A8518and A8518-1: Wide Input Voltage Range, High-Efficiency, Fault-Tolerant LED Driver

The A8518 is a multi-output LED driver for small-size LCD backlighting. It integrates a current-mode boost converter with internal power switch and two current sinks. The boost converter can drive up to 22 white LEDs, 11 LEDs per string, at 200 mA. The LED sinks can be paralleled together to achieve higher LED currents up to 400 mA. The A8518 operates from a single power supply from 4.5 to 40 V, which allows the part to withstand load dump condition encountered in automotive systems.

The A8518 can control LED brightness through digital (PWM) signal. LED brightness contrast ratio of 10,000:1 can be achieved using PWM dimming at 100 Hz; a higher ratio of 100,000:1 is possible when using a combination of PWM and analog dimming.

If required, the A8518 can drive an external P-Channel MOSFET to disconnect input supply from the system in the event of a fault. The A8518 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.

The A8518 has a fixed boost switching frequencies of 2.15 MHz. The high switching frequency allows the converter to operate above the AM radio band.

The A8518 offers dithering of boost switching frequency, which helps reduce EMI (electromagnetic interference). The A8518-1 is identical to the A8518, but without the dithering feature.

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• Automotive infotainment backlighting
• Automotive cluster
• Automotive center stack

• Automotive AEC-Q100 qualified
• Fully integrated 42 V MOSFET for boost converter
• Fully integrated LED current sinks
• Withstands surge input to 40 V_INfor load dump
• Operates down to 3.9 V_IN(max) for idle stop
• Drives two strings of LEDs
• Maximum output voltage 40 V
  • Up to 11 white LEDs in series
• Drive current for each string is 200 mA
• Fixed 2.15 MHz boost switching frequency
• Dithering of boost switching frequency to reduce EMI (A8518 only)
• Extremely high LED contrast ratio
  • 10,000:1 using PWM dimming alone
  • 100,000:1 when combining PWM and analog dimming
• Excellent input voltage transient response at lowest PWM duty cycle
• Gate driver for optional P-Channel MOSFET input disconnect switch
• LED current accuracy 0.7%
• LED string current matching accuracy 0.8%
• Protection against:
  • Shorted boost switch, inductor or output capacitor
  • Shorted I_SETresistor
  • Open or shorted LED pins and LED strings
  • 开放增加二极管
  • Overtemperature