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UL1642-2005 Datasheet(PDF) 7 Page - Littelfuse |
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UL1642-2005 Datasheet(HTML) 7 Page - Littelfuse |
7 / 8 page 7 c n I , e s u fl e tt i L 12 0 2 © The use of a LoRhoTM SMT PPTC in a Li-ion polymer battery pack The SMT form factor is optimized for Li-ion polymer cell pack construction. Li-ion polymer packs are used for low prole smartphone and tablet applications. The SMT PPTC allows for more efcient high volume manufacturing because the PPTC can be surface mounted directly on the PCM (Protection Circuit Module). Also, in low prole designs, the PCM board is mounted at in the same plane as the polymer pouch. This allows for the lowest prole thickness of the smartphone or tablet design. The low height capability of the LoRhoTM SMT PPTC makes it a great choice for this application. The PPTC can be added to the PCM while maintaining a minimum height prole of the total assembly. When using LoRhoTM SMT PPTCs, some design and application testing aspects must be considered: ● The overall space allocated for SMT PPTC needs to be balanced against the total hold current required. The designer rst needs to determine the maximum continuous current (this includes burst use or peak current use) and the maximum temperature that the PPTC can experience (ambient temperature in the PPTC’s vicinity). ● So, the rst step in selecting the appropriate PPTC is nding out how much current the device can hold at the maximum temperature. The advantage of using a LoRhoTM PPTC is that the device can hold a large amount of current in a relatively small form factor and low prole device. ● Application testing is suggested to verify that the selected PPTC can hold the required current at temperature. Typically, the device is subjected to the required current for 15 minutes, which is enough time to reach thermal stability. If device can hold the current for 15 minutes, then this is one data point that can be used to verify the correct device has been selected. Application Note: Use of Low Resistivity Surface Mount PPTC in Li-ion Polymer Battery Packs ● Holding the device in a tripped state for long periods of time will cause an increase in resistance. ● Any hand soldering may have a signicant effect if not performed properly and therefore is generally not recommended (particularly for SMT components) 4. PPTC devices have two distinct resistance ranges: ● RMIN: the minimum resistance of un-soldered devices ● R1MAX: the maximum resistance of a device at 20°C, measured one hour after tripping or reow soldering at 260°C for 20 seconds. When measuring resistance: ● Always perform the measurement at room temperature. ● Perform measurements at least one hour after any heating process to ensure that the device has cooled thoroughly (soldering, testing, etc.). ● Keep in mind that catalog specications (trip time, hold current, etc.) assume the parts have been mounted on a PCB and the resistance shift has already occurred. Other critical considerations for component selection include: ● Maximum circuit voltage ● Maximum available short circuit current ● Desired trip current and trip time ● Form factor ● Maximum ambient operating temperature ● Normal operating current ● Maximum operating voltage ● Maximum interrupt current |
Similar Part No. - UL1642-2005 |
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Similar Description - UL1642-2005 |
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