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TPS92641 Analog dimming

K.Hamamoto
Guru 12155 points
Other Parts Discussed in Thread: TPS92641EVM, TPS92641

Hi

Our customer evaluates TPS92641 with TPS92641EVM. And they modified the EVM to test the analog dimming.

IADJ pin  :  Radj1=10kohm, Radj2=15kohm, VREF pin is opened. And it is connected to the DC supply(3.3V)

CS pin : Rcs=0.33ohm

However the current does not become 0A at 0V. (it is 15mA.)

(0V=0%, 3,3V=100%)

Why does it so? Please give us any advice for this?

Regards,

Koji Hamamoto

  • 0
    TI__Mastermind 25500 points
    Depending on your input voltage, the LED stack voltage, and your switching frequency it is possible that you are hitting minimum on time and cannot reduce the current further. If you reduce the switching frequency (or the input voltage, or increase the output voltage) you should be able to get much lower. But you still may not be able to get all of the way to zero due to offsets, but there is a section in the datasheet titled "Analog Dimming and True-Zero Operation" in the datasheet that describes how to get to 0A.