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Today, mobile phones, digital cameras (camcorders), PDA, MP3 / 4 ... more and more products are lithium batteries Toshiba PA3191U-1BRS Battery as a power supply system circuit. Focus on the power requirements of battery size should be small, the energy density must be high, and no memory effect, but also repeated use of the advantages of recycling. However, the recent explosion of lithium batteries also occur.

Dong Hwa South Road, Yuexiu District, Guangzhou, 2009.1.30 Lenovo mobile phone shop in lithium battery explosion occurred in the incident, a young man inside the neck artery rupture, died on the spot.

So for the safety of lithium batteries is also drawn increasing attention. Lithium battery protection board select the appropriate chip fuse are extremely important.

1. The composition of a single lithium battery

Lithium batteries mainly by batteries and batteryLaptop Battery protection board composition (Figure 2)

Lithium battery protection panel main functions: (1) over-charging protection, (2) over-discharge protection, (3) over current / short circuit protection

Lithium battery protection panel main components: one, protect IC2, MOSFET3, SMDFUSE

2. A single lithium battery protection fuse panel selection

1, Packaging: According to customer's circuit board decided to try the size of normal size with the 1206/0603.

2, rated voltage: 24V or more

3, rated current: General use of 5A (to take into account in the lithium battery protection fuse panel is 2 times the protection, so

Taking into account the Toshiba PA3285U-1BRS Battery protection of the protection IC to determine the delay time fuse fusing time)

4, cold resistance: 15mΩ the following

5 Safety requirements: UL Certification

6, in line with RoHS requirements, and Halogen-Free requirements

The following give two examples to illustrate the fuse option.

For example, 1: A single-board lithium battery protection circuit shown in Figure 3, the protection IC with SII (Seiko) S8261ACJ, the basic parameters shown in Figure 4. Used in MOS tube BF9028DNJ/BF9028DNJ-A, some parameters shown in Figure 5.

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A: protection circuit is working correctly.

Protection of IC over-current protection principle: current Toshiba PA3384U-1BRS Battery when the discharge current is too large, or short circuit occurs, the protection of IC will be activated off (short circuit) current protection, over-current detection at this time is PowerMOS the Rds (on) as a sensor for monitoring the impedance the voltage drop in the case, if the ratio set by the overcurrent detection voltage is higher then stop discharging.

According to the formula 'V-(over-current detection voltage) = I (discharge current) * Rds (on) * 2' can be calculated discharge current is the minimum amount of protection IC to begin protection.

1: Short circuit protection: The

When the over-current detection voltage 0.9V, MOS tube resistance to take the maximum time, can detect over-current will be minimum. Calculated at this time over-current value of 15A, this time to protect IC protection delay time 320us;

When the over-current detection voltage 1.5V, MOS tube resistance to take the minimum time, can detect over-current will be maximum.

Calculated at this time over-current value of 46.875A, this time to protect IC protection delay time 380us.

Conclusion 1: The demand for Toshiba PA3383U-1BRS Battery fuse blowing time at 46.875A times greater than 380us, in order to ensure the short-circuit protection fuse without prior cases, to protect IC fuse.

B: protection circuit anomalies.

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At this point the protection IC can not play on the short-circuit protection, when the load short-circuit the time needed fuse quick fuse.

To consider the following factors:

Batteries Voltage: 3.8 ~ 4.2V

Batteries Resistance: <150mΩ

Protection Board Resistance: MOS Toshiba PA3107U-1BRS Battery tube fuse resistance + resistance (15mΩ) + PCB board resistance (10mΩ)

Short-circuit load resistance: 0 ~ 100mΩ

To consider the fast fuse fuse, so we consider the minimum short-circuit current, you can calculate the minimum short-circuit current

The value of 11A.

Conclusion 2: This requirement fuse for rapid currents in the 11A fuse.

Composite A, B both cases, this protection board select SARTS0603-F-5.0A to meet the requirements.

For example 2: A board used to protect Li-ion battery protection IC for the MM3177, MOSFET for AO8810

A: We can also protect the IC with an oscilloscope to test their short-circuit protection delay time.

Short-circuit situation: repeated short-circuit test found that the protection IC (MM3177) can play a good short-circuit protection, short circuit delay time 11.4ms. Short-circuit the short-circuit current situation shown in Figure 7 (for each short-circuit tests have found that small changes in delay time, whichever is the larger one), this time testing to short-circuit current of 16.4A.

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According to the test case that this section applied to the protection board battery protection IC (MM3177) is doing the output short-circuit protection to protect Toshiba PA2487U Battery when there is a delay time, from the test run 15A ~ 20A short-circuit current at the time, MM3177 short-circuit protection delay time of 10ms ~ 13ms .

(1) Testing S0603-B-5.0A fuse in the 20A fuse is as follows in Table 1

Specifications Model S0603-B-5.0A Test Date 2007-08-16
Fusing time test (BXC-35A-type Fuse Tester, Tektronix DPO4032 oscilloscope)
Test current time / current characteristic
(20A) 55.2 ms 51.1 ms 57.1 ms 56.2 ms 61.4 ms
56.4 ms 52.9 ms 60.8 ms 51.9 ms 56.7 ms

Table 1

(2) From the test data run S0603-B-5.0A longer than the 20A fuse to protect the first ICMM3177 with current circumstances to protect the delay time (11ms ~ 13ms).

(3) This battery protection board (using the MM3177) on the use of S0603-B-5.0A fuse, can better play a protective effect.

1,2 can be seen from the examples, select a single lithium battery protection IC fuse need to consider short-circuit protection time.

3. Sartre science and technology for lithium battery applications, fuse Reference

Sartre Technology Development Co., Ltd. Nanjing SMD fuse to focus on the development Toshiba Laptop Battery and production, attention to fuse lithium battery market requirements, has introduced S0603-F-5.0A, S0603-BA-5.0A, S0603-B-5.0A, etc. series of applications and single-cell lithium battery fuse, occupy a place in the market. Sartre's customers BYD Li-ion battery, Desai battery, Scud batteries.