Datasheet
DHC Circuit
VREF
Regulator
VCC
LM3463
DRn
GDn
SEn
GND
IOUTADJ
VREF
REFRTN
RIADJ1
RIADJ2
RISNSn
To LED
Cathode
LM3463
www.ti.com
SNVS807A –MAY 2012–REVISED MAY 2013
Overview
The LM3463 is a six channel linear current regulator which designed for LED lighting applications. The use of the
Dynamic Headroom Control (DHC) method secures high system power efficiency and prolongs system operation
lifetime by minimizing the power stress on critical components. The output currents of the LM3463 driver stage
are regulated by six individual low-side current regulators.
The current regulators are accompanied by a high precision current sensing circuit. In order to ensure excellent
current matching among output channels, the current sensing inputs are corresponding to a dedicated reference
point, the REFRTN pin to insulate the ground potential differences due to trace resistances. With this current
sensing circuit, the channel to channel output current difference is well controlled below ±10% when the output
current is reduced (DC LED current reduction) to 5%.
LED Current Regulators and Analog Dimming Control
The LM3463 provides six individual linear current regulators to perform LED current regulation. Each current
regulator includes an internal MOSFET driver and error amplifier and an external MOSFET and current sensing
resistor. The output current of every output channel is defined by the value of an external current sensing resistor
individually. The reference voltage of the regulators can be adjusted by changing the bias voltage at the
IOUTADJ pin.
When analog dimming control applies, the output current of all channels reduces proportional to the voltage
being applied to the IOUTADJ pin. Figure 18 shows the simplified block diagram of a current regulator.
Figure 18. Block diagram of a linear current regulator
Since the driving current of a LED string is determined by the resistance of the current sensing resistor R
ISNSn
individually, every channel can have different output current by using different value of R
ISNSn
. The LED current,
I
OUTn
is calculated using the following expression:
(1)
AND since:
(2)
Thus,
(3)
Copyright © 2012–2013, Texas Instruments Incorporated Submit Documentation Feedback 13
Product Folder Links: LM3463