15-05-2020, 10:57 AM
The nice thing about that IC is that it's self-contained.
Most volume control ICs have a serial interface, so need a microcontroller or similar to generate the control instructions. And that microcontroller also has to deal with the user input and some form of display. No need to worry about any of that with this IC - it's all built in. And it's nice that it includes an output buffer - not all of them do.
The downside of that Maxim part is the low supply voltage, which places a limit on the highest signal level you can handle (about 1.8V RMS). The nominal output level of a CD player at 0dBFS is 2V RMS, but many are higher - I've seen 2.4V RMS, which requires 6.8V rails. This means that an attenuator is required at the input to ensure clipping does not take place, and make-up gain after the IC might be required as a result.
I went through all this some 20 years ago, when I trialled quite a few of the volume control ICs that were available. They all had this restriction to some extent. I got quite close to using the LM1972, which runs from +/-5V (you can push it to +/-6V), and then the CSS310 (but sourcing it was tricky). But luckily, and with very fortunate timing, the PGA2310 was released. This is basically the perfect volume control IC - it runs from +/-15V rails, so no worries about headroom, and no messing about attenuating/amplifying pre/post the IC, with the compromises that brings. It covers a 127dB range in 0.5dB steps, and the serial interface is a simple shift-register type, so dead easy to write the code for.
I wrote it up on my website, and shortly afterwards someone from TI got in touch. At first, I thought I was in trouble for blagging free samples for a personal project (they weren't available to purchase from regular supplies in the UK at that point), but actually, he was delighted that I'd said such nice things about their new chip, and were really impressed with the project, so "thank you very much, and if there's any other ICs you'd like to sample, just drop me a line". That was really nice of them.
The PGA2310 is still in production, and is still available in DIP. They're not cheap - about £20 at the moment, but last time I checked they were more like £10. Still, for the level of performance, that's still good VfM really - you can easily pay £20 for a motorised potentiometer, which won't be as good.
But of course, you need a microcontroller... As I said, the Maxim IC is great for stand alone applications - just so simple to use
Also good to see some activity in the DIY section - one of our quieter bits of the forum, but let's hope that might change
Most volume control ICs have a serial interface, so need a microcontroller or similar to generate the control instructions. And that microcontroller also has to deal with the user input and some form of display. No need to worry about any of that with this IC - it's all built in. And it's nice that it includes an output buffer - not all of them do.
The downside of that Maxim part is the low supply voltage, which places a limit on the highest signal level you can handle (about 1.8V RMS). The nominal output level of a CD player at 0dBFS is 2V RMS, but many are higher - I've seen 2.4V RMS, which requires 6.8V rails. This means that an attenuator is required at the input to ensure clipping does not take place, and make-up gain after the IC might be required as a result.
I went through all this some 20 years ago, when I trialled quite a few of the volume control ICs that were available. They all had this restriction to some extent. I got quite close to using the LM1972, which runs from +/-5V (you can push it to +/-6V), and then the CSS310 (but sourcing it was tricky). But luckily, and with very fortunate timing, the PGA2310 was released. This is basically the perfect volume control IC - it runs from +/-15V rails, so no worries about headroom, and no messing about attenuating/amplifying pre/post the IC, with the compromises that brings. It covers a 127dB range in 0.5dB steps, and the serial interface is a simple shift-register type, so dead easy to write the code for.
I wrote it up on my website, and shortly afterwards someone from TI got in touch. At first, I thought I was in trouble for blagging free samples for a personal project (they weren't available to purchase from regular supplies in the UK at that point), but actually, he was delighted that I'd said such nice things about their new chip, and were really impressed with the project, so "thank you very much, and if there's any other ICs you'd like to sample, just drop me a line". That was really nice of them.
The PGA2310 is still in production, and is still available in DIP. They're not cheap - about £20 at the moment, but last time I checked they were more like £10. Still, for the level of performance, that's still good VfM really - you can easily pay £20 for a motorised potentiometer, which won't be as good.
But of course, you need a microcontroller... As I said, the Maxim IC is great for stand alone applications - just so simple to use
Also good to see some activity in the DIY section - one of our quieter bits of the forum, but let's hope that might change
