®
RT8509
3A, 14V Step-Up DC-DC Converter
General Description
The RT8509 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 RT8509 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 RT8509 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 3.5A (typ.). Other features include
programmable soft-start, over voltage protection, and over
temperature protection.
The RT8509 is available in a WDFN-10L 3x3 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
Programmable Soft-Start
V
OUT
Over Voltage Protection
Over Temperature Protection
Thin 10-Lead WDFN Package
RoHS Compliant and Halogen Free
Applications
GIP TFT LCD Panels
Pin Configuration
(TOP VIEW)
COMP
FB
EN
GND
GND
GND
1
2
3
4
5
10
9
8
7
6
Ordering Information
RT8509
Package Type
QW : WDFN-10L 3x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
11
SS
VIN
VSUP
LX
LX
WDFN-10L 3x3
Note :
½
Richtek products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
½
Marking Information
H4= : Product Code
H4=YM
DNN
YMDNN : Date Code
Suitable for use in SnPb or Pb-free soldering processes.
Typical Application Circuit
V
IN
12V
C
IN
10µF x 2
L1
4.7µH
D1
6, 7
LX
8
VSUP
R1
134k
R2
10k
C
SS
33nF
R3
56k
C1
1nF
C
OUT
4.7µF x 3
V
OUT
18V
R4
10
C2
1µF
9 VIN
C3
1µF
RT8509
FB
SS
2
10
1
Chip Enable
3 EN
4, 5, 11 (Exposed Pad)
GND
COMP
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8509-02 March 2018
www.richtek.com
1
RT8509
Functional Pin Description
Pin No.
1
2
3
Pin Name
COMP
FB
EN
Pin Function
Compensation pin for error amplifier. Connect a series RC from COMP to ground.
Feedback. 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.
Chip enable. Drive EN low to turn off the Boost.
Ground. The Exposed Pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Switch. LX is the drain of the internal MOSFET. Connect the inductor/rectifier diode
junction to LX and minimize the trace area for lower EMI.
Boost converter over voltage protection input. Bypass VSUP with a minimum 1F
ceramic capacitor directly to GND.
Supply input. Bypass VIN with a minimum 1μF ceramic capacitor directly to GND.
Soft-start control. 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.
4, 5,
GND
11 (Exposed Pad)
6, 7
8
9
10
LX
VSUP
VIN
SS
Functional Block Diagram
VIN
EN
COMP
FB
LX
OTP
Protection
Soft
Start
SS
LX
Control
and
Driver
Logic
Error Amplifier Summing
Comparator
+
-
-
1.25V
+
OVP
V
DD
Clock
VSUP
GND
Oscillator
Slope
Compensation
Current
Sense
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8509-02 March 2018
RT8509
Absolute Maximum Ratings
(Note 1)
LX, VSUP to GND ---------------------------------------------------------------------------------------------------------
−0.3V
to 28V
VIN, EN to GND ------------------------------------------------------------------------------------------------------------
−0.3V
to 16.5V
Other Pins to GND --------------------------------------------------------------------------------------------------------
−0.3V
to 6.5V
Power Dissipation, P
D
@ T
A
= 25°C
WDFN-10L 3x3 ------------------------------------------------------------------------------------------------------------- 1.429W
Package Thermal Resistance (Note 2)
WDFN-10L 3x3,
θ
JA
------------------------------------------------------------------------------------------------------- 70°C/W
WDFN-10L 3x3,
θ
JC
------------------------------------------------------------------------------------------------------- 8.2°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
Recommended Operating Conditions
(Note 4)
Ambient Temperature Range --------------------------------------------------------------------------------------------
−40°C
to 85°C
Junction Temperature Range --------------------------------------------------------------------------------------------
−40°C
to 125°C
Electrical Characteristics
(V
IN
= 3.3V, V
OUT
= 10V, T
A
=25°C unless otherwise specified)
Parameter
Supply Current
Input Voltage Range
Output Voltage Range
Under Voltage Lockout
Threshold
UVLO Hysteresis
VIN Quiescent Current
Symbol
V
IN
V
OUT
V
UVLO
V
UVLO
I
Q
Test Conditions
Min
2.8
Typ
--
--
2.5
200
1
5
155
10
26
1200
90
1.25
--
0.05
Max
14
24
3
--
--
--
--
--
--
1500
--
--
100
0.2
Unit
V
V
V
mV
mA
C
C
V
kHz
%
V
nA
%/V
--
V
IN
rising
V
FB
= 1.3V, LX not switching
V
FB
= 1V, LX switching
Temperature rising
--
--
--
--
--
--
VSUP rising
--
1000
--
--
--
--
Thermal Shutdown Threshold T
SD
Thermal Shutdown
T
SD
Hysteresis
VSUP Over Voltage
Threshold
Oscillator
Oscillator Frequency
Maximum Duty Cycle
Error Amplifier
FB Regulation Voltage
FB Input Bias Current
FB Line Regulation
V
REF
I
FB
f
OSC
D
MAX
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8509-02 March 2018
www.richtek.com
3
RT8509
Parameter
Transconductance
Voltage Gain
N-MOSFET
Current Limit
On-Resistance
Leakage Current
Current Sense
Transresistance
Soft-Start
Charge Current
Control Inputs
EN Input
Voltage
Logic-High
Logic-Low
V
IH
V
IL
1.5
--
--
--
--
0.5
V
I
LIM
R
DS(ON)
I
LEAK
R
CS
V
LX
= 24V
3
--
--
--
--
3.5
100
30
0.25
5
--
250
45
--
--
A
m
A
V/A
A
Symbol
gm
A
V
Test Conditions
I
= ±2.5μA at V
COMP
= 1V
FB to COMP
Min
--
--
Typ
100
700
Max
--
--
Unit
A/V
V/V
Note 1.
Stresses beyond those listed
“Absolute
Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2.
θ
JA
is measured under natural convection (still air) at T
A
= 25°C with the component mounted on a high effective-
thermal-conductivity four-layer test board on a JEDEC 51-7 thermal measurement standard.
θ
JC
is measured at the
exposed pad of the package.
Note 3.
Devices are ESD sensitive. Handling precaution is recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8509-02 March 2018
RT8509
Typical Operating Characteristics
Boost Efficiency vs. Load Current
100
100
Boost Efficiency vs. Load Current
V
IN
= 5V
Boost Efficiency (%)
V
IN
= 3.3V
80
Boost Efficiency (%)
90
90
V
IN
= 14V
V
IN
= 12V
V
IN
= 10V
80
70
70
60
60
50
0
0.1
0.2
V
OUT
= 13.5V, f
OSC
= 1.2MHz
0.3
0.4
0.5
50
0
0.3
0.6
V
OUT
= 18V, f
OSC
= 1.2MHz
0.9
1.2
1.5
Load Current (A)
Load Current (A)
Boost Reference Voltage vs. Temperature
1.5
1400
Boost Frequency vs. Temperature
Boost Reference Voltage (V)
Boost Frequency (kHz)
1.4
1300
1.3
1200
1.2
1100
1.1
1000
1
-50
-25
0
25
50
75
V
IN
= 3.3V
100
125
900
-50
-25
0
25
50
75
V
IN
= 3.3V
100
125
Temperature (°C)
Temperature (°C)
Boost Reference Voltage vs. Input Voltage
1.5
Boost Current Limit vs. Input Voltage
7
Boost Reference Voltage (V)
1.3
Boost Current Limit (A)
2
4
6
8
10
12
14
1.4
6
5
1.2
4
1.1
3
1
2
2
4
6
8
10
12
14
Input Voltage (V)
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
Input Voltage (V)
is a registered trademark of Richtek Technology Corporation.
DS8509-02 March 2018
www.richtek.com
5
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