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PSoC™ 5, 3 & 1 Forum Discussions

user_1665606
Level 2
Level 2
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I'm working on a project where I need 8 DC and AC (below audio range) voltage sources. The voltages are then converted to an appropriate range. The audio CODEC I wanted to use (8 out, 6 in) is expensive and I was wondering if PSoC 5LP can source 8 voltage sources? Again, DC and low frequency AC. Thank you fro your kind reply in advance!

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1 Solution

Len,

I believe that Cypress has a KBA on such VDAC->4xSample&Hold

/odissey1

P.S. Found it

Buy One Get Three Free - Making Four VDAC8s from One

The issue I see is combined update rate on all DACs running at 10kHz.

View solution in original post

11 Replies
RodolfoGL
Employee
Employee
250 sign-ins 5 comments on KBA First comment on KBA

You might consider to use Pseudo-DACs using PWM + RC circuit.

We have a component called TrimMargin that uses this technique.

https://www.cypress.com/documentation/component-datasheets/trim-and-margin

I don't know why I didn't consider this. Excellent idea! How many UDPs can I use with PSoC 5LP?

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RodolfoG_11​ I also need a DC source with 5-6 selectable voltage levels, this is perfect!

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user_166,

Can you specify how many AC (<10kHz) and DC (<100Hz) do you need. Also what is the input: USB-MIDI?

/odissey1

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Hi BoTa_264741 , the idea is that MIDI messages (from USB) are converted into varying voltage AC or DC to drive an analog synthesizer IC . For instance, note (pitch) messages from a MIDI keyboard are translated to voltages between the range -4V to +4V. The PSoC 5LP already has 4 PWMs and also has further UDP PWMs and DACs, I presume that's enough.

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user_166,

you can find an example of the PSoC MIDI piano here

Polyphonic piano basic demo using KIT-059 and MIDI Keyboard

It has useful part of receiving control commands from the MIDI keyboard, which you can convert into control voltages V1-V8 for the synth chip.

According to the synth chip datasheet you referenced above, it needs 8x of -4V to +4V control voltages. PSoC can generate only 0-4V output, so an external opamp is necessary to produce -4 to +4V. Manufacturer recommends using external 1x8 sample-and-hold chip to make 8 analog output voltages from a single DAC.  So, basically, your choice is either:  (a) using 8 PSoC DACs + 8 external Opamps, or (b) use single PSoC VDAC8 + one external Opamp + one external sample-and-hold chip.

/odissey1

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odissey1
Level 9
Level 9
First comment on KBA 1000 replies posted 750 replies posted

user_166,

What bit resolution and frequency range do you need?

/odissey1

The frequency range is approx. 0.01Hz to 5-10KHz. The idea is to generate voltage to control an analog synthesizer. DACs could generate LFOs and envelopes for modulation.

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/odissey1,

Could the VDACs be used with a muxed output (at lower frequency response) with an op amp in peak hold mode?

Len

Len
"Engineering is an Art. The Art of Compromise."

Len,

I believe that Cypress has a KBA on such VDAC->4xSample&Hold

/odissey1

P.S. Found it

Buy One Get Three Free - Making Four VDAC8s from One

The issue I see is combined update rate on all DACs running at 10kHz.

/oddisey1,

Thanks.

Len

Len
"Engineering is an Art. The Art of Compromise."
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