LED Driver with Pre-Emptive Boost for Ultra-High Dimming Ratio and Low Output Ripple


ALT80600 Package Image


Top Features


The ALT80600 is a multi-output LED driver for small-size LCD backlighting. It integrates a current-mode boost converter with internal power switch and four current sinks. The boost converter can drive up to 44 white LEDs, 11 LED per string, at 120 mA (VF = 3.3 V max). LED sinks can be paralleled together to achieve higher currents up to 480 mA.

The ALT80600 operates from single power supply from 4.5 to 40 V; once started, it can continue to operate down to 3.9 V. This allows the part to withstand stop/start, cold crank, and load dump conditions encountered in automotive systems.

The ALT80600 can control LED brightness through external PWM signal. By using the patented ‘Pre-emptive Boost’ control, an LED brightness contrast ratio of 15,000:1 can be achieved using PWM dimming at 200 Hz. A higher ratio of 150,000:1 is possible when using a combination of PWM and analog dimming.

Switching frequency can be either above or below AM band. A programmable dithering feature further reduces EMI. A synchronization pin allows switching frequency to be synchronized externally between 200 kHz and 2.3 MHz. A ‘Clock-Out’ pin allows other converters to be synchronized to the ALT80600’s switching frequency.

The ALT80600 provides protection against output short, overvoltage, open or shorted diode, open or shorted LED pin, and overtemperature. A cycle-by-cycle current limit protects the internal boost switch against high current overloads. An external P-MOSFET can optionally be used to disconnect input supply in case of output to ground short fault.

  • Automotive AEC-Q100 qualified
  • Wide input voltage range of 4.5 to 40 V for start/stop, cold crank, and load dump requirements
  • Fully integrated LED current sinks and boost converter with internal power MOSFET
  • Operate in Boost or SEPIC mode for flexible output
  • Drives up to 11 series white LED in 4 parallel strings, at up to 120 mA per string (VF = 3.3 V max).
  • Programmable boost switching frequency or sync externally from 200 kHz to 2.3 MHz
  • Clock-Out feature for internal switching frequency
  • Adjustable boost frequency dithering to reduce EMI
  • Advanced control allows minimum PWM on-time down to 0.3 μs, and avoids MLCC audible noises
  • LED contrast ratio: 15,000:1 at 200 Hz using PWM dimming alone, 150,000:1 when combining PWM and analog dimming
  • Excellent input voltage transient response even at lowest PWM duty cycle
  • Gate driver for optional PMOS input disconnect switch
  • Extensive protection against:
    • Shorted boost switch, inductor or output capacitor
    • Shorted FSET or ISET resistor
    • Open or shorted LED pins and LED strings
    • Open boost Schottky diode
    • Overtemperature

24-Pin 4 mm x 4 mm QFN with Wettable Flank

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Pre-Emptive Boost Control Improves LED Driver Performance