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I need help deciphering a BOM that comes with a particular TI reference design. If you look at "Partlist.rep" in the zip file, it looks something like this [I've edited it down a bit]:

R1          Resistor 0402                 R_270_0402_F                  
R2          Resistor 0402                 R_2_0402_F                                      
R4          Resistor 0402                 R_4K7_0402_G                  
R8          Resistor, 0402                R_0_0402  
L235        Inductor 0402                 L_12N_0402_J                  
L236        Inductor 0402                 L_1N8_0402_S                  
C1          Capacitor 0603                C_1U_0603_X5R_L_6P3           
C2          Capacitor 0603                C_4U7_0603_X5R_K_6            
C4          Capacitor, 0402               C_47P_0402_NP0_J_50           
C121        Capacitor 0402                C_100N_0402_X5R_K_10          
C191        Capacitor 0402                C_10N_0402_X7R_K_25                    
C214        Capacitor 0402                C_22P_0402_NP0_J_50           
C231        Capacitor 0402                C_1P0_0402_NP0_C_50               
C261        Capacitor 0402                C_220P_0402_NP0_J_50          
C291        Capacitor 0402                C_100N_0402_X5R_K_10          
C301        Capacitor 0402                C_1U_0402_X5R_K_6P3

I have some questions about interpreting part names:

  • Resistors: "R_270_0402_F" is a 270 Ohm resistor, 0402 package. But what does the 'F' signify? How about 'G', or the lack of a letter at all? Do these have something to do with tolerances, or type (thick film, thin film, etc.) ?

  • Inductors: "L_1N8_0402_S" is a 1.8 nH inductor in an 0402 package. What does the 'S' indicate? Or the 'J' ?

  • Capacitors: "C_1U_0402_X5R_K_6P3" is a 1 μF capacitor in an 0402 package. "X5R" ("X7R", "NP0") refers to the type/temperature characteristic. The following are educated guesses from reading datasheets: 'K' refers to capacitance tolerance: K = +/-10%, J = +/-5%, C = +/-0.25pF. Am I correct, and what about 'L'? The final number must refer to rated voltage, (10 = 10V, 25 = 25V, etc.) I assume "6P3" mean 6.3V.

Thanks for your help.

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1 Answer 1

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According to wikipedia the letter at the end of the resistor part number is its the MIL tolerance designation. Copied table below:

±5% J

±20% M

±10% K

±2% G

±1% F

±0.5% D

±0.25% C

±0.1% B

This page indicates that the letter is also the tolerance code for inductors.

inductor part number

Unfortunately I haven't got a clue what the extra L for capacitors is for (perhaps ask TI support?).

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  • \$\begingroup\$ I doubt that's it. If it were the case then R4 would be a 2% part, and those are either non-existent or super rare. \$\endgroup\$
    – user3624
    Commented Oct 10, 2012 at 16:59
  • \$\begingroup\$ Also, R1 ("R_270_0402_F") is just a resistor for an LED -- I don't think it would require such a tight (±1%) tolerance. \$\endgroup\$
    – David
    Commented Oct 10, 2012 at 17:14
  • \$\begingroup\$ True, it does seem kind of fishy. Probably another good question to ask TI support. The only other place I could find info on letters for resistor markings was in the resistor value itself (I've seen it used in EIA96 resistors), but that's not usually at the end of the part number. \$\endgroup\$
    – helloworld922
    Commented Oct 10, 2012 at 17:24
  • \$\begingroup\$ @DavidKessner Maybe I just live in a backwards part of the world, but my local electronics shop stocks quite a few 2% resistors and not many 1% (of course, 5% is the most common). This is definitely different from what I see online where 1% is very common and 2% is uncommon. \$\endgroup\$
    – helloworld922
    Commented Oct 10, 2012 at 17:26
  • \$\begingroup\$ @helloworld922 is right on all counts. I got a response from TI: e2e.ti.com/support/low_power_rf/f/156/p/210681/… . 'F' and 'G' do indicate ±1% and ±2% tolerances for resistors, respectively. For inductors, 'S' = ±0.3nH, and 'J' = ±5%. For capacitors, the 'L' appears to have been a ±15% tolerance code used by Murata at one point, between 'K' for ±10% and 'M' for ±20%, which are still in use. \$\endgroup\$
    – David
    Commented Oct 11, 2012 at 15:21

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