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RT9363
Smallest 60mA 3-Channel Charge Pump White LED Driver
with Low Dropout Current Source
General Description
Features
The RT9363 is a high efficiency and cost effective charge
pump white LED driver. It supports up to 3 white LEDs
with regulated constant current for uniform intensity. The
RT9363 maintains the highest efficiency by utilizing a
x1/x2 charge pump and low dropout current regulators.
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User can easily configure each LED current up to 20mA by
a pulse dimming control. The dimming of white LEDs
current can be achieved by applying a pulse signal to the
EN pin. There are totally 16 steps of current could be set
by users.
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The operating voltage range is 2.8V to 5.0V. Internal soft
start circuitry effectively reduces the inrush current while
both start-up and mode transition. RT9363 also provides
comprehensive protections such as short circuit protection.
The load is disconnected from VIN while shutdown and
the shutdown current is less than 10μA.
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Applications
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RT9363 is available in a TSOT-23-8 package (1.0mm max
height).
Very High Efficiency Over 80% of Battery Life
Support up to 3 White LEDs
Support up to 60mA Output Current
1% Typical LED Current Matching
Soft Start Function
Short Circuit Protection Function
Auto Charge Pump Mode Selection
250kHz Fixed Frequency Oscillator
Output Over Voltage Protection
16-Step Brightness Control
Low Input Noise and EMI
RoHS Compliant and 100% Lead (Pb)-Free
Mobile Phone, DSC, MP3
White LED Backlighting
LCD Display Supply
Pin Configurations
Richtek products are :
`
EN
CP
6
5
2
3
4
VIN
Note :
7
GND
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
8
LED3
Package Type
J8 : TSOT-23-8
LED1
RT9363
VOUT
(TOP VIEW)
LED2
Ordering Information
TSOT-23-8
RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020.
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Suitable for use in SnPb or Pb-free soldering processes.
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
DS9363-03 April 2011
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RT9363
Typical Application Circuit
RS
10k
Pulse
input
CS
100pF
4 VIN
CIN
4.7uF
+
2
6
VOUT
COUT
1uF
3
EN
GND
5
CP
RT9363
7
LED1
LED2 8
LED3
CP
1uF
1
Figure 1. For 3-WLEDs Application Circuit
RS
10k
Pulse
input
CS
100pF
4 VIN
CIN
4.7uF
+
2
VOUT
COUT
1uF
3
EN
GND
6
5
CP
1uF
CP
RT9363
7
LED1
LED2 8
LED3
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Figure 2. For 2-WLEDs Application Circuit
Functional Pin Description
Pin Number
Pin Name Pin Function
1
LED3
Current Sink for LED3. (If not in use, this pin must be connected to VIN)
2
VOUT
Output Voltage Source for LED1~3.
3
GND
Power Ground.
4
VIN
Input Voltage.
5
CP
Positive Terminal of Bucket Capacitor.
6
EN
Active High Enable. And connects 10k resistor to GPIO pin of MCU.
7
LED1
Current Sink for LED1. (If not in use, this pin must be connected to VIN)
8
LED2
Current Sink for LED2. (If not in use, this pin must be connected to VIN)
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DS9363-03 April 2011
RT9363
Function Block Diagram
CP
VIN
VOUT
Current
Limitation
Soft Start
Circuit
OVP
+
Gate Driver
250kHz
OSC
Mode Decision
Current
Bias
Vr1
LED1
LED2
UVLO
16 Steps Pulse
Dimming Controller
EN
GND
DS9363-03 April 2011
EN
Check
Shutdown
Delay
LED3
Current Source
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RT9363
Absolute Maximum Ratings
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(Note 1)
Supply Input Voltage -----------------------------------------------------------------------------------------------------Other I/O Pin Voltages --------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
TSOT-23-8 ------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
TSOT-23-8, θJA ------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ----------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------
Recommended Operating Conditions
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−0.3V to 6V
−0.3V to 6V
0.455W
220°C/W
260°C
125°C
−65°C to 150°C
2kV
200V
(Note 4)
Operation Voltage Range ----------------------------------------------------------------------------------------------- 2.8V to 5V
Junction Temperature Range -------------------------------------------------------------------------------------------- −40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 3.7V, TA = 25°C, unless otherwise specified)
Parameter
Input Supply Voltage
Symbol
Test Conditions
VIN
Under Voltage Lockout Threshold
VIN Rising
Under Voltage Lockout Hysteresis
Min
2.8
Typ
--
Max
5.0
Unit
V
--
2.2
--
V
--
100
--
mV
LEDs Current
ILED
100% Setting
--
20
--
mA
Shutdown Current
ISHDN
EN = 0V, VIN = 3.6V
--
3
10
μA
Quiescent Current
IQ
--
1
--
mA
ILED Accuracy
ILED-ERR
100% Setting, ILED1~3
−8
--
+8
%
ILED-LED-ERR 100% Setting, ILED1~3
−5
--
+5
%
--
3.6
--
V
--
250
--
kHz
--
--
250
mA
Logic-High VIH
1.5
--
--
Logic-Low VIL
--
--
0.25
(Note 6)
Current Matching
(Note 7)
x1 mode to x2 mode
Transition Voltage (VIN Falling)
VTRANS1X
Oscillator Frequency
F OSC
Inrush Current
IINRUSH
EN Threshold Voltage
EN Current
(V IN connect to LED1~3)
VLED = 3.4V, IOUT = 45mA
ILED1 = ILED2 = ILED3 = 15mA
VIN = 3.0V (x2 mode)
V
Logic-High IIH
VIH = 1.8V, RS = 10kΩ
--
200
--
Logic-Low IIL
VIL = GND
--
0.1
10
2
--
--
ms
0.1
--
0.3
ms
150
--
300
mA
EN Low Time for Shutdown
T SHDN
EN Low Time for Dimming
T LO
Short Circuit Current
EN = High, VIN = 3.6V, No Load
μA
(To be continued)
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DS9363-03 April 2011
RT9363
Parameter
Symbol
EN High Time for Dimming
THI
EN High Time for Holding
THO
Over Voltage Protection
V OVP
Test Conditions
(Note 5)
Open circuit at any LED that is
programmed to be in the on state
Min
Typ
Max
Unit
0.1
--
0.3
ms
0.1
--
--
ms
--
5.5
--
V
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in the natural convection at T A = 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. EN High time after the dimming sequence has being completed.
Note 6. ILED Accaracy = 100% x (ILED1/2/3 − 20mA).
Note 7. Current Matching = (ILED(MAX/MIN) − ILED, AVG) / ILED, AVG.
DS9363-03 April 2011
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RT9363
Typical Operating Characteristics
Efficiency vs. Input Voltage
Efficiency vs. Input Voltage
100%
100
ILED = 15mA, VF = 3.12V
90%
90
90%
90
80%
80
80%
80
Efficiency (%)
Efficiency (%)
100%
100
70%
70
60%
60
50%
50
40%
40
ILED = 20mA, VF = 3.12V
70%
70
60%
60
50%
50
40%
40
30
30%
30%
30
2.8
3.2
3.6
4
4.4
4.8
5.2
5.6
2.8
3.2
3.6
Input Voltage (V)
4
4.4
4.8
5.2
5.6
Input Voltage (V)
Input Current vs. Input Voltage
LED Current vs. Input Voltage
23
130
VF = 3.13V
TA = 25°C
120
22
Input Current (mA)
LED Current (mA)
110
21
20
19
100
90
80
70
60
18
50
40
17
2.5
3
3.5
4
4.5
5
3
5.5
3.1
3.2
Input Voltage (V)
x1 Mode LED Current vs. Temperature
3.4
3.5
3.6
3.7
x2 Mode LED Current vs. Temperature
22
22
21
21
20
LED1
LED3
19
LED2
18
17
LED Current (mA)
LED Current (mA)
3.3
Input Voltage (V)
20
LED1
19
LED3
LED2
18
17
16
16
-40
-20
0
20
40
Temperature (°C)
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60
80
100
-40
-20
0
20
40
60
80
100
Temperature (°C)
DS9363-03 April 2011
RT9363
Shutdown Current vs. Temperature
Quiescent Current vs. Temperature
4.5
0.98
VIN = 3.6V
0.97
Quiescent Current (mA)
Shutdown Current (uA)
4
3.5
3
2.5
2
0.96
0.95
0.94
0.93
0.92
0.91
0.9
1.5
0.89
-40
-25
-10
5
20
35
50
65
80
95
-40
-25
-10
5
Temperature (°C)
1.2
4.5
1.1
4
Quiescent Current (mA)
Quiescent Current (mA)
35
50
65
80
95
x2 Mode Quiescent Current vs. Input Voltage
x1 Mode Quiescent Current vs. Input Voltage
1
0.9
0.8
0.7
0.6
0.5
3.5
3
2.5
2
1.5
1
0.4
2.5
3
3.5
4
4.5
5
2.5
5.5
3
3.5
4.5
5
5.5
Mode Transition Hysteresis vs. Temperature
Input Voltage vs. Temperature
Mode Transition Hysteresis (mV)1
2.25
POR
2.20
2.15
POF
2.10
4
Input Voltage (V)
Input Voltage (V)
Input Voltage (V)
20
Temperature (°C)
2.05
2.00
1.95
360
x2 Mode, VIN = 3.3V
340
320
300
280
260
240
220
200
-40
-20
0
20
40
60
Temperature (°C)
DS9363-03 April 2011
80
100
-40
-20
0
20
40
60
80
100
Temperature (°C)
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RT9363
x1 Mode Inrush Current
OVP
5.62
5.61
CP
(2V/Div)
VOUT
(500mV/Div)
5.6
OVP (V)
5.59
5.58
5.57
5.56
EN
(1V/Div)
I IN
(100mA/Div)
5.55
5.54
VIN = 3.7V
5.53
2.8
3.3
3.8
4.3
4.8
5.3
5.8
Time (100μs/Div)
Input Voltage (V)
x2 Mode Mode Inrush Current
x1 Mode Normal Operation
VIN
(200mV/Div)
VOUT
(500mV/Div)
CP
(2V/Div)
VOUT
(500mV/Div)
CP
(2V/Div)
EN
(1V/Div)
I IN
(100mA/Div)
VIN = 3.2V
I LED
(20mA/Div)
Time (100μs/Div)
Time (10μs/Div)
x2 Mode Normal Operation
Ripple & Spike
VIN
(200mV/Div)
VOUT
(500mV/Div)
VIN ac
(100mV/Div)
VOUT
(500mV/Div)
CP
(2V/Div)
CP
(2V/Div)
I IN
(100mA/Div)
I IN
(100mA/Div)
VIN = 3.2V
Time (10μs/Div)
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VIN = 3.7V
VIN = 3.2V
Time (5μs/Div)
DS9363-03 April 2011
RT9363
Application Information
High Efficiency x1/x2 Charge Pump
Before the discussion of efficiency in RT9363, two things
need to be illustrated. One is the Li-ion battery life time,
the other is the forward voltage of white LED.
The Li-ion battery energy is not linearly proportion to battery
voltage. In the Figure 3, It shows the 80% battery life of Liion is arranged in 3.65V to 4.0V. The other voltage range
occupies less than 20% battery energy and is insignificant.
In the backlight application, the forward voltage of white
LEDs most likely falls in 3.2 to 3.5V @ILED = 20mA.
The development concept of RT9363 is based on the
backlight application with Li-ion battery. RT9363 is very
cost-effective product for driving white LEDs in backlight.
It extends the 80% battery life by the reduction of open
loop resistance at x1 mode and current source drop out
voltage. Figure 4 is the efficiency diagram of RT9363, 80%
battery life is marked by red rectangle. The RT9363
maximize the x1 mode operating range in the 80% battery
life. Therefore, the efficiency is not significant different to
that without x1.5 mode charge pump. The peak efficiency
of RT9363 is 93% and average is 84%. Comparing to the
LED drivers with x1.5 mode, only 1 to 2% efficiency loss
by x2 mode. (Assume 5% battery life in charge pump
mode and the efficiency difference of x1.5 and x2 modes
is 25%, the efficiency loss thus is 5%x25% = 1.25%)
Battery Voltage
(V)
80%
Battery Life
4.2
4.0
3.65
Capacity (mAH)
50
650
Figure 3. Li-ion Battery Energy Capacity Versus Battery
Voltage.
DS9363-03 April 2011
LED Efficiency vs. VIN
100
90
Efficiency (%)
The RT9363 is a high efficiency charge pump white LED
driver. It provides low drop-out voltage current source to
regulate 3 white LEDs current. For high efficiency, the
RT9363 implements x1/x2 mode charge pump with auto
mode selection. In the application with Li-ion battery, it
provides a very cost-effective and high efficiency solution
for driving white LEDs.
80
70
60
50
40
2.6
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
VIN (V)
Figure 4. Efficiency of RT9363. (ILED = 60mA, VF = 3.45V)
Soft Start
The RT9363 includes a soft start circuit to limit the inrush
current at power on and mode switching. Soft start circuit
holds the input current level long enough for output capacitor
COUT reaching a desired voltage level. When the soft start
is turning off, the RT9363 will not sink spike current from
V IN.
Mode Decision
The RT9363 uses a smart mode decision method to select
the working mode for maximum efficiency. Mode decision
circuit senses the output and LED voltage for up/down
selection.
Dimming Control
RT9363 implements the pulse dimming method being used
to control the brightness of white LEDs. There are 16 steps
to set the current of white LEDs. The maximum LED current
is up to 20mA that is sufficient for most application in
backlight. The detail operation of brightness dimming is
showed in the Figure 5.
At the beginning, the output current is set at 100% for
step 0. In every step change, the output current will be
reduced in 1/16 level from 16/16 until it reaches the
minimum value of 1/16. After it reaches the value of 1/16, it
will start a whole new cycle from 100% for continuous
step changes.
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RT9363
The GPIO signal determines the step changes. For a step
change, the duration of Logic Low signal must be within
the range of 0.1ms to 0.3ms. When the signal changes
from Low to High, it will trigger a step change to reduce
output current in 1/16 level. When the signal remains at
Logic High, the output current will be held and stays at the
same step.
Finally, when the signal stays longer than 2ms Logic Low,
the chip will shut down the output current.
Table 1 shows the corresponding dimming current for each
step.
0.1ms < tHO
0.1ms < tHI 0.1ms < tLO < 0.3ms
the output ripple, increasing the output capacitance COUT
is necessary. However, this will increase the start-up time
of output voltage. For LED driver applications, the input
voltage ripple is more important than output ripple. Input
ripple is controlled by input capacitor CIN, increasing the
value of input capacitance can further reduce the ripple.
Practically, the input voltage ripple depends on the power
supply impedance. Tantalum capacitors are not
recommended for use with the RT9363. So tantalum
capacitor values and ceramic capacitor values can use the
same. But COUT can set tantalum capacitor; because during
the charge pump is x2 mode the VOUT is negative voltage.
2ms < tSHDN
PCB Board Layout
0
Shutdown
1
2
3
4
5
14
100% 15/16
14/16 13/16
12/16 3/16
0
15
1
100%
2/16
2/16
15/16
1/16
Shutdown
Figure 5. Brightness control by pulse dimming. RT9363
implements 16 steps brightness control
Table 1. The Output Current Setting of 16 Steps
Step Output (mA/CH)
0
20
1
18.75
2
17.5
3
16.25
4
15
5
13.75
6
12.5
7
11.25
Step Output (mA/CH)
8
10
9
8.75
10
7.5
11
6.25
12
5
13
3.75
14
2.5
15
1.25
The RT9363 is a high-frequency switched-capacitor
converter. Careful PCB layout is necessary. For best
performance, place all peripheral components as close to
the IC as possible. Place CIN, COUT, and CP near to VIN,
VOUT, CP, EN, and GND pin respectively. A short connection
is highly recommended. The following guidelines should
be strictly followed when designing a PCB layout for the
RT9363.
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The GND must be soldered to a large ground plane for
heat sinking and noise prevention. The through-hole vias
located under IC is connected to ground plane of internal
layer.
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VIN traces should be wide to minimize inductance and
handle the high currents. The trace running from battery
to chip should be placed carefully and shielded strictly.
The anodes of LEDs must connect to CIN, not battery
directly.
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Input and output capacitors must be placed close to the
part. The connection between pins and capacitor pads
should be copper traces without any through-hole via
connection.
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The flying capacitors must be placed close to the part.
The traces running from the pins to the capacitor pads
should be as wide as possible. Long traces will also
produce large noise radiation caused by the large dv/dt
on these pins. Short trace is recommended.
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All the traces of LED and VIN running from pins to LCM
module should be shielded and isolated by ground plane.
The shielding prevents the interference of high frequency
noise coupled from the charge pump.
Short Circuit Protection
A current limiting circuit is also included in the RT9363 for
short circuit protection. Whenever output is shorted to GND
and source a dangerously high current, the current limiting
circuit takes over the output regulation circuit and reduces
the output current at an acceptable level.
Selecting Capacitors
To get the better performance of RT9363, the selecting of
peripherally appropriate capacitor and value is very
important. These capacitors determine some parameters
such as input and output ripple, power efficiency, maximum
supply current by charge pump, and start-up time. To
reduce the input and output ripple effectively, the low ESR
ceramic capacitors are recommended. Generally, to reduce
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DS9363-03 April 2011
RT9363
Input capacitor (CIN) should
be placed close to VIN and
connected to ground plane.
The Anodes of LEDs must
connect to CIN, not battery
directly.
COUT
All the traces of LED and VIN running from
chip to LEDs should be wide and short to
reduce the parasitic connection resistance
and shielded, isolated by ground plane .
LED3
1
8
LED2
VOUT
2
7
LED1
GND
3
6
EN
GPIO
Output capacitor (COUT) should
be placed close to VOUT and
connected to ground plane.
RS
CP
Battery
VIN
4
5
CP
CS
CIN
Ground Plane
The GND should be connected The traces running from pins to flying capacitor
to a strong ground plane for heat should be short and wide to reduce parasitic
resistance and prevent noise radiation. Long
sinking and noise protection.
parallel traces of EN and LED1 should be
prevented to reduce the noise coupling from
EN to LED1.
Figure 6. PCB Layout Guide.
Figure 7. PCB Layout Top Layer.
Figure 8. PCB Layout Bottom Layer.
DS9363-03 April 2011
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RT9363
Outline Dimension
H
D
L
C
B
b
A
A1
e
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
0.700
1.000
0.028
0.039
A1
0.000
0.100
0.000
0.004
B
1.397
1.803
0.055
0.071
b
0.220
0.380
0.009
0.015
C
2.591
3.000
0.102
0.118
D
2.692
3.099
0.106
0.122
e
0.585
0.715
0.023
0.028
H
0.080
0.254
0.003
0.010
L
0.300
0.610
0.012
0.024
TSOT-23-8 Surface Mount Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: marketing@richtek.com
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design,
specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed
by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
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DS9363-03 April 2011