A8519KETTR-R datasheet(16/35 Pages) ALLEGRO

16 / 35 page

Wide Input Voltage Range, High-Efficiency,

Fault-Tolerant LED Driver

A8519 and

A8519-1

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

This sets the maximum current through the LEDs, referred to as

the 100% current.

Table 4: LED Current Setting Resistors (Values Rounded to the

Nearest Standard Resistor Value)

Standard Closest RISET Resistor

Values

LED Current

ILED

7.15 kΩ

100 mA per LED

8.87 kΩ

80 mA per LED

11.8 kΩ

60 mA per LED

14.3 kΩ

50 mA per LED

17.8 kΩ

40 mA per LED

PWM Dimming

The LED current can be reduced from the 100% current level

by PWM dimming using the PWM pin. When the PWM pin is

pulled high, the A8519 turns on and all enabled LEDs sink 100%

current. When PWM is pulled low, the boost converter and LED

sinks are turned off. The compensation (COMP) pin is floated,

and critical internal circuits are kept active. The typical PWM

dimming frequencies fall between 200 Hz and 1 kHz.

The A8519 is designed to deliver a maximum dimming ratio of

10,000:1 at PWM frequency of 100 Hz. That means a minimum

PWM duty cycle of 0.01%, or an on-time of just 1 µs out of a

period of 10 ms.

Figure 13: Typical PWM Diagram Showing VOUT, ILED and COMP

Pin, as well as the PWM Signal. (PWM dimming Frequency is

500 Hz 50% duty cyle.)

Figure 14: Typical PWM Diagram Showing VOUT, ILED, and COMP

Pin, as well as the PWM Signal. (PWM dimming frequency is

500 Hz 1% duty cycle.)

Figure 15: Rising Edge PWM Signal to Total LED Current

ILED(TOTAL) Turn-On Delay; Time base = 100 ns

Figure 16: Falling Edge PWM Signal to Total LED Current

ILED(TOTAL) Turn-Off Delay; Time base = 100 ns

VOUT

VCOMP

ILED(TOTAL)

VPWM

VOUT

VCOMP

ILED(TOTAL)

VPWM

ILED(TOTAL)

VPWM

ILED(TOTAL)

VPWM

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