DAC43701: Cannot generate a constant audible signal

Napoleon Cornejo

Part Number: DAC43701
Other Parts Discussed in Thread: OPA363

Dear sirs:

We are currently working with the DAC43701DSGT in pair + amplifier + speaker to generate medical alarms. We have successfully generated medical alarms following the instructions of the datasheet on pg 48.

However we also want to be able a "buzzer", which is a constant sound at an audible frequency. We do the following procedure:

1. On DAC1 we generate sqr signal:

Reg 0xD1 --> 0xC000

Reg 0xD2 --> 0x0000

Reg 0x25 --> 0x0FFC

Reg 0x26 --> 0x0000

Reg 0xD3 --> 0x0100

2. On DAC2 we generate a constant signal

Reg 0xD1 --> 0x0000

Reg 0xD2 --> 0x0000

Reg 0x21 --> 0x0400

However unlike with the medical alarm, we do not hear any sound produced. Can you advise? Do you have any examples of the sequence (register, value) to generate a constat audible sound?

Thank you.

over 2 years ago

0 Katlynne Jones over 2 years ago

TI__Mastermind 41623 points

Hi Napoleon,

Can you share you schematic?

I believe you would need to configure the DAC2 output with a triangle wave output to hear a constant buzzer sound rather than a constant DAC code.

Best,

Katlynne Jones

0 Napoleon Cornejo over 2 years ago in reply to Katlynne Jones

Prodigy 10 points

Hi Katlynne, I will ask for permission to post our schematic as this is a public forum. What I can say is that the setup is the same as proposed in the datasheet:

It is exactly the same components in the same setup.

The medical alarms sound ok, but trying to generate a constant "buzzer" did not work with the sequence shown in the first post.

0 Paul_Frost over 2 years ago in reply to Napoleon Cornejo

TI__Guru 53773 points

Katlynne will respond tomorrow after the US holiday.

0 Katlynne Jones over 2 years ago in reply to Napoleon Cornejo

TI__Mastermind 41623 points

Hi Napoleon,

I will send you an e2e friend request and you can send me the schematic over a private message.

For the buzzer circuit, do you still have a second DAC channel connected to the shut down pin that is generating a square wave?

Best,

Katlynne Jones

0 Napoleon Cornejo over 2 years ago in reply to Katlynne Jones

Prodigy 10 points

Thanks Kalynne. I've sent you a PM.

0 Katlynne Jones over 2 years ago in reply to Napoleon Cornejo

TI__Mastermind 41623 points

Hi Napoleon,

Thanks for your schematic. Have you been able to measure the square wave output on the output of the OPA363? It looks like the voltage output from the DAC might not be high enough to enable the OPA363 via the enable pin. The OPA363 datasheet says that the enable pin should be 75% of the positive supply which looks like 3.3V based on your schematic:

You shared that you are writing 0x0400 to register 0x21 on the DAC which sets the DAC output to 0.825V. Can you try writing a larger value (at least 0x0C00) and make sure the square wave is seen on the OPA636 output?

Best,

Katlynne Jones

0 Napoleon Cornejo over 2 years ago in reply to Katlynne Jones

Prodigy 10 points

HI Katlynne, thanks for the reply. I will ask for the hardware to be double checked.

However I also want to confirm that the sequence of commands to the DACs is correct for what we want. So assumming that the hardware is set up correctly, is that that a correct sequence to generate a constant sound (buzzer) at an audible frequency?

Thanks.

0 Katlynne Jones over 2 years ago in reply to Napoleon Cornejo

TI__Mastermind 41623 points

Hi Napoleon,

Yes, the sequence looks correct. If changing the output code for the second DAC does not work then let me know and we can continue debugging.

Best,

Katlynne Jones

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DAC43701: Cannot generate a constant audible signal