A8509is a multi-output white LED for backlit LCD panelsdrive。 It integrates a current-mode boost controller and four separate current sinks.
This boost controller architecture greatly expands boost to optimize the solution for the required number of LEDs per string. The FSET/SYNC pin sets the desired boost switching frequency or synchronizes the value from 300 to 800 kHz.
The LED sink value can be set via an external ISET resistor (see Figure 1). The four LED sinks can also be combined to achieve higher currents for each LED string.
The A8509 provides output short-circuit and overvoltage protection, LED pin open or short-circuit protection, and over-temperature protection. Two-stage pulse-by-pulse current limit provides soft-start and protection against high current overload on external current switches. As an option, the A8509 can be driven with FAULT P-FETs pinned to disconnect input power from the system in the event of a short to ground in the boost converter.
Package options are available in 24-pin TSSOP (suffix LP) and SOICW (LB) packages. The TSSOP is fitted with an exposed heat sink, while the SOICW has four pins with internal fuses for better heat dissipation. Both packages are lead (Pb) free and feature 100% matte tin leadframe plating.
- Four integrated high current sinks for LED strings; Can be bonded together for higher currents
- Fixed frequency current mode control with gate driver/boost controller; Powerful gate drivers that drive external N-channel MOSFETs greatly expand the number of LEDs per string
- Can be operated in parallel with one master boost controller and up to three additional slave controllers; Up to 16 LED strings can be operated while only one main boost regulator is loaded
- Autonomous current sharing between LED strings enables 0.7% accuracy and 0.8% matching
- Wide input voltage range: 9 to 40 V
- Provides an internal bias supply (typically V) for single-supply operationIN = 12 or 24 V)
- Separate Enable and PWM pins serve as interfaces for Enable and PWM dimming
- Fset/Sync function that can be set at the boost converter switching frequency or synchronized at 800 kHz
- Protection features
- Open or shorted LED pin protection
- Open circuit Schottky protection
- Pulse-by-pulse current limit
- Over-Temperature Protection (OTP)