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RT9301
3-Channel Low Dropout RGB LED Driver
General Description
The RT9301 is a 3-Channel current source driver for RGB LED. It is easy to be designed in applications that need mixing RGB light source for multi-color output. The RT9301 also provide users with great flexibility and device performance. It uses a external resistor to set the bias current for three LEDs, which are matched to 3%. Users can adjust the output current from 2mA to 50mA by setting the ISET resistor. The RT9301 features very low dropout and under voltage lockout protection. It is available in a space-saving TSOT23-8 package.
Features
Input Voltage Range : 2.8V to 5.5V Low 60/45mV Dropout at 20/15mA Individual Current Setting by External Resistor Individual On/Off Control by Baseband MPU Up to 50mA LED Bias Current Simple LED Brightness Control 3% LED Current Matching Low 0.1uA Shutdown Current UVLO Protection Tiny TSOT-23-8 Package
Applications
Mobile phone, Smart Phone Multi-color LED Backlight Camera Flash White LED LCD Display Modules Keypad Backlight
Ordering Information
RT9301 Package Type J8 : TSOT-23-8 Operating Temperature Range P : Pb Free with Commercial Standard G : Green (Halogen Free with Commercial Standard)
Pin Configurations
(TOP VIEW)
ISET1 ISET2 LED2 LED1
Note : RichTek Pb-free and Green products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100%matte tin (Sn) plating.
8 1
LED3
7 2
GND
6 3
VIN
5 4
ISET3
Marking Information
For marking information, contact our sales representative directly or through a RichTek distributor located in your area, otherwise visit our website for detail.
TSOT-23-8 Note : There is no pin1 indicator on top mark for TSOT-23-8 type, and pin 1 will be lower left pin when reading top mark from left to right.
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RT9301
Typical Application Circuit
VBAT 1uF
ON GPIO OFF
VSET1 VSET2 VSET3
RSET1 RSET2 RSET3
VIN LED1 ISET1 ISET2 ISET3
LED2 LED3
RT9301 GND
Figure 1. Application circuit for RGB LED
VBAT 1uF
RSET1 GPIO RSET2 RSET3
VIN ISET1 ISET2 ISET3
LED1
LED2
LED3
RT9301 GND
Figure 2. Application circuit for backlight
VBAT 1uF
RSET1 GPIO RSET2 RSET3
VIN ISET1 ISET2 ISET3
LED1 LED2 LED3 RT9301 GND
Figure 3. Application circuit for keypad ILED1 ~ 3 = 800 x ISET1 ~ 3 = 800 x VSET 1 ~ 3 - 0.9V RSET1 ~ 3
GPIO (V) ILED (mA) 1.8 2.8 15 20 15 20 RSET (k) 48 36 101 76 Nearest Standard Values for RSET (k) 47.5 36 100 75
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RT9301
Function Block Diagram
VIN ISET1
+ -
UVLO
VREF ISET2
LED1
+
VREF ISET3
-
Current Source
LED2 LED3
+
VREF
-
GND
Functional Pin Description
Pin 1 2 3 4 5 6 7 8 Name LED3 GND VIN ISET3 ISET2 ISET1 LED1 LED2 Function RGB or White LED cathode connection pin. 2mA to 50mA Current flows into LED. Floating or connection to ground is used to disable this pin. Ground Pin. Power Input Pin. Current setting for LED3. Connect to GND if not use. Current setting for LED2. Connect to GND if not use. Current setting for LED1. Connect to GND if not use. RGB or White LED cathode connection pin. 2mA to 50mA Current flows into LED. Floating or connection to ground is used to disable this pin. RGB or White LED cathode connection pin. 2mA to 50mA Current flows into LED. Floating or connection to ground is used to disable this pin.
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RT9301
Absolute Maximum Ratings
(Note 1) -0.3V to 6V -0.3V to 6V 0.382W 262C/W 260C 150C -65C to 150C 2kV 200V Supply Input Voltage -----------------------------------------------------------------------------------------------------Other I/O Pin Voltages --------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25C TSOT-23-8 ------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 4) TSOT-23-8, JA ------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------Junction Temperature ---------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 2) HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) ------------------------------------------------------------------------------------------------------
Recommended Operating Conditions
(Note 3)
Junction Temperature Range -------------------------------------------------------------------------------------------Ambient Temperature Range --------------------------------------------------------------------------------------------
-40C to 125C -40C to 85C
Electrical Characteristics
(VIN = 3.6V, TA = 25C, Unless Otherwise specification)
Parameter Input Supply Voltage UVLO Threshold UVLO Hysteresis Dropout Voltage ISET Reference Voltage Quiescent Current ILED Matching ILED Accuracy Shutdown current VSET Enable Threshold VSET Disable Threshold
Symbol Test Condition VIN VUVLO_L Falling
Min 2.8 2 --
Typ -2.2 100 40 0.9 0.5 0 0 0.1 ---
Max 5.5 2.4 -120 1 1 +5 +5 2 -0.25
Units V V mV mV V mA % % A V V
VLED
90% of ILED = 12mA
-0.8
IQ
LED Open, ISET = 20 uA ILED = 16mA
--5 -5 -1.3 --
ILED
ILED = 16mA All VSET1~3 < 0.25V
VSET VIL
VSET connect RSET = 47k to ISET VSET connect RSET = 47k to ISET
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. Devices are ESD sensitive. Handling precaution recommended. Note 3. The device is not guaranteed to function outside its operating conditions. Note 4. JA is measured in the natural convection at TA = 25C on a low effective single layer thermal conductivity test board of JEDEC 51-3 thermal measurement standard.
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RT9301
Typical Operating Characteristics
LED Current vs. Input Voltage
25
LED Current vs. VSET
60
Vf1 = 3.02V, Vf2 = 3.06V, Vf3 = 3.17V
20
RSET = 36k
50
RSET = 51k RSET = 75k
LED1
LED Current (mA)
LED Current (mA)
LED2
40 30
15
LED3
10
RSET = 160k
20
5
RSET = 360k
10 0
0 2 2.5 3 3.5 4 4.5 5 5.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
VSET (V)
LED Current vs. Temperature
20.4
Dimming Operation
VBAT = 5.0V (1V/Div)
ILED = 20mA
20.3
LED Current (mA)
20.2
VSET
20.1 20 19.9 19.8 19.7 -40 -25 -10 5 20 35 50 65 80 95
(10mA/Div)
I LED
Time (100s/Div)
Temperature (C)
Enable & Shutdown Response
VBAT = 5.0V
Line Transient Response
VBAT = 3.7V to 4.2V, ILED = 20mA (1V/Div)
(1V/Div)
VSET
(10mA/Div)
VIN
(10mA/Div)
I LED
I LED Time (50s/Div) Time (50s/Div)
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RT9301
Applications Information
The RT9301 is a 3-Channel current source driver for RGB LED or white LEDs. The output current can be controlled from 2mA to 50mA by adjusting the setting current from external. It is easy to support a multi-color RGB LED. Input UVLO The input operating voltage range of the RT9301 is 2.8V to 5.5V. An input capacitor at the VIN pin could reduce ripple voltage. It is recommended to use a ceramic 1uF or larger capacitance as the input capacitor. 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. Output Current Setting The LED current is setting by the current of ISET pin. The LED current of the three channels (LED1, LED2, LED3) could be set from the ISET (ISET1, ISET2, ISET3) pins individually. The typical application circuit shows as Figure 1.
VBAT 1uF
The LED current of each channel can be controlled from 2mA to 50mA. It is easy to obtain a multi-color output by changing the current of ISET1, ISET2, and ISET3 respectively.
60
RSET = 36k
50
RSET = 51k RSET = 75k
LED Current (mA)
40 30
RSET = 160k
20
RSET = 360k
10 0 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
VSET (V)
Figure 2. LED Current Setting Figure 2 shows the characteristics of ILED vs. VSET. If the RSET is selected, the LED current could be controlled from VSET. The voltage of VSET must be higher than 1.3V to enable the LED. For low LED current application, it is recommended to use a higher resistance on RSET (for example: RSET = 360k). To disable the LED current, the ISET pin should be connected to ground or floating. For one LED or two LEDs application, the unused ISET pin should be connected to GND. In addition, don' t short VSETx to ISETx pin.
VSET1 VSET2 VSET3
RSET1 RSET2 RSET3
VIN LED1 ISET1 ISET2 ISET3
LED2 LED3
RT9301 GND
Figure 1. Typical Application Circuit
VBAT
The LED current can be controlled from an external voltage (VSET) and a resistor (RSET) between VSET and ISET pin. The voltage range of VSET is from 1.3V to 5.5V. The internal reference voltage at ISET pin is 0.9V typically. LED current is set as 800 times the current flowing into ISET pin. Therefore, the LED current can be calculated as the following equation. ILED1 ~ 3 = 800 x ISET1 ~ 3 = 800 x VSET1 ~ 3 - 0.9V RSET1 ~ 3
1uF
VSET1 VSET2
RSET1 RSET2
VIN LED1 ISET1 ISET2 ISET3
LED2 LED3
RT9301 GND
Figure 3. Application Circuit for Two LEDs For example, RSET1 = 45k and VSET1 = 1.8V, the current of LED1 is equal to 16mA.
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RT9301
GPIO Control Figure 4 shows an application circuit for backlight with GPIO. The three setting resistors are connected to GPIO. The LED current can be controlled by GPIO directly. The RT9301 provides low dropout voltage and 5% maximum current matching. It also allows dimming control frequency up to 10kHz.
VBAT 1uF
Figure 5 shows another application circuit for keypad backlight with GPIO. There are 9 LEDs operation in parallel. A battery or a regulated power source drives the LEDs. Each channel supports three LEDs. The LED brightness adjustment can be set with proper setting resistor for each channel and be controlled from GPIO. Thermal Considerations The RT9301 can support LED current up to 50mA over the operation junction temperature range. However, the maximum current must be derated at higher ambient temperature to ensure the junction temperature does not exceed 125C. With all possible conditions, the junction temperature must be within the range specified under recommended operating conditions. The power dissipation can be calculated based on the LED current and the voltage drop across the regulator. PD = (VIN -VFLED) x ILED + VIN x IQ where VIN is input voltage, VFLED is the forward voltage of LED, ILED is the current of LED, and IQ is the quiescent current of this chip. For continuous operation, do not exceed the maximum operation junction temperature 125C. The maximum power dissipation depends on the thermal resistance of IC package, PCB layout, the rate of surroundings airflow and temperature difference between junction and ambient. The maximum power dissipation can be calculated by following formula: PD(MAX) = ( TJ(MAX) - TA ) / JA Where T J(MAX) is the maximum operation junction temperature 125C, TA is the ambient temperature and the JA is the junction to ambient thermal resistance.
RSET1 GPIO RSET2 RSET3
VIN ISET1 ISET2 ISET3
LED1
LED2
LED3
RT9301 GND
Figure 4. Application Circuit for Backlight with GPIO The LED current can be set at different value with proper setting resistor. For typical application of GPIO 1.8V/2.8V and LED current 15mA/20mA, the recommended current setting resistors are showed as below table. Table 1. RSET Value Selection
GPIO (V) 1.8
ILED (mA) 15 20
RSET Nearest Standard Values for (k) 48 36 101 76 RSET (k) 47.5 36 100 75
2.8
15 20
VBAT 1uF
RSET1 GPIO RSET2 RSET3
VIN ISET1 ISET2 ISET3
LED1 LED2 LED3 RT9301 GND
For recommended operating conditions specification of RT9301, where T J(MAX) is the maximum junction temperature of the die (125C) and TA is the maximum ambient temperature. The junction to ambient thermal resistance JA is layout dependent. For TSOT-23-8 packages, the thermal resistance JA is 262C/W on the standard JEDEC 51-3 single-layer thermal test board. The maximum power dissipation at TA = 25C can be calculated by following formula: PD(MAX) = (125C - 25C) / 262C/W = 0.382 W for TSOT23-8 packages
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Figure 5. Application Circuit for Keypad Backlight
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RT9301
The maximum power dissipation depends on operating ambient temperature for fixed TJ (MAX) and thermal resistance JA . For RT9301 packages, the Figure 6 of derating curves allows the designer to see the effect of rising ambient temperature on the maximum power allowed.
500
Layout Consideration For best performance, careful PCB layout is necessary. Place all peripheral components 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 RT9301. 1. All the traces of LED and VIN pin running from chip to LEDs should be wide and short to reduce the parasitic connection resistance. 2. Input capacitor (CIN) must be placed close to LEDs and connected to ground plane. The anodes of LEDs must be connected to CIN, not battery directly. 3. Current setting resistors RSET should be placed as close to the chip as possible. 4. The GND should be connected to a strong ground plane for heat sinking and noise protection.
Maximum Power Dissipation (mW)1
Single Layer PCB
450 400 350 300 250 200 150 100 50 0 0 20 40 60 80 100 120 140
Ambient Temperature (C)
5. The current setting resistors should be placed as close to the IC as possible.
Figure 6. Derating Curves for RT9301 Packages
All the traces of LED and VIN running from chip to LEDs should be wide and short to reduce the parasitic connection resistance.
Input capacitor (CIN) should be placed close to LEDs Pin and connected to ground plane. The Anodes of LEDs must connect to CIN, not battery directly.
LED3 GND
1 2 3 4
8 7 6 5
LED2 LED1 ISET1 ISET2
Battery
VIN ISET3
Ground Plane The GND should be connected to a strong ground plane for heat sinking and noise protection.
Figure 7. PCB Layout Guide
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RT9301
Outline Dimension
H D L C B
b A e A1
Symbol A A1 B b C D e H L
Dimensions In Millimeters Min 0.700 0.000 1.397 0.220 2.591 2.692 0.585 0.080 0.300 Max 1.000 0.100 1.803 0.380 3.000 3.099 0.715 0.254 0.610
Dimensions In Inches Min 0.028 0.000 0.055 0.009 0.102 0.106 0.023 0.003 0.012 Max 0.039 0.004 0.071 0.015 0.118 0.122 0.028 0.010 0.024
TSOT-23-8 Surface Mount Package
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) 8F, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
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