RT9373A [RICHTEK]
3-Channel Charge Pump White LED Driver with Low Dropout Current Source; 3通道电荷泵白光LED驱动器，低压差电流源
| 型号： | RT9373A |
| 厂家： | 
RICHTEK TECHNOLOGY CORPORATION |
| 描述： | 3-Channel Charge Pump White LED Driver with Low Dropout Current Source |
| 文件： | 总11页 (文件大小：274K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
RT9373A
3-Channel Charge Pump White LED Driver with Low
Dropout Current Source
General Description
Features
z Very High Efficiency Over 80% of Battery Life
The RT9373Ais 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.
z Support up to 3 White LEDs
z Support Up to 60mA Output Current
z 1% Typical LED Current Matching
z Soft Start Function
z Auto Charge Pump Mode Selection
z 250kHz Fixed Frequency Oscillator
z Output Over Voltage Protection
z 16 Steps Brightness Control
User can easily configure each LEDcurrent 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.
z Low Input Noise and EMI
z RoHS Compliant and 100% Lead (Pb)-Free
RT9373Ais available in a WQFN3x3-16L package.
Applications
z Mobile Phone, DSC, MP3
z White LED Backlighting
z LCDDisplay Supply
Ordering Information
RT9373A
Package Type
QW : WQFN-16L 3x3 (W-Type)
Pin Configurations
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
(TOP VIEW)
Note :
Richtek products are :
16 15 14 13
12
NC
NC
EN
1
2
3
4
` 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.
11 NC
GND
GND
C1P
10
17
9
C2P
5
6
7
8
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
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1
RT9373A
Typical Application Circuit
C
C
PUMP2
1uF
PUMP1
1uF
4
7
9
6
C
OUT
2.2uF
5, 13
8
V
CC
VOUT
VIN
C
IN
2.8V to 5.5V
2.2uF
16
15
14
RT9373A
LED3
LED2
LED1
12
EN
GPIO
3, 10
GND
Figure 1. For 3-WLEDs Application Circuit
C
C
PUMP2
1uF
PUMP1
1uF
4
7
9
6
C
OUT
5, 13
2.2uF
V
CC
VIN
EN
8
VOUT
C
2.2uF
IN
2.8V to 5.5V
RT9373A
12
16
15
14
GPIO
LED3
LED2
LED1
3, 10
GND
Figure 2. For 2-WLEDs Application Circuit
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DS9373A-04 April 2011
RT9373A
Functional Pin Description
Pin No.
Pin Name
Pin Function
1, 2, 11,
17 (Exposed Pad)
NC
No Internal Connection.
Ground.
3
4
GND
C1P
Positive Terminal of Bucket Capacitor 1
Power Input Voltage.
5
VIN
6
C2N
C1N
VOUT
C2P
Negative Terminal of Bucket Capacitor 2.
Negative Terminal of Bucket Capacitor 1.
Output Voltage Source.
7
8
9
Positive Terminal of Bucket Capacitor 2.
Ground.
10
12
13
14
15
16
GND
EN
Chip Enable (Active High). Note that this pin is high impedance.
Power Input Voltage.
VIN
LED 1
LED 2
LED 3
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).
Function Block Diagram
x1/x1.5/x2
Charge Pump
VOUT
VIN
UVLO
Current
Limitation
Low Drop Out Current
Source (PMOS)
Soft Start
Circuit
Shut Down Delay
(2ms)
LED3
LED2
16 Steps Pulse
Dimming Controller
LED1
EN
GND
DS9373A-04 April 2011
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3
RT9373A
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage------------------------------------------------------------------------------------------------------ −0.3V to 6V
z Other I/O Pin Voltage----------------------------------------------------------------------------------------------------- −0.3V to 6V
z Power Dissipation, PD @ TA = 25°C
WQFN-16L 3x3 ------------------------------------------------------------------------------------------------------------ 1.47W
z Package Thermal Resistance (Note 2)
WQFN-16L 3x3, θJA ------------------------------------------------------------------------------------------------------- 68°C/W
z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
z Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C
z Storage Temperature Range -------------------------------------------------------------------------------------------- −40°C to 150°C
z ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions (Note 4)
z Junction Temperature Range-------------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range-------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 2.5V to 5.5V, CIN = COUT = CFLY = 1uF (ESR = 30mΩ), TA = 25°C, unless otherwise specification)
Parameter
Symbol
Test Condition
Min
Typ
Max Units
Input
Input Supply Voltage
VIN
2.8
1.6
--
5.0
2.5
V
V
Under-Voltage Lockout
Threshold
VIN Rising
2.1
Under-Voltage Lockout
Hysteresis
--
100
1
--
2
mV
mA
x1 Mode, No Load, All LED pins
connected to GND, VIN = 4V
Quiescent of x1 Mode
Quiescent of x2 Mode
IQ_x1
IQ_x2
0.5
x2 Mode, No Load, All LED pins floating,
1.5
0
2.5
0.1
5
10
--
mA
uA
V
VIN = 3.5V
Shutdown Current
Enable = 0.4V, VIN = 2.8V to 5.5V
x1 mode to x1.5 mode
VTS_x1.5 VF = 3.5V, IOUT = 80mA, ILEDx = 20mA
VTS_x2 VF = 3.5V, IOUT = 80mA, ILEDx = 20mA
--
3.75
Transition Voltage (VIN Falling)
x1.5 mode to x2 mode
--
--
3.0
--
--
V
Transition Voltage (VIN Falling)
Hysteresis of Mode Transition
150
mV
Output
Current Range of ILEDx
ILEDx Accuracy
2.8 < VIN < 5.5@VF = 3.2, IOUT = 60mA
1.25
−8
--
--
--
20
+8
+5
mA
%
100% Setting
ILED-ERR
100% Setting
Current Matching
−5
%
Enable
Logic-High Voltage VIH
Logic-Low Voltage VIL
1.5
--
--
--
--
V
V
EN
Threshold
0.4
To be continued
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DS9373A-04 April 2011
RT9373A
Parameter
Symbol
TIL
Test Condition
Min
0.5
0.5
--
Typ
--
Max Units
EN Low Time for Dimming
EN High Time for Dimming
500
--
us
us
TIH
--
High Current
EN Current
IIH
VIH = VIN
1
10
10
--
uA
uA
ms
Low Current
IIL
VIL = GND
--
1
EN Low Time for Shut Down
Frequency
TSHDN Pulse Dimming
--
2
Oscillator Frequency
fOSC
--
250
--
kHz
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 TA = 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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RT9373A
Typical Operating Characteristics
Efficiency vs. Input Voltage
LED Current vs. Input Voltage
21.0
95
90
85
80
75
70
65
60
55
50
VF = 3.2V
VF = 3.3V
20.5
20.0
19.5
19.0
18.5
18.0
LED2
LED1
LED3
2.5
3
3.5
4
4.5
5
5.5
2.6
3
3.4
3.8
4.2
4.6
5
5.4
5.8
Input Voltage (V)
Input Voltage (V)
Shutdown Current vs. Input Voltage
Quiescent Current vs. Input Voltage
1.5
1.2
0.9
0.6
0.3
0
4.5
4
x2 Mode
3.5
3
2.5
2
x1 Mode
1.5
1
0.5
0
2.5
3
3.5
4
4.5
5
5.5
2.6
3.1
3.6
4.1
4.6
5.1
5.6
Input Voltage (V)
Input Voltage (V)
Oscillator Frequency vs. Input Voltage
Enable Voltage vs. Input Voltage
300
250
200
150
100
50
1.20
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
Rising
Falling
0
2.5
3
3.5
4
4.5
5
5.5
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
Input Voltage (V)
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DS9373A-04 April 2011
RT9373A
Dimming Operation
Dimming Operation
VIN = 3.3V
VIN = 3.6V
VIN
(2V/Div)
VOUT
(2V/Div)
VIN
(2V/Div)
VOUT
(2V/Div)
EN
(2V/Div)
EN
(2V/Div)
ILED
(20mA/Div)
ILED
(20mA/Div)
Time (1ms/Div)
Time (1ms/Div)
x1 Mode Inrush Current Response
x1.5 Mode Inrush Current Response
VIN
(2V/Div)
VIN
(2V/Div)
VOUT
(5V/Div)
VOUT
(5V/Div)
EN
(2V/Div)
EN
(2V/Div)
IIN
IIN
VIN = 3.7V, CIN = COUT = 2.2uF, CPUMP = 1uF
Time (100us/Div)
VIN = 4.2V, CIN = COUT = 2.2uF, CPUMP = 1uF
Time (25us/Div)
(500mA/Div)
(500mA/Div)
x2 Mode Inrush Current Response
x2 Mode EN Pin Shutdown Response
VIN = 3V, CIN = COUT = 2.2uF, CPUMP = 1uF
CIN = COUT = 2.2uF, CPUMP = 1uF
C2N
(2V/Div)
VIN
(2V/Div)
VOUT
(5V/Div)
EN
VOUT
(5V/Div)
(2V/Div)
EN
(2V/Div)
ILED
(500mA/Div)
IIN
(500mA/Div)
Time (100us/Div)
Time (500us/Div)
DS9373A-04 April 2011
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7
RT9373A
x1.5 Mode Ripple & Spike
x2 Mode Ripple & Spike
VIN = 3.3V, CIN = COUT = 2.2μF
VIN = 3.0V, CIN = COUT = 2.2μF
VIN ac
(100mV/Div)
VIN ac
(100mV/Div)
VOUT ac
(200mV/Div)
VOUT ac
(200mV/Div)
C2N
(2V/Div)
C2N
(2V/Div)
Time (1us/Div)
Time (1us/Div)
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DS9373A-04 April 2011
RT9373A
Applications Information
20mA that is sufficient for most application in backlight.
The dimming of white LEDs' current can be achieved by
applying a pulse signal to the ENpin. There are totally 16
steps of current could be set by users. The detail operation
of brightness dimming is showed in the Figure 3.
The RT9373A is a high efficiency charge pump white LED
driver. It provides 3 channels low dropout voltage current
source to regulated 3 white LEDs current. For high
efficiency, the RT9373A implements a smart mode
transition for charge pump operation. The RT9373A
provides pulse dimming function for LED brightness
control.
Selecting Capacitors
To get the better performance of RT9373A, 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 the output ripple, increasing the output capacitance
COUT is necessary. However, this will increase the start-
up time of output voltage. For LEDdriver 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’ s impedance. If a single input capacitor CIN cannot
satisfy the requirement of application, it is necessary to
add a low-pass filter. C-R-C filter used to reduce input
ripple. The flying capacitor CPUMP1 and CPUMP2 determine
the supply current capability of the charge pump. The lower
value will limit the LED’ s current at low input voltage.
Soft Start
The RT9373A includes a soft start circuit to limit the inrush
current at power on and mode switching. Soft start circuit
limits the input current before output voltage reaching a
desired voltage level. When the soft start off, the RT9373A
won't sink spike current from VIN.
Mode Decision
The RT9373A uses a smart mode decision method to
select the working mode for maximum efficiency. The
charg pump can operation at x1, x1.5 or x2 mode. The
mode decision circuit senses the output and LEDvoltage
for up/down selection.
Brightness Control
The RT9373A implements the pulse dimming method
being used to control the brightness of white LEDs. The
part implements a 4-bitDAC for brightness control. Users
can easily configure the LEDcurrent from 1.25mAto 20mA
by a serial pulse. The maximum LED current is up to
2ms < t
SHDN
30us < t
0.5us < t < 500us
LO
0.5us < t
READY
HI
EN
0
1
2
3
4
0
14
15
1
5
100%
100%
15/16
15/16
14/16
13/16
12/16
Shutdown
ILEDX
Shutdown
2/16
1/16
Figure 3. Brightness control by pulse dimming. RT9373A implements 16 steps brightness control
DS9373A-04 April 2011
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9
RT9373A
Layout Consideration
The RT9373Ais a low dropout current source for white LEDdriver. Careful PCB layout is necessary. For best performance,
place all peripheral components as close to the IC as possible. Ashort connection is highly recommended. The following
guidelines should be strictly followed when designing a PCB layout for the RT9373A.
1. All the traces of LED pins running from chip to LEDs should be wide and short to reduce the parasitic connection
resistance.
2. Input capacitor (CIN) should be placed close to VIN (Pin 5) and connected to ground plane. The trace of VIN in the PCB
should be placed far away the sensitive devices or shielded by the ground.
3. The GND should be connected to a strong ground plane for heat sinking and noise protection.
4. Output capacitor (COUT) should be placed close to VOUT and connected to ground plane to reduce noise coupling from
charge pump to LEDs.
5. The traces running from pins to flying capacitor should be short and wide to reduce parasitic resistance and prevent
noise radiation.
All the traces of LED pins
running from chip to LEDs
should be wide and short to
reduce the parasitic
connection resistance.
The GND should be
connected to a strong
ground plane for heat
sinking and noise
protection.
1
2
3
4
12 EN
NC
NC
NC
11
10
9
GND
GND
C2P
C1P
C1
C2
Output capacitor (C
)
OUT
should be placed close to
V
and connected to
OUT
The traces running from pins
to flying capacitor should be
short and wide to reduce
parasitic resistance and
prevent noise radiation.
ground plane to reduce
noise coupling from
charge pump to LEDs.
C
OUT
C
IN
Input capacitor (C ) should be placed close to V
IN
IN
(Pin 5) and connected to ground plane. The trace
of V in the PCB should be placed far away the
IN
Ground Plane
Battery
sensitive devices or shielded by the ground.
Figure 4. PCB Layout Guide
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DS9373A-04 April 2011
RT9373A
Outline Dimension
SEE DETAIL A
D
D2
L
1
E
E2
1
2
1
2
e
b
DETAILA
A
A3
Pin #1 ID and Tie Bar Mark Options
A1
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
A1
A3
b
0.700
0.000
0.175
0.180
2.950
1.300
2.950
1.300
0.800
0.050
0.250
0.300
3.050
1.750
3.050
1.750
0.028
0.000
0.007
0.007
0.116
0.051
0.116
0.051
0.031
0.002
0.010
0.012
0.120
0.069
0.120
0.069
D
D2
E
E2
e
0.500
0.020
L
0.350
0.450
0.014
0.018
W-Type 16L QFN 3x3 Package
Richtek Technology Corporation
Headquarter
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
5F, No. 95, Minchiuan Road, Hsintien City
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.
DS9373A-04 April 2011
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