“With the development of lithium battery technology, the advantages of lithium batteries in energy density, cycle life, charging rate, etc. have become more and more obvious. In addition, lithium batteries do not contain harmful heavy metals, and lithium batteries are widely used in consumer electronics, industrial, automotive and other markets. However, due to the material characteristics, although lithium batteries are very powerful, they are also “squeamish”, and special protection circuits are required to ensure their safe operation.

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With the development of lithium battery technology, the advantages of lithium batteries in energy density, cycle life, charging rate, etc. have become more and more obvious. In addition, lithium batteries do not contain harmful heavy metals, and lithium batteries are widely used in consumer electronics, industrial, automotive and other markets. However, due to the material characteristics, although lithium batteries are very powerful, they are also “squeamish”, and special protection circuits are required to ensure their safe operation.

For the application of multi-cell lithium batteries, Nanxin has launched a stackable 2~5 series lithium battery protection IC SC5550 series products, which are used for multi-series mobile power supplies, outdoor power supplies, energy storage, cordless power tools, sweepers, hand-held vacuum cleaners, and electric scooters. And other products lithium battery safety escort.

SC5550 Product Introduction

SC5550 supports charging overvoltage protection OVP (protection point from 3.0 V to 4.575V optional), discharge undervoltage protection UVP (protection point from 1.2V to 3.0V optional), covering lithium iron phosphate, lithium ion/lithium polymer, etc. A variety of lithium batteries. In addition, the OVP and UVP protection detection delay of SC5550 can be configured through the dedicated pin RDP resistor, which supports users to flexibly configure the protection delay parameters.

Figure 2. SC5550 supports external resistors to adjust OVP and UVP delay

SC5550 Product Advantages

SC5550 supports two-level discharge overcurrent protection, short circuit protection and charging overcurrent protection; supports high temperature and low temperature protection in both directions of charging and discharging, to prevent the battery from being charged and discharged at high temperature or low temperature and affecting the battery life.

Due to vibration or other mechanical stress, the cell connecting wires and NTC wires may be disconnected in a multi-string battery pack. Once disconnected, the cell voltage and temperature detection will be abnormal. SC5550 supports cell disconnection detection function, and supports temperature detection NTC disconnection detection. When it is detected that the cell connection line is disconnected or the NTC connection line is disconnected, the SC5550 will turn off the charging and discharging paths until the error state is restored.

As everyone pays more attention to the safety of lithium batteries, many battery safety standards require batteries to do secondary protection.

On the basis of the above protection, SC5550 integrates OV secondary protection. When the secondary overvoltage protection is triggered, the OVP2 pin will be pulled high from the inside of the chip. This signal can be used to control a three-terminal fuse to fuse the circuit, even when charging and discharging. If the MOS tube fails, the circuit can not be disconnected, and the battery can be protected by the three-terminal fuse. In addition, the signal can also be used as an alarm signal output or indication.

Figure 3. SC5550 Integrated Secondary Protection

If high voltage and high power are required, more than 6 batteries in series need to be used. SC5550 supports stackable design. A single SC5550 supports 2~5 strings of batteries. By stacking 2~3 SC5550s, the number of supported strings can be expanded to 6~ 15S.

Figure 4. SC5550 can support 6~15 strings of batteries by stacking

Multiple strings of batteries are prone to unbalanced cells during use, which affects the service life of the batteries. SC5650, the same series as SC5550, integrates 100mA equalization function on the basis of supporting SC5550. If higher equalizing current is required, an external equalizing circuit can also be expanded by adding a MOSFET.

Figure 5. SC5650 supports internal and external equalization

Epilogue

Nanxin SC5550 series lithium battery protection IC has both comprehensive primary protection (overcharge, overdischarge, charging overcurrent, discharge overcurrent, short circuit, high temperature, low temperature) and secondary protection; both cell protection (electricity Core voltage, current, temperature detection), and protection board system protection (cell connection disconnection, NTC connection disconnection); it can be stacked and balanced, with comprehensive functions and low power consumption, 5uA in sleep state. Working current, so that the product has a longer standby time.