TPS922053: LED applictation with "dim2dark" feature by flexible dimming-mode?

Hi Stefan,

Stefan Pawelczyk said:

- dimming feature with "dim2dark" option (down to 0.1%)
- if hybrid dimming, there should be no sightable steps or jumps when switching from PWM to analog mode

Sorry but the minimum dimming ratio of hybrid dimming is 1/(2^8) = 1/256 = 0.4%. Please refer to Section 8.3.5.3 Hybrid Dimming from the datasheet.

However, with flexible dimming or PWM dimming, it is possible to achieve this 0.1% dimming ratio. May I understand what is your target PWM dimming frequency?

Stefan Pawelczyk said:

I just looked at the interesting "flexible dimming" mode, maybe there are any existing applications or example about the kind of controlling the PWM inputs?
I would like to forward this informartions to my software engineer. 

May I understand what applications and examples are you looking for? Are you looking for the design examples in Section 9.2 Typical Application from the datasheet?

Best Regards,

Steven

Hi Steven,

thank you for so fast reply. So it means "hybrid dimming" can only handle 256 steps / 8-bit?
So if we use this mode, can we exspect smooth dimming operation between 0.4-5 %?
We need to avoid sightable steps at LEDs in this dimming range. According datasheet ICswitch from analog to PWM mode @ 12.5%. Are there any cracks or flickering effects while switching from analog to PWM?

For target PWM freqency we need about 2 kHz or better 4 kHz.

Thank you in advance....

Hi Stefan,

You are welcome. Please refer to my comments below:

Stefan Pawelczyk said:

So it means "hybrid dimming" can only handle 256 steps / 8-bit?

Yes.

Stefan Pawelczyk said:

So if we use this mode, can we exspect smooth dimming operation between 0.4-5 %?

Yes. You can expect that.

Stefan Pawelczyk said:

We need to avoid sightable steps at LEDs in this dimming range. According datasheet ICswitch from analog to PWM mode @ 12.5%. Are there any cracks or flickering effects while switching from analog to PWM?

No.

Stefan Pawelczyk said:

For target PWM freqency we need about 2 kHz or better 4 kHz.

I think for PWM dimming mode, it will be possible to achieve 0.1% minimum dimming ratio with 2kHz or even 4kHz PWM dimming if you design the external components appropriately. For flexible dimming mode, it should be easy to achieve this, even with 4kHz EN/PWM pin input.

Best Regards,

Steven

Hi Steven,

thank you very much for your support. We made some test now for "hybrid dimming mode" and i got questions....
can you tell me how many of the 256steps are devided into analog dimming range 12.5 to 100% and pwm dimming range 0.4-12.5% ?  Since we want to use the IC as "buck" version, with 24VDC input, how many white LEDs can driven then, 6 pcs. is possible? Our LED current is at maximum 1A.

Additonal we like to know if there are any calculators (as application or online version) which helps to dimensioning the parts value for inductor, capacitor and else?

For another project we don´t  need automotive cert. and got LED currents about 300mA.  Important is the analog dimming feature down to 0.4%. For this you maybe can suggest some other LED IC?   

Thank you in advance for you help.

Hi Stefan,

Stefan Pawelczyk said:

can you tell me how many of the 256steps are devided into analog dimming range 12.5 to 100% and pwm dimming range 0.4-12.5% ? 

I need to check this point with our design team. However, our team is currently celebrating Chinese New Year and is out of office. I will reply to you about this point after Feb.18 when our team is back to office. Thanks for your understanding.

Stefan Pawelczyk said:

Since we want to use the IC as "buck" version, with 24VDC input, how many white LEDs can driven then, 6 pcs. is possible? Our LED current is at maximum 1A.

That will be based on the forward voltage of your LED. This E2E thread should give you some idea on the maximum LED string voltage and therefore the maximum number of LEDs TPS92205x can drive (Although that thread is for TPS922055, my answer there applies to all TPS922055 / TPS922054 / TPS922053 / TPS922052).

Stefan Pawelczyk said:

Additonal we like to know if there are any calculators (as application or online version) which helps to dimensioning the parts value for inductor, capacitor and else?

We are going to publish the calculation tool on ti.com later. But if you need it now, you can send me an e-mail and I can share with you my prototype version. By the way, Section 9.2 Typical Application from the datasheet should give you some idea on how to design the external components for TPS92205x.

Stefan Pawelczyk said:

For another project we don´t  need automotive cert. and got LED currents about 300mA.  Important is the analog dimming feature down to 0.4%. For this you maybe can suggest some other LED IC?   

May I understand what is your input voltage and LED (string) voltage? Do you only need analog dimming as your dimming method?

Best Regards,

Steven

Hi Seven,

thank you for helping for dimensioning the part values.....you sais i should send you a e-mail, so plese let me know your e-mail adress for further details.

Hi Stefan,

I just sent you a friendship request on this E2E forum. I will then provide my e-mail address through private message after you accept the friendship request.

Best Regards,

Steven