RT9385B [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： | RT9385B |
| 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：218K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
RT9385B
5 Channels 125mA x1/x1.5/x2 Charge Pump White LED Driver
General Description
Features
z 85% Average Efficiency Over Li-ion Battery
The RT9385B is a 5 channel WLEDdriver with auto mode
selection of x1, x1.5 and x2 mode with low dropout voltage
in current sources. The RT9385B 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. An internal 5-bit DAC is used for brightness
control. Users can easily configure up to 32 steps of LED
current by enable pin.
Discharge
z Support Up to 5 White LEDs
z Support Up to 25mA/Per Channel
z Support Up to 125mA Output Current
z Flexible 32 Step 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
The RT9385B 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 Low Input Noise and EMI Charge Pump
z 5V Over Voltage Protection
z Power On/Mode Transition Inrush Protection
z 1MHz Frequency Oscillator
z 0.4μA Low Shutdown Current
z RoHS Compliant and Halogen Free
Ordering Information
RT9385B
Package Type
QW : WQFN-16L 2x3 (W-Type)
Applications
z Camera Phone, Smart Phone
Lead Plating System
G : Green (Halogen Free and Pb Free)
z White LEDBacklighting
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)
16 15 14
1
2
3
4
5
13
12
11
10
9
LED3
LED4
LED5
VOUT
PGND
AGND
NC
VIN
EN
C2P
Marking Information
GND
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
17
6
7 8
WQFN-16L 2x3
DS9385B-01 April 2011
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1
RT9385B
Typical Application Circuit
C
FLY2
C
FLY1
1µF
1µF
8
7
9
6
C1P C1N C2P C2N
14,11
VIN
15
16
Pulse Input
LED1
LED2
LED3
LED4
LED5
C
1µF
IN
10
EN
RT9385B
1
2
3
4
VOUT
C
OUT
1µF
AGND
13
PGND
5
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
2
LED3
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
3
4
5
Ground.
6
Fly Capacitor 2 Negative Connection.
Fly Capacitor 1 Negative Connection.
Fly Capacitor 1 Positive Connection.
Fly Capacitor 2 Positive Connection.
Chip Enable (Active High).
7
C1N
8
C1P
9
C2P
10
11, 14
12
13
15
16
EN
VIN
Power Input.
NC
No Internal Connection.
AGND
LED1
LED2
Ground.
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 be 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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2
DS9385B-01 April 2011
RT9385B
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
Pulse Dimming
Controller
Shutdown Delay
EN
PGND
Current Source
Current
Bias
AGND
DS9385B-01 April 2011
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3
RT9385B
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage, VIN ---------------------------------------------------------------------------------------------- −0.3V to 5V
z PowerDissipation, 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 = 1μF, 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 Units
V
V
2.8
1.8
--
2
4.5
2.5
V
V
IN
Under-Voltage Lockout
Threshold
V
IN
Rising
UVLO
Under-Voltage Lockout
Hysteresis
ΔV
--
100
--
mV
UVLO
Quiescent Current
Shutdown Current
I
I
x1 Mode
--
--
1
2
2
mA
Q
V = 4.5V
IN
0.4
μA
SHDN
LED Current
LED Current Accuracy
Current Matching
Charge Pump
I
f
I
= 25mA
= 25mA
−5
−2
0
0
+5
+2
%
%
LEDx
LEDx
LEDx
I
Oscillator Frequency
Mode Decision
--
1000
--
kHz
OSC
x1 Mode to x1.5 Mode
I
I
= 125mA, I
= 125mA, I
= 25mA
= 25mA
--
--
3.65
200
3.8
--
V
OUT
LEDx
Transition Voltage (V Falling)
IN
Mode Transition Hystersis
Protection
mV
OUT
LEDx
OVP
V
IN
– V
4.5
5
5.5
V
OUT
To be continued
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4
DS9385B-01 April 2011
RT9385B
Parameter
Symbol
Test Conditions
Min
Typ
Max Units
Dimming
EN Low to Shutdown Delay
EN Low Time for Dimming
EN High Time for Dimming
En Pull Low Current
3
--
--
ms
T
0.5
0.5
--
--
500
--
μs
μs
IL
T
IH
I
--
--
2
--
μA
EN
Logic-Low Voltage
EN
V
V
--
0.2
V
IL
Threshold
Logic-High Voltage
1
--
2
4.5
V
IH
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.
DS9385B-01 April 2011
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5
RT9385B
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
LED VF = 3.02V
10
LED VF = 3.02V
4.2 4.4 4.6 4.8 5
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
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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DS9385B-01 April 2011
RT9385B
x1.5 Mode Inrush Current Response
x2 Mode Inrush Current Response
EN
VIN = 3.15V
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
Pulse Dimming Operation
VIN = 3.7V
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 (5ms/Div)
DS9385B-01 April 2011
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7
RT9385B
Applications Information
The RT9385B 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 Selecting
To get the better performance of the RT9385B, 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
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 RT9385B
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.
capacitor on the 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 droop. The soft-start
clamps the input current over a typical period of 50us.
The RT9385B implements a pulse dimming method to
control the brightness of white LEDs. Users can easily
configure the LED current by a serial pulse. The dimming
of white LEDs' current can be achieved by applying a pulse
signal to the EN pin. There are totally 32 steps of current
could be set by users. The detail operation of brightness
dimming is shown in the Figure 1.
Mode Decision
The RT9385B uses a smart mode selection method to
decide the working mode for optimizing the efficiency.
Mode decision circuit senses the output and LEDvoltage
for up/down selection. The RT9385B 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.
30us < t
0.5us < t
0.5us < t < 500us
IL
3ms < t
SHDN
IH, INIT
IH
EN
0
1
2
3
4
0
1
5
30
31
100%
100%
31/32
31/32
30/32
29/32
28/32
Shutdown
ILEDX
3/32
Shutdown
2/32
1/32
LED connection
Figure 1. 32 Step PulseDimming and ShutdownDelay
The RT9385B 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.
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8
DS9385B-01 April 2011
RT9385B
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 :
For best performance of the RT9385B, the following layout
guidelines should be strictly followed :
` Output Capacitor (COUT) should be placed close toVOUT
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.
PD(MAX) = ( TJ(MAX) − TA ) / θJA
Where TJ(MAX) is the maximum operation junction
temperature, TA is the ambient temperature and the θJA is
the junction to ambient thermal resistance.
` 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.
For recommended operating conditions specification of
the RT9385B, 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 :
` 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.
PD(MAX) = (125°C − 25°C) / (90°C/W) = 1.111W for
WQFN-16L 2x3 package
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal
resistance θJA. For RT9385B package, the Figure 2 of
derating curve allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation allowed.
16 15 14
Output capacitor
1
2
3
4
5
13
12
11
10
9
(C
OUT
) should
LED3
LED4
LED5
VOUT
PGND
AGND
NC
be placed close
to VOUT and
connected to
ground plane to
reduce noise
coupling from
charge pump to
LEDs.
GND
VIN
Battery
Input capacitor
EN
C2P
17
(C ) should be
IN
6
7
8
placed close to VIN
and connected to
ground plane. The
trace of VIN in the
GND
PCB should be
1.2
Four Layers PCB
1.1
GND
1.0
placed far away
from the sensitive
devices or shielded
by the ground.
0.9
The traces running from pins to flying capacitor
should be short and wide to reduce parasitic
resistance and prevent noise radiation.
WQFN-16L 2x3
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Figure 3. PCB LayoutGuide
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 2.Derating Curve for RT9385B Package
DS9385B-01 April 2011
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9
RT9385B
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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10
DS9385B-01 April 2011
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