RT8509A 4.5A Step-Up DC/DC Converter General Description Features 90% Efficiency The RT8509A is a high performance switching Boost Adjustable Output Up to 24V converter that provides a regulated supply voltage for active 2.8V to 14V Input Supply Voltage matrix thin film transistor (TFT) liquid crystal displays Input Supply Under-Voltage Lockout (LCDs). Fixed 1.2MHz Switching Frequency The RT8509A incorporates current mode, fixed-frequency, Adjustable Soft-Start pulse width modulation (PWM) circuitry with a built in V Over-Voltage Protection OUT N-MOSFET to achieve high efficiency and fast transient Over-Temperature Protection response. Thin 12-Lead WDFN Package The RT8509A has a wide input voltage range from 2.8V to RoHS Compliant and Halogen Free 14V. In addition, the output voltage can be adjusted up to 24V via an external resistive voltage divider. The maximum Applications peak current is limited to 4.5A (min.). Other features GIP TFT-LCD Panels include adjustable soft-start, over-voltage protection, and over-temperature protection. Ordering Information The RT8509A is available in the WDFN-12L 5x5 package. RT8509A Package Type Marking Information QW : WDFN-12L 5x5 (W-Type) RT8509AGQW : Product Number Lead Plating System RT8509A YMDNN : Date Code G : Green (Halogen Free and Pb Free) GQW Note : YMDNN Richtek products are : RoHS compliant and compatible with the current require- ments of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. Simplified Application Circuit D1 L1 V V IN OUT R4 C C IN OUT LX R1 VIN VOUT C2 C3 RT8509A R2 FB Enable EN C SS SS R3 GND COMP C1 Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS8509A-00 November 2013 www.richtek.com 1RT8509A Pin Configurations (TOP VIEW) COMP 1 12 SS 11 FB 2 VIN EN 3 10 VOUT GND GND 4 9 GND 5 LX GND 8 13 67 GND LX WDFN-12L 5x5 Functional Pin Description Pin No. Pin Name Pin Function Compensation Node for Error Amplifier. Connect a series RC from COMP to 1 COMP ground. Feedback Voltage Input. The FB regulation voltage is 1.25V nominal. Connect an external resistive voltage divider between the step-up regulators output (V ) OUT 2 FB and GND, with the center tap connected to FB. Place the divider close to the IC and minimize the trace area to reduce noise coupling. 3 EN Enable Control Input. Drive EN low to turn off the Boost. 4, 5, 6, 9, Ground. The Exposed Pad must be soldered to a large PCB and connected to GND 13 (Exposed Pad) GND for maximum power dissipation. Switch Node. LX is the Drain of the internal MOSFET. Connect the 7, 8 LX inductor/rectifier diode junction to LX and minimize the trace area for lower EMI. Over-Voltage Protection Input for Boost Converter. Bypass VOUT with a 10 VOUT minimum 1 F ceramic capacitor directly to GND. Supply Voltage Input. Bypass VIN with a minimum 1 F ceramic capacitor directly 11 VIN to GND. Soft-Start Time Setting. Connect a soft-start capacitor (C ) to this pin. The SS 12 SS soft-start capacitor is charged with a constant current of 5 A. The soft-start capacitor is discharged to ground when EN is low. Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS8509A-00 November 2013 2