LT3003

8

3003fa

currents to nano amp range ~10µs after PWM low edge.

This preserves the output capacitor voltage and results

in higher PWM dimming ratios.

Buck-Boost Mode: PWM Dimming

The LT3003 can also perform PWM dimming in buck-boost

mode. The buck-boost configuration requires the PWM

and SHDN pins to be tied together. This configuration can

support up to a 2000:1 PWM dimming ratio.

DRV

LED DRIVER

SW

PWM

L1

D1

C1

C2

D1A

D2A

D3A

D1B

D2B

D3B

D1C

D2C

D3C

+

LED1

PWM

SHDN

OT1

OT2

LED2

LT3003

LED3

GND

3003 F03

EA

Figure 3. Boost Mode

DRV

LED DRIVER

SW

C1

C2

D1

D1A

D2A

D3A

D1B

D2B

D3B

D1C

D2C

D3C

+

LED1

PWM

L1

PWM

OT1

OT2

SHDN

LED2

LT3003

LED3

GND

3003 F04

EA

Figure 4. Buck Mode

C1

C2

D3C

D3B

D3A

3003 F05

LED3

D2C

D2B

D2A

LED2

GND

D1C

D1B

D1A

LED1

OT1 OT2

SHDN PWM

PWM

LT3003

DRV

LED DRIVER

SW

+

EA

L1

D1

Figure 5. Buck-Boost Mode

Overtemperature Protection

The LT3003 incorporates internal junction temperature

sensing and provides two open-collector outputs, OT1 and

OT2, which become active low when junction temperature

exceeds 125°C. The active OT1 output can sink 100µA of

current and can be connected to system microprocessor.

The active low OT2 output can sink 300µA of current and

amplifier output to defeat switching. The LT3003 has to

cool down by 6°C (119°C) for OT1 and OT2 outputs to

reset (collector outputs high).

APPLICATIONS INFORMATION