DAC63204EVM: DAC63204EVM - Slew Rate and CODE STEP control is not responsive

Ariel Greenbaum

Part Number: DAC63204EVM

Hello,
I'm using the DAC63204EVM with your GUI.
I'm trying to generate a PWM signal. I connected the FB pin to a voltage divider to create VFB=0.5VDD and define the output as a triangle wave
.I've set MH and ML values.
However, when I attempt to adjust the SLEW RATE and CODE STEP, I don't see any response on my oscilloscope.
I'm trying to generate the signal at different frequencies around few KHz (3KHz- 7KHz).
According to the datasheet, I need control over the SLEW RATE to define different frequencies.

Can I achieve this frequency with this DAC?

See My calc below. am I using the formulas correctly?

Parameter	Value	Unit
VDD	5	V
R1	1	Kohm
R2	1	Kohm
Vfb	2.5	V
MarginHVoltage	3	V
MarginLVoltage	2	V
SlewRate	4.00E-06	sec/step
MarginH	2458
MarginL	1638
CodeStep	32	LSB
f	4.88E+03	Hz
Duty Cycle	50.000	%

Thanks,

Ariel Greenbaum

over 2 years ago

0 Katlynne Jones over 2 years ago

TI__Mastermind 42253 points

Hi Ariel,

When you start the triangular waveform do you see the PWM output? If so, you will need to stop the waveform generator, update the CODE_STEP and SLEW_RATE fields, and then restart the waveform generator. You cannot update those controls while the waveform generator is already running.

Best,

Katlynne Jones

0 Ariel Greenbaum over 2 years ago in reply to Katlynne Jones

Prodigy 95 points

Thanks, I will try it.

And to make sure, am I using the formulas correctly?

Ariel

0 Katlynne Jones over 2 years ago in reply to Ariel Greenbaum

TI__Mastermind 42253 points

Hi Ariel,

You are, but we found that there is an error in the formulas from the datasheet for code steps other than 1LSB. It has to do with the rounding when the MH and ML code don't subtract to an even multiple of code step. The corrected equations use a ceiling function to take this into consideration:

I made an excel calculator that implements these formulas with your parameters from above:

SmartDAC Frequency Calculator.xlsx

Best,

Katlynne Jones

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DAC63204EVM: DAC63204EVM - Slew Rate and CODE STEP control is not responsive