RT8237CZQW(2)

® RT8237C/D High Efficiency Single Synchronous Buck PWM Controller General Description Features The RT8237C/D PWM controller provides high efficiency, excellent transient response, and high DC output accuracy needed for stepping down high voltage batteries to generate low voltage CPU core, I/O, and chipset RAM supplies in notebook computers.  Wide Input Voltage Range : 4.5V to 26V  Output Voltage Range : 0.7V to 3.3V Built-in 0.5% 0.7V Reference Voltage Quick Load-Step Response within 100ns 4700ppm/°°C Programmable Current Limit by Low Side RDS(ON) Sensing 4 Selectable Frequency Setting Soft-Start Control Drives Large Synchronous-Rectifier FETs Integrated Boot Switch Built-in OVP/OCP/UVP Thermal Shutdown Power Good Indicator RoHS Compliant and Halogen Free       Applications     Notebook Computers CPU Core Supply Chipset/RAM Supply as Low as 0.7V Generic DC/DC Power Regulator Pin Configurations (TOP VIEW) PGOOD CS EN FB RF C : WDFN-10L 3x3 D : WQFN-12L 2x2 Note : Richtek products are :  RoHS compliant and compatible with the current require-  Suitable for use in SnPb or Pb-free soldering processes. ments of IPC/JEDEC J-STD-020. Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8237C/D-06 February 2014 10 9 4 5 8 7 6 11 BOOT UGATE PHASE VCC LGATE WDFN-10L 3x3 Package Type QW : WDFN-10L 3x3 (W-Type) QW : WQFN-12L 2x2 (W-Type) RT8237C LGATE 1 VCC PHASE 2 RF Lead Plating System Z : ECO (Ecological Element with Halogen Free and Pb free) 1 2 3 12 11 10 GND 13 3 4 5 6 PGOOD Pin 1 Orientation (2) : Quadrant 2, Follow EIA-481-D  GND (2)  NC RT8237  GND Ordering Information  BOOT The RT8237C/D achieves high efficiency at a reduced cost by eliminating the current sense resistor found in traditional current mode PWMs. Efficiency is further enhanced by its ability to drive very large synchronous rectifier MOSFETs and enter diode emulation mode at light load condition. The buck conversion allows this device to directly step down high voltage batteries at the highest possible efficiency. The pre-set frequency selections minimize design effort required for new designs. The RT8237C/D is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.7V. The RT8237C is available in a WDFN-10L 3x3 package, The RT8237D is available in a WQFN-12L 2x2 package. UGATE The constant on-time PWM control scheme handles wide input/output voltage ratios with ease and provides 100ns “instant-on” response to load transients while maintaining a relatively constant switching frequency.  9 FB 8 EN CS 7 WQFN-12L 2x2 RT8237D is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8237C/D Marking Information RT8237CZQW RT8237DZQW Z3 : Product Code 72 : Product Code YMDNN : Date Code Z3 YM DNN W : Date Code 72W Typical Application Circuit VCC R1 0 RT8237C/D VCC BOOT C1 1µF 16V R5 100k CBOOT 0.1µF 50V RBOOT 0 RUGATE UGATE VIN C2 10µF x 3 50V 0 PGOOD VOUT 1.05V LOUT 0.45µH Chip Enable EN PHASE LGATE RF RRF 470k RLGATE 0 C3* CS ROC_SET 30k RFB1 5.1k R3* COUT 330µF x 2 16V C4* C5* FB GND C6 10µF x 2 16V R2* RFB2 10k * : Optional Functional Pin Description Pin No. Pin Name Pin Function RT8237C RT8237D 1 6 PGOOD 2 7 CS 3 8 EN 4 9 FB 5 10 RF 6 1 LGATE Gate Drive Output for Low Side External MOSFET. 7 2 VCC Control Voltage Input. This pin provides the power for the buck controller, the low side driver and the bootstrap circuit for high side driver. Bypass to GND with a 1F ceramic capacitor. Open Drain Power Good Indicator. High impedance indicates power is good. Current Limit Threshold Setting Input. Connect a setting resistor to GND and the current limit threshold is equal to 1/8 of the voltage at this pin. PWM Enable. Pull low to GND to disable the PWM. VOUT Feedback Input. Connect FB to a resistor voltage divider from VOUT to GND to adjust the output from 0.7V to 3.3V Switching Frequency Selection. Connect a resistance to select switching frequency as shown in Electrical Characteristics. The switching frequency is detected and latched after startup. This pin also controls Diode emulation mode or forced CCM selection. Pull down to GND with resistor : Diode Emulation Mode. Connect to PGOOD with resistor : forced CCM after PGOOD becomes high. Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8237C/D-06 February 2014 RT8237C/D Pin No. Pin Name RT8237C RT8237D 8 3 PHASE 9 4 UGATE 10 5 BOOT --- 11 NC 11 12, 13 (Exposed Pad) (Exposed Pad) Pin Function External Inductor Connection Pin for PWM Converter. It behaves as the current sense comparator input for low side MOSFET RDS(ON) sensing and reference voltage for on time generation. Gate Drive Output for High Side External MOSFET. Supply Input for High Side Driver. Connect through a capacitor to the floating node (PHASE) pin. No Internal Connection. Ground. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. GND Function Block Diagram VCC TRIG On-time Compute 1-SHOT RF PHASE BOOT R - COMP S + FB 70% VREF + OV Latch S1 Q UV Latch S1 Q + PWM DRV UGATE PHASE VREF 125% VREF Q Min. tOFF Q TRIG 1-SHOT DRV LGATE GND - DEM/FCCM 125% VREF - PGOOD + VCC POR SS Timer EN - 90% VREF + Thermal Shutdown + X(1/8) + 10µA X(-1/8) CS Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8237C/D-06 February 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8237C/D Absolute Maximum Ratings (Note 1) VCC, FB, PGOOD, EN, CS, RF to GND ---------------------------------------------------------------------------BOOT to PHASE --------------------------------------------------------------------------------------------------------- PHASE to GND DC ----------------------------------------------------------------------------------------------------------------------------