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I am using LM4670SD/NOPB in my design. The IC is working at 5 V supply.

This IC requires an 8 Ω speaker.

My first question is,

  1. In that case do the lines Vo1 and Vo2 needs a differential impedance of 8 Ω (each line 4 Ω Single ended).

May I know my assumption is correct or not.

My second question about the current carrying capacity of Vo1 and Vo2 lines. In the datasheet page no 4 you can see the power specification as given below.

enter image description here

Considering the maximum power as 3 W from the 5 V rail, I calculated the current carrying capacity of Vo1 and Vo2 as 0.6 A.

May I know is this correct?

enter image description here

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    \$\begingroup\$ the IN terminals are the analogue inputs to the chip ... how are they coming from the microprocessor (microcontroller presumably ...) are you using this to amplify an audio signal? \$\endgroup\$
    – danmcb
    Commented Nov 27, 2023 at 8:36
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    \$\begingroup\$ Please don't add additional questions which invalidates answers and requires updating them. Also you need to provide schematics how the audio would come from "the microprocessor", because it now sounds like you are connecting this IC incorrectly to a microprocessor. Maybe start a new question about that subject. \$\endgroup\$
    – Justme
    Commented Nov 27, 2023 at 8:40
  • \$\begingroup\$ I will add new question. Will delete this edit \$\endgroup\$
    – Confused
    Commented Nov 27, 2023 at 8:46
  • \$\begingroup\$ New question is added electronics.stackexchange.com/questions/690680/… \$\endgroup\$
    – Confused
    Commented Nov 27, 2023 at 10:39

2 Answers 2

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  1. No. Differential impedance is unimportant at audio frequency. Actually this is switching so there will likely be signal at gigher frequencies, maybe 100kHz or so, but still - you don't need to worry about differential impedance until dealing with signals at least in the MHz range at normal track lengths.

  2. If you are running 5V into an 8 ohm load, the absolute maximum current possible is 5/8 or 0.625A. This would only really happen in a fault condition, the real working RMS current under normal operation would be rather less, but if the circuit failed you don't want the board burning so I would personally design for something like 1A minimum. It costs nothing to run thick tracks.

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Audio amplifier does not need characteristic impedance traces. The wavelength is about three orders of magnitude longer than any PCB trace would care about.

Yes, ampacity around an ampere will suffice.

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