Richtek RT8509A User Manual
RT8509A
®
DS8509A-00 November 2013 www.richtek.com
1
©
Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
4.5A Step-Up DC/DC Converter
General Description
The RT8509A is a high performance switching Boost
converter that provides a regulated supply voltage for active
matrix thin film transistor (TFT) liquid crystal displays
(LCDs).
The RT8509A incorporates current mode, fixed-frequency,
pulse width modulation (PWM) circuitry with a built in
N-MOSFET to achieve high efficiency and fast transient
response.
The RT8509A has a wide input voltage range from 2.8V to
14V. In addition, the output voltage can be adjusted up to
24V via an external resistive voltage divider. The maximum
peak current is limited to 4.5A (min.). Other features
include adjustable soft-start, over-voltage protection, and
over-temperature protection.
The RT8509A is available in the WDFN-12L 5x5 package.
Features
90% Efficiency
Adjustable Output Up to 24V
2.8V to 14V Input Supply Voltage
Input Supply Under-Voltage Lockout
Fixed 1.2MHz Switching Frequency
Adjustable Soft-Start
V
OUT
Over-Voltage Protection
Over-Temperature Protection
Thin 12-Lead WDFN Package
RoHS Compliant and Halogen Free
Applications
GIP TFT-LCD Panels
Ordering Information
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.
Package Type
QW : WDFN-12L 5x5 (W-Type)
RT8509A
Lead Plating System
G : Green (Halogen Free and Pb Free)
LX
RT8509A
VIN
EN
VOUT
FB
SS
COMPGND
R1
R2
C
OUT
V
OUT
C
SS
R3
C1
C2
R4
C
IN
V
IN
L1
D1
C3
Enable
Marking Information
RT8509A
GQW
YMDNN
RT8509AGQW : Product Number
YMDNN : Date Code
Simplified Application Circuit
RT8509A
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Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
Functional Pin Description
Pin No. Pin Name Pin Function
1 COMP
Compensation Node for Error Amplifier. Connect a series RC from COMP to
ground.
2 FB
Feedback Voltage Input. The FB regulation voltage is 1.25V nominal. Connect an
external resistive voltage divider between the step-up regulator’s output (V
OUT
)
and GND, with the center tap connected to FB. Place the divider close to the IC
and minimize the trace area to reduce noise coupling.
3 EN Enable Control Input. Drive EN low to turn off the Boost.
4, 5, 6, 9,
13 (Exposed Pad)
GND
Ground. The Exposed Pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
7, 8 LX
Switch Node. LX is the Drain of the internal MOSFET. Connect the
inductor/rectifier diode junction to LX and minimize the trace area for lower EMI.
10 VOUT
Over-Voltage Protection Input for Boost Converter. Bypass VOUT with a
minimum 1F ceramic capacitor directly to GND.
11 VI N
Supply Voltage Input. Bypass VIN with a minimum 1μF ceramic capacitor directly
to GND.
12 SS
Soft-Start Time Setting. Connect a soft-start capacitor (C
SS
) to this pin. The
soft-start capacitor is charged with a constant current of 5A. The soft-start
capacitor is discharged to ground when EN is low.
Pin Configurations
WDFN-12L 5x5
(TOP VIEW)
COMP
FB
GND
GND
SS
VIN
VOUT
LX
GND
EN
GND
LX
GND
13
11
10
9
1
2
3
4
5
12
67
8
RT8509A
3
DS8509A-00 November 2013 www.richtek.com
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Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
Function Block Diagram
Operation
The RT8509A is a high-performance step-up DC/DC
converter that provides a regulated and high precision
supply voltage. It incorporates current mode, fixed-
frequency, pulse-width modulation (PWM) circuitry with
a built-in N-Channel power MOSFET to achieve high
efficiency and fast transient response. The device features
an adjustable soft start time using an external soft-start
capacitor to reduce in-rush current.
Soft
Start
Control
and
Driver
Logic
Current
Sense
Protection
+
-
+
-
Slope
Compensation
Oscillator
OVP
LX
OTP
Error Amplifier
V
DD
1.25V
FB
COMP
EN
VIN
VOUT
Summing
Comparator
LX
SS
GND
Clock
RT8509A
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Copyright 2013 Richtek Technology Corporation. All rights reserved. is a registered trademark of Richtek Technology Corporation.
Electrical Characteristics
Recommended Operating Conditions
(Note 4)
Ambient Temperature Range --------------------------------------------------------------------------------------------
−40°C to 85°C
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Absolute Maximum Ratings (Note 1)
LX to GND ------------------------------------------------------------------------------------------------------------------- −0.3V to 28V
VIN, EN to GND ------------------------------------------------------------------------------------------------------------ −0.3V to 16.5V
Other Pins------------------------------------------------------------------------------------------------------------------- −0.3V to 6.5V
Power Dissipation, P
D
@ T
A
= 25°C
WDFN-12L 5x5 ------------------------------------------------------------------------------------------------------------- 3.38W
Package Thermal Resistance (Note 2)
WDFN-12L 5x5, θJA------------------------------------------------------------------------------------------------------- 29.5°C/W
WDFN-12L 5x5, θJC------------------------------------------------------------------------------------------------------- 7.5°C/W
Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
Storage Temperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C
Lead Temperature (Soldering, 10sec.) -------------------------------------------------------------------------------- 260°C
ESD Susceptibility (Note 3)
HBM (Human Body Model)---------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ----------------------------------------------------------------------------------------------------- 200V
(V
IN
= 3.3V, V
OUT
= 10V, TA =25°C unless otherwise specified)
Parameter Symbol Test Conditions Min Typ Max Unit
Supply Current
Input Voltage Range VIN
2.8 -- 14 V
Output Voltage Range
V
OUT
--
-- 24 V
Under Voltage Lockout
Threshold
V
UVLO
V
IN
Rising
-- 2.5 3 V
UVLO Hysteresis
V
UVLO
-- 200 -- mV
V
FB
= 1.3V, LX Not Switching
-- 1 --
VIN Quiescent Current
I
Q
V
FB
= 1V, LX Switching -- 5 --
mA
Thermal Shutdown Threshold
T
SD
Temperature Rising -- 155 --
C
Thermal Shutdown
Hysteresis
T
SD
-- 10 --
C
VOUT Over Voltage
Threshold
V
OUT
Rising
-- 26 -- V
Oscillator
Oscillator Frequency
f
OSC
1000 1200 1500 kHz
Maximum Duty Cycle
D
MAX
-- 90 -- %
Error Amplifier
FB Regulation Voltage
V
REF
1.2312 1.25 1.2688 V
FB Input Bias Current
I
FB
-- -- 100 nA
FB Line Regulation -- 0.05 0.2 %/V
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