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Part Number: TPS61165
Hi TI LED Driver Team,
I'm using TPS61165 for instrument cluster backlight driver and my schematic is as below:
And I'm using 5kHz to dimming the brightness, but when I decrease the PWM duty cycle to near 0.2%, it will enter into Easy-Scale mode sometimes. And the output current is wrong as below: Iout(green), PWM(yellow).
Do you have any commons on this phenomenon? How to avoid this kind of phenomenon? Thanks.
Yes, For TPS61165 ans similiar devices with Easy-Scale Mode, it may trigger Easy-Scale Mode at low dimming frequency or low duty cycle. Here is a detail analysis(take TPS61165 as an example):
The first detection delay time 100us is not very important, because the internal bandgap will enable when it receive a rising edge on CTRL pin, 100us was the safe time for internal bandgap start ready. The 160us calculation results is based on the maximum varivation, may be the corner data for your customer is about 196us, And please considering the worst case as I mentioned to choose the safety dimming frequency.
There are two solution for this question:
1. One is To ensure not to enter EasyScale mode, please make sure CTRL pin is never held low for more than 160us.
2. Another is to increase the PWM frequency, for example above 6.5kHz.
Hope that can help you. Thanks.
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