Table 1

Code	B	C	D	E	F	G	H	J	K	L	N	O	P	S	T
Rated current	0.125	0.2	0.25	0.375	0.5	0.75	1	1.25	1.5	1.75	2	2.5	3	4	5

　　Table 2

Code	e	f	g	h	i	k	m	n	q	r	s	t
Rated current	0.5	0.63	0.8	1	1.25	1.6	2	2.5	3.15	4	5	6.3

　　Table 3

Code	mm	nn	oo	pp	qq	rr	ss
Rated current	7	8	10	12	15	20	25

　　Figure 1 ~ 6
　　Table 4


Code marking method is simple and easy to identify. But it is difficult to find the corresponding rated current from the code. Although this paper gives some examples, but because there is no uniform code to develop rules, sometimes due to the manufacturer is different, it may be the same code that the phenomenon of different rated current. This will undoubtedly increase the difficulty of solving. As for the rated voltage and other parameters and characteristics, can not be directly obtained from the code. If you are buying a new product, you can ask the supplier to provide parameters or related information. If the insurance on the plate to be repaired, it can be based on the actual operating voltage of the circuit, the approximate estimate of the rated voltage. There is another way, that is, by its shape, size, color and code types and permutations, to determine its manufacturers and their products, in order to find the details of the product. But the last method needs to be a lot of manufacturers and product line of the patch insurance, beginners must be repeated practice, accumulate summary to master.
Two, commonly used PPTC self recovery chip fuse identification
PPTC self recovery fuse is the most popular over current protection devices, it has been widely used in computers, LCD TVs, mobile phones, automotive electronics and battery protection and other aspects of the group. PPTC is English Polymeric Positive Temperature Coefficent acronym, meaning the polymer positive temperature coefficient (thermistor). PPTC resettable high polymer matrix material, through a special process with a conductive particle (e.g. carbon black). A crystal like structure of polymers at room temperature, the conductive particles form chains of conductive path in which resistance is very low, so in series in the power supply circuit of PPTC self recovery fuse will not affect the normal operation of the circuit. Once the circuit short-circuit fault, when the current flows through the PPTC self recovery fuse reaches a certain value (trigger current IT), because the fuse fever, the expansion effect of polymer crystal structure will destroy the touch of the substrate, and a conductive path breaking chain conductive particles (referred to as the "trigger"), PPTC suddenly self resistance recovery fuse increases, to avoid the further expansion of the fault, so that the overcurrent protection function. After troubleshooting, the current recovery is normal, the polymer cooling volume shrinkage, and back to the original structure, conductive particles to form a conductive pathway, since the recovery of the fuse is low resistance. PPTC self recovery fuse is called polymer switch (PolySwitch), and the difference is that the fuse fuse, fuse fuse is the "stop" protection, can only be used once; while the PPTC self recovery fuse is actually a "current limiting protection", with "self-healing" function, can be used repeatedly.
The main characteristic parameters of PPTC self recovery fuse are: (1) hold current IH: maximum allowable current is not triggered, it is equivalent to the rated current of the fuse fuse. (2) the trigger current IT: minimum action current, equivalent to the fuse fuse current, but it is "triggered" into a high resistance, rather than fusing. (3) maximum operating voltage Vmax: maximum allowable supply voltage (DC), equivalent to the rated voltage of the fuse fuse. In addition, there is the maximum current Imax, action power Pdtyp, action time Ttrip, etc..
Three, commonly used PPTC self recovery fuse application examples
[example 1] 7 ~ 10 is a common type of PPTC self recovery fuse in the computer main board, the main body is green or dark green. Both of them have a similar letter "X" graphic, that is TYCO company‘s factory factory. See the figure is similar to the code, first by its size according to table 5 to determine if it belongs to the same series, and each patch code found items from the series, the corresponding models and parameters can be obtained. Because the print special symbol is more difficult, so the "code" column in Table 5 are standard with the letter "X" instead of. And similar figure 7 in the upside down to write the number (3), the table can only be used to write the number (3) to replace. Figure 7 self recovery fuse size is 4.5mm x 3.2mm, according to table 5 to determine it belongs to the miniSMDC series, the series of code "3X3" corresponds to the model is miniSMDC030F, parameter 0.30A/0.60A/30V. Figure 10 in the code is "3X3", but the size of a small number (2.5mm * 3.2mm), table 5, the model should be microSMD035F, parameter 0.35A/0.70A/6V. The difference between the two parameters is larger, so pay special attention to the size of the size! The code in Figure 8 is "X3", and to figure 7 is not too much, but the model is miniSMDC300F, parameter 3.00A/6.00A/6V, the difference is large, the search process it can not be sloppy!
[example 2] 11 ~ 13 PPTC self recovery fuse, the main body for the green. In front of the code has a lowercase "B", it is the company‘s factory manufacturer BEL. The model and main parameters are listed in table 6. From table 6 we can see that figure 11 of the self recovery fuse to maintain the current is 1.10A. In the table to keep current 1.10A products three, the maximum voltage were 8V, 16V and 24V, will usually be the minimum voltage according to the conventional 4 digit "0110" label code, two voltage larger only 3 digit "110" and below it charging voltage value (see Figure 11 from Figure 13 and table 6).
[example 3] Figure 14 and Figure 15 of the PPTC self recovery fuse, the main body for the ink green, code for the 3 digit. Code in front of all capital letters "L" and "F" together with the symbol, it is the manufacturer Figure 7 ~ 26


LITTLEFUSE company logo. For the compression of space, not listed the models, code and main parameter table, and the 3 digit code and maintain correspondence between the current directly from the table 6 to check. Table 4 most of the 6 digit code, find out the most in the table when the code in front of the "0", according to the 3 digit code to deal with. As shown in Figure 14 of the PPTC self recovery fuse, code for "260", by the table 6 code "0260" can be found to maintain the current 2.60A. And Figure 15 of the patch, the code is 030, but no code in table 0030 6, then we can according to the law of the table 6 data to determine the patch 030 to maintain the current 0.30A. Here should be noted that because the difference between manufacturers and models, so only correspondence from table 6 to check the 3 digit code and maintain current, trigger current, and the relationship between the 3 digit code can not check its type and maximum voltage. Otherwise it will go wrong!
[example 4] two digital code PPTC self recovery fuse. The 3 and 4 digit code in general and to maintain the current numerical counterparts, so easy to read. The two digit code to make this correspondence is difficult. So some manufacturers will code the "size" of the relationship to break (see Table 7), some manufacturers simply in a series of products inserted into the 3 bit code (see Table 8). Here are a few examples: Figure 16 and Figure 17, the main body for the green, code for 2 digits, code in front of all have a capital letter "F", which is the manufacturer FUZETEC/ company logo. The model and main parameters are listed in table 7. From table 7, we can see that figure 16 of the self recovery fuse to maintain the current 0.10A, Figure 17 of the self recovery fuse to maintain a current of 1.10A. The code "10" and "11" is almost the same, but the two corresponding holding current is l0 times!
Figure 18 PPTC self recovery fuse, the main body is black or dark green. The code has a capital letter "P", which is the identification of the POLYTRONICS company. Their models, codes and main parameters are given in table 8. From table 8 we can see that figure 18 of the self recovery fuse to maintain the power flow 1.10A. Figure 16 and Figure 18 of the self recovery fuse, the code is "10", but the corresponding current to maintain the former is 0.10A, the latter is 1.10A, visible difference between the manufacturers and the logo is also very important!
Figure 19 PPTC self recovery fuse body is brown or brown black, gold plated ends, marked with the character "503Y". This is the BOURNS company MFMSMF series of products, according to the manufacturer‘s instructions, in front of the character "503Y" of the two numbers (50) representative models, called the main code; third digits (3) representing the year 3, in 2003 fourth production; capital letters, that is the factory of the time of the first few years week (A for first ~ second weeks, B for third ~ fourth weeks... Z stands for fifty-first to fifty-second weeks. Figure 20 and figure 21 patch PPTC is MFMSMF series. At first glance, the 4 character label I began reading from either side, but just remember "the first 3 numbers, finally to uppercase", is read out in Figure 20 is "167L", 21 is "026S". The main code "50", "16" and "02" can be judged, figure 19 figure 21 ~ PPTC resettable models are MF-MSMF050, MF-MSMFl60 and MF-MSMF020, the corresponding holding current were 0.50A, 1.60A and 0.20A.
[example 5] 1 digits (or letter) code PPTC self recovery fuse. Figure 22 PPTC self recovery fuse body is brown, gold plated ends, above the standard instrument 1 number "5", this is SEALANG SMD0805 series products. Their models, codes and main parameters are given in table 9. From table 9 we can see that figure 22 of the self recovery fuse to maintain the current is 0.50A.
Figure 23 PPTC self recovery fuse body also is brown, gold plated ends, marked with 1 digit "2" and 1 letters "R", this is the BOURNS company MF USMF series products. According to the manufacturer‘s instructions, the number on the top of the model, the main code; below the letter for the ex factory date (the first few weeks), the specific meaning can be referenced to 3. Their models, codes and main parameters are given in table 10. From table 10 we can see that figure 23 of the self recovery fuse to maintain the current is 0.20A. The horizontal bar below capital letters (R) "-" is "green product", that is, the product does not contain lead and halide[example 6] with the letter as the code of PPTC self recovery fuse. Figure 24 PPTC self recovery fuse, the main body for the green or dark green, above the standard only 1 letters (C), which is the 1206L LITTLEFUSE series of products. Their models, codes and main parameters are given in table 11. From table 11 we can see that the self recovery fuse to maintain the current is 0.20A, the maximum operating voltage is 24V. PPTC self recovery fuse with the letter as the code, generally only a letter. Even if there are two letters, only one is the main code, and the other (mostly in front of the main code) is the manufacturer‘s code. For example, figure 25 of the self re fuse bC. BEL company‘s products, the main code for the C, the model is OZCA0005EF2E, to maintain the current 0.05A, the maximum voltage of 60V. As shown in Figure 26 of the self re fuse FC, FUZETEC company‘s products, the main code for the C, model is FSMD035 - 1206, to maintain a current of 0.35A, the maximum voltage of 16V. For compressed space, this paper does not list the two product series models, code and the main parameters of the relationship table. Figure 24 ~ three of the 26 devices with the same size, code (the main code) is also basically the same, but the main parameters are different. Fortunately, there are manufacturers code can be distinguished.
Through the above examples, I believe we have a preliminary understanding of the patch fuse, but also to experience a variety of small component code. As long as the repeated practice, learning and accumulation of summary, the patch of insurance will be you gradually master.

　　Table 5

型號	代碼	保 持 電流IH	觸 發 電流IT	最大電 壓Vmax
microSMD系列（尺寸3.2mm×2.5mm）
MicroMD005F	X05	0.05	0.15	30
MicroMD010F	X10	0.1	0.25	30
MicroMD035F	3X3	0.35	0.75	6
MicroMD050F	X50	0.5	1	13.2
MicroMD075F	X75	0.75	1.5	6
MicroMD110F	X11	1.1	2.2	6
MicroMD150F	X15	1.5	3	6
MicroMD175F	X17	1.75	3.5	6
MicroMD200F	X20	2	4	6
miniSMDC系列（尺寸4.5mm×3.2mm）
MiniSMDC010F	X10	0.1	0.3	60
MiniSMDC014F	X14（或14×14）	0.14	0.28	60
MiniSMDC020F	2X2	0.2	0.4	30
MiniSMDC030F	3X3	0.3	0.6	30
MiniSMDC050F	5X5	0.5	1	24
MiniSMDC075F	7X7	0.75	1.5	13.2
MiniSMDC075F/24	X075F24V	0.75	1.5	24
MiniSMDC100F	1X1	1.1	2.2	8
MiniSMDC110F	1X1	1.1	2.2	8
MiniSMDC110F/16	X110F16V	1.1	2.2	16
MiniSMDC110F/24	X110F24V	1.1	2.2	24
MiniSMDC125F	X12	1.25	2.5	6
MiniSMDC125F/16	X125F16V	1.25	2.5	16
MiniSMDC150F	X15	1.5	3	6
MiniSMDC150F/12	X150F12V	1.5	2.8	12
MiniSMDC150F/16	X150F16V	1.5	2.8	16
MiniSMDC150F/24	X150F24V	1.5	3	24
MiniSMDC160F	X16	1.6	3.2	9
MiniSMDC200F	X20	2	4	8
MiniSMDC260F	X260F（或X26）	2.6	5	6
MiniSMDC260F/12	X260F12V	2.6	5	12
MiniSMDC260F/13.2	X260F13V	2.6	5	13.2
MiniSMDC260F/16	X260F16V	2.6	5	16
MiniSMDC300F	X30（或X3）	3	6	6
miniSMDE系列（尺寸11.5mm×5.0mm）
MiniSMDE190F	19X19	1.9	3.8	16

　　Table 6

型號	代碼	保  持 電流IH	觸  發 電流IT	最大電 壓Vmax
OZCC0014FF2C	14	0.14	0.3	60
OZCC0020FF2C	20	0.2	0.4	30
OZCC0035FF2C	35	0.35	0.7	16
OZCC0050FF2C	50	0.5	1	16
OZCC0075FF2C	75	0.75	1.5	16
OZCC0075AF2B	075/24	0.75	1.5	24
OZCC0075BF2B	075/33	0.75	1.5	33
OZCC0110FF2C	110	1.1	2.2	8
OZCC0110AF2C	110/16	1.1	1.95	16
OZCC0110BF2B	110/24	1.1	2.2	24
OZCC0125FF2C	125	1.25	2.5	6
OZCC0150FF2C	150	1.5	3	6
OZCC0150AF2C	150/12	1.5	3	12
OZCC0150BF2C	150/24	1.5	3	24
OZCC0160FF2C	160	1.6	3.2	6
OZCC0160AF2C	160/12	1.6	3.2	12
OZCC0160BF2C	160/24	1.6	3.2	16
OZCC0200FF2C	200A	2	3.5	8
OZCC0260FF2C	260	2.6	5	6
OZCC0260AF2B	260/13	2.6	5	13.2
OZCC0260BF2B	260/16	2.6	5	16
OZCC0300FF2B	300	3	5	6

　　Table 7

型號	代碼	保  持 電流IH	觸  發 電流IT	最大電 壓Vmax
FSMD005－1210	5	0.05	0.15	60
FSMD010－1210	10	0.1	0.25	60
FSMD020－1210	20	0.2	0.4	30
FSMD035－1210	35	0.35	0.7	16
FSMD050－1210	50	0.5	1	16
FSMD075－1210	75	0.75	1.5	8
FSMD110－1210	11	1.1	2.2	6
FSMD150－1210	15	1.5	3	6
FSMD175－1210	17	1.75	4	6
FSMD200－1210	21	2	4	6

　　Table 8

型號	代碼	保  持 電流IH	觸  發 電流IT	最大電 壓Vmax
SMD1210P005TF	5	0.05	0.15	30
SMD1210P010TF	10	0.1	0.3	30
SMD1210P020TF	2	0.2	0.4	30
SMD1210P035TF	3	0.35	0.7	6
SMD1210P050TF	5	0.5	1	13.2
SMD1210P075TF	7	0.75	1.5	6
SMD1210P075TF/24	75	0.75	1.5	24
SMD1210P110TFT	10	1.1	2.2	8
SMD1210P150TFT	15	1.5	3	6
SMD1210P175TF	17	1.75	3.5	6
SMD1210P200TF	20	2	4	6
SMD1210P260TF	26	2.6	5	6

　　Table 9

型號	代碼	保  持 電流IH	觸  發 電流IT	最大電 壓Vmax
SMD0805－010	1	0.1	0.3	15
SMD0805－020	2	0.2	0.5	6
SMD0805－035	3	0.35	0.75	6
SMD0805－050	5	0.5	1	6
SMD0805－075	7	0.75	1.5	6
SMD0805－100	0	1	1.95	6

　　Table 10

型號	代碼	保  持 電流IH	觸  發 電流IT	最大電 壓Vmax
MF－USMF005	0	0.05	0.15	30
MF－USMF010	1	0.1	0.3	30
MF－USMF020	2	0.2	0.4	30
MF－USMF035	3	0.35	0.75	6
MF－USMF050	4	0.5	1	13.2
MF－USMF075	5	0.75	1.5	6
MF－USMF110	6	1.1	2.2	6
MF－USMF150	8	1.5	3	6
MF－USMF175X	9	1.75	3.5	6

　　Table 11

型號	代碼	保  持 電流IH	觸  發 電流IT	最大電 壓Vmax
1206L012	A	0.125	0.29	30
1206L016	B	0.16	0.37	30
1206L020－C	C	0.2	0.42	24
1206L025－C	D	0.25	0.5	16
1206L035－C	E	0.35	0.75	6
1206L035/16	J	0.35	0.75	16
1206L050－C	F	0.5	1	6
1206L050/15	M	0.5	1	15
1206L075－C	G	0.75	1.5	6
1206L100	N	1	1.8	6
1206L110－C	H	1.1	2.2	6
1206L150－C	K	1.5	3	6