The datasheet for the TI TPA3100D2 (a class D stereo power amp) contains a couple of these symbols in the block diagram on page 7:

enter image description here

I'm referring to the dotted circles around schematic lines. The arrows and highlighting were added by me.

The ROUTN, ROUTP, LOUTN, and LOUTP pins that those circles are near are the outputs of the amplifier. The circles are on a line connected to the "SC Detect" area of the fault block. I'm pretty sure that stands for "short circuit detect", since the chip does have that capability.

What are these symbols?

  • 1
    \$\begingroup\$ Usually it hints at a screened cable, but not here ... look where the signal leads ... to the short circuit detector per jp314's answer. \$\endgroup\$
    – user16324
    Dec 31, 2021 at 0:06
  • 1
    \$\begingroup\$ I just found out they fixed their datasheets in the meantime, which I really appreciate. \$\endgroup\$ Jan 1, 2022 at 20:56

1 Answer 1


It means the current is sensed. Likely via current sensing resistors in those lines, or sensing FETs (and combined for push- and pull stages). In an IC it's not likely to be a magnetic (Rogowski coil) sense technology.

Note the datasheet says: "The outputs are fully protected against shorts to GND, VCC, and output-to-output shorts..."

  • \$\begingroup\$ Personally, I'd never use that particular symbol when using a current-sense resistor; I've always felt it implied a non-invasive sensing method, such as a current transformer or Hall-effect/GMR sensor. It certainly could be a Hall sensor in an IC, I have seen that before; I'm not sure if that would be more or less expensive than a trimmed resistor (you have to trim it in an IC, there's too much variance otherwise). \$\endgroup\$
    – Hearth
    Jan 2, 2022 at 18:14
  • \$\begingroup\$ In an IC, it may not be implemented as a resistor at that location; likely it is either a R in the power line ( and GND), or a replica FET. The schematic is just for explanation. \$\endgroup\$
    – jp314
    Jan 2, 2022 at 18:35

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