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ADPD105 minimal LED current

Based on the document: 
http://www.analog.com/media/en/technical-documentation/data-sheets/ADPD105-107.pdf (page 45) the equation for LED current setting is:
LED3PEAK = LED3COARSE × LED3FINE × LED3SCALE

where:
LED3PEAK is the LEDX3 peak target value (mA).
LED3COARSE = 50.3 + 19.8 × (Register 0x22, Bits[3:0]).
LED3FINE = 0.74 + 0.022 × (Register 0x25, Bits[15:11]).
LED3SCALE = 0.4 + 0.6 × (Register 0x22, Bit 13).

So the minimal LED current is 50.3 x 0.74 x 0.4 = 14.88 [mA] but on the first page of this document there is information "Three 8 mA to 370 mA LED drivers". Additionally, on Figure 13 (page 14) you can find that the minimal LED current is +/- 29 mA, so after scaling 40%(LEDSCALE=0.4) the final minimal current should be about 11.6 mA. Do I miss something or there are some inconsistencies 
in this document? Is it possible to get 8 mA LED current?

  • Hi jj,

    Good point. It appears that the references you make to lower LED currents, e.g. 8mA, are carry-overs from the previous device in this family, the ADPD103. The LED current for the ADPD105/107 should be calculated using the equations you referenced from pg 45 of the datasheet. If you require lower LED currents than the ADPD105 can provide then you would want to use the ADPD103 as long as the 103 can achieve the performance you require. 

    Regards,

    Kevin