RT8284 2A, 23V, 340kHz Synchronous Step-Down Converter General Description Features 1.5% High Accuracy Feedback Voltage The RT8284 is a high efficiency, monolithic synchronous Input Voltage Range : 4.5V to 23V step-down DC/DC converter that can deliver up to 2A output 2A Output Current current from a 4.5V to 23V input supply. The RT8284 s Integrated N-MOSFETs current mode architecture and external compensation Current Mode Control allow the transient response to be optimized over a wide 340kHz Fixed Frequency Operation range of loads and output capacitors. Cycle-by-cycle Output Adjustable Voltage Range : 0.923V to 20V current limit provides protection against shorted outputs Efficiency Up to 95% and soft-start eliminates input current surge during start- Programmable Soft-Start up. The RT8284 also provides under voltage protection Stable with Low ESR Ceramic Output Capacitors and thermal shutdown protection. The low current (< 3A) Cycle-by-Cycle Over Current Protection shutdown mode provides output disconnect, enabling easy Input Under Voltage Lockout power management in battery powered systems. The Output Under Voltage Protection RT8284 is a available in a SOP-8 and SOP-8 Thermal Shutdown Protection (Exposed Pad) package. RoHS Compliant and Halogen Free Ordering Information Applications RT8284 Wireless AP/Router Package Type Set-Top-Box S : SOP-8 SP: SOP-8(Exposed Pad-Option 1) Industrial and Commercial Low Power Systems Lead Plating System LCD Monitors and TVs G : Green (Halogen Free and Pb Free) Green Electronics/Appliances Note : Point of Load Regulation of High-Performance DSPs Richtek products are : RoHS compliant and compatible with the current require- Pin Configurations ments of IPC/JEDEC J-STD-020. (TOP VIEW) Suitable for use in SnPb or Pb-free soldering processes. Marking Information 8 BOOT SS 2 7 VIN EN RT8284GS 3 6 SW COMP RT8284GS : Product Number RT8284 4 5 GND FB YMDNN : Date Code GSYMDNN SOP-8 RT8284GSP 8 RT8284GSP : Product Number BOOT SS RT8284 2 7 VIN EN YMDNN : Date Code GND GSPYMDNN 3 6 SW COMP 9 4 5 GND FB SOP-8 (Exposed Pad) DS8284-01 March 2011 www.richtek.com 1RT8284 Typical Application Circuit 1 V 2 IN VIN BOOT 4.5V to 23V C C IN BOOT L RT8284 10F 10nF 10H V OUT 3 SW 3.3V/2A R EN 100k R1 7 EN 26.1k C OUT 8 5 SS FB 22F x 2 C C C R SS C R2 3.3nF 0.1F 13k 10k 4, 9 (Exposed Pad) 6 COMP GND C P Open Recommended Component Selection V (V) R1 (k) R2 (k) R (k) C (nF) L (H) C (F) OUT C C OUT 8 76.8 10 27 3.3 22 22 x 2 5 45.3 10 20 3.3 15 22 x 2 3.3 26.1 10 13 3.3 10 22 x 2 2.5 16.9 10 9.1 3.3 6.8 22 x 2 1.8 9.53 10 5.6 3.3 4.7 22 x 2 1.2 3 10 3.6 3.3 3.6 22 x 2 Functional Pin Description Pin No. Pin Name Pin Function SOP-8 SOP-8 (Exposed Pad) Bootstrap for High-Side Gate Driver. Connect a 10nF or greater 1 1 BOOT ceramic capacitor from BOOT to SW pins. Input Supply Voltage, 4.5V to 23V. Must bypass with a suitably large 2 2 VIN ceramic capacitor. 3 3 SW Phase Node. Connect this pin to external L-C filter. 4, Ground. The exposed pad must be soldered to a large PCB and 4 GND 9 (Exposed Pad) connected to GND for maximum power dissipation. Feedback Input Pin. This pin is connected to the converter output. It is used to set the output of the converter to regulate to the desired 5 5 FB value via an internal resistive divider. For an adjustable output, an external resistive divider is connected to this pin. Compensation Node. COMP is used to compensate the regulation 6 6 COMP control loop. Connect a series RC network from COMP to GND. In some cases, an additional capacitor from COMP to GND is required. Enable Input pin. A logic high enables the converter a logic low forces the RT8284 into shutdown mode reducing the supply current 7 7 EN to less than 3A. Attach this pin to VIN with a 100k pull up resistor for automatic startup. Soft-Start Control Input. SS controls the soft-start period. Connect a 8 8 SS capacitor from SS to GND to set the soft-Start period. A 0.1F capacitor sets the soft-start period to 15.5ms . www.richtek.com DS8284-01 March 2011 2