[SOLVED] Need help to design led drivers (ZXLD1370)

Hi,

I'm working on the LED Dimming for automotive.

Driver IC : ZXLD1370
Input : 12V
LED cuttent : 100mA (24V)
Boost Mode
PWM frequency (15 Pin) : 1KHz

This noise is generated in the ZXLD1370.

To reduce the noise? Solve other?



ZXLD1370 datasheet
**broken link removed**

not sure what noise you are referring to............

kam1787 said:

not sure what noise you are referring to............

Click to expand...

noisd -> high frequency sounds

shock225 said:

noise -> high frequency sounds

Click to expand...

likely the 1KHz or harmonics thereof from the PWM

use a LC or PI filter on the output

IS YOUR INDUCTOR CURRENT smooth?
Have a look at the voltage across the sense resistance...is it a regular triangle wave?
If not then maybe you have instability.
Sometimes, surface mount inductors cam make noise esp if the inductor current is not smooth.....also maybe the 1khz pwm may be making the inductor coils vibrate and make noise...maybe you need to go thru hole inductor to solve it....ceramic caps can also make noise, but my money os on the inductor....desolder it and solder in twisted pair wire to its pade, and solder a inductor to the end of this twisted pair and see if you still get the noise.

Maybe it is your layout though...maybe you have routed the noisy switching node over the controller...? maybe you need to correct this, or increase the fet series gate resistance to delay the drain voltage transition.

also GI, ADJ TADJ and REF pins....are you sure they shouldn't have a decoupling capacitor connected to them? to ground.

My money is on the layout, or the inductor

shock225 said:

noise -> high frequency sounds

Click to expand...

Details? Voltage ripple or Acoustic noise
How much?

Hi,

Did you manage to solve the problem? I am having the same problem... Anyone ideas?

Kind Regards