LT3754IUH Просмотр технического описания (PDF) - Linear Technology

Номер в каталоге

Компоненты Описание

производитель

LT3754IUH

16-Channel × 50mA LED Driver

Linear Technology 

LT3754

Block Diagram

SHDN/UVLO

13

+

600k 1.476V –

12

VIN

11

INTVCC

7V(REGULATED) UVLO(+) = 3.8V, UVLO(−) = 3.4V

R

S

VC

SLOPE

OSC

REF

1.485V

PWM

27

31 VREF

CTRL

29

INTVCC_UV

VIN_UV

SHDN_UV

4.2V(+)

3.7V(−)

1.485V

EN

EN

6V

1V

+++–

LED CURRENT

CONTROL

CHANNEL X

LED

LOGIC

–

+

1.1V

LED AMP

52mV

PEAK

CURRENT

SOFT

START

SS

OVERVOLTAGE

AMP

Q

GATE 10

EN

SYNC 15

RT

25

100mV

OVER

CURRENT

HICCUP__MODE

SENSE 9

VOUT 16

LEDx

1-8, 17-24

FAULT

14

EN

PWM

56R

VPTAT

TSET

30

ISET

32

EXPOSED PAD (GND)

33

VC

26

R

OVPSET

28

3754 BD

Figure 1. LT3754 Block Diagram

Operation

The operation of the LT3754 is best understood by referring

to the typical application circuit on the front page and the

Block Diagram in Figure 1. The LT3754 drives 16 strings

of LEDs by using a constant switching frequency, current

mode boost controller to generate a single output voltage

VOUT for the top (anode) of all LED strings. LED string

current is generated and controlled by connection of the

bottom LED in each string (cathode) to a current source

contained in each corresponding LED pin. Each LED pin

contains an accurate current sink to ground, programmable

between 10mA to 50mA using a single resistor at the ISET

pin. LED channels can be paralleled to achieve higher LED

currents. For applications requiring less than 16 strings

of LEDs, channels can be paralleled or disabled (connect

LED pin to VOUT before start-up). For optimum efficiency,

VOUT regulates to the lowest possible voltage allowable to

maintain regulated current in each LED string. Any OPEN

LED fault is indicated by the FAULT pin driven low without

effecting the operation of the connected LED strings.

The Block Diagram in Figure 1 illustrates the key functions

of the LT3754. It can be seen that two external supplies,

VREF and INTVCC, are generated by the LT3754. The VREF

pin provides a precision 1.485V output for use with external

resistors to program the CTRL, OVPSET and TSET input

pins. The INTVCC pin provides a regulated 7V output to

supply the gate driver for the boost controller GATE pin.

An accurate 1.476V threshold on the SHDN/UVLO pin

combined with a SHDN/UVLO pin current hysteresis allows

a programmable resistor divider from VIN to SHDN/UVLO

3754fc

9

Share Link: