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RT8249D
Dual-Channel Synchronous DC/DC Step-Down Controller with 5V/3.3V LDOs
General Description
The RT8249D is a dual-channel step-down, controller generating supply voltages for battery-powered systems. It includes two Pulse-Width Modulation (PWM) controllers adjustable from 2V to 5.5V, and two fixed 5V/3.3V linear regulators. Each linear regulator provides up to 100mA output current and 3.3V linear regulator provides 1% accuracy under 35mA. The RT8249D provides a mode selection pin, SKIPSEL, to select Diode-Emulation Mode (DEM) or Audio Skipping Mode (ASM). Other features include on-board power-up sequencing, a power-good output, internal soft-start, and soft-discharge output that prevents negative voltage during shutdown.
A constant current ripple PWM control scheme operates without sense resistors and provides 100ns response to load transient. For maximizing power efficiency, the RT8249D automatically switches to the diode-emulation mode in light load applications. The RT8249D is available in the WQFN-20L 3x3 package.
Features
Support Connected Standby Mode for Ultrabook CCRCOT Control with 100ns Load Step Response PWM Maximum Duty Ratio > 98% 5V to 25V Input Voltage Range Dual Adjustable Output :
CH1 : 2V to 5.5V CH2 : 2V to 4V 5V/3.3V LDOs with 100mA Output Current 1% Accuracy on 3.3V LDO Output Oscillator Driving Output for Charge Pump Application Internal Frequency Setting 500kHz/600kHz (CH1/CH2) Internal Soft-Start and Soft-Discharge 4700ppm/°C RDS(ON) Current Sensing Independent Switcher Enable Control Built in OVP/UVP/OCP/OTP Non-latch UVLO Power Good Indicator 20-Lead WQFN Package RoHS Compliant and Halogen Free
Simplified Application Circuit
VIN
VOUT1
VIN UGATE2
RT8249D
BOOT2
UGATE1 BOOT1
PHASE2 LGATE2
PHASE1
LGATE1
FB2 CS1
BYP1
CS2
FB1
Channel 1 Enable
EN1
Channel 2 Enable
On
Off
EN2
LDO5
PGOOD LDO3
GND
VOUT2
5V PGOOD Indicator 3.3V
Copyright ©2016 Richtek Technology Corporation. All rights reserved. DS8249D-00 May 2016
is a registered trademark of Richtek Technology Corporation.
www.richtek.com 1
RT8249D
Applications
Notebook and Sub-Notebook Computers System Power Supplies 3-Cell and 4-Cell Li+ Battery-Powered Devices
Pin Configurations
(TOP VIEW)
EN1 SKIPSEL PHASE1 BOOT1 UGATE1
Ordering Information
RT8249D
Pin 1 Orientation***
(2) : Quadrant 2, Follow EIA-481-D
Package Type QW : WQFN-20L 3x3 (W-Type)
Lead Plating System G : Green (Halogen Free and Pb Free)
Note : ***Empty means Pin1 orientation is Quadrant 1 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.
CS1 FB1 LDO3 FB2 CS2
20 19 18 17 16
1 15 LGATE1 2 14 BYP1 3 GND 13 LDO5 4 21 12 VIN 5 11 LGATE2
6 7 8 9 10
EN2 PGOOD PHASE2 BOOT2 UGATE2
WQFN-20L 3x3
Marking Information
RT8249DGQW
9N=YM DNN
9N= : Product Code YMDNN : Date Code
Functional Pin Description
Pin No. 1
2 3 4
5 6
Pin Name CS1
FB1 LDO3 FB2
CS2 EN2
Pin Function
Current Limit Setting. Connect a resistor to GND to set the threshold for Channel 1 synchronous RDS(ON) sense. The GND PHASE1 current limit threshold is 1/8th the voltage seen at CS1 over a 0.2V to 2V range. There is an internal 50A current source from LDO5 to CS1.
Feedback Voltage Input for Channel 1. Connect FB1 to a resistive voltage divider from VOUT1 to GND to adjust output from 2V to 5.5V.
3.3V Linear Regulator Output. It is always on when VIN is higher than VINPOR threshold.
Feedback Voltage Input for Channel 2. Connect FB2 to a resistive voltage divider from VOUT2 to GND to adjust output from 2V to 4V.
Current Limit Setting. Connect a resistor to GND to set the threshold for Channel 2 synchronous RDS(ON) sense. The GND PHASE2 current limit threshold is 1/8th the voltage seen at CS2 over a 0.2V to 2V range. There is an internal 50A current source from LDO5 to CS2.
Enable Control Input for Channel 2.
7
PGOOD
Power Good Indicator Output for Channel 1 and Channel 2. (Logical AND)
Switch Node of Channel 2 MOSFETs. PHASE2 is the internal lower supply rail for
8
PHASE2
the UGATE2 high-side gate driver. PHASE2 is also the current-sense input for the
Channel 2.
9
BOOT2
Bootstrap Supply for Channel 2 High-Side Gate Driver. Connect to an external capacitor according to the typical application circuits.
10
UGATE2
High-Side Gate Driver Output for Channel 2. UGATE2 swings between PHASE2 and BOOT2.
Copyright ©2016 Richtek Technology Corporation. All rights reserved. www.richtek.com 2
is a registered trademark of Richtek Technology Corporation.
DS8249D-00 May 2016
RT8249D
Pin No. 11 12 13 14 15
16
17
Pin Name LGATE2 VIN LDO5 BYP1 LGATE1
UGATE1
BOOT1
18 PHASE1
19 SKIPSEL
20 EN1
21 (Exposed Pad)
GND
Pin Function
Low-Side Gate Driver Output for Channel 2. LGATE2 swings between GND and LDO5.
Power Input for 5V and 3.3V LDO Regulators and Buck Controllers.
5V Linear Regulator Output. LDO5 is a.