RT9373A
3-Channel Charge Pump White LED Driver with Low
Dropout Current Source
General Description
The RT9373A 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
RT9373A maintains the highest efficiency by utilizing a
x1/x1.5/x2 charge pump and low dropout current
regulators.
User can easily configure each LED current from 1.25mA
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.
RT9373A is available in a WQFN3x3-16L package.
Features
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
Auto Charge Pump Mode Selection
250kHz Fixed Frequency Oscillator
Output Over Voltage Protection
16 Steps Brightness Control
Low Input Noise and EMI
RoHS Compliant and 100% Lead (Pb)-Free
Applications
Mobile Phone, DSC, MP3
White LED Backlighting
LCD Display Supply
Ordering Information
RT9373A
Package Type
QW : WQFN-16L 3x3 (W-Type)
Lead Plating System
P : Pb Free
G : Green (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.
Pin Configurations
(TOP VIEW)
LED3
LED2
LED1
VIN
12
11
17
5
6
7
8
10
9
16 15 14 13
NC
NC
GND
C1P
1
2
3
4
EN
NC
GND
C2P
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
WQFN-16L 3x3
DS9373A-04 April 2011
VOUT
VIN
C2N
C1N
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1
RT9373A
Typical Application Circuit
C
PUMP1
1uF
4
5, 13
C
IN
2.2uF
12
C1P
C
PUMP2
1uF
9
C2P
7
C1N
6
8
16
15
14
C
OUT
2.2uF
C2N
VOUT
LED3
LED2
LED1
V
CC
2.8V to 5.5V
GPIO
VIN
EN
RT9373A
3, 10
GND
Figure 1. For 3-WLEDs Application Circuit
C
PUMP1
1uF
4
C1P
C
PUMP2
1uF
9
C2P
7
C1N
6
C2N
V
CC
2.8V to 5.5V
GPIO
5, 13
C
IN
2.2uF
VIN
VOUT
8
16
C
OUT
2.2uF
12
EN
RT9373A
LED3
LED2
15
3, 10
GND
LED1
14
Figure 2. For 2-WLEDs Application Circuit
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DS9373A-04 April 2011
RT9373A
Functional Pin Description
Pin No.
Pin Name
No Internal Connection.
Ground.
Positive Terminal of Bucket Capacitor 1
Power Input Voltage.
Negative Terminal of Bucket Capacitor 2.
Negative Terminal of Bucket Capacitor 1.
Output Voltage Source.
Positive Terminal of Bucket Capacitor 2.
Ground.
Chip Enable (Active High). Note that this pin is high impedance.
Power Input Voltage.
Output Current for LED1. (If not in use, pin should be connected to GND).
Output Current for LED2. (If not in use, pin should be connected to GND).
Output Current for LED3. (If not in use, pin should be connected to GND).
Pin Function
1, 2, 11,
NC
17 (Exposed Pad)
3
4
5
6
7
8
9
10
12
13
14
15
16
GND
C1P
VIN
C2N
C1N
VOUT
C2P
GND
EN
VIN
LED 1
LED 2
LED 3
Function Block Diagram
C1N
C2N
C1P
C2P
VIN
x1/x1.5/x2
Charge Pump
VOUT
UVLO
Current
Limitation
Soft Start
Circuit
16 Steps Pulse
Dimming Controller
Low Drop Out Current
Source (PMOS)
Shut Down Delay
(2ms)
EN
GND
LED3
LED2
LED1
DS9373A-04 April 2011
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3
RT9373A
Absolute Maximum Ratings
(Note 1)
−0.3V
to 6V
−0.3V
to 6V
1.47W
68°C/W
150°C
Supply Input Voltage ------------------------------------------------------------------------------------------------------
Other I/O Pin Voltage -----------------------------------------------------------------------------------------------------
Power Dissipation, PD @ T
A
= 25°C
WQFN-16L 3x3 ------------------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
WQFN-16L 3x3,
θ
JA
-------------------------------------------------------------------------------------------------------
Junction Temperature -----------------------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C
Storage Temperature Range --------------------------------------------------------------------------------------------
−40°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions
(Note 4)
Junction Temperature Range --------------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range --------------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 2.5V to 5.5V, C
IN
= C
OUT
= C
FLY
= 1uF (ESR = 30mΩ), T
A
= 25°C, unless otherwise specification)
Parameter
Input
Input Supply Voltage
Under-Voltage Lockout
Threshold
Under-Voltage Lockout
Hysteresis
Quiescent of x1 Mode
Quiescent of x2 Mode
Shutdown Current
x1 mode to x1.5 mode
Transition Voltage (V
IN
Falling)
x1.5 mode to x2 mode
Transition Voltage (V
IN
Falling)
Hysteresis of Mode Transition
Output
Current Range of I
LEDx
I
LEDx
Accuracy
Current Matching
Enable
Symbol
V
IN
V
IN
Rising
Test Condition
Min
2.8
1.6
--
Typ
--
2.1
100
1
2.5
0.1
3.75
3.0
150
--
--
--
Max
5.0
2.5
--
2
5
10
--
--
--
20
+8
+5
Units
V
V
mV
mA
mA
uA
V
V
mV
mA
%
%
I
Q_x1
I
Q_x2
x1 Mode, No Load, All LED pins
connected to GND, V
IN
= 4V
x2 Mode, No Load, All LED pins floating,
V
IN
= 3.5V
Enable = 0.4V, V
IN
= 2.8V to 5.5V
0.5
1.5
0
--
--
--
V
TS_x1.5
V
F
= 3.5V, I
OUT
= 80mA, I
LEDx
= 20mA
V
TS_x2
V
F
= 3.5V, I
OUT
= 80mA, I
LEDx
= 20mA
2.8 < V
IN
< 5.5@V
F
= 3.2, I
OUT
= 60mA
I
LED-ERR
100% Setting
100% Setting
1.25
−8
−5
Logic-High Voltage V
IH
EN
Threshold Logic-Low Voltage V
IL
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4
1.5
--
--
--
--
0.4
V
V
To be continued
DS9373A-04 April 2011
RT9373A
Parameter
EN Low Time for Dimming
EN High Time for Dimming
EN Current
High Current
Low Current
EN Low Time for Shut Down
Frequency
Oscillator Frequency
f
OSC
--
250
--
kHz
Symbol
T
IL
T
IH
I
IH
I
IL
T
SHDN
V
IH
= V
IN
V
IL
= GND
Pulse Dimming
Test Condition
Min
0.5
0.5
--
--
--
Typ
--
--
1
1
2
Max
500
--
10
10
--
Units
us
us
uA
uA
ms
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.
θ
JA
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 highly recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
DS9373A-04 April 2011
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