TPS92641: Maximum PWM Dimming Frequency

Hello Nicky,

The TPS92641 can support 50kHz+ dimming. The only issue is how much linear dimming range you need. The higher the frequency you use the more the current rise/fall times will affect linearity, especially at low duty cycles.

However with that input voltage range and a 50V LED stack you would not be able to use a buck converter. You need to have the input voltage higher than the LED stack and buck converters are the only types capable of high speed shunt FET dimming. If you really need that full input voltage range you will need to use a buck-boost type converter that will likely not be capable of 50kHz dimming.

Regards,

Clint

Hello Nicky,

It really depends on what kind of linearity you need or if that matters. Both native PWM dimming and shunt FET PWM dimming can achieve probably 1% or lower, but the linearity will disappear at some point depending on which you use. Where it becomes non-linear also depends on a lot of factors like switching frequency, inductor value (more for native PWM), and input/output voltages. It would need to be tested for a particular application. But usually shunt FET dimming does pretty well at 50kHz in most cases.

Regards,

Clint