RT8293B 3A, 23V, 1.2MHz Synchronous Step-Down Converter General Description Features zz z zz 1.5% High Accuracy Feedback Voltage The RT8293B is a high efficiency, monolithic synchronous zz z zz 4.5V to 23V Input Voltage Range step-down DC/DC converter that can deliver up to 3A zz z zz 3A Output Current output current from a 4.5V to 23V input supply. The zz z zz Integrated N-MOSFET Switches RT8293B s current mode architecture and external zz z zz Current Mode Control compensation allow the transient response to be zz z zz Fixed Frequency Operation : 1.2MHz optimized over a wide range of loads and output capacitors. zz z zz Adjustable Output from 0.8V to 15V Cycle-by-cycle current limit provides protection against zz z zz Up to 95% Efficiency shorted outputs and soft-start eliminates input current zz z zz Programmable Soft-Start surge during start-up. The RT8293B provides output under zz z zz Stable with Low ESR Ceramic Output Capacitors voltage protection and thermal shutdown protection. The zz z zz Cycle-by-Cycle Over Current Protection low current (<3A) shutdown mode provides output zz z zz Input Under Voltage Lockout disconnect, enabling easy power management in battery- zz z zz Output Under Voltage Protection powered systems. The RT8293B is available in a zz z zz Thermal Shutdown Protection SOP-8 (Exposed Pad) package. zz z zz RoHS Compliant and Halogen Free Ordering Information RT8293B Applications Package Type z Wireless AP/Router SP : SOP-8 (Exposed Pad-Option 1) z Set-Top-Box Lead Plating System z Industrial and Commercial Low Power Systems G : Green (Halogen Free and Pb Free) z LCD Monitors and TVs Z : ECO (Ecological Element with Halogen Free and Pb free) z Green Electronics/Appliances z Point of Load Regulation of High-Performance DSPs H : UVP Hiccup L : UVP Latch-Off Pin Configurations Note : (TOP VIEW) Richtek products are : RoHS compliant and compatible with the current require- 8 BOOT SS ments of IPC/JEDEC J-STD-020. 2 7 VIN EN GND Suitable for use in SnPb or Pb-free soldering processes. 3 6 SW COMP 9 4 5 GND FB SOP-8 (Exposed Pad) Marking Information RT8293BxGSP RT8293BxZSP RT8293BxGSP : Product Number RT8293BxZSP : Product Number RT8293Bx RT8293Bx x : H or L x : H or L GSPYMDNN ZSPYMDNN YMDNN : Date Code YMDNN : Date Code DS8293B-03 March 2011 www.richtek.com 1RT8293B Typical Application Circuit V 2 1 IN BOOT VIN 4.5V to 23V C C BOOT IN L 10F x 2 RT8293B 100nF 3.6H V 3 OUT SW 3.3V/3A R 100k EN R1 7 EN 75k C OUT 8 5 SS FB 22F x 2 C C C R SS C R2 2.2nF 0.1F 22k 24k 4, 9 (Exposed Pad) 6 COMP GND C P Open Table 1. Recommended Component Selection V (V) R1 (kW) R2 (kW) R (kW) C (nF) L (mH) C (mF) OUT C C OUT 8 27 3 51 2.2 10 22 x 2 5 62 11.8 33 2.2 6.8 22 x 2 3.3 75 24 22 2.2 3.6 22 x 2 2.5 25.5 12 16 2.2 3.6 22 x 2 1.5 10.5 12 10 2.2 2 22 x 2 1.2 12 24 8.2 2.2 2 22 x 2 1 3 12 6.8 2.2 2 22 x 2 Functional Pin Description Pin No. Pin Name Pin Function Bootstrap for High Side Gate Driver. Connect a 0.1F or greater ceramic 1 BOOT capacitor from BOOT to SW pins. Input Supply Voltage, 4.5V to 23V. Must bypass with a suitably large ceramic 2 VIN capacitor. 3 SW Switch Node. Connect this pin to an external L-C filter. 4, Ground. The exposed pad must be soldered to a large PCB and connected to GND 9 (Exposed Pad) GND for maximum power dissipation. Feedback Input. This pin is connected to the converter output. It is used to set the output of the converter to regulate to the desired value via an internal 5 FB resistive divider. For an adjustable output, an external resistive divider is connected to this pin. Compensation Node. COMP is used to compensate the regulation control 6 COMP loop. Connect a series RC network from COMP to GND. In some cases, an additional capacitor from COMP to GND is required. Chip Enable (Active High). A logic low forces the RT8293B into shutdown 7 EN mode reducing the supply current 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 capacitor 8 SS from SS to GND to set the soft-start period. A 0.1F capacitor sets the soft-start period to 13.5ms. www.richtek.com DS8293B-03 March 2011 2