LM3464 datasheet(11/14 Pages) NSC

11 / 14 page

The total output power of the LED lighting system can be ex-

panded by cascading the LM3464 evaluation boards. In cas-

cade operation, the system involves one master unit and

multiple slave units. Both master and slave units are LM3464

evaluation boards with minor modifications to program the

LM3464 into master or slave modes. The connection diagram

for cascade operation is shown in figure 8. The master unit is

responsible to provide functions as listed in below:

1. Detect rail voltage upon system startup

2. Command slave units to turn on LEDs as its VLedFB volt-

age reaches 2.5V

3. Provide dimming signal to slave units according to the

PWM dimming signal received at its DIM pin

4. Provide dimming signal to slave units according to the volt-

age of its Thermal pin

By default, the LM3464 evaluation board is set to master

mode. To set the board to slave mode, the following changes

to the board are required:

• Remove resistors RFB1 and RFB2

• Connect VLEDFB to VCC

When connecting the master and slaves, the following con-

nections are required:

• Connect the VIN terminal of master and slave units together

and then to the POSITIVE output of the AC/DC power supply

• Connect the PGND terminal of master and slave units to-

gether and then to the NEGATIVE output of the AC/DC power

supply

• Connect the SYNC terminal of the master unit to DIM ter-

minal of the next slave unit in the chain.

• Connect the VFB terminal of master and slave units together

and then to the voltage feedback node of the AC/DC power

supply.

If more than one slave unit is required, the SYNC pin of the

first slave unit should connect to the DIM pin of the next slave

unit to allow propagation of the control signal along the system

chain.

LM3464 bảng dữ liệu(PDF) 11 Page - National Semiconductor (TI)