This week’s EYE ON NPI (video) is in a category of its personal, it’s Richtek’s RT9120S Collection Class-D Audio Amplifier with DRC Management, a robust amplifier with a large working voltage vary, excessive effectivity, excessive wattage and plenty of supported enter codecs.
We love I2S audio amplifiers right here, they’re an enormous step up from PWM + analog amplifiers in that you’ll get a lot greater audio high quality because of having true analog output and the DAC being tuned for 16, 24 or 32-bit audio. Most straightforward PWM is possibly 8 or 10 bits! So long as your microcontroller or microcomputer has I2S output assist, you need to use 3 or 4 pins to generate a bitstream of audio.
For instance, our Stereo Bonnet provides two single-channel I2S amplifiers to the Raspberry Pi in order that it could possibly drive 3 Watt audio system.
However what should you want extra MOAR energy? That is the place this I2S amp will shine: it could possibly deal with as much as 30W per channel, stereo, and better of all it doesn’t require an MCLK enter sign so it is going to work nice on Raspberry Pi computer systems of any dimension – though in fact it is going to work on different microcontrollers and microcomputers as nicely. Let’s have a look and a few of the options we like on this chip.
Very first thing to notice is that there are a number of choices within the RT9120 household: the RT9120 is the unique, the RT9120S is an improve – it could possibly now assist 30W as a substitute of 20W due to an RDS(on) as little as 90 mΩ and has 94% effectivity over 92%. It does appear to be pin appropriate, so should you’re utilizing the non-S model this should be pin-compatible for an improve.
This amp is Class D, which suggests should you’re used to class AB amps that require large heat-sinking, you’ll be please to know you’ll be able to probably get away with out requiring a heat-sink – though you’ll in all probability desire a large again floor aircraft and a couple of ouncescopper to assist dissipate by way of the thermal-package floor pad.
The commerce off is you’ll need some passive elements on the output of the amplifier, as a result of it generates a excessive frequency – as much as 1.5MHz – PWM sign that must be filtered right down to 10-20KHz. It seems like this amp can use easy ferrite bead + capacitor outputs, however for the very best EMI filtering and sound, a 10uH + 0.47uF capacitor is required for every ‘leg’ of output.
As this can be a highly effective amp, and since individuals will need to play it loud, and also you’ll need to keep away from nasty clipping, the RT9120 additionally options Dynamic Vary Compression which is able to slowly flip down the acquire because the sign will get louder, so that you simply don’t get sq. wave distortion.
Lastly, you’ll need to manage the chip over I2C, it isn’t free-running. Nonetheless, this implies you’ll be able to allow filters, change the Class D frequency, alter the acquire digitally as a substitute of decreasing the sign depth, and get an error output report back to know if there’s a brief or open on the audio system, or lacking I2S sign traces.
Nonetheless, should you’re utilizing a Linux-based system there’s already a Richtek-authored kernel driver you need to use.
Sounds good? I believe so! And the truth that the Richtek RT9120S Collection Class-D Audio Amplifier with DRC Management is in inventory proper now at DigiKey for fast cargo at a really good worth is music to my ears.
You can too decide up an eval board for a really affordable worth which is able to get you began rapidly, significantly if it is advisable implement an I2C driver. Order immediately and DigiKey will ship your order immediately, it is possible for you to to start out including booming high quality sound to your design by tomorrow afternoon.
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