RT9378 [RICHTEK]
4 CHs 100mA x1/x1.5/x2 Charge Pump White LED Driver; 4簇头100毫安X1 / X1.5 / X2电荷泵白光LED驱动器
| 型号： | RT9378 |
| 厂家： | 
RICHTEK TECHNOLOGY CORPORATION |
| 描述： | 4 CHs 100mA x1/x1.5/x2 Charge Pump White LED Driver |
| 文件： | 总10页 (文件大小：212K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
RT9378
4 CHs 100mA x1/x1.5/x2 Charge Pump White LED Driver
General Description
Features
z Efficiency Up to 93% Over Li-ion Battery Discharge
z Typical 85% Average Efficiency Over Li-ion Battery
Discharge
The RT9378 is a 4 CH WLED driver with auto mode
selection of x1, x1.5 and x2 mode with low dropout voltage
in current sources. The RT9378 can power up to 4 white
LEDs with regulated constant current for uniform intensity.
Each channel (LED1 to LED4) can support up to 25mA.
The part maintains highest efficiency by utilizing x1/x1.5/
x2 fractional charge pump and low dropout current
regulators. For the brightness control, user can easily use
a PWM signal generated from GPIO to control the
brightness of WLEDs.
z Support Up to 4 White LEDs
z Support Up to 25mA/Per Channel
z Support Up to 100mA Output Current
z PWM Brightness Control
z 60mV Typical Current Source Dropout
z 1% Typical LED Current Accuracy
z 0.7% Typical LED Current Matching
z Automatic x1/x1.5/x2 Charge Pump Mode
Transition
The RT9378 is available in a WQFN-12L 2x2 package.
Small 0.22μF capacitors can be used for fly capacitors. It
provides the best backlighting solution with high efficiency
and smallest board space for portable application.
z Low Input Noise and EMI Charge Pump
z 5V Over Voltage Protection
z Power On/Mode Transition In-rush Protection
z 1MHz Switching Frequency
Ordering Information
RT9378
z 0.4μA Low Shutdown Current
z RoHS Compliant and Halogen Free
Package Type
QW : WQFN-12L 2x2
Applications
z Camera Phone, Smart Phone
Lead Plating System
G : Green (Halogen Free and Pb Free)
z White LED Backlighting
Note :
Richtek products are :
Pin Configurations
` 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.
(TOP VIEW)
12 11 10
1
2
3
9
8
7
C1N
GND
C1P
LED3
LED2
LED1
Typical Application Circuit
GND
13
C
FLY1
C
FLY2
0.22µF
0.22µF
4
5
6
3
1
4
12
C1P C1N C2P C2N
V
WQFN-12L 2x2
IN
5
VIN
2.8V to 4.5V
C
1µF
IN
7
LED1
8
LED2
LED3
LED4
RT9378
6
Marking Information
EN
9
PWM Dimming
10
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
2, Exposed pad (1
3)
11
GND
VOUT
C
1µF
OUT
DS9378-03 April 2011
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1
RT9378
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
C1N
Fly Capacitor 1 Negative Connection.
2
Ground Pin. The exposed pad must be soldered to a large PCB and connected
to GND for maximum power dissipation.
GND
13 (Exposed Pad)
3
4
5
6
7
8
9
C1P
C2P
VIN
Fly Capacitor 1 Positive Connection.
Fly Capacitor 2 Positive Connection.
Power Input.
EN
Chip Enable (Active High).
LED1
LED2
LED3
Current Sink for LED1. (If not in use, connect this pin to VIN)
Current Sink for LED2. (If not in use, connect this pin to VIN)
Current Sink for LED3. (If not in use, connect this pin to VIN)
10
11
LED4
VOUT
C2N
Current Sink for LED4. (If not in use, connect this pin to VIN)
Charge Pump Output.
12
Fly Capacitor 2 Negative Connection.
Function Block Diagram
C2N
C2P
C1N
C1P
VIN
VOUT
Soft Start
Circuit
+
-
Vr1
1MHz
OSC
Gate Driver
Mode Decision
UVLO
Min VDS
LED1
LED2
LED3
LED4
PWM Dimming
Controller
Shutdown Delay
EN
Current Source
OVP
2µA
Current
Bias
GND
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DS9378-03 April 2011
RT9378
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ −0.3V to 5V
z Output Voltage, VOUT ----------------------------------------------------------------------------------------------------- −5V to 0.3V
z Power Dissipation, PD @ TA = 25°C
WQFN-12L 2x2 ------------------------------------------------------------------------------------------------------------ 0.606W
z Package Thermal Resistance (Note 2)
WQFN-12L 2x2, θJA ------------------------------------------------------------------------------------------------------- 165°C/W
z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
z Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C
z Storage Temperature Range -------------------------------------------------------------------------------------------- −65°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 = 3.6V, VF = 3.5V, CIN = COUT = 1μF, CFLY1 = CFLY2 = 0.22μF, ILED1 to LED4 = 15mA, TA = 25°C, unless otherwise specified)
Parameter
Input Power Supply
Input Supply Voltage
Symbol
Test Conditions
Min
Typ
Max
Unit
VIN
2.8
1.8
--
2
4.5
2.5
V
V
Under-Voltage Lockout
Threshold
VUVLO
VIN Rising
Under-Voltage Lockout
Hysteresis
ΔVUVLO
--
100
--
mV
Quiescent Current
IQ
x1 Mode
--
--
1
2
2
mA
Shutdown Current
LED Current
ISHDN
VIN = 4.5V
0.4
μA
ILEDx Accuracy
Current Matching
Charge Pump
ILEDx = 25mA
ILEDx = 25mA
−5
−2
0
0
5
2
%
%
Oscillator Frequency
PWM Dimming Frequency
Mode Decision
fOSC
--
1
1
--
4
MHz
kHz
Minimum Turn On > 20μs
--
x1 Mode to x2 Mode
Transition Voltage (VIN Falling)
IOUT = 100mA, ILEDx = 25mA
IOUT = 100mA, ILEDx = 25mA
--
--
3.6
3.8
--
V
Mode Transition Hystersis
Protection Function
OVP
200
mV
VIN – VOUT
--
5
--
V
To be continued
DS9378-03 April 2011
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RT9378
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
Enable
EN Low Time for Shutdown
3
--
--
--
ms
V
Logic-Low
VIL
--
0.2
EN Threshold
Voltage
Logic-High
VIH
1
--
2
--
--
V
EN Pull Low Current
--
μA
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 single layer thermal conductivity test board
of JEDEC 51-3 thermal measurement standard. The case point of θJC is on the exposed pad for the WQFN package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
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DS9378-03 April 2011
RT9378
Typical Operating Characteristics
LED Current vs. Input Voltage
Efficiency vs. Input Voltage
30
28.5
27
100
90
80
70
60
50
40
30
20
25.5
24
LED1
LED2
LED3
LED4
22.5
21
19.5
18
16.5
15
10
LED VF = 3.42V
LED VF = 3.42V
0
2.8
3
3.2 3.4 3.6 3.8
4
4.2 4.4 4.6 4.8
5
2.8
3
3.2 3.4 3.6 3.8
4
4.2 4.4 4.6 4.8
5
Input Voltage (V)
Input Voltage (V)
x2 Mode Quiescent Current vs. Input Voltage
4
x1 Mode Quiescent Current vs. Input Voltage
1
3.75
3.5
3.25
3
0.95
0.9
0.85
0.8
2.75
2.5
2.25
2
0.75
0.7
0.65
0.6
1.75
1.5
1.25
1
0.55
0.5
2.8
3
3.2 3.4 3.6 3.8
4
4.2 4.4 4.6 4.8
5
2.8
3
3.2 3.4 3.6 3.8
4
4.2 4.4 4.6 4.8
5
Input Voltage (V)
Input Voltage (V)
Shutdown Current vs. Input Voltage
x1 Mode Inrush Current Response
1.2
1
VIN = 3.7V
EN
(5V/Div)
0.8
0.6
0.4
0.2
0
VOUT
(2V/Div)
C2P
(2V/Div)
IIN
(200mA/Div)
2.8
3
3.2 3.4 3.6 3.8
4
4.2 4.4 4.6 4.8
5
Time (100μs/Div)
Input Voltage (V)
DS9378-03 April 2011
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RT9378
x1.5 Mode Inrush Current Response
x2 Mode Inrush Current Response
VIN = 3.1V
VIN = 2.8V
EN
(5V/Div)
VOUT
(2V/Div)
EN
(5V/Div)
VOUT
(2V/Div)
C2P
(2V/Div)
C2P
(2V/Div)
IIN
IIN
(200mA/Div)
(200mA/Div)
Time (100μs/Div)
Time (100μs/Div)
x1 Mode Dimming Operation
Ripple & Spike
VIN
(50mV/Div)
EN
(2V/Div)
VOUT
(20mV/Div)
C2P
(5V/Div)
IIN
ILED
(10mA/Div)
(100mA/Div)
VIN = 3.2V
VIN = 3.7V
Time (1μs/Div)
Time (1ms/Div)
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DS9378-03 April 2011
RT9378
Applications Information
C
FLY1
C
FLY2
The RT9378 uses a fractional switched capacitor charge
pump to power up to four white LEDs with a programmable
current for uniform intensity. The part integrates current
sources and automatic mode selection charge pump. It
maintains the high efficiency by utilizing an x1/x1.5/x2
fractional charge pump and current sources. The small
equivalent x1 mode open loop resistance and ultra-low
dropout voltage of current source extend the operating
time of x1 mode and optimize the efficiency in white LED
applications.
0.22µF
0.22µF
3
1
4
12
C1P C1N C2P C2N
V
BAT
5
VIN
2.8V to 4.5V
C
1µF
IN
7
LED1
LED2
LED3
LED4
8
RT9378
6
EN
9
10
PWM Dimming
2, Exposed pad (1
3)
11
GND
VOUT
C
1µF
OUT
Figure 1. Application Circuit for One ChannelDisabled
Input UVLO
Capacitor Selection
The input operating voltage range of the LEDdriver is from
2.8V to 4.5V.An input capacitor at the VINpin could reduce
ripple voltage. It is recommended to use a ceramic 1μF or
larger capacitance as the input capacitor. This RT9378
provides an under voltage lockout (UVLO) function to
prevent it from unstable issue when startup. The UVLO
threshold of input rising voltage is set at 2V typically with
a hysteresis of 100mV.
To get the better performance of the RT9378, the selection
of peripherally appropriate capacitor and value is very
important. These capacitors determine some parameters
such as input/output ripple voltage, power efficiency and
maximum supply current by charge pump. To reduce the
input and output ripple effectively, the low ESR ceramic
capacitors are recommended. 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 impedance. The flying capacitor CFLY1
and CFLY2 determine the supply current capability of the
charge pump to influence the overall efficiency of the
system. The lower value will improve efficiency. Howere,
it will limit the LED’ s current at low input voltage. For 4
X25mAload over the entire input range of 2.8V to 4.5V, it
is recommended to use a 0.22μF ceramic capacitor on
the flying capacitor CFLY1 and CFLY2.
Soft Start
The charge pump employs a soft-start feature to limit the
inrush current. The soft-start circuit prevents the excessive
inrush current and input voltage droop. The soft-start
clamps the input current over a typical period of 50μs.
Mode Decision
The RT9378 uses a smart mode selection method to decide
the working mode for optimizing the efficiency. Mode
decision circuit senses the output and LED voltage for
up/down selection. The RT9378 automatically switches
to x1.5 or x2 mode whenever the dropout condition is
detected from the current source and returns to x1 mode
whenever the dropout condition releases.
Brightness Control
The RT9378 implements a PWM dimming method to
control the brightness of white LEDs. When an external
PWM signal is connected to the EN pin, brightness of
white LED is adjusted by the duty cycle. The suggest
PWM dimming frequency is 1kHz to 4kHz and the PWM
minimum turn on time must be >20μs.
LED connection
The RT9378 supports up to 4 white LEDs. The 4 LEDs
are connected from VINto pin7, 8, 9, and 10 respectively.
If the LED is not used, the LED pin should be connected
to VIN directly.
DS9378-03 April 2011
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RT9378
Thermal Considerations
Layout Considerations
For continuous operation, do not exceed absolute
maximum operation junction temperature. The maximum
power dissipation depends on the thermal resistance of
IC package, PCB layout, the rate of surroundings airflow
and temperature difference between junction to ambient.
The maximum power dissipation can be calculated by
following formula :
The RT9378 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, CFLY1, and CFLY2
near to VIN, VOUT, CP1, CN1, CP2, CN2, and GND pin
respectively. Ashort connection is highly recommended.
The following guidelines should be strictly followed when
designing a PCB layout for the RT9378.
PD(MAX) = ( TJ(MAX) − TA ) / θJA
` The exposed GND pad must be soldered to a large
ground plane for heat sinking and noise prevention. The
throughhole vias located at the exposed pad is
connected to ground plane of internal layer.
Where TJ(MAX) is the maximum operation junction
temperature, TAis the ambient temperature and the θJA is
the junction to ambient thermal resistance.
For recommended operating conditions specification of
RT9378, The maximum junction temperature is 125°C.
The junction to ambient thermal resistance θJA is layout
dependent. For WQFN-12L 2x2 packages, the thermal
resistance θJA is 165°C/W on the standard JEDEC 51-3
single layer thermal test board. The maximum power
dissipation at TA = 25°C can be calculated by following
formula :
` VIN traces should be wide enough to minimize
inductance and handle the high currents. The trace
running from battery to chip should be placed carefully
and shielded strictly.
` 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.
PD(MAX) = (125°C − 25°C) / (165°C/W) = 0.606W for
WQFN-12L 2x2 packages
` 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.
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal
resistance θJA. For RT9378 packages, the Figure 2 of
derating curves allows the designer to see the effect of
rising ambient temperature on the maximum power
allowed.
` All the traces of LEDand VINrunning 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.
0.8
Single Layer PCB
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
` Output capacitor must be placed between GND and
VOUT to reduce noise coupling from charge pump to
LEDs.
0
10 20 30 40 50 60 70 80 90 100 110 120
Ambient Temperature (°C)
Figure 2.Derating Curves for RT9378 Packages
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DS9378-03 April 2011
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RT9378
Output capacitor (C
) should be placed close to
OUT
V
and connected to ground plane to reduce
OUT
noise coupling from charge pump to LEDs.
All the traces of
C
OUT
LED pins running
from chip to LEDs
should be wide and
short to reduce the
parasitic connection
resistance.
12 11 10
1
2
3
9
8
7
C1N
GND
C1P
LED3
LED2
LED1
GND
13
The traces running
from pins to flying
capacitor should
be short and wide
to reduce parasitic
resistance and
prevent noise
4
5
6
Battery
GND
Input capacitor (C ) should be placed close to V
C
IN
radiation.
IN
IN
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.
Figure 2. PCB Layout for RT9378
DS9378-03 April 2011
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9
RT9378
Outline Dimension
D
D2
SEE DETAIL A
1
E2
b
L
E
A
e
A3
A1
2
1
2
1
DETAILA
Pin #1 ID and Tie Bar Mark Options
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
0.031
0.002
0.010
0.010
0.083
0.083
A
A1
A3
b
0.700
0.000
0.175
0.150
1.900
1.900
0.800
0.050
0.250
0.250
2.100
2.100
0.028
0.000
0.007
0.006
0.075
0.075
D
E
e
0.400
0.016
D2
E2
L
0.850
0.850
0.250
0.950
0.950
0.350
0.033
0.033
0.010
0.037
0.037
0.014
W-Type 12L QFN 2x2 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.
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DS9378-03 April 2011
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