Audio Codec info on STM32f469-Disco

Forum|Forum|1 year ago
September 12, 2024
3 replies
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I'm using a STM32F469i- discovery board for developing a prototype & would like to use the Audio DAC feature in it and it is given in the datasheet that one set of pins (15 & 16 in CN12). I checked this discovery board's and also the controller's datasheet but were unable to find any information regarding the resistance of the speaker that can be connected to the pins. Will this pins(15,16 in CN12) be able to comfortably drive a 8 ohm speaker, having watt-rating less than 1 W? Would love to get some insights on this

Cheers, Have a great day

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Best answer by mƎALLEm

@ashutoshr

if I connect a 4 ohms speaker, rated with a power of 1W, I can safely drive the speaker using only STM32f469 since it has a audio codec integrated.

According to the following graph I dressed which is based on the data of the datasheet, you can connect 4 ohm speaker but at 3.3V you cannot exceed ~850mW (by interpolation).

In any case, you need to contact Cirrus Logic for confirmation as its the IC manufacturer: https://www.cirrus.com/support/

Hope I answered your question.

M

mƎALLEm

Technical Moderator

Hello @ashutoshr and welcome to the community,

This something related to the codec itself so need to refer to the CS43L22 datasheet.

According to its document:

For more details you can contact the Codec manufacturer "Cirrus Logic".

W

waclawek.jan

Super User

~~No.~~

~~No pin on STM32 is to be loaded by an 8Ohm load, but with those pins, things get even "worse".~~

I haven't looked at what are pins 15&16@CN12, but I assume you are talking about the DAC output pins, PA4 and PA5.

[EDIT] This was an incorrect assumption, thus rest of my post is moot; see next posts of this thread. [/EDIT]

In fact the DAC has a relatively high output impedance, read datasheet. You can have an internal buffer switched off or on, but even with the internal buffer the output impedance is far higher than needed to drive directly a speaker. And, you can also damage the DAC, if you overload it or abuse in any other way (e.g. ESD).

~~In other words, you need an audio amplifier. One solution could be to use something like PC speakers.~~

JW