RT9385 [RICHTEK]
5 Channels 125mA x1/x1.5/x2 Charge Pump White LED Driver; 5通道125毫安X1 / X1.5 / X2电荷泵白光LED驱动器
| 型号： | RT9385 |
| 厂家： | 
RICHTEK TECHNOLOGY CORPORATION |
| 描述： | 5 Channels 125mA x1/x1.5/x2 Charge Pump White LED Driver |
| 文件： | 总10页 (文件大小：224K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
RT9385
5 Channels 125mA x1/x1.5/x2 Charge Pump White LED Driver
General Description
Features
z 85% Average Efficiency Over Li-ion Battery
The RT9385 is a 5 Channel WLEDdriver with auto mode
selection of x1, x1.5 and x2 mode with low dropout voltage
in current sources. The RT9385 can power up to 5 white
LEDs with regulated constant current for uniform intensity.
Each channel (LED1 to LED5) 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.
Discharge
z Support Up to 5 White LEDs
z Support Up to 25mA/Per Channel
z PWM Brightness Control
z 60mV Current Source Dropout
z 1% LED Current Accuracy
z 0.7% LED Current Matching
z Automatic x1/x1.5/x2 Charge Pump Mode
Transition
z Low Input Noise and EMI
The RT9385 is available in a WQFN-16L 2x3 package.
Small 1μF capacitors can be used for fly capacitors. It
provides the best backlighting solution with high efficiency
and smallest board space for portable application.
z Over Voltage Protection
z Power On/Mode Transition Inrush Protection
z 1MHz Switching Frequency
z 0.4μA Low Shutdown Current
z RoHS Compliant and Halogen Free
Ordering Information
RT9385
Package Type
Applications
z Camera Phone, Smart Phone
QW : WQFN-16L 2x3 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
z White LED Backlighting
Note :
Pin Configurations
Richtek products are :
(TOP VIEW)
` 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.
16 15 14
1
2
3
4
5
13
12
11
10
9
LED3
LED4
LED5
VOUT
PGND
AGND
CF
VIN
EN
C2P
Marking Information
GND
17
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
6
7 8
WQFN-16L 2x3
DS9385-01 April 2011
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1
RT9385
Typical Application Circuit
C
FLY2
C
FLY1
1µF
1µF
8
7
9
6
C1P C1N C2P C2N
14,11
VIN
15
16
PWM Input
LED1
LED2
LED3
LED4
LED5
C
1µF
IN
10
4
EN
RT9385
1
2
3
VOUT
C
12
OUT
CF
1µF
AGND
13
PGND
C
CF
5
0.1µF
Functional Pin Description
Pin No.
Pin Name
LED3
Pin Function
1
2
Current Sink for LED3. (If not in use, this pin should be connected to VIN)
Current Sink for LED4. (If not in use, this pin should be connected to VIN)
Current Sink for LED5. (If not in use, this pin should be connected to VIN)
Charge Pump Output.
LED4
LED5
VOUT
PGND
C2N
C1N
C1P
3
4
5
Ground.
6
Fly Capacitor 2 Negative Connection.
7
Fly Capacitor 1 Negative Connection.
8
Fly Capacitor 1 Positive Connection.
9
C2P
Fly Capacitor 2 Positive Connection.
10
11, 14
12
13
15
16
EN
Chip Enable (Active High).
VIN
Power Input.
CF
PWM Filter Capacitor Connection, No Connection if this pin is not in use.
Ground.
AGND
LED1
LED2
Current Sink for LED1. (If not in use, this pin should be connected to VIN)
Current Sink for LED2. (If not in use, this pin should connected to VIN)
The exposed pad must be soldered to a large PCB and connected to GND for
maximum power dissipation.
17 (Exposed Pad) GND
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DS9385-01 April 2011
RT9385
Function Block Diagram
C1P
C2N
C1N C2P
VIN
VOUT
Soft Start
Circuit
OVP
1MHz
OSC
UVLO
Gate Driver
Mode Decision
LED1
LED2
LED3
LED4
LED5
PWM Dimming
Controller
CF
Shutdown Delay
EN
PGND
Current Source
Current
Bias
AGND
DS9385-01 April 2011
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3
RT9385
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage, VIN ------------------------------------------------------------------------------------------------ −0.3V to 5V
z Power Dissipation, PD @ TA = 25°C
WQFN-16L 2x3 ------------------------------------------------------------------------------------------------------------ 1.111W
z Package Thermal Resistance (Note 2)
WQFN-16L 2x3, θJA ------------------------------------------------------------------------------------------------------- 90°C/W
WQFN-16L 2x3, θJC ------------------------------------------------------------------------------------------------------ 15°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 = 1uF, CFLY1 = CFLY2 = 1μF, ILED1 to LED5 = 25mA, 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
Shutdown Current
IQ
x1 Mode
--
--
1
2
2
mA
ISHDN
VIN = 4.5V
0.4
μA
LED Current
LED Current Accuracy
Current Matching
ILEDx
ILEDx = 25mA
ILEDx = 25mA
−5
−2
0
0
+5
+2
%
%
Charge Pump
Oscillator Frequency
PWM Dimming Frequency
Internal CF Resistance
Mode Decision
fOSC
--
1
--
1000
--
--
200
--
kHz
kHz
kΩ
160
x1 Mode to x1.5 Mode
Transition Voltage (VIN Falling)
IOUT = 125mA, ILEDx = 25mA.
IOUT = 125mA, ILEDx = 25mA.
--
--
3.65
200
3.8
--
V
Mode Transition Hystersis
mV
To be continued
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DS9385-01 April 2011
RT9385
Parameter
Protection
Symbol
Test Conditions
Min
Typ
Max
Unit
OVP
VIN – VOUT
4.5
5
5.5
V
Enable
EN Low Time for Shutdown
3
--
--
--
ms
V
Logic-Low Voltage VIL
Logic-High Voltage VIH
--
0.2
EN
Threshold
1
--
2
4.5
--
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 high effective four layers thermal conductivity test board of
JEDEC 51-7 thermal measurement standard. The case point of θJC is on the exposed pad for 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.
DS9385-01 April 2011
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5
RT9385
Typical Operating Characteristics
LED Current vs. Input Voltage
Efficiency vs. Input Voltage
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
100
90
80
70
60
50
40
30
20
LED1
LED2
LED3
LED4
LED5
10
LED VF = 3.02V
LED VF = 3.02V
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)
x1 Mode Quiescent Current vs. Input Voltage
1.30
x2 Mode Quiescent Current vs. Input Voltage
4.5
1.25
1.20
1.15
1.10
1.05
1.00
4.0
3.5
3.0
2.5
2.0
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)
Shutdown Current vs. Input Voltage
x1 Mode Inrush Current Response
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
EN
(5V/Div)
VOUT
(1V/Div)
C2P
(2V/Div)
IIN
(200mA/Div)
VIN = 3.2V
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)
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DS9385-01 April 2011
RT9385
x1.5 Mode Inrush Current Response
x2 Mode Inrush Current Response
VIN = 3.15V
EN
VIN = 3.1V
(5V/Div)
EN
(5V/Div)
VOUT
(1V/Div)
VOUT
(1V/Div)
C2P
(2V/Div)
C2P
(2V/Div)
IIN
IIN
(200mA/Div)
(200mA/Div)
Time (100μs/Div)
Time (100μs/Div)
Ripple & Spike
PWM Dimming Operation
VIN = 3.7V, CCF = 56nF, Duty = 50%, f = 10kHz
VIN
(50mV/Div)
EN
(2V/Div)
VOUT
(50mV/Div)
C2P
(5V/Div)
ILED
(10mA/Div)
IIN
(200mA/Div)
VIN = 3.1V
Time (1μs/Div)
Time (250μs/Div)
DS9385-01 April 2011
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7
RT9385
Applications Information
The RT9385 uses a fractional switched capacitor charge
pump to power up to five 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.
Capacitors Selection
To get the better performance of the RT9385, 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. However,
it will limit the LED's current at low input voltage. For
5x25mAload over the entire input range of 2.8V to 4.5V, it
is recommended to use a 1μF ceramic capacitor on the
Input UVLO
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. The RT9385
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.
flying capacitor CFLY1 and CFLY2
.
Soft Start
Brightness Control
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 drop. The soft-start clamps
the input current in a typical period of 50μs.
The RT9385 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 suggested
PWM dimming frequency range is from 1kHz to 200kHz.
Mode Decision
The RT9385 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 RT9385 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.
Thermal 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 :
LED connection
P
D(MAX) = ( TJ(MAX) − TA ) / θJA
The RT9385 supports up to 5 white LEDs. The 5 LEDs
are connected from VIN to pin1, 2, 3, 15 and 16
respectively. If the LED is not used, the LED pin should
be connected to VIN directly.
Where TJ(MAX) is the maximum operation junction
temperature, TA is the ambient temperature and the θJA is
the junction to ambient thermal resistance.
For recommended operating conditions specification of
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DS9385-01 April 2011
RT9385
the RT9385, The maximum junction temperature is 125°C.
The junction to ambient thermal resistance θJA is layout
dependent. For WQFN-16L 2x3 package, the thermal
resistance θJA is 90°C/W on the standard JEDEC 51-7
four layers thermal test board. The maximum power
dissipation at TA = 25°C can be calculated by following
formula :
` Input capacitor (CIN) should be placed close to VINand
connected to ground plane. The trace of VINin the PCB
should be placed far away from the sensitive devices or
shielded by the ground.
` The traces running from pins to flying capacitor should
be short and wide to reduce parasitic resistance and
prevent noise radiation.
PD(MAX) = (125°C − 25°C) / (90°C/W) = 1.111W for
WQFN-16L 2x3 package
All the traces of LED pins running from
chip to LEDs should be wide and short to
reduce the parasitic connection resistance.
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal
resistance θJA. For RT9385 package, the Figure 1 of
derating curve allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation allowed.
The trace from CF pin
to external capacitance
should be as short as
possible.
Output capacitor
(C
) should
OUT
16 15 14
be placed close
to VOUT and
connected to
ground plane to
reduce noise
coupling from
charge pump to
LEDs.
1
2
3
4
5
13
12
11
10
9
LED3
LED4
LED5
VOUT
PGND
AGND
CF
1.2
GND
VIN
Four Layers PCB
Battery
1.1
EN
1.0
Input capacitor
C2P
17
(C ) should be
IN
0.9
6
7
8
WQFN-16L 2x3
placed close to VIN
and connected to
ground plane. The
trace of VIN in the
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
GND
GND
PCB should be
placed far away
The traces running from pins to flying capacitor from the sensitive
should be short and wide to reduce parasitic
resistance and prevent noise radiation.
devices or shielded
by the ground.
Figure 2. PCB Layout Guide
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 1.Derating Curve for RT9385 Package
Layout Considerations
For best performance of the RT9385, the following layout
guidelines should be strictly followed :
` Output Capacitor (COUT) should be placed close to VOUT
and connected to ground plane to reduce noise coupling
from charge pump to LEDs.
` All the traces of LED pins running from chip to LED's
should be wide and short to reduce the parasitic
connection resistance.
` The trace from CF pin to external capacitance should
be as short as possible.
DS9385-01 April 2011
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9
RT9385
Outline Dimension
D
D2
SEE DETAIL A
e
E
E2
1
2
1
2
L
b
DETAILA
Pin #1 ID and Tie Bar Mark Options
A
Note : The configuration of the Pin #1 identifier is optional,
but must be located within the zone indicated.
A3
A1
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
0.800
0.050
0.250
0.250
2.100
0.800
3.100
1.800
Min
Max
0.700
0.000
0.175
0.150
1.900
0.700
2.900
1.700
0.028
0.000
0.007
0.006
0.075
0.028
0.114
0.067
0.031
0.002
0.010
0.010
0.083
0.031
0.122
0.071
A
A1
A3
b
D
D2
E
E2
e
0.400
0.016
L
0.325
0.425
0.013
0.017
W-Type 16L QFN 2x3 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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DS9385-01 April 2011
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