The hottest single chip lithium battery protection

2022-08-06
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High integration single chip lithium battery protection solution

at present, lithium batteries are more and more widely used. From portable devices such as, MP3, MP4, GPS, toys to gas meters that need to continuously save data, their market capacity has reached hundreds of millions per month. In order to prevent abnormal conditions such as charging, over discharge and over current from affecting the battery life, lithium battery protection devices are usually used to prevent damage to the battery due to abnormal conditions

the circuit principle of the lithium battery protection device is shown in Figure 1, which is mainly realized by the battery protection control IC, the external discharge switch M1 and the charging switch m2. When the p+/p- terminal is connected to the charger to charge the battery normally, M1 and M2 are in the conduction state; When the control IC detects abnormal charging, turn off m2 to terminate charging. When the p+/p- end is connected to the load and the battery is normally discharged, M1 and M2 are conductive; When the control IC detects abnormal discharge, turn off M1 to terminate discharge

Figure 1: circuit principle of lithium battery protection device

several existing lithium battery protection schemes

Figure 2 is a common lithium battery protection board designed based on the above lithium battery protection principles. The Sotl in the figure encapsulates the control IC, and the sop8 encapsulates the double switch tubes M1 and M2. Since the process of manufacturing control IC is different from that of manufacturing switch tube, the two chips in Figure 2 are manufactured from different process flows. Usually, the two chips are also provided by different chip manufacturers

Figure 2: traditional battery protection scheme

in recent years, there has been a trend in the industry to package several chips together to improve integration and reduce the area of the final scheme. Lithium battery protection market is no exception. The two lithium battery protection schemes a and B in Figure 3 seem to integrate the two chips in Figure 2 into one chip, but in fact their encapsulated internal controller IC and switch chip are still separate from different manufacturers. This scheme only seals the two together, commonly known as "two cores in one"

Figure 3: "two in one" lithium battery protection scheme

as the two chips inside are the main manufacturing bases of Honeywell's characteristic materials and technical groups, the chip actually comes from different manufacturers, and the shape cannot be well matched, resulting in different final package shapes. In many cases, universal packaging cannot be used. This kind of package has a large volume and can not save peripheral components, so this "two core in one" scheme can not actually save much space. In terms of cost, although the cost of two packages is reduced to the cost of one package, the cost advantage is not obvious compared with the traditional two chip scheme because the package is usually large, some are not general-purpose packages, and some need to use the package form of chip superposition in order to reduce the package size

Figure 4 is a true single-chip solution that integrates the controller chip and the switch chip on the same wafer. The switch tube in the schematic diagram 1 of the traditional scheme is an n-type tube, which is connected between b- and p- in Figure 1, commonly known as negative pole protection. Due to technical reasons, the switch tube in Figure 4 can only be changed into a p-type tube, which is connected between b+ and p+, commonly known as positive protection. After completing the protection board scheme with this chip, the user needs to replace the test equipment and concept when testing the protection board. Although this scheme reduces the packaging cost to a certain extent, the chip cost has not been reduced, and there is no real cost advantage when competing with a large number of mature traditional schemes. On the contrary, the concept of positive pole protection, which is incompatible with the traditional scheme, has become a huge obstacle to its promotion

Figure 4: lithium battery protection scheme with positive pole protection

although the "two in one" scheme and single chip positive pole protection scheme above have brought certain advantages to users in terms of scheme area and cost, the advantages are still not obvious. These schemes also bring some disadvantages. Therefore, in the process of competing with mature traditional schemes for customers, the price war can only be fought by reducing the gross profit space. As the true original cost of these schemes has no obvious advantage, with the price reduction of control IC and switch chip of traditional schemes, these "two core in one" schemes or positive pole protection schemes have not been able to shake the market dominance of traditional schemes

in recent years, there have been many new switch chip manufacturers in the market. In order to reduce the cost, the original gold wire is replaced by copper wire when packaging, and the switch is not equipped with ESD protection. Although these products have some differences in performance compared with brand switches, they quickly seize the secondary market because of their cost advantages, and also make a great contribution to the success of the traditional scheme in the market competition with the "two core in one" and positive pole protection scheme

fully integrated lithium battery protection scheme

through a number of independently developed device and circuit patents and unique process technology, Symantec microelectronics integrates the control IC and the switch tube into the same chip, and introduces the world's smallest lithium battery protection scheme xb430x series products. This series of products adopts the traditional n-type switch tube, which is consistent with the negative pole protection principle of the traditional scheme. The protection board manufacturer or battery manufacturer does not need to replace any test equipment or concept. This series of chips is a complete lithium battery protection servo cylinder scheme, which can realize the function of lithium battery protection without any external components. To prevent noise on the VCC line, it is recommended to connect a capacitor between the VCC and the negative terminal of the battery when using xb430x series chips, as shown in Figure 5

figure 5:xb430x series lithium battery protection scheme

xb430x series chips are highly integrated. They not only integrate the traditional control IC and switch tube, but also integrate R1 and R2 in schematic diagram 1 into the same chip. The integrated chip is very small, and the smallest chip can be packaged in the general Sotl package on the market. The chip series switches have very low internal resistance, and the minimum internal resistance can reach 40m? Below, equivalent to the internal resistance of the best switch tube on the market. When the smallest package Sotl is used, the continuous charge and discharge current can reach 2.5 amps without heat dissipation. If the continuous charge and discharge current is greater than 2.5 A, it is recommended to use sop8 package products in xb430x series

xb430x has all the protection functions in the traditional protection scheme: overcharge protection, over discharge protection, over-current protection and short-circuit protection. Moreover, since the control IC and the switch are integrated in the same chip, the control IC can detect the chip temperature of the switch at any time. When the battery is used in high temperature environment for a long time, or the current during charging and discharging exceeds the normal charging and discharging current, but does not reach the overcurrent protection threshold, which causes the chip temperature to be too high, the over-temperature protection function will be started to protect the chip and battery. In addition, the built-in switch tube has ESD protection function, which can greatly improve the yield of the protection board and battery in the processing process

the xb430x internal control IC and switch tube are from the same production process and the same manufacturer, and the most mature and common packaging form is selected for packaging. Therefore, the consistent performance is much higher than the traditional scheme, "two core in one" scheme and positive pole protection scheme

with xb4301 series chips, only two components are required to complete the final battery protection scheme (as shown in Figure 5). Compared with the five components of the traditional scheme, the capacity and efficiency of each Mounter can be increased to 2.5 times of the original. Compared with the traditional scheme, the protection board manufacturer not only does not buy resistors and switch chips, which simplifies the resource chain, but also reduces the solder pads of two resistors and eight solder joints of switch tubes when making the protection board, thus greatly reducing the production cost of the protection board. (end)

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