A8519KETTR-R datasheet(24/35 Pages) ALLEGRO

24 / 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

Figure 38: Output Voltage Ripple Frequency Due to Dithering =

12.4 kHz at VIN = 12 V, and PWM Ratio = 100%

Figure 39: Output Voltage Ripple Amplitude Due to Dithering =

100 mV at VIN = 12 V, and PWM Ratio = 100%

VSW

VOUT

VSW

VOUT

Dithering Feature

To minimize the switching frequency harmonics, a dithering

feature is implemented in A8519. This feature simplifies the input

filters needed to meet the automotive CISPR 25 conducted and

radiated emission limits. The dithering sweep is internally set

at ±5%. The switching frequency will ramp from 0.95 times the

programmed frequency to 1.05 times the programmed frequency.

The rate or modulation at which the frequency sweeps is gov-

erned by an internal 12.5 kHz triangle pattern.

Figure 36: Minimum Dithering Switching Frequency = 2.02 MHz at

VIN = 12 V, and PWM Ratio = 100%

Figure 37: Maximum Dithering Switching Frequency = 2.23 MHz

at VIN = 12 V, and PWM Ratio = 100%

A8519KETTR-R Arkusz danych(PDF) 24 Page - Allegro MicroSystems