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  Richtek Technology Electronic Components Datasheet  

RT8238A Datasheet

Single Synchronous Buck PWM Controller

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RT8238A pdf
RT8238A
Single Synchronous Buck PWM Controller
General Description
The RT8238A 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 constant on-time PWM control scheme handles wide
input/output voltage ratios with ease and provides 100ns
instant-onresponse to load transients while maintaining
a relatively constant switching frequency.
The RT8238A 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 Audio Skipping Mode (ASM)
setting maintains the switching frequency above 25kHz,
which eliminates noise in audio applications. The buck
conversion allows this device to directly step down high
voltage batteries at the highest possible efficiency. The
RT8238A is intended for CPU core, chipset, DRAM, or
other low voltage supplies as low as 0.5V. The RT8238A
is available in a WQFN-12L 2x2 package.
Ordering Information
RT8238A
Package Type
QW : WQFN-12L 2x2 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Z : ECO (Ecological Element with
Halogen Free and Pb free)
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.
Features
z Built in 1% 0.5V Reference Voltage
z Adjustable 0.5V to 3.3V Output Range
z Quick Load Step Response within 100ns
z 4700ppm/°C Programmable Current Limit by Low
Side RDS(ON) Sensing
z 4.5V to 26V Battery Input Range
z Resistor Programmable Frequency
z Internal Ramp Current Limit Soft-Start Control
z Drives Large Synchronous Rectifier FETs
z Integrated Boost Switch
z Over/Under Voltage Protection
z Thermal Shutdown
z Power Good Indicator
z RoHS Compliant and Halogen Free
Applications
z Notebook Computers
z CPU Core Supply
z Chipset/RAM Supply as Low as 0.5V
z Generic DC/DC Power Regulator
Pin Configurations
(TOP VIEW)
12 11 10
LGATE
PHASE
UGATE
1
2
3
GND
13
9 PGOOD
8 EN
7 MODE
4 56
WQFN-12L 2x2
RT8238A-06 October 2011
www.richtek.com
1


  Richtek Technology Electronic Components Datasheet  

RT8238A Datasheet

Single Synchronous Buck PWM Controller

No Preview Available !

RT8238A pdf
RT8238A
Marking Information
RT8238AGQW
CP : Product Code
CPW
W : Date Code
RT8238AZQW
CP : Product Code
CPW
W : Date Code
Typical Application Circuit
RTON
VDDP
R2
100k
11
TON
RT8238A
BOOT
4
5 VCC
C2
1µF
UGATE 3
PHASE 2
LGATE 1
R4
0
R5
0
VIN
4.5V to 26V
C4
10µF
C3
0.1µF
Q1
L1
Q2 R7*
PGOOD
Chip Enable
9 PGOOD
10 CS
R6
8 EN
FB 6
MODE 7
To 5V : DEM
To 2.5V : ASM
To GND : Forced-CCM
GND 12, 13 (Exposed Pad)
C7*
VOUT
1V
* : Optional
C5* C6*
R8
10k
C1
220µF
R9
10k
Functional Pin Description
Pin No.
1
2
3
4
5
6
7
8
Pin Name
Pin Function
LGATE Gate Drive Output for Low Side External MOSFET.
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.
UGATE Gate Drive Output for High Side External MOSFET.
BOOT
VCC
Supply Input for High Side Driver. Connect through 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 1μF
ceramic capacitor.
FB
MODE
VOUT Feedback Input. Connect FB to a resistive voltage divider from VOUT to
GND to adjust the output from 0.5V to 3.3V
Pull down to GND for Forced CCM Mode.
Pull up to 2.5V for Audio Skipping Mode (ASM).
Pull up to 5V for Diode Emulation Mode (DEM).
EN PWM Chip Enable. Pull low to GND to disable the PWM.
www.richtek.com
2
To be continued
RT8238A-06 October 2011


Part Number RT8238A
Description Single Synchronous Buck PWM Controller
Maker RICHTEK
Total Page 15 Pages
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