®
RT8241D
High Efficiency Single Synchronous Buck PWM Controller
General Description
Features
The RT8241D 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.
z
Meet Intel VCCSA Voltage Slew Rate
z
Built-in 1% Reference Voltage
2-Bit Programmable Output Voltage with Integrated
Transition Support
Quick Load-Step Response within 100ns
4700ppm/°°C Programmable Current Limit by Low
Side RDS(ON) Sensing
4.5V to 26V Battery Input Range
Internal Ramp Current Limit Soft-Start Control
Drives Large Synchronous Rectifier FETs
Integrated Boost Switch
Over/Under Voltage Protection
Thermal Shutdown
Power Good Indicator
RoHS Compliant and Halogen Free
z
z
z
z
z
z
z
z
z
Applications
z
z
z
z
Notebook Computers
CPU/GPU Core Supply
Chipset/RAM Supply
Generic DC/DC Power Regulator
Pin Configurations
The RT8241D is available in a WQFN-12L 2x2 package.
RT8241D
Lead Plating System
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Note :
LGATE
1
PHASE
UGATE
2
12
11
10
GND
13
3
4
5
6
EN
Package Type
QW : WQFN-12L 2x2 (W-Type)
FB
Ordering Information
CS
(TOP VIEW)
GND
The RT8241D 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 RT8241D is intended for CPU core,
chipset, DRAM, or other low voltage supplies as low as
0.675V.
z
VCC
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.
BOOT
The RT8241D supports on chip voltage programming
function between 0.675V and 0.9V by controlling GX digital
inputs.
z
9
PGOOD
8
G1
G0
7
WQFN-12L 2x2
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.
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS8241D-03
January 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
RT8241D
Marking Information
RT8241DGQW
RT8241DZQW
38 : Product Code
38 : Product Code
38W
W : Date Code
W : Date Code
38W
Typical Application Circuit
For Fixed Voltage Regulator :
VCC
RT8241D
5 VCC
BOOT 4
R1
CBYPASS
R2
Chip Enable
UGATE 3
C1
CIN
R4
11 CS
12,
13 (Exposed Pad)
VIN
Q1
9 PGOOD
6 EN
RCS
R3
LOUT
PHASE 2
VOUT
COUT
R5*
LGATE 1
GND
Q2
G0 7
G1 8
C2*
FB 10
* : Optional
For Adjustable Voltage Regulator :
VCC
RT8241D
5 VCC
BOOT 4
R1
CBYPASS
UGATE 3
R2
Chip Enable
C1
CIN
R4
11 CS
12,
13 (Exposed Pad)
VIN
Q1
9 PGOOD
6 EN
RCS
R3
LOUT
PHASE 2
R5*
LGATE 1
Q2
G0 7
G1 8
GND
RFB1
C3*
VOUT
COUT
C2*
RFB2
FB 10
* : Optional
G0
0
0
1
1
Table 1. VID Table
G1
0
1
0
1
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
VFB
0.9V
0.8V
0.725V
0.675V
is a registered trademark of Richtek Technology Corporation.
DS8241D-03
January 2014
RT8241D
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
LGATE
Gate Drive Output for Low Side External MOSFET.
2
PHASE
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.
3
UGATE
4
BOOT
5
VCC
6
EN
Chip Enable (Active High).
7
G0
2-Bit Input Pin.
8
G1
2-Bit Input Pin.
9
PGOOD
Open Drain Power Good Indicator. High impedance indicates power is good.
10
FB
11
CS
Output Voltage Feedback Input.
Current Limit Threshold Setting Input. Connect a setting resistor to GND and
the current limit threshold is equal to 1/8 of the voltage seen at this pin.
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Gate Drive Output for the High Side External MOSFET.
Supply Input for High Side Driver. Connect a capacitor to the floating node
(PHASE) pin.
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
4.7μF ceramic capacitor.
12, 13 (Exposed Pad) GND
Function Block Diagram
PHASE
FB
TRIG
On-time compute
One shot
R
- COMP
GM
+
SS
(Internal)
TON
VREF
-
1.1V
-
0.45V
DRV
VCC
Voltage
Programmer
ZCD +
-
+
85% VREF
Thermal
Shutdown
SS
G1
Diode
Emulation
GND
PGOOD
leakage
10µA
+
-
EN
CS
1/8
OC threshold
Copyright © 2014 Richtek Technology Corporation. All rights reserved.
DS8241D-03
LGATE
LG RDS(ON)
-
G0
UGATE
PHASE
DRV
UV Latch
S1 Q
+
BST switch
resistance
UG RDS(ON)
Min toff
Q
TRIG
One shot
OV Latch
S1 Q
+
BOOT
S Q
+
January 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3
RT8241D
Absolute Maximum Ratings
(Note 1)
VCC, FB, PGOOD, EN, CS, G0, G1 to GND ----------------------------------------------------------------------PHASE to GND
DC ----------------------------------------------------------------------------------------------------------------------------
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