LM3463_12 Datasheet, PDF (29/40 Pages) Texas Instruments – LM3463 Dynamic Headroom Controller with Thermal Control Interface and Individual Channel Dimming Control

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PWM
dimming duty
256/256
255/256
254/256
253/256
252/256
5.7V - 0.8V
V_LSB = ₂₅₆
6/256
5/256
4/256
3/256
2/256
(Skipped) 1/256
0
LM3463
SNVS807 – MAY 2012
Analog voltage
at the DIMn pin
Figure 18. Conversion characteristic of the analog voltage to PWM dimming control circuit
Using Less than Six Output Channels
If less than 6 output channels are needed, the unused output channel(s) of the LM3463 can be disabled by not
installing the external MOSFET and current sensing resistor. The drain voltage sensing pin (DRn), gate driver
output pin (GDn) and current sensing input pin (SEn) of a disabled channel must be left floating to secure proper
operation. The output channel(s) which has no external MOSFET and current sensing resistor installed is
disabled and excluded from DHC loop at system startup while the V_RAIL reaches V_{DHC_READY}.
A total of five output channels of the LM3463 can be disabled. The channel 0 must be in use regardless of the
number of disabled channel. This feature also applies in cascade operation.
Cascading of LM3463
For the applications that require more than six output channels, two or more pieces of LM3463 can be cascaded
to expand the number of output channel. Dimming control is allowed in cascade operation. The connection
diagrams for cascade operation in different modes of dimming control are as shown in Figure 19.
Serial interface mode in cascade operation
In the serial interface mode, the master LM3463 accepts external data frames through the serial data interface
which consists of the DIM01, DIM23 and DIM4 pins and passes the frames to the following slave LM3463
through its serial data output interface (SYNC and CLKOUT pins). Every slave unit shifts data in and out bit by
bit to its following slave unit.
DC interface mode in cascade operation
In the DC interface mode, the master unit accepts four individual analog dimming control signals from external
signal sources (via the DIM01, DIM23, DIM4 and DIM5 pins) and encodes the analog signals into 8-bit serial
dimming control signals. The master LM3463 passes the encoded dimming control signals serially to the
following slave unit through its serial data output interface (SYNC and CLKOUT pins). Every slave unit shifts data
in and out bit by bit to its following slave unit.
Direct PWM dimming mode in cascade operation
Copyright © 2012, Texas Instruments Incorporated
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