TPS922052: How to increase LED current rapidly in the analog dimming mode.

Kazuya Nakai59

Guru 21595 points

Part Number: TPS922052

Tool/software:

Hello guys,

One of my customers is considering using TPS922052 for their new products.

At this moment, they have the following questions.
Could you please give me your reply?

Q1.
They'd like to control LED brightness using ADIM/HD pin only.
Also they'd like to increase LED current rapidly like Figure 9-17 case in the device datasheet.
But the datasheet says on page 15 that the initial change takes approximately 5ms if VREF is 200 mV.
Could you please tell me how to increase LED current rapidly in the analog dimming mode?

Is one of solution to start ADIM/HD signal H/L pulse after 5ms from 1'st ADIM/HD pulse?

Q2.
Do you have any waveforms like Figure 9-17 that show the ADIM/HD signal, SW voltage, inductor current, and LED current?

Your reply would be much appreciated.

Best regards,
Kazuya.

over 1 year ago

0 Steven Li over 1 year ago

TI__Mastermind 23190 points

Hi Kazuya,

Please refer to my comments below:

If the customer wants to accelerate the soft-start (around 5 ms) time, they can use flexible dimming in the way shown in this E2E FAQ - [FAQ] How to get a quick transition of TPS922055 / TPS922054 / TPS922053 / TPS922052 from shutdown into flexible dimming mode? - Power management forum - Power management - TI E2E support forums.
Please refer to Figure 9-6 from the datasheet.

Best Regards,

Steven

0 Kazuya Nakai59 over 1 year ago in reply to Steven Li

Guru 21595 points

Hi Steven,

Thank you very much for your reply.

Could I ask you an additional question?

Q. About the inductor current at timing diagram in the FAQ, does the inductor current increase in a straight line to the target current set by duty ratio of ADIM/HD pin, like the inductor current in Figure 9-17 in the device datasheet after the EN/PWM signal changes from L to H?

Thank you again and best regards,
Kazuya.

0 Steven Li over 1 year ago in reply to Kazuya Nakai59

TI__Mastermind 23190 points

Hi Kazuya,

If you design the circuit components well and follow the procedure in the FAQ mentioned above, you can accelerate the soft-start (around 5 ms) time and let the inductor current rise fast after the EN/PWM signal changes from L to H to generate a current pulse.

Best Regards,

Steven

Power management

Power management forum

TPS922052: How to increase LED current rapidly in the analog dimming mode.