TPS92512: 1 series LED reguration

Hi, Sorry for delayed reply. Thank you for your support. They are starting to design the schematics. So they have a couple of thing to make sure.

- Which is the better input voltage for Vf=2.0V, 5V or 12V? They want to use 10uH inductor and to set fsw=around 500kHz. They are thinking the consideration are the minimum on time and the inductor ripple current.

- How much is the variation of VINuvlo at over operating temperature range? They don't need gurantee. They will use it as reference.

- According to datasheet, the minimum UVLO setting is recommended 4.5V. Why is it recommended 4.5V?

- They need ON/OFF control by external signal. What the difference of ON/OFF control, by UVLO pin and by PDIM pin?

- According to the datasheet, the recommended dimming frequency range is 100Hz to 1kHz. Why is this range recommended? They want around 5kHz under the following dimming condition. Can the IC allow 5kHz dimming frequency at their condition?
     Dimming condition
       Dimming range=20% to 100%
       Resolution=interval of 10% (20%, 30%, ... 90%, 100%)
       Accuracy=they allow rough accuracy

- They are considering switching analog dimming and PWM dimming while the IC is operating. Are there any concerns about this usage?

- They are concerned about the reverse voltage input to LED. Are there any recommended circuits of reverse polarity protection for LED?

Best Regards,
tateo

Hello Tateo,

To answer your questions:

-The input voltage really depends on what you need. Minimum on time is a consideration given the same switching frequency. So you will have more analog dimming range with 5V if that is a concern. But if you don't need the maximum analog dimming range possible (it will still have decent range with 12V) I would recommend using 12V. At 5V you do not have as much BOOT voltage as it cannot charge to maximum, so at 12V you will have better switch gate drive and probably a little better PWM dimming range.

-The typical variation for VINuvlo is likely to be around +/-20%.

-As mentioned above when the input gets below the BOOT regulation voltage you start reducing the switch gate drive capability. The 4.5V minimum recommendation stems from that, it starts losing performance below that.

-The difference between UVLO and PDIM is that pulling UVLO low will put the part in a low power shutdown mode. PDIM keeps the part alive but just stops the device from switching.

-The recommended range is really just the range where you can get a lot of range. If you only need to dim down to 20% then it should work fine at 5kHz considering you do not need extreme accuracy and range.

-They can be used fine at the same time while the IC is running.

-I'm not really sure about reverse polarity protection. Don't some LEDs come with that built in? You could implement an output over-voltage protection perhaps if that would help.

Regards,

Clint

Hi, Sorry for delayed reply. Thank you for your kind support. They are considering using the IC at the below condition.

Vin=12V
Vf=2.0V(typ) / 2.5V(max)
If=0.8A
PWM Dimming=5kHz (20% to 100%, interval of 10%)
fsw=570kHz
L=10uH

They are concerned the inductor ripple current will be big. Are there any concerns for that?

Best Regards,
tateo