RT8205A Datasheet, PDF (1/28 Pages) Richtek Technology Corporation – High Efficiency, Main Power Supply Controllers for Notebook Computers

®
RT8205A/B/C
High Efficiency, Main Power Supply Controllers
for Notebook Computers
General Description
The RT8205A/B/C dual step-down, switch-mode power-
supply controller generates logic-supply voltages in
battery-powered systems. The RT8205A/B/C includes two
pulse-width modulation (PWM) controllers fixed at 5V/
3.3V or adjustable from 2V to 5.5V. An alternative LGATE1
output LG1_CP can be used for external charge pump
(RT8205B). And an optional external charge pump can be
monitored through SECFB (RT8205C). This device also
features 2 linear regulators providing fixed 5V and 3.3V
outputs. The linear regulator each provides up to 70mA
output current with automatic linear-regulator bootstrapping
to the PWM outputs. The RT8205A/B/C includes on-board
power-up sequencing, the power-good output, internal soft-
start, and internal soft-discharge output that prevents
negative voltages on shutdown.
A constant on-time PWM control scheme operates without
sense resistor and provides 100ns response to load
transients while maintaining a relatively constant switching
frequency. The unique ultrasonic mode maintains the
switching frequency above 25kHz, which eliminates noise
in audio applications. Other features include diode-
emulation mode (DEM), which maximizes efficiency in
light-load applications, and fixed-frequency PWM mode,
which reduces RF interference in sensitive application
Features
z Wide Input Voltage Range 6V to 25V
z Dual Fixed 5V/3.3V Outputs or Adjustable from 2V
to 5.5V, 1.5% Accuracy.
z Alternative LGATE1 Output (LG1_CP) acts as Clock
for Charge Pump (RT8205B)
z Secondary Feedback Input Maintains Charge Pump
Voltage (RT8205C)
z Fixed 3.3V and 5V LDO Output : 70mA
z 2V Reference Voltage ±1% : 50μA
z Constant ON-Time Control with 100ns Load Step
Response
z Frequency Selectable via TONSEL Setting
z R_DS(ON) Current Sensing and Programmable Current
Limit combined with Enable Control
z Selectable PWM, DEM, or Ultrasonic Mode
z Internal Soft-Start and Soft-Discharge
z High Efficiency up to 97%
z 5mW Quiescent Power Dissipation
z Thermal Shutdown
z RoHS Compliant and Halogen Free
Applications
z Notebook and Sub-Notebook Computers
z 3-Cell and 4-Cell Li+ Battery-Powered Devices
Ordering Information
RT8205
Package Type
QW : WQFN-24L 4x4 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Pin Function
A : Default
B : With LG1_CP
C : With SECFB
Note :
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 ©2012 Richtek Technology Corporation. All rights reserved.
DS8205A/B/C-06 July 2012
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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