High Efficiency, Main Power Supply Controller
for Notebook Computers
The RT8243A/B/C is a dual step down, Switch Mode Power
Supply (SMPS) controller which generates logic supply
voltages for battery powered systems. It includes two
Pulse Width Modulation (PWM) controllers adjustable
from 2V to 5.5V and also two fixed 5V/3.3V linear
regulators. One of the controllers (LDO5) provides
automatic switch over to the BYP1 input connected to
the main SMPS1 output for maximized efficiency. An
optional external charge pump can be monitored through
SECFB (RT8243B/C). Other features include on board
power up sequencing, a power good output, internal soft-
start, and a soft discharge output that prevents negative
voltage during shutdown.
A constant on-time PWM control scheme operates without
sense resistors and assures fast load transient response
while maintaining nearly constant switching frequency. To
eliminate noise in audio applications, an ultrasonic mode
is included, which maintains the switching frequency
above 25kHz. Moreover, a diode emulation mode
maximizes efficiency for light load applications. The
SMPS1/SMPS2 switching frequency can be adjustable
from 200kHz/233kHz to 400kHz/466kHz respectively.
The RT8243A/B/C is available in a WQFN-20L 3x3
package, and operates over an extended temperature range
from −40°C to 85°C.
5.5V to 25V Input Voltage Range
2V to 5.5V Output Voltage Range
No Current Sense Resistor Needed
5V/3.3V Linear Regulators
4700ppm/°C RDS(ON) Current Sensing
Internal Current Limit Soft-Start and Soft Discharge
Built In OVP/UVP/OCP
Selectable Operation Mode with Switcher Enable
SECFB Input Maintains Charge Pump Voltage
Power Good Indicator (RT8243B/C includes SECFB)
RoHS Compliant and Halogen Free
System Power Supplies
3- and 4- Cell Li+ Battery-Powered Device
QW : WQFN-20L 3x3 (W-Type)
Lead Plating System
Z : ECO (Ecological Element with
Halogen Free and Pb free)
Pin Function With
A : ENM
B : SECFB
C : SECFB, Ultrasonic Mode
Richtek products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
DS8243A/B/C-07 November 2014
is a registered trademark of Richtek Technology Corporation.