LED5000 datasheet(12/52 Pages) STMICROELECTRONICS

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Functional description

LED5000

12/51

Doc ID 023951 Rev 1

During normal operation a new soft-start cycle takes place in case of:

●

thermal shutdown event

●

UVLO event

The soft-start is disabled during the dimming operation to maximize the dimming

performance.

4.4

Dimming block

The DIM input features the LED brightness control with the PWM dimming operation (see

Chapter 5.8).

4.5

Inhibit block

The inhibit block features the standby mode accordingly with

Table 5: Electrical

characteristics. The INH pin high level disables the device so the power consumption is

reduced to less than 40 µA. The INH pin is 5 V tolerant.

4.6

Error amplifier

The voltage error amplifier is the core of the loop regulation. It is a transconductance

operational amplifier whose non inverting input is connected to the internal voltage

reference (200 mV), while the inverting input (FB) is connected to the output current sensing

resistor.

The error amplifier output is compared with the inductor current sense information to

perform PWM control.

4.7

Thermal shutdown

The shutdown block generates a signal that disables the power stage if the temperature of

the chip goes higher than a fixed internal threshold (150±10 °C typical). The sensing

element of the chip is close to the PDMOS area, ensuring fast and accurate temperature

detection. A 15 °C typical hysteresis prevents the device from turning ON and OFF

continuously during the protection operation.

Table 6.

Uncompensated error amplifier characteristics

Description

Values

Transconductance

2200 µS

Low frequency gain

90 dB

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