A8501High Power WLED/RGB Driver for Medium Displays with Output Disconnect

Description

The A8501 is a multioutput WLED/RGB driver for backlighting medium-size displays. The A8501 integrates a boost converter and four 100 mA current sinks. LED channels can be tied together for up to 400 mA sink capability. It can work from a single power supply of 8 to 21 V and withstand up to 40 V. The boost converter is a constant frequency, current-mode converter.

Operating frequency can be set to 2 MHz in order to avoid interference with the AM radio band. The integrated boost DMOS switch is rated for 40 V at 3.6 A. PWM dimming allows LED currents to be controlled at up to a 1000:1 ratio. Additional 4:1 dimming can be achieved by using the DIM pin.

The A8501 provides protection against output connector shorts through an integrated output disconnect switch. An optional external thermistor can be used to limit LED current based on panel temperature.

The device is supplied in a surface mount, 28-pin TSSOP package (suffix LP), with exposed thermal pad for enhanced thermal dissipation. It is lead (Pb) free, with a leadframe plating choice of 100% matte-tin (suffix T) or tin-bismuth (suffix B).

Output Disconnect

Features

• 600 kHz to 2.2 MHz switching frequency¡ªability to operate above the AM band
• Internal bias supply for single-supply operation (V_IN = 8 to 21 V)
• Boost converter with integrated 40 V DMOS switch and OVP¡ªload-dump protection
• 3.5 µA shutdown current¡ªlimits battery drain
• Active current sharing between LED strings for 0.8% current matching and 0.7% accuracy
• Drive up to 9 series LEDs in 4 parallel strings, 36 LEDs maximum (V_f = 3.5 V, I_f = 100 mA)
• LED sinks rated for 100 mA each (400 mA total)
• PWM dimming with LED PWM duty cycle control
• 4000:1 dimming range
• Extensive fault mode protection schemes:
  • Shorted LED protection against misconnected loads¡ª with true output disconnect
  • Open LED disconnect protects against LED failures
  • External thermistor sensing to limit LED temperature
  • Output overvoltage protection (OVP): 19.5 V default can be adjusted as high as 38 V
  • Open Schottky and open OVP resistor protection against external component failure
  • Input under- and overvoltage protection (UVLO and OVLO) against VIN variation
  • Boost current limit, output short circuit limit, overtemperature protection (OTP), and soft start

Applications

• GPS navigation systems
• Automotive infotainment
• Back-up camera displays
• Cluster backlighting
• Portable DVD players
• Industrial LCD displays