RT2856 6A, 18V, Synchronous Step-Down Converter General Description Features zz z zz Low R Power MOSFET Switches 26m/19m DS(ON) The RT2856 is a high efficiency, monolithic synchronous zz z zz Input Voltage Range : 4.5V to 18V step-down DC/DC converter that can deliver up to 6A output zz z zz Adjustable Switching Frequency : 200kHz to 1.6MHz current from a 4.5V to 18V input supply. The RT2856 zz z zz Current-Mode Control current-mode architecture with external compensation zz z zz Synchronous to External Clock : 200kHz to 1.6MHz allows the transient response to be optimized over a wide zz z zz Accurate Voltage Reference 0.8V 1%, Over 40C range of loads and output capacitors. Cycle-by-cycle to 85C current limit provides protection against shorted outputs zz z zz Monotonic Start-Up into Pre-biased Outputs and soft-start eliminates input current surge during start- zz z zz Adjustable Soft-Start up. Fault condition protections include output under-voltage zz z zz Power Good Indicator protection, output over-voltage protection, and over- zz z zz Under-Voltage and Over-Voltage Protection temperature protection. The low current shutdown mode zz z zz Input Under-Voltage Lockout provides output disconnection, enabling easy power zz z zz RoHS Compliant and Halogen Free management in battery-powered systems. Marking Information Applications 00= : Product Code z High Performance Point of Load Regulation YMDNN : Date Code 00=YM z Notebook Computers DNN z High Density and Distributed Power Systems Simplified Application Circuit RT2856 BOOT V VIN IN C IN C BOOT L PVIN LX V OUT R1 Enable EN FB C PGOOD OUT PGOOD R COMP1 R OSC COMP R2 RT/SYNC C C COMP1 COMP2 C SS SS/TR GND Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. DS2856-04 October 2013 www.richtek.com 1RT2856 Ordering Information Pin Configurations RT2856 (TOP VIEW) Package Type QW : WQFN-14AL 3.5x3.5 (W-Type) Lead Plating System 1 14 G : Green (Halogen Free and Pb Free) 2 13 GND BOOT Note : 3 12 GND LX 4 11 PVIN GND LX Richtek products are : PVIN 5 10 EN RoHS compliant and compatible with the current require- 15 6 9 VIN SS/TR ments of IPC/JEDEC J-STD-020. 7 8 Suitable for use in SnPb or Pb-free soldering processes. WQFN-14AL 3.5x3.5 Functional Pin Description Pin No. Pin Name Pin Function Oscillator Resistor and External Frequency Synchronization Input. Connecting a 1 RT/SYNC resistor from this pin to GND sets the switching frequency or connecting an external clock to this pin changes the switching frequency. System Ground. Provide the ground return path for the control circuitry and 2, 3, GND low-side power MOSFET. The exposed pad must be soldered to a large PCB 15 (Exposed Pad) and connected to GND for minimum power dissipation. 4, 5 PVIN Power Input. Supplies the power switches of the device. Supply Voltage Input. Supplies the control circuitry and internal reference of the 6 VIN device. Feedback Voltage Input. This pin is used to set the desired output voltage via an 7 FB external resistive divider. The feedback reference voltage is 0.8V typically. Compensation Node. The current comparator threshold increases with this 8 COMP control voltage. Connect external compensation elements to this pin to stabilize the control loop. Soft-Start and Tracking Control Input. Connect a capacitor from SS to GND to 9 SS/TR set the soft-start period. The soft-start period can be used to track and sequence when the external voltage on this pin overrides the internal reference. Enable Control Input. Floating this pin or connecting this pin to logic high can 10 EN enable the device and connecting this pin to GND can disable the device. Switch Node. LX is the switching node that supplies power to the output and 11, 12 LX connect the output LC filter from LX to the output load. Bootstrap Supply for High-Side Gate Driver. Connect a 100nF or greater 13 BOOT capacitor from LX to BOOT to power the high-side switch. Power Good Indicator Output. This pin is an open-drain logic output that is pulled 14 PGOOD to ground when the output voltage is lower or higher than its specified threshold under the conditions of OVP, OTP, dropout, EN shutdown, or during slow start. Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation. www.richtek.com DS2856-04 October 2013 2 FB RT/SYNC COMP PGOOD