RT9300A/B
1
DS9300A/B-05 April 2011 www.richtek.com
Features
zz
zz
zLow 60/45mV Dropout at 20/15mA
zz
zz
z5% LED Current Matching
zz
zz
zSimple LED Brightness Control
zz
zz
z2.5V to 5.5V Supply Voltage Range
zz
zz
zThermal Shutdown Protection
zz
zz
zRoHS Compliant and 100% Lead (Pb)-Free
Applications
zNext-Generation Wireless Handsets
zPDAs, Palmtops, a nd Ha ndy Terminals
zDigital Ca meras, Camcorders
zBattery-Powered Equipment
Tiny Package, Low Dropout Current Source
Ordering Information
General Description
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.
(TOP VIEW)
SOT-23-6
Typical Application Circuit
Pin Configurations
Figure 1. Application Circuit f or Ba cklight.
Note :
Richtek products are :
` 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.
Marking Information
For marking information, conta ct our sales representative
directly or through a Richtek distributor located in your
area.
LED4LED3LED2LED1
GND
EN
Enable
VIN
6543
1
2
RT9300A/B
C
0.1uF
EN GND LED4
LED1 LED2LED3
4
23
56
RT9300A/B
Package Type
E : SOT-23-6
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Sink Current
A : 20mA
B : 15mA
RT9300A/B
2DS9300A/B-05 April 2011www.richtek.com
Function Block Diagram
Functional Pin Description
Pin Name Function
1 EN Chip Enable (Active High).
2 GND Ground
3 LED4 LED4 Cathode C o nnection. Current flowing into LED4 is Constant. (20mA/15 mA)
LED4 is High Im pedance when EN is Low.
4 LED3 LED3 Cathode Connection. Current flowing into LED3 is Constant. (20mA/15 mA)
LED3 is High Im pedance when EN is Low.
5 LED2 LED2 Cathode Connection. Current flowing into LED2 is Constant. (20mA/15 mA)
LED2 is High Im pedance when EN is Low.
6 LED1 LED1 Cathode Connection. Current flowing into LED1 is Constant. (20mA/15 mA)
LED1 is High Im pedance when EN is Low.
+
-
Current Source
UVLO
Bandgap
OTP
LED1
LED2LED3LED4
EN
IREF
VREF
Figure 2. Application Circuit f or Keypad.
LED4LED3LED2LED1
GND
EN
PWM
VIN
6543
1
2
RT9300A/B
C
0.1uF
Keypad
LED
RT9300A/B
3
DS9300A/B-05 April 2011 www.richtek.com
Absolute Maximum Ratings (Note 1)
zSupply Input Voltage, VIN ------------------------------------------------------------------------------------------------ −0.3V to 6V
zThe other pins-------------------------------------------------------------------------------------------------------------- −0.3V to 6V
zPower Dissipation, PD @ TA = 25°C
SOT-23-6 -------------------------------------------------------------------------------------------------------------------- 0.4W
zPa ckage Thermal Resista nce (Note 2)
SOT-23-6, θJA --------------------------------------------------------------------------------------------------------------- 250°C/W
zLead T emperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C
zOperation T emperature Range ----------------------------------------------------------------------------------------- −40°C to 85°C
z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
zStorage T emperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C
zESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
Electrical Characteristics
Parameter Symbol Test Conditions Min Typ Max Unit
Syst e m Supply In put
Operation Voltage Range VEN 2.5 -- 5.5 V
Under Voltage Lock Out V(UVLO) Falling -- 2.1 -- V
UVLO Hysteresis -- 100 -- mV
RT9300A 18 20 22
LED Sink Current RT9300B 13.5 15 16.5
mA
Quiescent Current IEN I
LED = 0 -- -- 600 uA
ILED = 20mA -- 60 --
LED Dropout Voltage ILED = 15mA -- 45 -- mV
LED Current Deviation Matching -- -- 5 %
E N High-Level Input Voltage VEN_H 2.5 -- -- V
E N Low-Level Input Voltage VEN_L -- -- 0.7 V
OTP -- 170 -- °C
OTP Hysteresis -- 10 -- °C
Shutdown Current ISHDN V
EN < 0.4V -- -- 1 uA
(VIN = 3.7V, TA = 25°C, Unless Otherwise specification)
Recommended Operating Conditions (Note 4)
zJunction T emperature Range-------------------------------------------------------------------------------------------- −40°C to 125°C
zAmbient T emperature Range-------------------------------------------------------------------------------------------- −40°C to 85°C
RT9300A/B
4DS9300A/B-05 April 2011www.richtek.com
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.
RT9300A/B
5
DS9300A/B-05 April 2011 www.richtek.com
Typical Operating Characteristics
LE D Current vs. EN Voltage
0
2
4
6
8
10
12
14
16
18
1.5 1.75 2 2.25 2.5 2.75 3 3.25 3.5
EN Vol tage ( V)
LED Curr ent (mA)
VIN = 3.7V
EN Current vs. EN Supply Voltage
0
50
100
150
200
250
300
350
400
1.522.533.544.5
EN Supply Voltage (V)
EN Current (uA)
VIN = 3.5V
LE D Current vs. In put Voltage
0
2
4
6
8
10
12
14
16
18
22.533.544.55
In put Voltage ( V)
LED Curr ent (mA)
LED 1
LED 2
LED 3
LED 4
(°C)
LED Current vs. Te m pe rature
15
15.1
15.2
15.3
15.4
15.5
-40-30-20-100 102030405060708090
Temperature
LED Current (mA)
EN Pin Dimming Operation
Time (50us/Div)
(2V/Div)
(10mA/Div)
LED
Current
EN Pin
Voltage
VEN = 0V to 3V
EN Pin Shutdown Response
Time (50us/Div)
EN Pin
Voltage
LED
Current
(2V/Div)
(10mA/Div)
EN Current vs. EN Supply Voltage
EN Supply Voltage (V)
EN Current (uA)
LED Current vs. EN Voltage
EN Voltage (V)
LED Current (mA)
RT9300A/B
6DS9300A/B-05 April 2011www.richtek.com
VIN = 3.2V to 3.7V
Line Transient Response
Time (100us/Div)
Input
Voltage (1V/Div)
(25mA/Div)
LED
Current
RT9300A/B
7
DS9300A/B-05 April 2011 www.richtek.com
Applications Information
The RT9300A/B is a 4-Channel current source driver fo r
white LEDs.
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,
a nd LED4 into a high-impeda nce state.
LED Current
RT9300A/B provides a constant current for white LED.
Figure 1 shows a typical application circuit for 4 white
LEDs. Ea ch 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 con sta nt 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 a pplying 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 ra nge 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
surroundings airflow and temperature difference between
junction to a mbient. The maxi mum power dissipation ca n
be calculated by following formula :
PD(MAX) = ( TJ(MAX) - TA ) / θJA
Where TJ(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 TJ(MAX) is the maximum junction
temperature of the die (125°C) and TA is the maximum
ambient temperature. The junction to ambient thermal
resistance θJA 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.
Figure 1. Derating Curves for RT9300 Packages
0
50
100
150
200
250
300
350
400
450
500
0 255075100125
Ambient Tem perat ur e (°C)
Maxi mum Power Di ssipation (mW )
SOT-23-6
Single Layer PCB
RT9300A/B
8DS9300A/B-05 April 2011www.richtek.com
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 resista nce.
`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 a nd noise protection.
LED3LED2
LED1
LED4
GNDEN
4
23
56
1
PWM
Battery
All the traces of LED and VIN 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. GND
Figure 2
RT9300A/B
9
DS9300A/B-05 April 2011 www.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.
Richtek Technology Corporation
Headquarter
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 95, Minchiuan Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8862)86672399 Fax: (8862)86672377
Email: marketing@richtek.com
Outline Dimension
AA1
e
b
B
D
C
H
L
SOT-23-6 Surface Mount Package
Dimensions In Millimeters Dimens ions In In ch e s
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
