RT8237AZQW

® RT8237A/B High Efficiency Single Synchronous Buck PWM Controller General Description Features The RT8237A/B 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 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. 4 5 8 7 6 11 BOOT UGATE PHASE VCC LGATE LGATE 1 VCC PHASE 2 RF RT8237A 12 11 10 GND 13 3 4 UGATE Note : 10 9 WDFN-10L 3x3 Lead Plating System G : Green (Halogen Free and Pb Free) Z : ECO (Ecological Element with Halogen Free and Pb free) A : WDFN-10L 3x3 B : WQFN-12L 2x2 1 2 3 GND Package Type QW : WDFN-10L 3x3 (W-Type) QW : WQFN-12L 2x2 (W-Type)  NC RT8237  5 6 BOOT Ordering Information  PGOOD The RT8237A/B 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 RT8237A/B is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.7V. The RT8237A is available in a WDFN-10L 3x3 package, The RT8237B is available in a WQFN-12L 2x2 package. GND 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 RT8237B Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8237A/B-06 February 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 1 RT8237A/B Marking Information RT8237AGQW RT8237BGQW 37= : Product Code 35 : Product Code YMDNN : Date Code 37=YM DNN W : Date Code 35W RT8237AZQW RT8237BZQW 37 : Product Code 35 : Product Code YMDNN : Date Code 37 YM DNN W : Date Code 35W Typical Application Circuit VIN VCC R1 0 RT8237A/B C1 1µF VCC BOOT R5 100k PGOOD Chip Enable CBOOT RBOOT 0.1µF 0 RUGATE 0 UGATE C2 10µF x 3 50V VOUT 1.05V LOUT 0.45µH EN PHASE RF RRF 470k CS LGATE ROC_SET 30k GND RLGATE 0 C6 10µF x 2 16V R2* C3* RFB1 5.1k R3* COUT 330µF x 2 16V C4* C5* FB RFB2 10k * : Optional Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 2 is a registered trademark of Richtek Technology Corporation. DS8237A/B-06 February 2014 RT8237A/B Functional Pin Description Pin No. Pin Name RT8237A RT8237B 1 6 PGOOD 2 7 CS 3 8 EN 4 9 FB 5 10 RF 6 1 LGATE 7 2 VCC 8 3 PHASE 9 4 UGATE 10 5 BOOT --- 11 NC 11 12, 13 (Exposed Pad) (Exposed Pad) GND Pin Function 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 Pin. 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. Gate Drive Output for the Low Side External MOSFET. Control voltage input 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. 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 the 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. Copyright © 2014 Richtek Technology Corporation. All rights reserved. DS8237A/B-06 February 2014 is a registered trademark of Richtek Technology Corporation. www.richtek.com 3 RT8237A/B Function Block Diagram TRIG On-time Compute 1-SHOT RF PHASE VCC BOOT R - COMP S + FB 70% VREF + OV Latch S1 Q UV Latch S1 Q + PWM DRV UGATE PHASE VREF 120% VREF Q Min. TOFF Q TRIG 1-SHOT DRV LGATE GND - DEM/FCCM 120% VREF - PGOOD + VCC POR EN SS Timer - 90% VREF + Thermal Shutdown + X(1/8) + 10µA X(-1/8) CS Copyright © 2014 Richtek Technology Corporation. All rights reserved. www.richtek.com 4 is a registered trademark of Richtek Technology Corporation. DS8237A/B-06 February 2014 RT8237A/B Absolute Maximum Ratings (Note 1) VCC, FB, PGOOD, EN, CS, RF to GND ---------------------------------------------------------------------------PHASE to GND DC ----------------------------------------------------------------------------------------------------------------------------