BD18377EFV-M Datasheet, PDF (15/32 Pages) Rohm – 12 Channel Constant Current LED Driver IC

BD18377EFV-M
Datasheet
Dimming
Figure 9. Illustration of Calibration and dimming of Output Current describes the relation between calibration and dimming.
The maximum current, IDmax, is set by the reference resistor, REXT. Setting the calibration bits will change the value of the
switched current in the corresponding channel whilst controlling the PWM_B/OEN_B input will modulate the current in all
active channels in the time domain.
PWM is fully independent of the clock signal.
In the example below, D0 and D1 have been calibrated below the maximum current set by REXT while D1 has been set to
less output current than D0. At the same time, brightness of both channels is set by the global PWM_B/OEN_B pin.
The independence between the value of the switched current and the switching duty cycle ensures that calibration changes
will not influence the dimming curve or cause any harmonic distortion. Output to input linearity is ensured by equal rising and
falling propagation delays.
I_D
IDmax
6bit amplitude +REXT
PWM
T=1/fPWM
time
D0
D1
Figure 9. Illustration of Calibration and dimming of Output Current
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TSZ02201-0W1W0C500020-1-2
19.APR.2016 Rev.005