DAC43401: PWM Generation

ReedKacz

Part Number: DAC43401
Other Parts Discussed in Thread: TPS61169

Hi DAC Team,

I am wondering if it is possible to use the DAC43401 as a square wave generator with an adjustable duty cycle. There is a use where the DAC would need to operate the PWM input of a LED driver, requiring >5kHz PWM signal with duty cycles from 0% to 100%.

Is this possible with the built in square wave generation? Is it possible to drive >5KHz outputs with these duty cycles?

Thanks!
Reed

over 5 years ago

0 Paul_Frost over 5 years ago

TI__Guru 53773 points

Hi Reed,

Can you give more detail of the application? I am a bit confused about why you would also need an LED driver as well as the DAC43401? Its external feedback pin allows for simple LED drive features as well.

http://www.ti.com/lit/an/slaa884/slaa884.pdf

Thanks,

Paul

0 ReedKacz over 5 years ago in reply to Paul_Frost

TI__Expert 3462 points

Hi Paul,

This is to drive a 10x LED string (3.4V per LED) that will need a boost converter to generate a 34V supply and then a current sink. A device like the TPS61169 is required to generate the higher voltage. The customer does not have a way to generate the PWM locally. I am hoping that running a I2C line to the LED board would allow a DAC43401 to generate the PWM drive.

Thank you,
Reed

0 Paul_Frost over 5 years ago in reply to ReedKacz

TI__Guru 53773 points

I understand. The square wave frequency is defined as:

SLEW_RATE is defined as:

The frequency is a bit limited. In regards to ≥5kHz the device supports 19.531kHz, 15.625kHz, 13.020kHz, & 11.160kHz (and a few higher frequencies).

Another thought is that you can just use a regular SMPS and then use the DAC43401 as the current sink.

Thanks,

Paul

0 ReedKacz over 5 years ago in reply to Paul_Frost

TI__Expert 3462 points

Hi Paul,

Thanks for the comments. How about the ability to adjust the duty cycle of the PWM? I think this is very close to being able to work for us as long as we can easily slide the duty cycle of the 11kHz output.

Thanks,

Reed

0 Paul_Frost over 5 years ago in reply to ReedKacz

TI__Guru 53773 points

Hi Reed,

The duty cycle is not adjustable, only the high and low voltage levels.

Thanks,

Paul

Data converters

Data converters forum

DAC43401: PWM Generation