TPS61165: I can't enter in PWM mode

Hi,

Proper engineer has been assigned to take a look at this and will reply you soon.

Due to Chinese new year holidays, response maybe delayed.

Thanks for your understanding.

Regards,
Kenneth

Hi,

The frequency of CTRL on the picture is 100kHz. I have tried too at 20kHz and it is the same behaviour.

Hi
I suggest you use 5kHz, I have met some several case that came into ES mode under low dimming frequency. What 's your duty and could you give detail description on your application.
Regards
Sean

Hi,

Thanks for your help.

TPS61165 is used for a backlight managed by a Linux kernel.

I think I have found a solution. If I power up manually with PWM pin = 0V and after few hundred ms I send a square at 100kHz or 5kHz on PWM signal the dimming is done. Otherwise is PWM signal is not to ground, I backlight keeps off.

Problem seems to be that PWM signal need to be low during few ms after power up (or enable active). I am trying this solution in few days and I am coming back to post result.

Hi,
Is there any update? Have you solved this yet?Thanks.
Regards
Sean

I need to check a solution tomorrow with our device.

I will give some feedback to you as soon as possible.

Best regards

Hi
Is there any update?
Regards
Sean

Hi, 

If I needn't PWM,I just want to the LEDs to work full, can I pull the Ctrl pin up all the time?

Brs,

Ren

Hi Ren,
Sure, you can pull up CTRL all the time, that means 100% duty cycle.
Regards
Sean

Hi Sean,
According to the SPEC of tps61165 ,we know Iled=200mv/Rset,so when the resistor is equal to 5 ohms, the current should be 40ma, but after measurement, the current can reach about 100ma, and when I lower the input voltage, the current will become larger,I'm so confused.

Hi Ren,
You' d better upload your schematic and LED configuration, I need to check the schematic first.
Regards
Sean

Hi Sean,

The picture is the schematic,I want LEDs to work at current and voltage conditions like this.,V(per LED)=5.6v,I(per LED)=43ma.I'm using 3 LEDs in series.

Hi Ren,
You need to remove C216, this add a another pole in the control loop and it will affcct our loop.
Regards
Sean

Hi Sean，
Thank you for your help,Sean.I will try.I have another question I‘d like to confirm with you.If Vin=12v,the load is 2 LEDs（Vper led=3.3v） in parallel,does the chip not work properly?I've tried this before and found that FB voltages can reach 400mv.
Brs
Ren

Hi Ren,
No, TPS61165 is a boost topology, when Vin is larger than Vout, it can't work properly.
Regards
sean

Thank you so much!Sean.