CC8531 based headset schematic picture,in detail battery charger part

There, in a high lighted area, are elements named "3 port, 0402 package, zero ohm resistor". Could anyone tell me what it is and how can I implement it in my design? But it has 2 terminal in the datasheet. Thanks for your help! (Manufacturer: Koa , Part Number: RK73Z1ETTP )


1 Answer 1


It's likely that this is 3 pads in a row, with the middle one connected to the IC, and the other ones connected to VBUS and GND. This allows you to take a normal 0402 0 ohm resistor and put it on either the left, or the right, connecting the IC pin to either GND or VBUS (or leaving it floating if you install no resistor).

For example, for ISET2, connecting to VBUS means the USB charge current limit is 500ma, while connecting to GND makes it 100ma, and leaving it open disables USB charging.

This is what it would look like connected to GND (resistor is black and white). enter image description here

  • \$\begingroup\$ Sounds like a nightmare for production control, populate left half vs right half of a designator. \$\endgroup\$
    – crasic
    Commented Sep 2, 2020 at 4:08
  • \$\begingroup\$ Nice explanation of how the same circuit board can be assembled differently for different sized batteries. \$\endgroup\$ Commented Sep 2, 2020 at 4:10
  • 1
    \$\begingroup\$ @crasic its not really a huge problem if you have good process control. Its definitely very useful in prototypes and small batch, but also in large batches with long pcb fab lead times \$\endgroup\$
    – BeB00
    Commented Sep 2, 2020 at 4:56
  • 1
    \$\begingroup\$ It does guarantee the placement, since two footprints on the PCB would require manual alignment. You could do some stuff like making one one have a footprint, but then thats extra complication, so i'm not sure theres a perfect way (except having 4 pads, which is what I have done, except that takes up more room). \$\endgroup\$
    – BeB00
    Commented Sep 2, 2020 at 9:03
  • 1
    \$\begingroup\$ especially bizzarre using the top terminal as the output instead of the middle, \$\endgroup\$ Commented Sep 2, 2020 at 9:34

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