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ADP8866 Output Current for each LED channel

Question asked by sdesai on Jul 11, 2018
Latest reply on Jul 18, 2018 by Jon.Kraft


I am trying to match the current I observe the ADP8866 draw versus the expected current (obtained from Register Settings). There are 8 LEDs total connected to the ADP8866. 2 Blue LEDs(D1,D2: Part Number:SMS1105BWC) and 6 white LEDs (D3 to D8, Part Number: NSSW304GT-HG). I am turning ON one LED at a time and measuring the current the ADP8866 draws. (Current is measured by reading the voltage across a 100milliOhm resistor connected between VCC and Vin of the chip). 
Observed current values:

SET A:

Register settings: Reg0x06 = 0x04, Reg0x07 = 0x04 (20.8mA), Reg0x08=0xff, Reg0x23 to 0x2B = 0x4F

Observed Currents: Blue LEDs = 15.92mA White LEDs: 9.13 to 9.32mA

SET B:

Register Settings: Same as SET A except: reg0x06 = 0x01

Observed Currents: Blue LEDs = 8.9 or 9.3mA White LEDs: 8.9 or 9.3mA

 

For SET B I can work out that I set 20.8 mA using LEVEL_SET bits (reg0x07 = 0x04) and using TABLE39 in the datasheet for a DAC Code of 4F and a full scale of 25mA current to be expected should be about 9.67mA. But I cannot figure out SET A

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