LTC3452 datasheet(6/16 Pages) LINER

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LTC3452

3452f

PI FU CTIO S

VIN (Pin 1): Signal Voltage Input Supply Pin (2.7V ≤ VIN ≤

5.5V). Recommended bypass capacitor to GND is 2.2

µF

ceramic or larger. Connect to PVIN (Pin 20).

ENL (Pin 2): Enable Input Pin and PWM Brightness Control

for Low Power LED Bank. Active high. For constant IMAXL

operation, connect the ENL pin to VIN (or any voltage

>1.2V). For ENL voltage <0.2V, all low power bank LED

current source outputs are Hi-Z (if both ENL and ENH are

<0.2V, the part is in shutdown and the input supply current

drops to ~6

µA). For brightness control between zero

current and IMAXL, drive the ENL pin with a PWM waveform

of frequency

≥10kHz. The low power LED bank currents

will be equal to a percentage of IMAXL as given in Table 1.

The ENL pin is high impedance and should not be floated.

ISETL (Pin 3): Low Power LED Bank Current Programming

Pin. A resistor to ground programs each low power bank

current source output maximum to ILEDLx|MAX = 256 •

(0.8V/RISETL). Enabled by ENL (Pin 2). PWM brightness

control also via ENL.

LEDL1 to LEDL5 (Pins 4 to 8): Individual Low Dropout

Current Source Outputs for Low Power LED Bank Current

Biasing. Connect each low power LED between VOUT and

an individual LEDLx pin. Unused LEDLx outputs should be

connected to VOUT.

GND (Pins 9 and 11): Signal Ground Pins. Connect

together and to PGND (Pin 18) and Exposed Pad ground

(Pin 21).

LEDH1, LEDH2 (Pins 10, 12): Individual Low Dropout

Current Source Outputs for High Power LED Bank Current

Biasing. Connect each high power LED between VOUT and

an individual LEDHx pin. Unused LEDHx outputs should be

connected to VOUT.

ISETH (Pin 13): High Power LED Bank Current Program-

ming Pin. A resistor to ground programs each high power

bank current source output to ILEDHx = 768(0.8V/RISETH).

Enabled by ENH (Pin 14).

ENH (Pin 14): Enable Input Pin for High Power LED Bank.

Active high. The ENH pin is high impedance and should not

be floated.

VC (Pin 15): Compensation Point for the Internal Error

Amplifier Output. Recommended compensation capacitor

to GND is 0.1

µF ceramic or larger.

VOUT (Pin 16): Buck-Boost Output Pin. Recommended

bypass capacitor to GND is 4.7

µF ceramic.

SW2 (Pin 17): Switching Node Pin. Connected to internal

power switches C and D. External inductor connects

between SW1 and SW2. Recommended value is 4.7

µH.

PGND (Pin 18): Power Ground Pin. Connect to GND (Pins

9 and 11).

SW1 (Pin 19): Switching Node Pin. Connected to internal

power switches A and B. External inductor connects

between SW1 and SW2. Recommended value is 4.7

µH.

PVIN (Pin 20): Power Voltage Input Supply Pin. Connect to

VIN (Pin 1).

Exposed Pad (Pin 21): Heat Sink Ground. Connect to GND

(Pins 9 and 11) and solder to PCB ground for electrical

contact and rated thermal performance.

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