We would like to know the horizontal axis of Figure-9.
Fig-10 to 13 were also missing those data.
I retook the image, please see attached. The div for Fig 9 should be 20ms.
Sorry about that. I'll try to find the original oscope picts. If not, I can retake that image. Is it the time from EN to LED current that you are wondering about? The ADD5205 does have a longer EN delay time than our other LED drivers. This is because the PWM to DC current filter needs to gather enough PWM cycles to produce a constant filter output.
- Jon Kraft
Here's the attachment:
Thank you very much for your support.
I got Fig9 horizontal axis was 20mSec/div
and, Fig10 - 13 must be 1uSec/div, right?
May I ask some questions?
>This is because the PWM to DC current filter needs to gather enough PWM cycles to produce a constant filter output.
Could you show us how to minimize start up time?
Does "PWM to DC current filter" mean C_FILTER?
When EN goes low for a moment, it needs 100msec to work again?
The startup time from when EN first goes high to when the LEDs turn on is a fixed internal delay. It is not effected by the C_FILTER value.
If EN goes low for a long time (more than about 100ms), then the LEDs turn off. And if the LEDs turn off, then you will have the 60ms delay if EN goes high again. However, if EN goes low for just a short period of time (<30 ms), then the C_FILTER averages the EN pulses and dims the LEDS to a constant DC current.
Please let me know if you have any other questions.
Thank you very much for your good support.
I got it.
so What's for that 60ms internal delay ?
To initialize output voltage?
I believe that the 60ms delay is to give the PWM filter several PWM cycles to establish the duty cycle. Then, when the LED turns on, it turns on to the correct brightness level. Otherwise, the LED would start at some level, and then quickly change as the PWM filter charged to its correct value.
Thank you for your support.
It might be good that the stable brightness by slow LED current decision.
and it might be suitable for stable brightness at power-on that Vout rises after a brightness setup of LED.
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