AnsweredAssumed Answered

ADPD105 minimal LED current

Question asked by jj. on Sep 23, 2016
Latest reply on Sep 23, 2016 by Buckley

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?

 

 

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