Document
®
RT7241A
12A, 23V, 500kHz, ACOTTM Synchronous Buck Converter with VTT LDO for Memory Power Supply
General Description
The RT7241A provides a complete power supply for DDR3/ DDR3L/LPDDR3/DDR4 memory systems. It integrates an Advanced Constant On-Time (ACOTTM) mode synchronous Buck converter with a 1.5A sink/source tracking linear regulator.
The PWM converter provides low quiescent supply current, high efficiency, excellent transient response, and high DC output accuracy needed for stepping down highvoltage batteries to generate low-voltage chipset RAM supplies in notebook computers. The ACOTTM control scheme handles wide input/output voltage ratios with ease and provides a very fast response to load transients with no external compensators.
The 1.5A sink/source VTT LDO maintains fast transient response only requiring 10μF ceramic output capacitance. The RT7241A supports all of the sleep state controls placing VTT at high-Z in S3 and discharging VDDQ and VTT in S4/S5.
The RT7241A provides complete protection features including OCP, OVP, UVP, and thermal shutdown. The RT7241A is available in the UQFN-18L 3x4 package.
Applications
DDR3/DDR3L/LPDDR3/DDR4 Memory Power Supplies Notebook computers
Marking Information
00= : Product Code
00=YM DNN
YMDNN : Date Code
Simplified Application Circuit
VIN
VDD RPGOOD
PGOOD
S3 S5
VIN BOOT CIN RT7241A
PHASE
VDD CVDD
FB
PGOOD
PGND VDDQ
S3 S5
GND
VLDOIN
VTT VTTSNS VTTGND
CS
CB L
R1 R2
VTT CVTT RCS
COUT
VDDQ
Copyright ©2016 Richtek Technology Corporation. All rights reserved. DS7241A-00 January 2016
is a registered trademark of Richtek Technology Corporation.
www.richtek.com 1
RT7241A
Features
DDR3/DDR3L/LPDDR3/DDR4 Complete Solution PWM Converter (VDDQ)
100μA Low Quiescent Supply Current at S3 Mode ACOTTM Mode Performs Fast Transient Response Support MLCC Output Capacitors Integrated Low On-Resistance MOSFETs 17mΩ of High-Side MOSFET 4.5mΩ of Low-Side MOSFET Adjustable from 0.6V to 1.5V Output Range for 1.5V (DDR3), 1.35V (DDR3L), 1.2V (LPDDR3) and 1.2V (DDR4) 4.5V to 23V Battery Input Range 500kHz Switching Frequency Resistor Adjustable Valley Current Limit Over-/Under-Voltage Protection Internal Voltage Ramp Soft-Start Power Good Indicator 1.5A LDO (VTT) Capable to Sink and Source up to 1.5A LDO Input Available to Optimize Power Losses Require Only 10μF Ceramic Output Capacitor Integrated Divider Tracks 1/2 VDDQ for VTT Accuracy ±20mV for VTT Support High-Z in S3 and Soft-Off in S4/S5 Tracking Mode Discharge Control Thermal Capable Flip-chip (FC) Package for 12A VDDQ Converter and 1.5A VTT LDO RoHS Compliant and Halogen Free
Ordering Information
RT7241A
Package Type QUF : UQFN-18L 3x4 (FC) (U-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.
Pin Configurations
(TOP VIEW)
S5 CS FB GND VDD
S3
BOOT PHASE
18 17 16 15 14
13 PGOOD
1
2 12 VIN
3
11 PGND
PHASE 4
10 PGND
5678 9
VDDQ VLDOIN
VTT VTTGND VTTSNS
UQFN-18L 3x4 (FC)
Copyright ©2016 Richtek Technology Corporation. All rights reserved.
www.richtek.com 2
is a registered trademark of Richtek Technology Corporation.
DS7241A-00 January 2016
RT7241A
Function Pin Description
Pin No. Pin Name
Pin Function
1 S3
VTT LDO Enable Control Input. Do not leave this pin floating.
2 BOOT
3, 4 PHASE 5 VDDQ 6 VLDOIN
Bootstrap Supply for High-Side Gate Driver. A capacitor is needed to drive the power switch's gate above the supply voltage. It is connected between the PHASE and BOOT pins to form a floating supply across the power switch driver.
Switch Node. External inductor connection for VDDQ.
Reference Input for the VTT LDO. An internal discharging circuit is connected to this pin.
Power Supply for the VTT LDO.
7 VTT
Power Output for the VTT LDO.
8 9 10, 11
VTTGND VTTSNS PGND
Power Ground for the VTT LDO.
Voltage Sense Input for the VTT LDO. Connect to the terminal of the VTT LDO output capacitor.
Power Ground for VDDQ.
12 VIN
Supply Input for VDDQ.
13 PGOOD
Open-Drain Power Good Indicator Output.
14 VDD
Analog Supply Input.
15 GND 16 FB 17 CS
Analog Ground.
Feedback Voltage Input. Connect to a resistive voltage divider from VDDQ to GND to adjust the output of PWM converter.
Current Limit Threshold Setting Input. Connect to GND through the setting resistor.
18 S5
PWM Converter Enable Control Input. Do not leave this pin floating.
Copyright ©2016 Richtek Technology Corporation. All rights reserved. DS7241A-00 January 2016
is a registered trademark of Richtek Technology Corporation.
www.richtek.com 3
RT7241A
Function Block Diagram
Buck Converter
VIN VDD
S5
FB
UVLO 4.2V
Internal SST
Thermal Protection
PWM Control and Protect
Logic
0.6V
+ -
GND
Over Curre.