RT8055BGQW

RT8055B 3A, 2MHz, Synchronous Step-Down Converter General Description Features The RT8055B is a high efficiency synchronous, step-down DC/DC converter. Its input voltage range is from 2.6V to 5.5V and provides an adjustable regulated output voltage from 0.8V to 5V while delivering up to 3A of output current. z The RT8055B is operated in forced continuous PWM Mode which minimizes ripple voltage and reduces the noise and RF interference. The RT8055B is available in the WDFN-10L 3x3 package. z z z z z z z z Applications z z z z z Ordering Information z RT8055B z Package Type QW : WDFN-10L 3x3 (W-Type) Lead Plating System G : Green (Halogen Free and Pb Free) Note : Richtek products are : ` RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. ` Suitable for use in SnPb or Pb-free soldering processes. Low RDS(ON) Internal Switches : 100mΩ Ω Programmable Frequency : 300kHz to 2MHz No Schottky Diode Required 0.8V Reference Voltage Allows for Low Output Voltage Forced Continuous Mode Operation 100% Duty Cycle Operation Input Over Voltage Protection Power Good Output Voltage Indicutor RoHS Compliant and Halogen Free Portable Instruments Battery-Powered Equipment Notebook Computers Distributed Power Systems IP Phones Digital Cameras 3G/3.5G Data Card Pin Configurations (TOP VIEW) SHDN/RT GND LX LX PGND 1 2 3 4 5 GND The internal synchronous low on-resistance power switches increase efficiency and eliminate the need for an external Schottky diode. The switching frequency is set by an external resistor. The 100% duty cycle provides low dropout operation extending battery life in portable systems. Current mode operation with external compensation allows the transient response to be optimized over a wide range of loads and output capacitors. z High Efficiency : Up to 95% 11 10 9 8 7 6 COMP FB PGOOD VDD PVDD WDFN-10L 3x3 Marking Information K3= : Product Code K3=YM DNN YMDNN : Date Code DS8055B-03 April 2011 www.richtek.com 1 RT8055B Typical Application Circuit 6 VIN 5V CIN 22µF RT8055B 3, 4 PVDD LX R3 R4 100k 7 8 ROSC 180k 1 2,11 (Exposed Pad) 5 VOUT1 3.3V/3A CF 22pF VDD FB 9 C1 PGOOD L1 2µH PGOOD COMP R1 75k COUT 22µF x 2 R2 24k 10 SHDN/RT RCOMP 30k GND CCOMP 470pF PGND Note : Using X5R/X7R Ceramic Capacitors Table 1. Recommended Component Selsction VOUT 3.3 2.5 1.8 1.5 1.2 1.0 R1 (kΩ) 75 51 30 21 12 6 R2 (kΩ) 24 24 24 24 24 24 RCOMP (kΩ) 30 27 22 18 15 13 CCOMP (nF) 0.47 0.47 0.47 0.47 0.47 0.47 L1 (μH) 2.2 2.2 2.2 2.2 1.0 1.0 C OUT (μF) 22 x 2 22 x 2 22 x 2 22 x 2 22 x 2 22 x 2 Functional Pin Description Pin No. 1 Pin Name Pin Function Shutdown Control or Frequency Setting Input. Connect a resistor to ground from SHDN/RT this pin sets the switching frequency. Force this pin to VDD or GND causes the device to be shut down. Signal Ground. All small-signal components and compensation components should 2, 11 (Exposed Pad) GND be connected to this ground, which in turn connects to PGND at one point. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. 3, 4 LX Internal Power MOSFET Switches Output. Connect this pin to the inductor. 5 PGND Power Ground. Connect this pin close to the negative terminal of CIN and COUT. 6 PVDD Power Supply Input. Decouple this pin to PGND with a capacitor. 7 VDD 8 PGOOD Power Good Indicator. The pin is an open drain logic output that is pulled to Ground. 9 FB Feedback Pin. This pin receives the feedback voltage from a resistive divider connected across the output. Signal Supply Input. Decouple this pin to GND with a capacitor. Generally, VDD is equal to PVDD. Error Amplifier Compensation Point. The current comparator threshold increases 10 www.richtek.com 2 COMP with this control voltage. Connect external compensation elements to this pin to stabilize the control loop. DS8055B-03 April 2011 RT8055B Function Block Diagram SHDN/RT PVDD ISEN SD OSC Slope Comp. COMP 0.8V EA FB OC Limit Output Clamp Internal Soft-Star Driver 0.9V LX Control Logic 0.7V NISEN OTP 0.4V VREF POR PGND N-MOSFET ILIM PGOOD GND VDD DS8055B-03 April 2011 www.richtek.com 3 RT8055B Absolute Maximum Ratings z z z z z z z z z z (Note 1) Supply Input Voltage, VDD, PVDD ---------------------------------------------------------------------------- −0.3V to 6.5V LX Pin Switch Voltage -------------------------------------------------------------------------------------------- −0.3V to (PVDD + 0.3V)