I am looking at the data sheet for the iC-NZN N-type laser diode driver.


What does the marked symbol stand for?

It appears in a number of places, always marking IO pins. My guess would have been that it is a current limiter, but then why not just draw a resistor...

  • \$\begingroup\$ Who provided the diagram? Did they provide a legend? Somewhere? \$\endgroup\$ – Solar Mike Aug 5 '18 at 9:13
  • \$\begingroup\$ I have never seen this symbol on a IC data-sheet before but on circuit before but on circuit diagrams for a PCB it is often used as a net-tie or star-point where to signals are routed separately then joined together at a single point. \$\endgroup\$ – Warren Hill Aug 5 '18 at 9:16
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    \$\begingroup\$ The symbol will normally be used for a current source. \$\endgroup\$ – keffe Aug 5 '18 at 9:18
  • \$\begingroup\$ @solar-mike I posted the link to the datasheet. It is issued by the manufacturer of the IC. \$\endgroup\$ – polwel Aug 5 '18 at 9:43
  • \$\begingroup\$ @Mathias They draw current sources the usual way (see just left of the CIS pin in the image I posted). A current source makes no sense in this context. \$\endgroup\$ – polwel Aug 5 '18 at 9:43

Here, it is only used for connections to power and ground.

I would guess, it is a low inductance connection with multiple wirebonds with the same effect as Litz wire. This is of great benefit to reduce ringing in pulsed lasers.

It is similar to a shielded signal but without a flat line below the circle.

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  • \$\begingroup\$ Makes sense to me, thanks. Bonus question: why would I prefer to use such a presumably low-L connection to GND through the IC, rather than just large trace on the board? I am specifically talking about the RGND pin, not shown in the image I posted. \$\endgroup\$ – polwel Aug 5 '18 at 11:22
  • \$\begingroup\$ The RGND is not used for pulsed laser current so requirements are lower frequency noise and lower DC current over DC return. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 5 '18 at 11:43
  • \$\begingroup\$ Exactly, that's my point. It seems to me I could do the same, but better, with a separate trace. \$\endgroup\$ – polwel Aug 5 '18 at 11:47
  • \$\begingroup\$ CLDA needs low L connections to LDA and AGND to lower impedance (L/C) and raise resonant frequency ^2 =1/(LC) \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 5 '18 at 11:54

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