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RT6541A
High Efficiency Single Synchronous Buck PWM Controller
General Description
The RT6541A 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.
The RT6541A supports on chip voltage programming function between 0.8V and 1.05V by controlling GX digital inputs.
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.
The RT6541A 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 RT6541A is intended for CPU core, chipset, DRAM, or other low voltage supplies as low as 0.8V.
The RT6541A is available in a WDFN-14L 3x2 package.
Features
Intel SKL VR support Built-in 1% Reference Voltage 2-Bit Programmable Output Voltage with Integrated
Transition Support Support Intel LPM (Low-Power Mode) Feature 4700ppm/°C Programmable Current Limit by Low-
Side RDS(ON) Sensing 3V to 26V Battery Input Range Internal Voltage Ramp 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 Tiny 14-Lead WDFN Package
Applications
Notebook Computers CPU/GPU Core Supply Chipset/RAM Supply Generic DC-DC Power Regulator
Simplified Application Circuit VIN
RT6541A
VCC
VCC CBYPASS
UGATE
BOOT
R2 PGOOD
PHASE
EN
LGATE
RCS CS
LPM
GND MODE
RGND FB G0
G1
Copyright ©2021 Richtek Technology Corporation. All rights reserved. DS6541A-03 May 2021
Q1 R4 R3
C1
Q2
CIN
LOUT
R5* C2*
COUT
VOUT
is a registered trademark of Richtek Technology Corporation.
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RT6541A
Ordering Information
RT6541A
Package Type QW : WDFN-14L 3x2 (W-Type)
(Exposed Pad-Option 1)
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 Configuration
(TOP VIEW)
MODE 1 PGOOD 2
EN 3 LPM 4 BOOT 5 UGATE 6 PHASE 7
GND
15
14 CS 13 FB 12 RGND 11 G1 10 G0 9 VCC 8 LGATE
WDFN-14L 3x2
Marking Information
0TW
0T : Product Code W : Date Code
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
MODE
VCCIO/PCH_Core/EDRAM select pin.
2
PGOOD
Open drain power good indicator. High impedance indicates power is good.
3
EN
PWM enable control input. Do not leave this pin floating.
4
LPM
Low power mode control pin.
5
BOOT
BOOT bootstrap supply for high-side gate driver.
6
UGATE
High-side gate driver output.
7
PHASE
Switch node. External inductor connection for VDDQ and behave as the current sense comparator input for Low-Side MOSFET RDS(ON) sensing.
8
LGATE
Low-side gate driver output.
9
VCC
Supply voltage input for the analog supply and LGATE gate driver.
10
G0
2-bit input pin.
11
G1
2-bit input pin.
12
RGND
Remote voltage sense ground pin.
13
FB
14
CS
15 (Exposed Pad) GND
Output voltage feedback input. Connect VOUT to converter output node.
Current limit threshold setting input. Connect a setting resistor to GND and the current limit threshold is equal to 1/10 of the voltage at this pin.
Ground. The Exposed Pad must be soldered to a large PCB and connected to GND for maximum power dissipation.
Copyright ©2021 Richtek Technology Corporation. All rights reserved. www.richtek.com 2
is a registered trademark of Richtek Technology Corporation.
DS6541A-03 May 2021
Functional Block Diagram
RT6541A
PHASE
TRIG On-time compute
One shot
Comp
FB
-
+
R SQ
Min Toff
Q
TRIG
One shot
DRV
BOOT
UGATE PHASE
VCC
LPM G0 G1
MODE
RGND EN
+
1.2V
-
0.3V +
Latch
OV S1
Q
Latch
UV S1
Q
0.675V +
Voltage Programmer
SS Timer
Thermal Shutdown
ZCD +
-
DRV
LGATE GND
PGOOD
DEM
+ -
OC threshold 1/10
10µA CS
Operation
The RT6541A is a constant on-time synchronous stepdown controller. In normal operation, the high-side NMOSFET is turned on when the output voltage is lower than VREF, and is turned off after the internal one-shot timer expires. While the high-side N-MOSFET is turned off, the low-side N-MOSFET is turned on to conduct the inductor current until next cycle begins.
Soft-Start (SS) For internal soft-start function, an internal current source charges an internal capacitor to build the soft-start ramp voltage. The output voltage will tra.