LED5000 datasheet(10/52 Pages) STMICROELECTRONICS

10 / 52 page

Functional description

LED5000

10/51

Doc ID 023951 Rev 1

Functional description

The LED5000 is based on a “peak current mode” architecture with fixed frequency control.

As a consequence the intersection between the error amplifier output and the sensed

inductor current generates the control signal to drive the power switch.

The main internal blocks shown in the block diagram in

Figure 3 are:

●

A fully integrated sawtooth oscillator with a typical frequency of 850 kHz

●

A transconductance error amplifier

●

An high side current sense amplifier to track the inductor current

●

A pulse width modulator (PWM) comparator and the circuitry necessary to drive the

internal power element

●

The soft-start circuitry to decrease the inrush current at power-up

●

The dimming block to implement PWM dimming

●

The inhibit block for standby operation

●

The current limitation circuit based on the pulse-by-pulse current and the HICCUP

protection

●

The bootstrap circuitry to drive the embedded N-MOS switch

●

A circuit to implement the thermal protection function

Figure 3.

LED5000 block diagram

VIN

OSC

E/A

DRIVER

DMD

MOSFET

CONTROL

LOGIC

REGULATOR

DIMMING

I_ SENSE

COMP

OCP

REF

0.1V

SOFTSTART

Vsum

OCP

UVLO

Vdrv_p

Vdrv_n

I2V

R SENSE

GND

DIM

COMP

INH

AM13487v1

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