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I'm trying to replicate this design and I cannot find the 6K/1% resistor in any online store (Digikey, Mouser). What can I do? the design I'm trying to replicate is this

enter image description here

As per @Huisman request, all the resistors on the board are SMD, it also seems to be a 1005 package

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    \$\begingroup\$ It's a 6K resistor, with 1% tolerance. ATM, Mouser has 15 available, but only Through Hole or Chassis Mount, so please provide required package as well (by updating your question using the edit button) \$\endgroup\$ – Huisman Sep 18 '19 at 19:41
  • \$\begingroup\$ Look on the board as well and verify the size of the resistor, i.e. if it's SMD, what size? \$\endgroup\$ – KingDuken Sep 18 '19 at 19:44
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    \$\begingroup\$ If you can get only E12 values put 10K and 15K in parallel. But they both need to be 1%. (There is a common misconception that two resistors of e.g. 5% give 2.5% accuracy. They do not, neiter in series nor in parallel) \$\endgroup\$ – Oldfart Sep 18 '19 at 19:53
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    \$\begingroup\$ I am wondering why they are pulling the RTX line down to ground with a 6k \$\endgroup\$ – Voltage Spike Sep 18 '19 at 20:15
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    \$\begingroup\$ 6k04 is E96 Standard value and will work just as well. It's the value used in the BPI-M2 Zero forum.banana-pi.org/t/bpi-m2-zero-schematic-diagram-public/4111 \$\endgroup\$ – Bruce Abbott Sep 18 '19 at 20:56
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You can use a resistor combination calculator to find possible combinations of E96 values. 6K is not an E96 value so it will not be that easy to find. The percentage indicates the nominal error. You can use 5900 1% in series with 100 ohms 5%, but generally both should be 1%.

If you use a parallel combination, for one or two, you can stack the resistors manually.

5900 + 100 = 6000 (0 %)

4870 + 1130 = 6000 (0 %)

4530 + 1470 = 6000 (0 %)

4420 + 1580 = 6000 (0 %)

4220 + 1780 = 6000 (0 %)

3740 + 2260 = 6000 (0 %)

3570 + 2430 = 6000 (0 %)

10000 || 15000 = 6000 (0 %)

10500 || 14000 = 6000 (0 %)

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The schematic calls for 6kΩ at 1% tolerance.

That allows a range of actual values from 6kΩ x 0.99 = 5.94kΩ to 6kΩ x 1.01 = 6.06kΩ.

Looking at some distributors' parametric search tools, 5.97kΩ is the nearest adjacent value known to be manufactured.

Of course, a 5.97kΩ 1% resistor would not satisfy the requirement, because at minimum this could be 5.97kΩ x 0.99 = 5.9103kΩ which falls outside the specified range of 6kΩ 1%.

But what about at tighter tolerance? A 5.97kΩ 0.5% resistor would have a range from 5.97kΩ x 0.995 = 5.94015kΩ to 5.97kΩ x 1.005 = 5.99985kΩ. Both these extremes are within the specified range. So a 5.97kΩ resistor is an acceptable substitute for 6kΩ 1%, provided its tolerance is 0.5% or better.

And at the time of writing, 5.97kΩ 0.1% is in stock at Digi-Key in 0402 size, which is more than sufficiently accurate.

This is quite a common trick when filling unusual values in a circuit - sometimes the nominal value you want is not available, but a nearby value is available with a tolerance tight enough to meet the requirements.

A better plan still, however, would be to find the datasheet for the PHY chip and check why this value has been specified. It is likely to be a reference resistor for a bias current or similar, and the chip datasheet will probably give the actual range that is acceptable.

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  • \$\begingroup\$ If you search for "Allwinner ephy_rtx 6k" you'll find a datasheet that specifies the resistance as 6k to ground. No tolerance is specified. If it's a one-off design I'd be happy using the closest E24 value at 1%. Bias current settings are not generally critical at the 1% level. For a commercial / volume product, OP should consult the factory. \$\endgroup\$ – elchambro Sep 19 '19 at 3:45

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