RICHTEK RT9300A_11

RT9300A/B
Tiny Package, Low Dropout Current Source
General Description
Features
The RT9300A/B low-dropout bias supply for white LEDs
is a high-performance alternative to the simple ballast
resistors used in conventional white LED designs. The
RT9300A/B uses an internal resistor to set the bias
current for four LEDs, which are matched to 5%. The
RT9300A/B's advantages over ballast resistors include
much lower bias variation with supply voltage variation,
significantly lower dropout voltage, and in some applications,
significantly improved efficiency. The RT9300A/B requires
only a 60/45mV dropout voltage at a 20/15mA load on
each output to match the LED brightness.
z
Low 60/45mV Dropout at 20/15mA
z
5% LED Current Matching
Simple LED Brightness Control
2.5V to 5.5V Supply Voltage Range
Thermal Shutdown Protection
RoHS Compliant and 100% Lead (Pb)-Free
z
z
z
z
Applications
z
z
z
z
Next-Generation Wireless Handsets
PDAs, Palmtops, and Handy Terminals
Digital Cameras, Camcorders
Battery-Powered Equipment
Ordering Information
RT9300A/B
Pin Configurations
Package Type
E : SOT-23-6
(TOP VIEW)
LED1 LED2 LED3
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
6
Sink Current
A : 20mA
B : 15mA
2
3
SOT-23-6
Richtek products are :
Marking Information
RoHS compliant and compatible with the current require-
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
ments of IPC/JEDEC J-STD-020.
`
4
EN GND LED4
Note :
`
5
Suitable for use in SnPb or Pb-free soldering processes.
Typical Application Circuit
VIN
C
0.1uF
6
LED1
Enable
1
EN
5
LED2
4
LED3
3
LED4
RT9300A/B
GND
2
Figure 1. Application Circuit for Backlight.
DS9300A/B-05 April 2011
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RT9300A/B
VIN
Keypad
LED
C
0.1uF
5
6
LED1
1
PWM
LED2
4
LED3
3
LED4
RT9300A/B
EN
GND
2
Figure 2. Application Circuit for Keypad.
Function Block Diagram
LED2
LED4
LED1
LED3
EN
Bandgap
VREF
+
-
UVLO
Current Source
OTP
IREF
Functional Pin Description
Pin
Name
Function
1
EN
Chip Enable (Active High).
2
GND
Ground
3
LED4
LED4 Cathode Connection. Current flowing into LED4 is Constant. (20mA/15 mA)
LED4 is High Impedance when EN is Low.
4
LED3
LED3 Cathode Connection. Current flowing into LED3 is Constant. (20mA/15 mA)
LED3 is High Impedance when EN is Low.
5
LED2
LED2 Cathode Connection. Current flowing into LED2 is Constant. (20mA/15 mA)
LED2 is High Impedance when EN is Low.
6
LED1
LED1 Cathode Connection. Current flowing into LED1 is Constant. (20mA/15 mA)
LED1 is High Impedance when EN is Low.
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DS9300A/B-05 April 2011
RT9300A/B
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------The other pins -------------------------------------------------------------------------------------------------------------z Power Dissipation, PD @ TA = 25°C
SOT-23-6 -------------------------------------------------------------------------------------------------------------------z Package Thermal Resistance (Note 2)
SOT-23-6, θJA --------------------------------------------------------------------------------------------------------------z Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------z Operation Temperature Range ----------------------------------------------------------------------------------------z Junction Temperature ----------------------------------------------------------------------------------------------------z Storage Temperature Range -------------------------------------------------------------------------------------------z ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) -----------------------------------------------------------------------------------------------------z
z
Recommended Operating Conditions
z
z
−0.3V to 6V
−0.3V to 6V
0.4W
250°C/W
260°C
−40°C to 85°C
150°C
−65°C to 150°C
2kV
200V
(Note 4)
Junction Temperature Range -------------------------------------------------------------------------------------------Ambient Temperature Range --------------------------------------------------------------------------------------------
−40°C to 125°C
−40°C to 85°C
Electrical Characteristics
(VIN = 3.7V, TA = 25°C, Unless Otherwise specification)
Parameter
Symbol
Test Conditions
Min
Typ
Max
Unit
2.5
--
5.5
V
--
2.1
--
V
--
100
--
mV
RT9300A
18
20
22
RT9300B
13.5
15
16.5
ILED = 0
--
--
600
ILED = 20mA
--
60
--
ILED = 15mA
--
45
--
--
--
5
%
System Supply Input
Operation Voltage Range
VEN
Under Voltage Lock Out
V(UVLO)
Falling
UVLO Hysteresis
LED Sink Current
Quiescent Current
mA
IEN
LED Dropout Voltage
LED Current Deviation Matching
uA
mV
EN High-Level Input Voltage
VEN_H
2.5
--
--
V
EN Low-Level Input Voltage
VEN_L
--
--
0.7
V
OTP
--
170
--
°C
OTP Hysteresis
--
10
--
°C
--
--
1
uA
Shutdown Current
DS9300A/B-05 April 2011
ISHDN
VEN < 0.4V
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RT9300A/B
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.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. Floating connection or pull low to disable this function.
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DS9300A/B-05 April 2011
RT9300A/B
Typical Operating Characteristics
LEDCurrent
Current vs. EN Voltage
LED
Voltage
LED Current vs. Input Voltage
18
18
16
16
VIN = 3.7V
14
LED 1
LED 2
LED 3
LED 4
12
10
LED
LED Current
Current (mA)
(mA)
LED Current (mA)
14
8
6
4
12
10
8
6
4
2
2
0
0
2
2.5
3
3.5
4
4.5
5
1.5
1.75
2
2.25
2.5
2.75
3
3.25
Input Voltage (V)
EN Voltage
Voltage (V)
EN
(V)
LED Current vs. Temperature
ENCurrent
Current vs.
vs. EN
EN Supply
EN
Supply Voltage
Voltage
15.5
3.5
400
VIN = 3.5V
350
15.4
EN
EN Current
Current (uA)
(uA)
LED Current (mA)
300
15.3
15.2
250
200
150
100
15.1
50
15
0
-40 -30 -20 -10 0
10 20 30 40 50 60 70 80 90
1.5
2
2.5
3
3.5
4
Temperature (°C)
ENSupply
Supply Voltage
Voltage (V)
EN
(V)
EN Pin Dimming Operation
EN Pin Shutdown Response
4.5
VEN = 0V to 3V
(2V/Div)
EN Pin
Voltage
LED
Current
EN Pin
Voltage
(2V/Div)
(10mA/Div)
LED
Current
Time (50us/Div)
DS9300A/B-05 April 2011
(10mA/Div)
Time (50us/Div)
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RT9300A/B
Line Transient Response
VIN = 3.2V to 3.7V
Input
Voltage
LED
Current
(1V/Div)
(25mA/Div)
Time (100us/Div)
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DS9300A/B-05 April 2011
RT9300A/B
Applications Information
Enable Input
EN powers the input of the RT9300A/B. This IC provides
an under voltage lockout (UVLO) function to prevent it from
unstable issue when startup. The UVLO threshold of input
falling voltage is set at 2.1V typically with a hysteresis
0.1V.Drive EN high to enable the device; drive EN low to
disable the device. When driven high, EN draws 350uA to
power the IC. Driving EN low forces LED1, LED2, LED3,
and LED4 into a high-impedance state.
LED Current
RT9300A/B provides a constant current for white LED.
Figure 1 shows a typical application circuit for 4 white
LEDs. Each channel supports up to 20mA/15mA current
and regulates a constant current for uniform intensity. For
keypad LED application, the all channels must be
connected to LED as shown in Figure 2. In order to maintain
LED constant current, the input voltage must provide the
required LED forward voltage and current source dropout
voltage. If the forward voltage of white LEDs is 3.3V, the
input voltage should be higher than 3.4V to provide enough
voltage headroom for maintaining constant brightness.
LED Brightness Dimming Control
For controlling the LED brightness, the RT9300A/B can
perform the dimming control by applying a PWM signal to
EN pin. When an external PWM signal is connected to
the EN pin, brightness of white LED is adjusted by the
duty cycle. The average LED current is proportional to the
PWM signal duty cycle. The magnitude of the PWM signal
must be higher than the minimum level of enable input
high level, in order to let the dimming control perform
correctly, the suggested PWM frequency range is 10kHz
to 200Hz.
Thermal Considerations
For continuous operation, do not exceed absolute
maximum operation junction temperature 125°C. The
maximum power dissipation depends on the thermal
resistance of IC package, PCB layout, the rate of
DS9300A/B-05 April 2011
surroundings airflow and temperature difference between
junction to ambient. The maximum power dissipation can
be calculated by following formula :
PD(MAX) = ( TJ(MAX) - TA ) / θJA
Where T J(MAX) is the maximum operation junction
temperature 125°C, TA is the ambient temperature and
the θJA is the junction to ambient thermal resistance.
For recommended operating conditions specification of
RT9300, where T J(MAX) is the maximum junction
temperature of the die (125°C) and TA is the maximum
ambient temperature. The junction to ambient thermal
resistance θ JA is layout dependent. For SOT-23-6
packages, the thermal resistance θJA is 250°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 :
PD(MAX) = (125°C − 25°C) / (250°C/W) = 0.4W for
SOT-23-6 packages
The maximum power dissipation depends on operating
ambient temperature for fixed TJ(MAX) and thermal resistance
θJA. For RT9300 packages, the Figure 1 of derating curves
allows the designer to see the effect of rising ambient
temperature on the maximum power allowed.
500
Maximum Power Dissipation (mW)
The RT9300A/B is a 4-Channel current source driver for
white LEDs.
Single Layer PCB
450
400
350
SOT-23-6
300
250
200
150
100
50
0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 1. Derating Curves for RT9300 Packages
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RT9300A/B
Layout Considerations
For best performance, careful PCB layout is necessary.
All peripheral components should be placed as close to
the IC as possible. A short connection is highly
recommended. The following guidelines should be strictly
followed when designing a PCB layout for the RT9300A/
B.
` All the traces of LED and VIN running from chip to LEDs
should be wide and short to reduce the parasitic
connection resistance.
` The capacitor should be placed close to the anodes of
LEDs and connected to ground plane.
` The GND should be connected to a strong ground plane
for heat sinking and noise protection.
All the traces of LED and VIN running from
chip to LEDs should be wide and short to
reduce the parasitic connection resistance.
Battery
The GND should be
connected to a strong
ground plane for heat
sinking and noise
protection. GND
PWM
LED1 LED2 LED3
6
5
4
1
2
3
EN
GND LED4
Figure 2
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DS9300A/B-05 April 2011
RT9300A/B
Outline Dimension
H
D
L
C
B
b
A
A1
e
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
0.889
1.295
0.031
0.051
A1
0.000
0.152
0.000
0.006
B
1.397
1.803
0.055
0.071
b
0.250
0.560
0.010
0.022
C
2.591
2.997
0.102
0.118
D
2.692
3.099
0.106
0.122
e
0.838
1.041
0.033
0.041
H
0.080
0.254
0.003
0.010
L
0.300
0.610
0.012
0.024
SOT-23-6 Surface Mount Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: [email protected]
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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