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ADP8140 Evalboard current Measurement

Hello allthogether,

i made some experiments with the evalboard ADP8140. I followed the evalboard description. I chose the jumper settings for analog Dimming. Everthing ist o.k. After some tests i want to reproduce, the diagramm in the description for "LED current scaling using DC Voltage at DIM Pin (figure 10 in the description). My measurement setup was to connect the multimeter (current measure) between the testpad (sink current 1) and the AGND PAD. I made analog Dimming and during that, i compared the voltage at "DIM-Pin" with the current (multimeter current measurement). I got a "new" characteristic curve (you can see it in the attachment). After that i changed the measurement setup "correctley" and i saw the right characteristic curve in the diagramm.

My first questions: Can you explain me, which current i measure, by connecting the multimeter (current measure) between "current sink 1Testpad" an AGND in the Evalboard (Low DIM Voltage 0V.. 0,6V has a simular charachteristic curve).

My second questions: can you say me the switching frequency from the controller inside? I suppose 400kHz, because the max PWM frequency is 40kHz with a factor of 10 is 400kHz. I need this value for the exposure time.

greetings and many thanks in advance.

Johannes


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