Multi-output LED driver with patented control technique eliminates audible PWM noise

The ALT80600 LED driver for small size LCD backlighting uses Allegro 's innovative patented Pre-Emptive Boost (PEB) control technology in a small 4x4 package to achieve ultra-high true PWM dimming contrast while eliminating the normally audible noise.

ALT80600

Technical advantages

The PEB control technology used by ALT80600 greatly reduces Vout ripple and eliminates the audible noise generated by ceramic output capacitors during the common PWM dimming process , while only requiring a smaller output capacitor. The system can achieve an LED brightness contrast ratio of 15,000:1 using only 200Hz PWM dimming. If a combination of PWM and analog dimming is used, a higher contrast ratio of 150,000:1 can be achieved.

ALT80600 Functional Block Diagram

ALT80600 integrates a switching converter and its MOS tube, and four constant current sources, and can be configured as a boost or SEP I C topology to meet a variety of different application requirements. The switching converter is specially designed to reduce electromagnetic interference, including programmable switching frequency, controllable switching slope, and programmable frequency jitter. In addition, the clock output pin allows other switching converters to synchronize with the ALT80600 switching frequency to improve the anti-electromagnetic interference performance of the entire system.

The ALT80600 devices are suitable for various types of automotive backlighting applications, including audio/video systems, instrument panels, and head-up displays (HUDs). These devices operate from a single power supply with a wide input voltage range of 4.5V to 40V. Once started, the devices can continue to operate at voltages as low as 3.9V, thus being able to withstand stop/start, cold start, dual battery , and load dump conditions in automotive systems.

ALT80600 Typical Applications

ALT80600 key features are certified to AEC-Q100 automotive electronics test standards

4.5～40V wide input voltage range to meet startup/shutdown, cold start and load dump requirements

LED current sink and boost converter   fully integrated with internal power MOSFET

Operates in Boost or SEPIC mode for flexible output

Capable of driving up to 11 series white LEDs in 4 parallel LED string mode, each string can reach 120mA (VF = 3.3Vmax)

Programmable Boost Switching Frequency or External Synchronization (200kHz to 2.3MHz)

Internal switching frequency clock output function

Adjustable boost frequency jitter to reduce EMI

Advanced control reduces PWM on-time to 0.3μs and avoids  MLCC  audible noise

LED contrast ratio: 15000:1 (200Hz, using PWM dimming only), 150000:1 (using PWM and analog dimming together)

Excellent input voltage transient response even at lowest PWM duty cycles

Gate Driver for Optional PMOS Input Disconnect Switch

Extensive protection features: boost switch, inductor or output capacitor short protection, FSET or ISET  resistor short protection, LED pin and LED string open or short protection, open boost Schottky diode protection, and over-temperature protection

The ALT80600 is a member of the A8060x series, which provides a large number of safety and protection functions required for automotive applications, so it has very high reliability. The ALT80600 and A80603 in the A8060x series can drive four LED strings, each with a current of up to 120mA, so the total current is up to 480mA. The A80601 and A80602 can provide a total current of up to 840mA, and can drive 4 or 6 LED strings respectively.

This LED driver series effectively addresses customer concerns about audible noise, reduces device size, provides excellent PMW dimming ratio without analog adjustment, and eliminates audible noise from ceramic capacitors, making it ideal for applications such as automotive.