Tool/software:
Hi team,
1) I would like to know how much delay there is between PWM signal hitting the SDIM pin and current passing though the LEDs (the red arrow in diagram below, in terms of ns/us).
Also, 2) what is the maximum frequency of SDIM/SDRV pins? About 5MHz seems to be the upper limit according to my calculations using tSDIM-RIS/FALL; is there any other limitations?
Best Regards,
Yu
Hi Yu,
Please refer to my comments below:
1) If the delay you mention here is the delay between the "SDIM goes high" and "SDRV falling", then there is a parameter t_SDIM-FALL for this delay. Please refer to the datasheet.
If the delay you mention here is the delay between the "SDIM goes high" and "LED current reaches the target value", then it is hard to give a specific value for this delay as this will depend on a lot of factors like your LED forward voltage, output current and your output capacitor (if there is), etc.
2) Normally the frequency of SDIM/SDRV signal will never exceed the switching frequency. Therefore, the theoretically maximum frequency of SDIM/SDRV signal will be lower than 1MHz. However, in practice, this maximum frequency is also limited by other factors like LED forward voltage, output current and your output capacitor (if there is), etc.
Best Regards,
Steven
