LM3463_12 Datasheet, PDF (15/40 Pages) Texas Instruments – LM3463 Dynamic Headroom Controller with Thermal Control Interface and Individual Channel Dimming Control

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LM3463
SNVS807 – MAY 2012
(3)
The above equations apply when V_IOUTADJ is equal to or below V_REF (2.5V). Generally the V_IOUTADJ should not be
set higher than V_REF. Applying a voltage high than V_REF to the IOUTADJ pin could result in inaccurate LED
driving currents which fall out of the guaranteed specification. Figure 2 shows the relationship of V_IOUTADJ and
V_SEn.
0.25
0.20
0.15
0.10
0.05
0.00
01234567
VIOUTADJ(V)
Figure 2. V_SEn versus V_IOUTADJ
Since the analog dimming control interface is designed for slow brightness control only, the rate of change of the
voltage at the IOUTADJ pin must not be higher than 1.25V/sec to allow good tracking of the output current and
changing of the V_IOUTADJ. The voltage at the IOUTADJ pin can be provided by an external voltage source as
shown in Figure 3.
LM3463
External
voltage source V
0V - 2.5V
IOUTADJ
REFRTN
GND
GND
Figure 3. Adjust V_SEn by external voltage
To secure high accuracy and linearity of dimming control, the voltage of the IOUTADJ pin can be provided by a
voltage divider connecting across the VREF and REFRTN pins as shown in Figure 4.
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