/10A 3/2.2A 100A 100A 100A 100A 100A Operating Temperature Range 1.7-2.3A -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C Agency approval cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV RoHS Compliant Yes Yes Yes Yes Yes Yes Yes Yes Lead-Free Yes Yes Yes Yes Yes Yes Yes Yes • Beijing, China Phone: +86 10 8454 9408 Fax: +86 10 8454 9409 • Shanghai, China Phone: +86 21 5383 8016 Fax: +86 21 5383 7476 • Shenzhen, China Phone: +86 755 8207 0760 Fax: +86 755 8207 0759 • Singapore Phone: +65 6885 9111 Fax: +65 6885 9113 • Yokohama, Japan Phone: +81 45 478 1088 Fax: +81 45 478 1089 • Seoul, Korea Phone: +82 2 6000 8600 Fax: +82 2 6000 8655 • Taipei, Taiwan Phone: +886 2 8751 1234 Fax: +886 2 8751 1177 Central and South America • São Paulo, Brasil Phone: +55 113 835 3780 Fax: +55 113 645 0612 Chip Size Hold Current (IHOLD) Asia/Pacific • Hong Kong, China Phone: +852 2810 5099 Fax: +852 2810 5500 COMPETITOR CROSS Tyco/Raychem Series Amp Rating Max voltage RXE TR250 TR600 SRP LTP LR4 VTP VLR 0.100-3.75A 0.080-0.180A 0.150-0.160A 1.20-4.20A 0.700-3.40A 1.7-13A 1.10-2.40A 2.10-2.30A 16V 60-72V 60/250V 60/600V 15/30V 24V 15/20V 16V MF-R/MF-RX MF-R/250 MF-R/600 MF-S MF-LS MF-LR MF-VS Amp Rating 0.10-3.75A 0.08-0.18A 0.15-0.16A 1.2-4.2A 0.70-3.4A 1.9-9.0A 1.7-2.4A NA Max voltage 60V 60/250V 60/600V 15-30V 15-24V 15-20V 16V NA Bourns Series NA = Not Available 5 FORM NO. EC327-E © November 2006, Littelfuse Inc. Printed in U.S.A. Specifications, descriptions and illustrative material in this literature are as accurate as known at the time of publication, but are subject to change without notice. Research and Manufacturing Facilities: • Arcola, Illinois USA • Des Plaines, Illinois USA • Dongguan, China • Dundalk, Ireland • Dünsen, Germany • Irving, Texas USA • Lipa City, Philippines • Matamoros, Mexico • Piedras Negras, Mexico • Suzhou, China • Swindon, England • Witten, Germany • Wuxi, China • Yangmei, Taiwan Surface Mount Battery Strap Radial Leaded High Voltage Radial Leaded Recognized under the Component Program of Underwriters Laboratories to UL Standard 1434 for Thermistors. The devices have also been approved for use in Canada by Underwriters Laboratories. Approvals for fuses include Recognition under the Component Program of Underwriters Laboratories and the CSA Component Acceptance Program. In addition, many fuses are listed in accordance with UL/CSA/ANCE (Mexico) 248-14, Supplemental Fuses. OPERATING VOLTAGE RATING: Log resistance (ohms) General use PTCs are not rated above 60V while fuses are rated up to 600V. Trip Point 0805L 1206L 1210L 1812L 2920L Ul60950 ,TIA-968-A, GR-1089 Requirements X X ITU-T Recoomendations X X CPE (Customer Premises Equipment) X X Analog Line Card X X T1/E1/J1 And HDSL X X ISDN X X ADSL X X Cable Telephony X X PBX/KTS And Key Telephone System X X USB X X IEEE1284 Parallel Data Bus The terminology used for PTCs is often similar but not the same as for fuses. Two parameters that fall into this category are leakage current and fault current rating. X X X X X X X IEEE 802.3 X IEEE 1394 I/O Ports PC Card X SCSI Video Port LCD Monitor X Set Top Box Consumer Electronics Temperature Derating Curves Comparing PTCs to Fuses Chart Key C 140 Curve A Thin-Film Fuses and 313 Series (.010 to .150A) 100 B 80 A 60 Medical Battery electronic PERCENT OF RATING Curve B FLAT-PAK®, Telelink®, Nano2®, PICO®, Blade Terminal, Special Purpose and other leaded and cartridge fuses (except 313.010 – .150A) B X X X X X X X X X X X X X X X X X X X X X X ST LT LR VT Powered Device (PD) X X X Data Pair USB 2.0 USB Port X X X Linear AC/DC Adapter X X X X Portable Electronic Input Port X X X X -20°C -4°F 0°C 32°F 20°C 68°F 40°C 104°F 60°C 140°F 80°C 176°F 100°C 212°F X X (2) V0402MHS03 X 1206L150 D+ D- (2) PGB1010603 (PulseGuard® ESD Suppressor) Signal Ground Shield Ground X X X X X X X X X Lithium Cell Battery Pack Signal Ground Shield Ground IEEE 1394 – FireWire X X X X X X X X X X 1394 Port Tip/Ring circuit – Metallic 1394 Controller RJ11 Connector Tx/Rx Circuits V33MLA1206 VBU Voltage / Current Input Terminal X X 1812L110/33 120°C 248°F 3 TPA+ TPATPB+ TPB- Tip 600R Series 250R Series SMD/leaded SIDACtor® Device Ring (PulseGuard® ESD Suppressor) Shield Ground AMBIENT TEMPERATURE 2 VBUS D+ D- X 20 -40°C -40°F USB Controller V5.5MLA063 VBU X Mobile Phone USB Port USB Controller 1206L150 X Smart Card Reader Shield Ground USB 1.1 X Signal Ground X C -60°C -76°F (3) V5.5MLA0402 (Multilayer Varistor) Data Pair (4) PGB1010603 Curve C Resettable PTCs Control VL X NOTE: The application summary is for reference only. Determination of suitability for a specific application is the responsibility of the customer. 25°C 40 60R X X Electromagnetic Loads, Motor A Battery + V5.5MLA0603 X X Solenoid Protection 120 Battery Controller IC Data Pair X X Loudspeaker Understanding the differences in performance between the two types of devices will make the best circuit protection choice easier. The most obvious difference is that the PTC is resettable. This is an inherent characteristic in which the PTC resets (returns to low resistance state) after power is removed and the device cools down. There are a number of other operating characteristics that differentiate the two types of products. 30R Battery Connector Power Source Equipment (PSE) BATTERY STRAP (AXIAL LEADED) 600R specifications indicates that similarly-rated PTCs have about twice (sometimes more) the resistance of fuses. Temperature (°C) USBR Powered End Station Battery - RADIAL LEADED 2016L Swtich/Hub Data Pair 250R CPU Comparing the time-current curves of PTCs to time-current curves of fuses show that the speed of response for a PTC is similar to the time delay of a Slo-Blo® fuse. (operating) current rating for PTCs can be up to 14A while the maximum level for fuses can exceed 30A. Series Name Li-ion Battery Pack Application RESISTANCE: Reviewing product TIME-CURRENT CHARACTERISTIC: HOLD CURRENT RATING: The hold SURFACE MOUNT Power Over Ethernet Cell Phone FAULT CURRENT: The PTC is rated for a maximum short circuit current at rated voltage. This fault current level is the maximum current that the device can safely limit keeping in mind that the PTC will not actually interrupt the current flow (see LEAKAGE CURRENT above). The typical short circuit rating of a board-mounted PTC is 40A; for battery strap PTCs, this value can reach 100A. Fuses do in fact interrupt the current flow in response to the overload and the range of interrupting ratings vary from tens of amperes up to 10,000 amperes at rated voltage. The application selection guide below should be used as an aid in selecting the proper device for your end application. Please consult the datasheets on www.littelfuse.com for detailed technical specifications. complete protection for the circuit. Contact your location Littelfuse application expert for additional design assistance or visit www.littelfuse.com/PTCs. Outside World AGENCY APPROVALS: PTCs are PTCs are used as circuit protection in applications where sensitive components are at risk of damage from overcurrent conditions. The ability of PTCs to reset themselves after exposure to a fault current makes them ideal for use in circuits that are not easily accessible to a user or technician. Typical applications include port protection on personal computers (USB, Firewire, keyboard/mouse, and serial ports), peripherals (hard drives, video cards, and hubs), cell phone, battery packs, industrial controls, lighting ballast and motor controls. required. The following are typical examples of circuits using POLYFUSE® resettable PTCs in combination with other Littelfuse circuit protection devices to provide Littelfuse offers a full range of battery strap, surface mount and radial leaded resettable PTC devices designed to protect applications where overcurrent protection is Telco Additional operating characteristics can be reviewed by the circuit designer in making the decision to choose a PTC or a fuse for overcurrent protection. Systems Interface) Standard for this large market includes a statement that “....a Positive Temperature Coefficient device must be used instead of a fuse, to limit the maximum amount of current sourced”. When to apply a resettable PTC vs. a traditional fuse is always the choice of the designer or technician but in some cases, PTC’s offer a convenient form of circuit protection to improve the reliability of an application. There is an important area of applications where the use of resettable fuses (PTCs) has become a requirement. Much of the design work for personal computers and peripheral devices is strongly influenced by the Microsoft and Intel System Design Guide which states that “Using a fuse that must be replaced each time an overcurrent condition occurs is unacceptable.” And the SCSI (Small Computer Outside World Overcurrent circuit protection can be accomplished with the use of either a traditional fuse or the more recently developed resettable PTC. Both devices function by reacting to the heat generated by the excessive current flow in the circuit. The fuse element melts open, interrupting the current flow, while the PTC changes from low resistance to high resistance to limit current flow. The graph below shows the response of the PTC device to temperature. Protection is accomplished by limiting the current flow to a low leakage level. Leakage current can range from less than a hundred milliamps at rated voltage up to a few hundred milliamps at lower voltages. The fuse on the other hand completely interrupts the current flow and this open circuit results in no leakage current after it has been subjected to an overload current. PTC Applications Outside World This function is called “tripping” of the overcurrent protection device. TEMPERATURE DERATING: The useful upper limit for a PTC is generally 85°C while the maximum operating temperature for fuses is 125°C. The following temperature derating curves (see chart at bottom of page) that compare PTCs to fuses illustrate that more derating is required for a PTC at a given temperature. have “tripped” when it has transitioned from its low resistance state to a high resistance state due to overload current. Telecom A polymeric PTC (positive temperature coefficient) overcurrent protector is an element placed in series with the circuit or assembly to be protected. The PTC element protects the circuit by changing from a low-resistance to a high resistance state in response to an overcurrent. LEAKAGE CURRENT: A PTC is said to Computer PTC Characteristics and Terminology Signal Ground Signal Ground 4 Selection Process 1. that the circuit parameters do not exceed these ratings. Determine the following circuit operating parameters: 4. Verify that the ambient operating temperature within close proximity to the device is within its normal operating range. Thermally derate IHOLD and IMAX as necessary. See equation below. • Normal operating current – IHOLD • Maximum circuit voltage – VMAX • Maximum interrupt current – IMAX • Ambient operating temperature 2. Select the suitable form factor. 3. Compare the PTC data sheet ratings on littelfuse.com for VMAX and IMAX to ensure IHOLD = IMAX 5. Check that the trip time protects the circuit. 6. Verify that the post trip resistance (R1MAX) of the device is taken into account in the circuit design. 7. Independently test and evaluate the suitability and performance of the PTC in the actual application. Thermal derating factor SURFACE MOUNT 0805L 1206L 1210L RADIAL LEADED 1812L 2016L 2920L USBR 30R International Sales, Distribution and Engineering Facilities: Photos Chip Size 0805 (2012) 1206 (3216) 1210 (3225) 1812 (4532) 2016 (5041) 2920 (7351) Hold Current (IHOLD) 0.10-1.00A 0.125-2.00A 0.05-1.75A 0.10-2.60A 0.3-2.00A 0.30-3.00A 0.75-2.5A 0.9-9.00A Max voltage (VMAX) 15V 30V 30V 60V 60V 60V 16V 30V Max fault current (IMAX) 40A 100A 100A 100A 40A 40A 40A 40A -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C Agency approval cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV RoHS Compliant Yes Yes Yes Yes Yes Yes Yes Yes Lead-Free Yes Yes Yes Yes Yes Yes Yes Yes Operating Temperature Range COMPETITOR CROSS Tyco/Raychem Series nano SMD micro SMD mini SMD mid SMD SMD RUSB RUE Amp Rating NA 0.500-1.50A 0.050-1.50A 0.140-2.60A 0.300-2.00A 0.300-3.00A 0.750-2.50A 0.900-9.00A Max voltage NA 6V 6-30V 6-60V 6-60V 6-60V 16V 30V MF-NSMF MF-USMD MF-MSMD MF-SMDF MF-SM Bourns Series MF-R Amp Rating NA 0.12-2.00 0.05-1.50A 0.05-1.50A 0.55-2.00A 0.300-2.5A NA 0.90-9.0A Max voltage NA 6-30V 6-30V 6-30V 10-60V 6-60V NA 30V PTC Selection Table (cont.) BATTERY STRAP (AXIAL LEADED) 60R North America • Birmingham, Michigan USA Des Plaines, Illinois USA and Irving, Texas USA Technical Assistance Phone: 800 999 9445 847 824 1188 Fax: 847 391 0459 Europe • Dünsen, Germany Phone: +49 4244 8190 Fax: +49 4244 819 139 • Munich, Germany Phone: +49 8955 27660 Fax: +49 8955 276 699 • Utrecht, The Netherlands Phone: +31 30 299 9900 Fax: +31 30 299 9800 NO = Not offered Series Name World Headquarters Littelfuse, Inc. 800 E. Northwest Highway Des Plaines, IL 60016 USA www.littelfuse.com PTC Selection Table Series Name POLYFUSE® PTC SELECTION GUIDE 250R 600R ST LT LR VT VL • Swindon, England Phone: +44 1793 720770 Fax: +44 1793 720771 Photos 0.1-3.75A 0.08-0.18A 0.15-0.16A 1.2-4.2A 0.7-3.4A 1.9-10.00A 1.7-2.4A Max voltage (VMAX) 60V 60/250V 60/600V 15/24V 15/24V 15/20V 16V 12V Max fault current (IMAX) 40A 3/10A 3/2.2A 100A 100A 100A 100A 100A Operating Temperature Range 1.7-2.3A -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C Agency approval cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV RoHS Compliant Yes Yes Yes Yes Yes Yes Yes Yes Lead-Free Yes Yes Yes Yes Yes Yes Yes Yes • Beijing, China Phone: +86 10 8454 9408 Fax: +86 10 8454 9409 • Shanghai, China Phone: +86 21 5383 8016 Fax: +86 21 5383 7476 • Shenzhen, China Phone: +86 755 8207 0760 Fax: +86 755 8207 0759 • Singapore Phone: +65 6885 9111 Fax: +65 6885 9113 • Yokohama, Japan Phone: +81 45 478 1088 Fax: +81 45 478 1089 • Seoul, Korea Phone: +82 2 6000 8600 Fax: +82 2 6000 8655 • Taipei, Taiwan Phone: +886 2 8751 1234 Fax: +886 2 8751 1177 Central and South America • São Paulo, Brasil Phone: +55 113 835 3780 Fax: +55 113 645 0612 Chip Size Hold Current (IHOLD) Asia/Pacific • Hong Kong, China Phone: +852 2810 5099 Fax: +852 2810 5500 COMPETITOR CROSS Tyco/Raychem Series Amp Rating Max voltage RXE TR250 TR600 SRP LTP LR4 VTP VLR 0.100-3.75A 0.080-0.180A 0.150-0.160A 1.20-4.20A 0.700-3.40A 1.7-13A 1.10-2.40A 2.10-2.30A 16V 60-72V 60/250V 60/600V 15/30V 24V 15/20V 16V MF-R/MF-RX MF-R/250 MF-R/600 MF-S MF-LS MF-LR MF-VS Amp Rating 0.10-3.75A 0.08-0.18A 0.15-0.16A 1.2-4.2A 0.70-3.4A 1.9-9.0A 1.7-2.4A NA Max voltage 60V 60/250V 60/600V 15-30V 15-24V 15-20V 16V NA Bourns Series NA = Not Available 5 FORM NO. EC327-E © November 2006, Littelfuse Inc. Printed in U.S.A. Specifications, descriptions and illustrative material in this literature are as accurate as known at the time of publication, but are subject to change without notice. Research and Manufacturing Facilities: • Arcola, Illinois USA • Des Plaines, Illinois USA • Dongguan, China • Dundalk, Ireland • Dünsen, Germany • Irving, Texas USA • Lipa City, Philippines • Matamoros, Mexico • Piedras Negras, Mexico • Suzhou, China • Swindon, England • Witten, Germany • Wuxi, China • Yangmei, Taiwan Surface Mount Battery Strap Radial Leaded High Voltage Radial Leaded Recognized under the Component Program of Underwriters Laboratories to UL Standard 1434 for Thermistors. The devices have also been approved for use in Canada by Underwriters Laboratories. Approvals for fuses include Recognition under the Component Program of Underwriters Laboratories and the CSA Component Acceptance Program. In addition, many fuses are listed in accordance with UL/CSA/ANCE (Mexico) 248-14, Supplemental Fuses. OPERATING VOLTAGE RATING: Log resistance (ohms) General use PTCs are not rated above 60V while fuses are rated up to 600V. Trip Point 0805L 1206L 1210L 1812L 2920L Ul60950 ,TIA-968-A, GR-1089 Requirements X X ITU-T Recoomendations X X CPE (Customer Premises Equipment) X X Analog Line Card X X T1/E1/J1 And HDSL X X ISDN X X ADSL X X Cable Telephony X X PBX/KTS And Key Telephone System X X USB X X IEEE1284 Parallel Data Bus The terminology used for PTCs is often similar but not the same as for fuses. Two parameters that fall into this category are leakage current and fault current rating. X X X X X X X IEEE 802.3 X IEEE 1394 I/O Ports PC Card X SCSI Video Port LCD Monitor X Set Top Box Consumer Electronics Temperature Derating Curves Comparing PTCs to Fuses Chart Key C 140 Curve A Thin-Film Fuses and 313 Series (.010 to .150A) 100 B 80 A 60 Medical Battery electronic PERCENT OF RATING Curve B FLAT-PAK®, Telelink®, Nano2®, PICO®, Blade Terminal, Special Purpose and other leaded and cartridge fuses (except 313.010 – .150A) B X X X X X X X X X X X X X X X X X X X X X X ST LT LR VT Powered Device (PD) X X X Data Pair USB 2.0 USB Port X X X Linear AC/DC Adapter X X X X Portable Electronic Input Port X X X X -20°C -4°F 0°C 32°F 20°C 68°F 40°C 104°F 60°C 140°F 80°C 176°F 100°C 212°F X X (2) V0402MHS03 X 1206L150 D+ D- (2) PGB1010603 (PulseGuard® ESD Suppressor) Signal Ground Shield Ground X X X X X X X X X Lithium Cell Battery Pack Signal Ground Shield Ground IEEE 1394 – FireWire X X X X X X X X X X 1394 Port Tip/Ring circuit – Metallic 1394 Controller RJ11 Connector Tx/Rx Circuits V33MLA1206 VBU Voltage / Current Input Terminal X X 1812L110/33 120°C 248°F 3 TPA+ TPATPB+ TPB- Tip 600R Series 250R Series SMD/leaded SIDACtor® Device Ring (PulseGuard® ESD Suppressor) Shield Ground AMBIENT TEMPERATURE 2 VBUS D+ D- X 20 -40°C -40°F USB Controller V5.5MLA063 VBU X Mobile Phone USB Port USB Controller 1206L150 X Smart Card Reader Shield Ground USB 1.1 X Signal Ground X C -60°C -76°F (3) V5.5MLA0402 (Multilayer Varistor) Data Pair (4) PGB1010603 Curve C Resettable PTCs Control VL X NOTE: The application summary is for reference only. Determination of suitability for a specific application is the responsibility of the customer. 25°C 40 60R X X Electromagnetic Loads, Motor A Battery + V5.5MLA0603 X X Solenoid Protection 120 Battery Controller IC Data Pair X X Loudspeaker Understanding the differences in performance between the two types of devices will make the best circuit protection choice easier. The most obvious difference is that the PTC is resettable. This is an inherent characteristic in which the PTC resets (returns to low resistance state) after power is removed and the device cools down. There are a number of other operating characteristics that differentiate the two types of products. 30R Battery Connector Power Source Equipment (PSE) BATTERY STRAP (AXIAL LEADED) 600R specifications indicates that similarly-rated PTCs have about twice (sometimes more) the resistance of fuses. Temperature (°C) USBR Powered End Station Battery - RADIAL LEADED 2016L Swtich/Hub Data Pair 250R CPU Comparing the time-current curves of PTCs to time-current curves of fuses show that the speed of response for a PTC is similar to the time delay of a Slo-Blo® fuse. (operating) current rating for PTCs can be up to 14A while the maximum level for fuses can exceed 30A. Series Name Li-ion Battery Pack Application RESISTANCE: Reviewing product TIME-CURRENT CHARACTERISTIC: HOLD CURRENT RATING: The hold SURFACE MOUNT Power Over Ethernet Cell Phone FAULT CURRENT: The PTC is rated for a maximum short circuit current at rated voltage. This fault current level is the maximum current that the device can safely limit keeping in mind that the PTC will not actually interrupt the current flow (see LEAKAGE CURRENT above). The typical short circuit rating of a board-mounted PTC is 40A; for battery strap PTCs, this value can reach 100A. Fuses do in fact interrupt the current flow in response to the overload and the range of interrupting ratings vary from tens of amperes up to 10,000 amperes at rated voltage. The application selection guide below should be used as an aid in selecting the proper device for your end application. Please consult the datasheets on www.littelfuse.com for detailed technical specifications. complete protection for the circuit. Contact your location Littelfuse application expert for additional design assistance or visit www.littelfuse.com/PTCs. Outside World AGENCY APPROVALS: PTCs are PTCs are used as circuit protection in applications where sensitive components are at risk of damage from overcurrent conditions. The ability of PTCs to reset themselves after exposure to a fault current makes them ideal for use in circuits that are not easily accessible to a user or technician. Typical applications include port protection on personal computers (USB, Firewire, keyboard/mouse, and serial ports), peripherals (hard drives, video cards, and hubs), cell phone, battery packs, industrial controls, lighting ballast and motor controls. required. The following are typical examples of circuits using POLYFUSE® resettable PTCs in combination with other Littelfuse circuit protection devices to provide Littelfuse offers a full range of battery strap, surface mount and radial leaded resettable PTC devices designed to protect applications where overcurrent protection is Telco Additional operating characteristics can be reviewed by the circuit designer in making the decision to choose a PTC or a fuse for overcurrent protection. Systems Interface) Standard for this large market includes a statement that “....a Positive Temperature Coefficient device must be used instead of a fuse, to limit the maximum amount of current sourced”. When to apply a resettable PTC vs. a traditional fuse is always the choice of the designer or technician but in some cases, PTC’s offer a convenient form of circuit protection to improve the reliability of an application. There is an important area of applications where the use of resettable fuses (PTCs) has become a requirement. Much of the design work for personal computers and peripheral devices is strongly influenced by the Microsoft and Intel System Design Guide which states that “Using a fuse that must be replaced each time an overcurrent condition occurs is unacceptable.” And the SCSI (Small Computer Outside World Overcurrent circuit protection can be accomplished with the use of either a traditional fuse or the more recently developed resettable PTC. Both devices function by reacting to the heat generated by the excessive current flow in the circuit. The fuse element melts open, interrupting the current flow, while the PTC changes from low resistance to high resistance to limit current flow. The graph below shows the response of the PTC device to temperature. Protection is accomplished by limiting the current flow to a low leakage level. Leakage current can range from less than a hundred milliamps at rated voltage up to a few hundred milliamps at lower voltages. The fuse on the other hand completely interrupts the current flow and this open circuit results in no leakage current after it has been subjected to an overload current. PTC Applications Outside World This function is called “tripping” of the overcurrent protection device. TEMPERATURE DERATING: The useful upper limit for a PTC is generally 85°C while the maximum operating temperature for fuses is 125°C. The following temperature derating curves (see chart at bottom of page) that compare PTCs to fuses illustrate that more derating is required for a PTC at a given temperature. have “tripped” when it has transitioned from its low resistance state to a high resistance state due to overload current. Telecom A polymeric PTC (positive temperature coefficient) overcurrent protector is an element placed in series with the circuit or assembly to be protected. The PTC element protects the circuit by changing from a low-resistance to a high resistance state in response to an overcurrent. LEAKAGE CURRENT: A PTC is said to Computer PTC Characteristics and Terminology Signal Ground Signal Ground 4 Recognized under the Component Program of Underwriters Laboratories to UL Standard 1434 for Thermistors. The devices have also been approved for use in Canada by Underwriters Laboratories. Approvals for fuses include Recognition under the Component Program of Underwriters Laboratories and the CSA Component Acceptance Program. In addition, many fuses are listed in accordance with UL/CSA/ANCE (Mexico) 248-14, Supplemental Fuses. OPERATING VOLTAGE RATING: Log resistance (ohms) General use PTCs are not rated above 60V while fuses are rated up to 600V. Trip Point 0805L 1206L 1210L 1812L 2920L Ul60950 ,TIA-968-A, GR-1089 Requirements X X ITU-T Recoomendations X X CPE (Customer Premises Equipment) X X Analog Line Card X X T1/E1/J1 And HDSL X X ISDN X X ADSL X X Cable Telephony X X PBX/KTS And Key Telephone System X X USB X X IEEE1284 Parallel Data Bus The terminology used for PTCs is often similar but not the same as for fuses. Two parameters that fall into this category are leakage current and fault current rating. X X X X X X X IEEE 802.3 X IEEE 1394 I/O Ports PC Card X SCSI Video Port LCD Monitor X Set Top Box Consumer Electronics Temperature Derating Curves Comparing PTCs to Fuses Chart Key C 140 Curve A Thin-Film Fuses and 313 Series (.010 to .150A) 100 B 80 A 60 Medical Battery electronic PERCENT OF RATING Curve B FLAT-PAK®, Telelink®, Nano2®, PICO®, Blade Terminal, Special Purpose and other leaded and cartridge fuses (except 313.010 – .150A) B X X X X X X X X X X X X X X X X X X X X X X ST LT LR VT Powered Device (PD) X X X Data Pair USB 2.0 USB Port X X X Linear AC/DC Adapter X X X X Portable Electronic Input Port X X X X -20°C -4°F 0°C 32°F 20°C 68°F 40°C 104°F 60°C 140°F 80°C 176°F 100°C 212°F X X (2) V0402MHS03 X 1206L150 D+ D- (2) PGB1010603 (PulseGuard® ESD Suppressor) Signal Ground Shield Ground X X X X X X X X X Lithium Cell Battery Pack Signal Ground Shield Ground IEEE 1394 – FireWire X X X X X X X X X X 1394 Port Tip/Ring circuit – Metallic 1394 Controller RJ11 Connector Tx/Rx Circuits V33MLA1206 VBU Voltage / Current Input Terminal X X 1812L110/33 120°C 248°F 3 TPA+ TPATPB+ TPB- Tip 600R Series 250R Series SMD/leaded SIDACtor® Device Ring (PulseGuard® ESD Suppressor) Shield Ground AMBIENT TEMPERATURE 2 VBUS D+ D- X 20 -40°C -40°F USB Controller V5.5MLA063 VBU X Mobile Phone USB Port USB Controller 1206L150 X Smart Card Reader Shield Ground USB 1.1 X Signal Ground X C -60°C -76°F (3) V5.5MLA0402 (Multilayer Varistor) Data Pair (4) PGB1010603 Curve C Resettable PTCs Control VL X NOTE: The application summary is for reference only. Determination of suitability for a specific application is the responsibility of the customer. 25°C 40 60R X X Electromagnetic Loads, Motor A Battery + V5.5MLA0603 X X Solenoid Protection 120 Battery Controller IC Data Pair X X Loudspeaker Understanding the differences in performance between the two types of devices will make the best circuit protection choice easier. The most obvious difference is that the PTC is resettable. This is an inherent characteristic in which the PTC resets (returns to low resistance state) after power is removed and the device cools down. There are a number of other operating characteristics that differentiate the two types of products. 30R Battery Connector Power Source Equipment (PSE) BATTERY STRAP (AXIAL LEADED) 600R specifications indicates that similarly-rated PTCs have about twice (sometimes more) the resistance of fuses. Temperature (°C) USBR Powered End Station Battery - RADIAL LEADED 2016L Swtich/Hub Data Pair 250R CPU Comparing the time-current curves of PTCs to time-current curves of fuses show that the speed of response for a PTC is similar to the time delay of a Slo-Blo® fuse. (operating) current rating for PTCs can be up to 14A while the maximum level for fuses can exceed 30A. Series Name Li-ion Battery Pack Application RESISTANCE: Reviewing product TIME-CURRENT CHARACTERISTIC: HOLD CURRENT RATING: The hold SURFACE MOUNT Power Over Ethernet Cell Phone FAULT CURRENT: The PTC is rated for a maximum short circuit current at rated voltage. This fault current level is the maximum current that the device can safely limit keeping in mind that the PTC will not actually interrupt the current flow (see LEAKAGE CURRENT above). The typical short circuit rating of a board-mounted PTC is 40A; for battery strap PTCs, this value can reach 100A. Fuses do in fact interrupt the current flow in response to the overload and the range of interrupting ratings vary from tens of amperes up to 10,000 amperes at rated voltage. The application selection guide below should be used as an aid in selecting the proper device for your end application. Please consult the datasheets on www.littelfuse.com for detailed technical specifications. complete protection for the circuit. Contact your location Littelfuse application expert for additional design assistance or visit www.littelfuse.com/PTCs. Outside World AGENCY APPROVALS: PTCs are PTCs are used as circuit protection in applications where sensitive components are at risk of damage from overcurrent conditions. The ability of PTCs to reset themselves after exposure to a fault current makes them ideal for use in circuits that are not easily accessible to a user or technician. Typical applications include port protection on personal computers (USB, Firewire, keyboard/mouse, and serial ports), peripherals (hard drives, video cards, and hubs), cell phone, battery packs, industrial controls, lighting ballast and motor controls. required. The following are typical examples of circuits using POLYFUSE® resettable PTCs in combination with other Littelfuse circuit protection devices to provide Littelfuse offers a full range of battery strap, surface mount and radial leaded resettable PTC devices designed to protect applications where overcurrent protection is Telco Additional operating characteristics can be reviewed by the circuit designer in making the decision to choose a PTC or a fuse for overcurrent protection. Systems Interface) Standard for this large market includes a statement that “....a Positive Temperature Coefficient device must be used instead of a fuse, to limit the maximum amount of current sourced”. When to apply a resettable PTC vs. a traditional fuse is always the choice of the designer or technician but in some cases, PTC’s offer a convenient form of circuit protection to improve the reliability of an application. There is an important area of applications where the use of resettable fuses (PTCs) has become a requirement. Much of the design work for personal computers and peripheral devices is strongly influenced by the Microsoft and Intel System Design Guide which states that “Using a fuse that must be replaced each time an overcurrent condition occurs is unacceptable.” And the SCSI (Small Computer Outside World Overcurrent circuit protection can be accomplished with the use of either a traditional fuse or the more recently developed resettable PTC. Both devices function by reacting to the heat generated by the excessive current flow in the circuit. The fuse element melts open, interrupting the current flow, while the PTC changes from low resistance to high resistance to limit current flow. The graph below shows the response of the PTC device to temperature. Protection is accomplished by limiting the current flow to a low leakage level. Leakage current can range from less than a hundred milliamps at rated voltage up to a few hundred milliamps at lower voltages. The fuse on the other hand completely interrupts the current flow and this open circuit results in no leakage current after it has been subjected to an overload current. PTC Applications Outside World This function is called “tripping” of the overcurrent protection device. TEMPERATURE DERATING: The useful upper limit for a PTC is generally 85°C while the maximum operating temperature for fuses is 125°C. The following temperature derating curves (see chart at bottom of page) that compare PTCs to fuses illustrate that more derating is required for a PTC at a given temperature. have “tripped” when it has transitioned from its low resistance state to a high resistance state due to overload current. Telecom A polymeric PTC (positive temperature coefficient) overcurrent protector is an element placed in series with the circuit or assembly to be protected. The PTC element protects the circuit by changing from a low-resistance to a high resistance state in response to an overcurrent. LEAKAGE CURRENT: A PTC is said to Computer PTC Characteristics and Terminology Signal Ground Signal Ground 4 Selection Process 1. that the circuit parameters do not exceed these ratings. Determine the following circuit operating parameters: 4. Verify that the ambient operating temperature within close proximity to the device is within its normal operating range. Thermally derate IHOLD and IMAX as necessary. See equation below. • Normal operating current – IHOLD • Maximum circuit voltage – VMAX • Maximum interrupt current – IMAX • Ambient operating temperature 2. Select the suitable form factor. 3. Compare the PTC data sheet ratings on littelfuse.com for VMAX and IMAX to ensure IHOLD = IMAX 5. Check that the trip time protects the circuit. 6. Verify that the post trip resistance (R1MAX) of the device is taken into account in the circuit design. 7. Independently test and evaluate the suitability and performance of the PTC in the actual application. Thermal derating factor SURFACE MOUNT 0805L 1206L 1210L RADIAL LEADED 1812L 2016L 2920L USBR 30R International Sales, Distribution and Engineering Facilities: Photos Chip Size 0805 (2012) 1206 (3216) 1210 (3225) 1812 (4532) 2016 (5041) 2920 (7351) Hold Current (IHOLD) 0.10-1.00A 0.125-2.00A 0.05-1.75A 0.10-2.60A 0.3-2.00A 0.30-3.00A 0.75-2.5A 0.9-9.00A Max voltage (VMAX) 15V 30V 30V 60V 60V 60V 16V 30V Max fault current (IMAX) 40A 100A 100A 100A 40A 40A 40A 40A -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C Agency approval cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV RoHS Compliant Yes Yes Yes Yes Yes Yes Yes Yes Lead-Free Yes Yes Yes Yes Yes Yes Yes Yes Operating Temperature Range COMPETITOR CROSS Tyco/Raychem Series nano SMD micro SMD mini SMD mid SMD SMD RUSB RUE Amp Rating NA 0.500-1.50A 0.050-1.50A 0.140-2.60A 0.300-2.00A 0.300-3.00A 0.750-2.50A 0.900-9.00A Max voltage NA 6V 6-30V 6-60V 6-60V 6-60V 16V 30V MF-NSMF MF-USMD MF-MSMD MF-SMDF MF-SM Bourns Series MF-R Amp Rating NA 0.12-2.00 0.05-1.50A 0.05-1.50A 0.55-2.00A 0.300-2.5A NA 0.90-9.0A Max voltage NA 6-30V 6-30V 6-30V 10-60V 6-60V NA 30V PTC Selection Table (cont.) BATTERY STRAP (AXIAL LEADED) 60R North America • Birmingham, Michigan USA Des Plaines, Illinois USA and Irving, Texas USA Technical Assistance Phone: 800 999 9445 847 824 1188 Fax: 847 391 0459 Europe • Dünsen, Germany Phone: +49 4244 8190 Fax: +49 4244 819 139 • Munich, Germany Phone: +49 8955 27660 Fax: +49 8955 276 699 • Utrecht, The Netherlands Phone: +31 30 299 9900 Fax: +31 30 299 9800 NO = Not offered Series Name World Headquarters Littelfuse, Inc. 800 E. Northwest Highway Des Plaines, IL 60016 USA www.littelfuse.com PTC Selection Table Series Name POLYFUSE® PTC SELECTION GUIDE 250R 600R ST LT LR VT VL • Swindon, England Phone: +44 1793 720770 Fax: +44 1793 720771 Photos 0.1-3.75A 0.08-0.18A 0.15-0.16A 1.2-4.2A 0.7-3.4A 1.9-10.00A 1.7-2.4A Max voltage (VMAX) 60V 60/250V 60/600V 15/24V 15/24V 15/20V 16V 12V Max fault current (IMAX) 40A 3/10A 3/2.2A 100A 100A 100A 100A 100A Operating Temperature Range 1.7-2.3A -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C Agency approval cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV cULus, TUV RoHS Compliant Yes Yes Yes Yes Yes Yes Yes Yes Lead-Free Yes Yes Yes Yes Yes Yes Yes Yes • Beijing, China Phone: +86 10 8454 9408 Fax: +86 10 8454 9409 • Shanghai, China Phone: +86 21 5383 8016 Fax: +86 21 5383 7476 • Shenzhen, China Phone: +86 755 8207 0760 Fax: +86 755 8207 0759 • Singapore Phone: +65 6885 9111 Fax: +65 6885 9113 • Yokohama, Japan Phone: +81 45 478 1088 Fax: +81 45 478 1089 • Seoul, Korea Phone: +82 2 6000 8600 Fax: +82 2 6000 8655 • Taipei, Taiwan Phone: +886 2 8751 1234 Fax: +886 2 8751 1177 Central and South America • São Paulo, Brasil Phone: +55 113 835 3780 Fax: +55 113 645 0612 Chip Size Hold Current (IHOLD) Asia/Pacific • Hong Kong, China Phone: +852 2810 5099 Fax: +852 2810 5500 COMPETITOR CROSS Tyco/Raychem Series Amp Rating Max voltage RXE TR250 TR600 SRP LTP LR4 VTP VLR 0.100-3.75A 0.080-0.180A 0.150-0.160A 1.20-4.20A 0.700-3.40A 1.7-13A 1.10-2.40A 2.10-2.30A 16V 60-72V 60/250V 60/600V 15/30V 24V 15/20V 16V MF-R/MF-RX MF-R/250 MF-R/600 MF-S MF-LS MF-LR MF-VS Amp Rating 0.10-3.75A 0.08-0.18A 0.15-0.16A 1.2-4.2A 0.70-3.4A 1.9-9.0A 1.7-2.4A NA Max voltage 60V 60/250V 60/600V 15-30V 15-24V 15-20V 16V NA Bourns Series NA = Not Available 5 FORM NO. EC327-E © November 2006, Littelfuse Inc. Printed in U.S.A. Specifications, descriptions and illustrative material in this literature are as accurate as known at the time of publication, but are subject to change without notice. Research and Manufacturing Facilities: • Arcola, Illinois USA • Des Plaines, Illinois USA • Dongguan, China • Dundalk, Ireland • Dünsen, Germany • Irving, Texas USA • Lipa City, Philippines • Matamoros, Mexico • Piedras Negras, Mexico • Suzhou, China • Swindon, England • Witten, Germany • Wuxi, China • Yangmei, Taiwan Surface Mount Battery Strap Radial Leaded High Voltage Radial Leaded