R1208x Series
PWM Low Supply Current Step-up DC/DC Converter
NO.EA-314-211027
OUTLINE
The R1208x is a low supply current CMOS-based PWM control step-up DC/DC converter. Internally, a single
converter consists of an NMOS FET, an oscillator, a PWM comparator, a voltage reference unit, an error amplifier,
a current limit circuit, an under voltage lockout circuit (UVLO), an over-voltage protection circuit (OVP), a thermal
shutdown protection circuit and current drivers for four white LED channels.
By simply using an inductor, a resistor, capacitors and a diode, white LEDs can be driven with constant current
and high efficiency. The LED current can be determined by the value of current setting resistor. The brightness of
the LEDs can be adjusted quickly by applying a PWM signal (200 Hz to 300 kHz) to the CE pin.
Protection circuits included in the R1208x are a current limit circuit which limits the LX peak current, an UVLO
circuit which prevents the malfunction of the device at low input voltage, an OVP circuit which monitors the excess
output voltage and a thermal shutdown protection circuit which detects the overheating of the device and stops
the operation to protect the device from damage.
The R1208x is offered in 12-pin DFN(PLP)2730-12 package.
FEATURES
• Input Voltage Range .................................................. 2.7 V to 22 V
• Supply Current ........................................................... Typ. 600 µA
• Standby Current ......................................................... Typ. 1.5 µA
• Lx Current Limit .......................................................... Typ. 2 A
• Overvoltage Protection (OVP) ................................... Typ. 23 V / 33 V / 43.5 V
• Oscillator Frequency .................................................. Typ. 750 kHz / 450 kHz
• Maximum Duty Cycle ................................................. 95% (750 kHz) / 97% (450 kHz)
• Nch MOSFET ON Resistance ................................... Typ. 0.28 Ω
• Undervoltage Lockout (UVLO) ................................... Typ. 2.4 V
• Thermal Shutdown ..................................................... Typ. 150°C
• LED Dimming Control ................................................ By sending a PWM signal (200 Hz to 300 kHz) to the CE pin
• Package ..................................................................... DFN(PLP)2730-12
APPLICATIONS
• LED backlight driver for LCD displays for portable equipment
• LED backlight driver for LCD displays for Tablets and Note PCs.
1
R1208x
NO.EA-314-211027
SELECTION GUIDE
The OVP threshold voltage and the oscillator frequency are user-selectable options.
Selection Guide
Product Name
R1208Kx12∗-TR
Package
Quantity per Reel
Pb Free
Halogen Free
DFN(PLP)2730-12
5,000 pcs
Yes
Yes
x: Specify the OVP threshold voltage.
(1) 23 V
(2) 33 V
(3) 43.5 V
∗: Specify the oscillator frequency.
(A) 750 kHz
(B) 450 kHz
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R1208x
NO.EA-314-211027
BLOCK DIAGRAMS
UVLO
Ramp
Compensation
VIN
Current
Feedback
Internal
Regulator
CE
LED
OVP
Chip
Enable
LED
Feedback
Selector
PWM
Control
ISET
Current
Control
VOUT
Current
Limit
LX
Switching
Control
Vref
VS
VOUT
OVP
Max
Duty
Thermal
Shutdown
PGND
LED1
LED Current Source
Soft
Start
LED2
LED Current Source
LED3
LED Current Source
LED4
GND
LED Current Source
R1208x Block Diagram
3
R1208x
NO.EA-314-211027
PIN DESCRIPTION
Top View
12 11 10 9
8
7
Bottom View
7
8
9 10 11 12
*1
1
2
3
4
5
6
6
5
4
3
2
1
DFN(PLP)2730-12 Pin Configurations
DFN(PLP)2730-1 Pin Description
Pin No.
Symbol
*1
Description
1
VIN
Power Input Pin
2
LED1
LED1 pin
3
ISET
LED Current Control Pin
4
VS
Power Input Pin (VIN < 5 V), Internal Regulator Pin (VIN > 5 V)
5
CE
Chip Enable Pin (Active-high)
6
PGND
7
LX
8
VOUT
9
GND
10
LED4
LED 4 Pin
11
LED3
LED 3 Pin
12
LED2
LED 2 Pin
Power GND Pin
Switching Pin
*1
Output Pin
Analog GND Pin
The exposed tab is substrate level (GND). It is recommended that the exposed tab be connected to the ground plane
on the board or otherwise be left floating.
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R1208x
NO.EA-314-211027
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum Ratings
Symbol
*1
(GND / PGND = 0 V)
Item
Rating
Unit
VIN
VIN Pin Voltage
−0.3 to 24
V
VS
VS Pin Voltage
−0.3 to 6.5
V
VCE
CE Pin Voltage
−0.3 to 6.5
V
VISET
ISET Pin Voltage
−0.3 to 6.5
V
VOUT
VOUT Pin Voltage
−0.3 to 48
V
VLX
LX Pin Voltage
−0.3 to 48
V
VLED
LED1, LED2, LED3, LED4 Pin Voltage
−0.3 to 24
V
ILX
LX Pin Current
2500
mA
PD
Power Dissipation*1
(JEDEC STD. 51-7 Test Land Pattern)
3100
mW
Tj
Junction Temperature Range
−40 to 125
°C
Tstg
Storage Temperature Range
−55 to 125
°C
Refer to POWER DISSIPATION for detailed information.
ABSOLUTE MAXIMUM RATINGS
Electronic and mechanical stress momentarily exceeded absolute maximum ratings may cause the permanent
damages and may degrade the life time and safety for both device and system using the device in the field. The
functional operation at or over these absolute maximum ratings is not assured.
RECOMMENDED OPERATING CONDITIONS
Symbol
Item
Rating
Unit
VIN
Input Voltage
2.7 to 22
V
Ta
Operating Temperature Range
−40 to 85
°C
RECOMMENDED OPERATING CONDITIONS
All of electronic equipment should be designed that the mounted semiconductor devices operate within the recommended
operating conditions. The semiconductor devices cannot operate normally over the recommended operating conditions,
even if when they are used over such ratings by momentary electronic noise or surge. And the semiconductor devices
may receive serious damage when they continue to operate over the recommended operating conditions.
5
R1208x
NO.EA-314-211027
ELECTRICAL CHARACTERISTICS
The specifications surrounded by
in production.
are over −40°C ≤ Ta ≤ 85°C.and guaranteed by design but not tested
Electrical Characteristics
Symbol
Item
VIN
(Ta = 25°C)
Conditions
Operating Input Voltage
Min.
2.7
VIN = 5.5 V, no load, no switching
IDD
Supply Current
Istandby Standby Current
Typ.
VIN = 5.5 V, no load, switching,
R1208Kx12A
VIN = 5.5 V, no load, switching,
R1208Kx12B
VIN = 22 V, VCE = 0 V
Unit
22
V
0.6
mA
2.2
mA
1.5
mA
1.5
10.0
UVLO Detector Threshold
VIN falling
VUVLO2
UVLO Released Voltage
VIN rising
VCEH
CE Input Voltage "H"
VIN = 22 V
VCEL
CE Input Voltage "L"
VIN = 2.7 V
RCE
CE Pull-down Resistance
VIN = 8 V
1200
kΩ
VS
VS Active Voltage
VIN = 8 V
5
V
ILED
LED1-4 Current Accuracy
RISET = 10 kΩ, 1 string = 20 mA,
VIN = 3.6 V,
∆ILED
/∆Ta
LED1-4 Current
Temperature Coefficient
−40°C ≤ Ta ≤ 85°C, VIN = 3.6 V
ILEDM
LED1-4 Current Matching
ILEDM2
LED1-4 Current Matching 2
ILEDMAX
2.4
µA
VUVLO1
CEduty CE Input Duty Range
2.3
Max.
VUVLO1
+0.1
V
2.6
1.5
V
0.4
−3%
20
+3%
(IMAX − IAVE) / IAVE,
1 string = 20 mA,
VIN = 3.6 V,
(IMAX − IAVE) / IAVE,
1 string = 2 mA
2.3
LED1-4 Max. Current Setting
(100% dimming)
VIN = 3.6 V
80
LED1-4 Active Voltage
V
mA
ppm
/°C
±100
VIN = 3.6 V, RISET = 10 kΩ
V
2.5
%
10
%
100
%
100
mA
VIN = 3.6 V, 1 string = 30 mA
0.75
V
LED1-4 Leakage Current
VIN = VLED1-4 = 22 V, VCE = 0 V
0
NMOS ON Resistance
ILX = 100 mA , VIN = 3.6 V
ILXLEAK
NMOS Leakage Current
VIN = VLED1-4 = 22 V, VCE = 0 V
ILXLIM
NMOS Current Limit
VIN = 3.6 V
fosc
Oscillator Frequency
VLED1
ILEDLEAK
RON
3.0
0.28
µA
Ω
0
3.0
µA
1.5
2
2.5
A
VIN = 3.6 V (R1208Kx12A)
675
750
825
kHz
VIN = 3.6 V (R1208Kx12B)
400
450
500
kHz
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R1208x
NO.EA-314-211027
ELECTRICAL CHARACTERISTICS (continued)
The specifications surrounded by
in production.
are over −40°C ≤ Ta ≤ 85°C.and guaranteed by design but not tested
Electrical Characteristics
Symbol
Item
Maxduty Maximum Duty Cycle
VOVP1
VOVP2
VOVP3
VOUT OVP Detector Threshold
VOUT OVP Release Voltage
(Ta = 25°C)
Conditions
VIN = 3.6 V
VIN = 3.6 V,
VOUT rising
VIN = 3.6 V,
VOUT falling
Typ.
Max.
92
Unit
%
R1208K112∗
22
23
24
V
R1208K212∗
31.5
33
34.5
V
R1208K312∗
42
43.5
45
V
R1208K112∗
21
VOVP1
−0.5
V
R1208K212∗
30.5
VOVP1
−1
V
R1208K312∗
39.5
VOVP1
−1.5
V
LED OVP Detector Threshold
VIN = 3.6 V, VLED1-4 rising
TSS
Soft Start Time
VIN = 3.6 V
TTSD
Thermal Shutdown Temperature VIN = 3.6 V
Thermal Shutdown
VIN = 3.6 V
Release Temperature
TTSR
Min.
10
10
11.5
V
15
32
ms
150
°C
120
°C
All test items listed under ELECTRICAL CHARACTERISTICS are done under the pulse load condition (Tj ≈ Ta = 25°C).
7
R1208x
NO.EA-314-211027
THEORY OF OPERATION
Operation of Step-Up DC/DC Converter and Output Current
i2
VIN
IOUT
Diode
L
VOUT
i1
Lx Tr
CL
GND
Discontinuous mode
Continuous mode
IL
ILmax
IL
ILmax
ILmin
ILmin
topen
t
toff
ton
T=1/fosc
t
ton
toff
T=1/fosc
There are two operation modes of the step-up PWM control-DC/DC converter. That is the continuous mode and
discontinuous mode by the continuousness inductor.
When the transistor turns ON, the voltage of inductor L becomes equal to VIN voltage. The increase value of
inductor current (i1) will be
∆i1 = VIN × ton / L ........................................................................................................... Formula 1
As the step-up circuit, during the OFF time (when the transistor turns OFF) the voltage is continually supply from
the power supply. The decrease value of inductor current (i2) will be
∆i2 = (VOUT − VIN) × topen / L .......................................................................................... Formula 2
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R1208x
NO.EA-314-211027
At the PWM control-method, the inductor current become continuously when topen=toff, the DC/DC converter
operate as the continuous mode.
In the continuous mode, the variation of current of i1 and i2 is same at regular condition.
VIN × ton / L = (VOUT - VIN) × toff / L .................................................................................. Formula 3
The duty at continuous mode will be
duty (%)= ton / (ton + toff) = (VOUT - VIN) / VOUT ................................................................ Formula 4
The average of inductor current at tf = toff will be
IL(Ave.) = VIN × ton / (2 × L) ........................................................................................... Formula 5
If the input voltage = output voltage, the IOUT will be
IOUT = VIN2 × ton / (2 × L × VOUT) ...................................................................................... Formula 6
If the IOUT value is large than above the calculated value (Formula 6), it will become the continuous mode, at this
status, the peak current (ILmax) of inductor will be
ILmax = IOUT × VOUT / VIN + VIN × ton / (2 × L) ................................................................... Formula 7
ILmax = IOUT × VOUT / VIN + VIN × T × (VOUT - VIN) / (2 × L × VOUT) ..................................... Formula 8
The peak current value is larger than the IOUT value. In case of this, selecting the condition of the input and the
output and the external components by considering of ILmax value.
The explanation above is based on the ideal calculation, and the loss caused by LX switch and the external
components are not included.
The actual maximum output current will be between 50% and 80% by the above calculations. Especially, when
the IL is large or VIN is low, the loss of VIN is generated with on resistance of the switch. Moreover, it is necessary
to consider Vf of the diode (approximately 0.8V) about VOUT.
9
R1208x
NO.EA-314-211027
•
Soft-Start Function
At startup, by forcibly switching Lx for a certain period of time, VOUT is raised with the LED current flowing about
4mA. During this period, the rush current is suppressed by gradually increasing the current limit. After the time
required to raise the VOUT has elapsed, gradually change the LED current from about 4mA to the set current value.
The soft start time (Tss = typ.15ms) is the time from CE= ”L”→”H” to 90% of the set current for ILED.
CE
0V
VOUT
0V
Tss
90%
ILED
about 4mA
0mA
•
Current Limit Function
If the peak current of inductor (ILmax) exceeds the current limit, current limit function turns the driver off and turns
it on in every switching cycle to continually monitor the driver current.
•
Under Voltage Lockout (UVLO) Function
UVLO function stops DC/DC operation to prevent malfunction when the supply voltage falls below the UVLO
detector threshold.
•
Overvoltage Protection (OVP) Circuit
OVP circuit monitors the VOUT pin voltage and halts oscillation once it reaches the OVP detect voltage. Oscillation
resumes when the VOUT pin voltage decreases below 0.3 V. In case the cause of the excess VOUT pin voltage is
not removed the OVP circuit will stop and resume repeatedly in order to limit the VOUT pin voltage.
•
Thermal Shutdown Function
Thermal shutdown circuit detects overheating of the converter if the output pin is shorted to the ground pin (GND)
etc. and stops the converter operation to protect it from damage. If the junction temperature of the device exceeds
the specified temperature, the thermal shutdown stops the converter operation and resumes the converter
operation if the junction temperature decreases below the thermal shutdown release temperature.
10
R1208x
NO.EA-314-211027
APPLICATION INFORMATION
Typical Applications
VIN = 5 V~22 V
C4
VIN
LED2
LED1
LED3
ISET
LED4
RSET
C3
R1208x
VS
GND
CE
VOUT
10 LEDs x 4 Parallels
LX
PGND
D1
C2
L1
C1
Typical Application 1. 10 LEDs in series x 4 parallels, up to 80 mA per LED,
5 V or higher power supply voltage, using 4 LED channels
VIN = 2.7V ~ 5 V
C4
VIN
LED2
LED1
LED3
ISET
LED4
RSET
R1208x
VS
GND
CE
VOUT
LX
PGND
C1
10 LEDs x 4 Parallels
D1
L1
C2
Typical Application 2. 10 LEDs in series x 4 parallels, up to 80 mA per LED,
less than 5 V power supply voltage, using 4 LED channels
11
R1208x
NO.EA-314-211027
VIN = 5 V ~ 22 V
VIN
LED2
10 LEDs x 4 Parallels
C4
LED1
LED3
ISET
LED4
RSET
C3
R1208x
VS
GND
CE
VOUT
10 LEDs x 4 Parallels
10 LEDs x 4 Parallels
10 LEDs x 16 Parallels
LX
PGND
D1
C2
L1
C1
Typical Application 3. 10 LEDs in series x 16 parallels, up to 20 mA per LED,
5 V or higher power supply voltage, using 4 LED channels
VIN = 5 V ~ 22 V
C4
VIN
LED2
LED1
LED3
ISET
LED4
RSET
C3
R1208x
VS
GND
CE
VOUT
LX
PGND
C1
10 LEDs x 6 Parallels
D1
L1
C2
Typical Application 4. 10 LEDs in series x 6 parallels, up to 40 mA per LED,
5 V or higher power supply voltage, using 3 LED channels
12
R1208x
NO.EA-314-211027
VIN = 5 V ~ 22 V
C4
VIN
LED2
LED1
LED3
ISET
LED4
RSET
C3
10 LEDs x 2 Parallels
R1208x
VS
GND
CE
VOUT
LX
PGND
D1
C2
L1
C1
Typical Application 5. 10 LEDs in series x 2 parallels, up to 160 mA per LED,
5 V or higher power supply voltage, using 4 LED channels
VIN = 2.7 V ~ 5 V
C4
VIN
LED2
LED1
LED3
ISET
LED4
RSET
R1208x
VS
GND
CE
VOUT
LX
PGND
C1
10 LEDs x 2 Parallels
D1
L1
C2
Typical Application 6. 10 LEDs in series x 2 parallels, up to 80 mA per LED,
less than 5 V power supply voltage, using 2 LED channels
13
R1208x
NO.EA-314-211027
Recommended Inductors
Frequency (kHz)
L1 (μH)
750
10
450
22
Parts No.
Rated Current (mA)
Size (mm)
VLS252010ET-100M
550
2.5 × 2.0 × 1.0
VLF302512MT-100M
620
3.0 × 2.5 × 1.2
VLF403212MT-100M
900
4.0 × 3.2 × 1.2
VLF504012MT-100M
1320
5.0 × 4.0 × 1.2
VLF302512MT-220M
430
3.0 × 2.5 × 1.2
VLF403212MT-220M
540
4.0 × 3.2 × 1.2
VLF504012MT-220M
890
5.0 × 4.0 × 1.2
VLS5045EX-220M
1800
5.0 × 5.0 × 4.5
Recommended Components
Symbol
•
Parts No.
60
CRS12
60
RB060M-60
C1
25
C3225JB1E475M
C2
50
C3
25
C1608X5R1E224M
C4
6.3
CM105B105K06
D1
*1
Rated Voltage (V)
C2012X5R1H225K
C2012X5R1H105K*1
When ILED = 80 mA or lower at 750 kHz
Selection of Inductor
Peak current of inductor (ILmax) in normal mode when the efficiency is 80% can be calculated by the following
formula.
ILmax = 1.25 x IOUT x VOUT / VIN + 0.5 x VIN x (VOUT − VIN) / (L1 x VOUT x fosc)
When starting up the IC or when adjusting the brightness of LEDs, a large transient current may flow into an
inductor (L1). ILmax should be equal or smaller than the current limit of the IC. When deciding the rated current
of inductor, ILmax should be considered. It is recommended that L1 with 10 µH to 22 µH be used.
•
Selection of Capacitor
Set a 1 µF or more input capacitor (C1) between the VIN and GND pins as close as possible to the pins.
Set a 1 µF output capacitor (C2) between the VOUT and GND pins if ILED ≤ 80 mA and an inductor is 10 µH.
In other cases, set a 2.2 µF or more output capacitor (C2) between the VOUT and GND pins.
14
R1208x
NO.EA-314-211027
•
Selection of Diode
For a rectifier diode, use a schottky barrier diode that has low VF.
It is recommended to select a schottky barrier diode that has low reverse current and low parasitic capacitance.
•
VS Pin Connection at VIN < 5 V
When using the VS pin at VIN < 5 V, it is recommended that the VIN pin and the VS pin be short-circuited each
other. Refer to Typical Application 2 and 6. There’s no capacitor required between the VS pin and the GND pin.
If the VIN pin and the VS pin are not shorted each other, a capacitor (C3) is required between the VS pin and the
GND pin. Refer to Typical Application 1, 3, 4, and 5.
•
LED Current Setting
The LED current (ILEDSET) when a ”H” PWM signal is applied to the CE pin (Duty = 100%) can be determined by
the value of feedback resistor (RSET). If a 10 kΩ resistor (RSET) is placed between the ISET pin and the GND pin,
the LED pin current will be set to 20 mA.
ILEDSET = 0.103 × RSET / (41.5 k + RSET)
Choose 4.4 kΩ (10 mA) to 143 kΩ (80 mA) for RSET.
By using the application example of Typical Application 5, the LED current can be set between 80 mA to 160 mA.
The LED current can be set up to 320 mA by using the four LED pins.
•
LED Dimming Control
The brightness of the LEDs can be adjusted by applying a PWM signal to the CE pin. If the High-Duty of PWM
input of the CE is Hduty, the current of LED can be calculated by the following formula.
ILED = Hduty × ILEDSET
The minimum High-duty of a PWM signal can be controlled up to 2.3% (Ta = 25°C).
However,the ILED current is controlled to approximately 4mA during the soft start time.
By inputting “L” voltage for a certain period of time (Typ. 12 ms for R1208KxxxA/ 18 ms for R1208KxxxB), the IC
goes into standby mode and turns off LEDs.
15
R1208x
NO.EA-314-211027
•
PWM Dimming Adjustment Frequency
The frequency range of a PWM signal should be set within the range of 200 Hz to 300 kHz.
In the case of using a 20 kHz or less PWM signal for dimming the LEDs, the increasing or decreasing of the
inductor current (IL) may generate noise in the audible band. In this case, connect a capacitor (C4) between the
ISET pin and GND pin.
In the case of using a 20 kHz or more PWM signal, connecting a capacitor is not required. Refer to Typical
Application 2, Typical Application 5 and Typical Application 6 for details.
ISET
•
RSET
C4 (opt.)
Unused LED Current Source
Unused LED pin should be connected to GND. When using two or three LED pins, it is recommended that the
rest of the LED pins should be connected as below.
Using two LED pins: LED 2 and LED 4 should be connected to GND. Refer to Typical Application 6.
Using three LED pins: LED 4 should be connected to GND. Refer to Typical Application 4.
16
R1208x
NO.EA-314-211027
TECHNICAL NOTES
Current Path on PCB
Figure 1 and Figure 2 show flows of current paths of the application circuits when MOSFET is ON and when
MOSFET is OFF, respectively. Parasitic elements (impedance, inductance or capacitance) in the paths pointed
with red arrows in Figure 1 and Figure 2 influence stability of the system and cause noise outbreak. It is
recommended that these parasitic elements be minimized. In addition, except for the paths of LED load, it is
recommended that the all wirings of the current paths be made as short and wide as possible.
Load
Load
Figure 1. MOSFET-ON
Figure 2. MOSFET-OFF
Layout Guide for PCB
⋅ Place C1 as close as possible to the VIN and GND pins. Also, connect the GND pin to the wider GND plane.
⋅ Make the LX land pattern as small as possible.
⋅ Make the wirings between the LX pin, the inductor and the diode as short as possible. Also, connect C2 as close
as possible to the cathode of the diode.
⋅ Place C2 as close as possible to the GND pin.
17
R1208x
NO.EA-314-211027
PCB Layout
Topside
Backside
DFN(PLP)2730-12 Typical Board Layout less than 5 V power supply voltage
Topside
Backside
DFN(PLP)2730-12 Typical Board Layout more than 5 V power supply voltage
18
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS
1) Efficiency vs. Output Current of R1208xx12A/B
1-1) Efficiency vs. Output Current with Different Input Voltages
R1208x312B
VLF504012MT-100M / 6LED × 4 Parallel
(VOUT=17.3V at 80mA)
R1208x312B
VLF504012MT-220M / 6LED × 4 Parallel
(VOUT=17.3V at 80mA)
EFFICIENCY [%]
95
90
85
80
75
70
VIN=3.6V
65
VIN=5V
60
55
VIN=8V
EFFICIENCY [%]
100
VIN=12V
50
0
80
160
240
Output Currrent 4Parallel [mA]
100
95
90
85
80
75
70
65
60
55
50
VIN=3.6V
VIN=5V
VIN=8V
VIN=12V
0
320
95
90
95
90
85
80
VIN=3.6V
65
VIN=5V
60
55
VIN=12V
VIN=8V
50
EFFICIENCY [%]
EFFICIENCY [%]
100
320
85
80
75
70
65
VIN=3.6V
60
55
VIN=8V
VIN=5V
VIN=12V
50
80
160
240
Outpu Currrent 4Parallel [mA]
240
R1208x312B
VLF504012MT-220M / 8LED × 4 Parallel
(VOUT=22.8V at 80mA)
100
0
160
Output Current 4Parallel [mA]
R1208x312B
VLF504012MT-100M / 8LED × 4 Parallel
(VOUT=22.8V at 80mA)
75
70
80
320
0
80
160
240
Output Current 4Parallel [mA]
320
19
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
R1208x312A
VLF504012MT-100M / 10LED × 4
Parallel(VOUT=28V at 80mA)
100
100
95
90
95
90
85
80
75
70
VIN=3.6V
65
VIN=5V
60
55
VIN=8V
EFFICIENCY [%]
EFFICIENCY [%]
R1208x312B
VLF504012MT-220M / 10LED × 4 Parallel
(VOUT=28V at 80mA)
VIN=12V
50
0
80
160
240
Output Current 4Parallel [mA]
85
80
75
70
VIN=3.6V
65
VIN=5V
60
VIN=8V
55
VIN=12V
50
0
320
100
100
95
90
95
90
85
80
50
0
320
85
80
VIN=3.6V
VIN=5V
VIN=8V
65
60
VIN=8V
VIN=12V
55
VIN=12V
VIN=5V
55
240
75
70
VIN=3.6V
65
60
160
R1208x312A
VLF504012MT-100M / 12LED × 4
Parallel(VOUT=33.7V at 80mA)
EFFICIENCY [%]
EFFICIENCY [%]
R1208x312B
VLF504012MT-220M / 12LED × 4 Parallel
(VOUT=33.7V at 80mA)
75
70
80
Output Current 4Parallel [mA]
80
160
240
Output Current 4Parallel [mA]
50
320
0
80
160
240
320
Outpur Current 4Parallel [mA]
20
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
1-2) Efficiency vs. Output Current with Different Inductors (VOUT = 28 V at 80 mA)
R1208x312B
VIN = 3.6V / 10LED × 4 Parallel
100
100
95
95
90
90
85
85
80
75
70
VLF302512MT-100M
65
VLF403212MT-100M
60
EFFICIENCY [%]
EFFICIENCY [%]
R1208x312A
VIN = 3.6V / 10LED × 4 Parallel
VLF504012MT-100M
55
0
20
40
60
75
70
VLF302512MT-220M
65
VLF403212MT-220M
60
VLF504012MT-220M
55
VLF504012MT-220M
50
80
VLF504012MT-100M
50
80
0
20
100
100
95
95
90
90
85
85
80
75
VLF302512MT-100M
VLF403212MT-100M
60
VLF504012MT-100M
55
VLF504012MT-220M
50
0
40
80
120
Output Current 4Parallel [mA]
80
R1208x312B
VIN = 5V / 10LED × 4 Parallel
160
EFFICIENCY [%]
EFFICIENCY [%]
R1208x312A
VIN = 5V / 10LED × 4 Parallel
65
60
IOUT [mA]
Output Current 4Parallel [mA]
70
40
80
75
70
VLF302512MT-220M
65
VLF403212MT-220M
60
VLF504012MT-220M
55
VLF504012MT-100M
50
0
40
80
120
160
Output Current 4Parallel [mA]
21
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
R1208x312A
VIN = 8V / 10LED × 4 Parallel
100
100
95
95
80
75
70
VLF302512MT-100M
65
VLF403212MT-100M
60
VLF504012MT-100M
55
0
80
160
80
75
70
VLF403212MT-220M
VLF504012MT-220M
VLF504012MT-100M
50
240
0
80
160
Output Current 4Parallel [mA]
Output Current 4Parallel [mA]
R1208x312A
VIN = 12V / 10LED × 4 Parallel
R1208x312B
VIN = 12V / 10LED × 4 Parallel
100
100
95
95
90
90
85
85
80
75
70
VLF302512MT-100M
65
VLF403212MT-100M
60
VLF504012MT-100M
55
VLF504012MT-220M
50
0
VLF302512MT-220M
65
55
VLF504012MT-220M
50
85
60
80
160
240
Output Current 4Parallel [mA]
320
EFFICIENCY [%]
EFFICIENCY [%]
85
EFFICIENCY [%]
90
90
EFFICIENCY [%]
R1208x312B
VIN = 8V / 10LED × 4 Parallel
240
80
75
70
VLF302512MT-220M
65
VLF403212MT-220M
60
VLF504012MT-220M
55
VLF504012MT-100M
50
0
80
160
240
Output Current 4Parallel [mA]
320
22
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
2) Onduty vs. ILED (ISET = 10 kΩ)
R1208x312A
VIN = 5.0V / 10LED × 4Paralle
25
f = 200Hz
ILED1 [mA]
20
f = 2kHz
f = 20kHz
f = 300kHz
15
10
5
0
0
10
20
30
40
50
60
Duty [%]
70
80
90
100
3) Electrical Characteristics
3-1) Supply Current (No switching) vs. Ambient Temperature
No switching VIN Current R1208Kx12x
1100
VIN=2.7V
VIN=3.6V
1000
VIN=5.5V
VIN=22V
ICC1 (uA)
900
800
700
600
500
400
300
-40
-15
10
35
60
85
Temperature Ta (゚C)
23
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
3-2) Supply Current (Switching) vs. Ambient Temperature
Switching VIN Current with No Load
R1208Kx12A
Switching VIN Current with No Load
R1208Kx12B
2400
1900
2200
1700
2000
ICC2 (uA)
1600
1400
1200
VIN=2.7V
VIN=3.6V
VIN=5.5V
VIN=22V
1000
800
600
-40
-15
10
35
60
Temperature Ta (゚C)
1100
900
VIN=2.7V
VIN=3.6V
VIN=5.5V
VIN=22V
700
500
300
-40
-15
10
35
60
Temperature Ta (゚C)
85
3-4) VS Voltage vs. Ambient Temperature
VS Voltage
UVLO Voltage
2.6
1300
85
3-3) UVLO Voltage vs. Ambient Temperature
5.9
Detect
2.55
5.7
Release
5.5
2.5
VS (V)
UVLO (V)
ICC2 (uA)
1500
1800
2.45
2.4
5.3
5.1
4.9
2.35
VIN=8V
4.7
2.3
VIN=22V
4.5
-40
-15
10
35
Temperature Ta (゚C)
60
85
-40
-15
10
35
60
85
Temperature Ta (゚C)
24
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
3-5) LED Current Accuracy vs. Ambient Temperature
LED Current ILED/1string=20mA
20.6
VIN=2.7V
ILED (mA)
20.4
VIN=3.6V
VIN=22V
20.2
20
19.8
19.6
19.4
-40
-15
10
35
60
85
Temperature Ta (゚C)
3-6) Channnel Matching vs. Ambient Temperature
1 String: 20 mA
3-7) Channel Matching vs. Ambient Temperature
1 String: 2 mA
LED Current 1-4 matching
ILED/1string=20mA
LED Current 1-4 matching
ILED/1string=2mA
2.5
5
VIN=2.7V
VIN=3.6V
VIN=22V
1.5
1
2
1
0
0
-15
10
35
Temperature Ta (゚C)
60
85
VIN=3.6V
VIN=22V
3
0.5
-40
VIN=2.7V
4
ILEDM2 (%)
ILEDM (%)
2
-40
-15
10
35
60
85
Temperature Ta (゚C)
25
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
3-8) NMOS ON Resistance vs. Ambient Temperature 3-9) NMOS Limit Current vs. Ambient Temperature
2500
0.45
2400
0.4
2300
0.35
2200
ILXLIM (mA)
RON (Ω)
NMOS ON Resistance
0.5
0.3
0.25
0.2
0.15
0.05
0
-40
-15
10
35
60
Temperature Ta (゚C)
VIN=2.7V
VIN=3.6V
VIN=5.5V
VIN=22V
2100
2000
1900
1800
VIN=2.7V
VIN=3.6V
VIN=5.5V
VIN=22V
0.1
NMOS Limit Current
1700
1600
1500
-50
85
-25
0
25
50
75
100
Temperature Ta (゚C)
3-10) Operating Frequency vs. Ambient Temperature
Oscillator Frequency R1208Kx12A
825
VIN=2.7V
VIN=3.6V
VIN=22V
775
750
725
VIN=2.7V
VIN=3.6V
VIN=22V
490
480
FOSC (kHz)
FOSC (kHz)
800
Oscillator Frequency R1208Kx12B
500
470
460
450
440
430
420
700
410
400
675
-40
-15
10
35
Temperature Ta (゚C)
60
85
-40
-15
10
35
60
85
Temperature Ta (゚C)
26
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
3-11) Maxduty vs. Ambient Temperature
Maximum Duty R1208Kx12B
Maximum Duty R1208Kx12A
98
98
VIN=2.7V
97
VIN=3.6V
VIN=22V
96
95
94
MAXDUTY (%)
MXDUTY (%)
97
96
95
94
93
93
92
92
-40
-15
10
35
60
VIN=2.7V
VIN=3.6V
VIN=22V
-40
85
-15
35
60
85
Temperature Ta (゚C)
Temperature Ta (゚C)
3-12) VOUT OVP Detector Threshold vs.
Ambient Temperature
3-13) LED OVP Detector Threshold vs.
Ambient Temperature
VOUTOVP Voltage(VIN=3.6V) R1208K312x
LEDOVP Detect Voltage
45
44.5
44
VOUTOVP (V)
10
Detect
11.5
Release
11.0
VOVP3 (V)
43.5
43
42.5
42
VIN=2.7V
VIN=3.6V
VIN=22V
10.5
10.0
9.5
9.0
41.5
41
-40
-15
10
35
Temperature Ta (゚C)
60
85
8.5
-40
-15
10
35
60
85
Temperature Ta (゚C)
27
R1208x
NO.EA-314-211027
TYPICAL CHARACTERISTICS (continued)
3-14) Soft-start Time vs. Ambient Temperature
Soft Start Time
45
VIN=2.7V
VIN=3.6V
40
VIN=22V
TSS (ms)
35
30
25
20
15
10
-40
-15
10
35
60
85
Temperature Ta (゚C)
28
POWER DISSIPATION
DFN(PLP)2730-12
Ver. A
The power dissipation of the package is dependent on PCB material, layout, and environmental conditions.
The following measurement conditions are based on JEDEC STD. 51-7.
Measurement Conditions
Item
Measurement Conditions
Environment
Mounting on Board (Wind Velocity = 0 m/s)
Board Material
Glass Cloth Epoxy Plastic (Four-Layer Board)
Board Dimensions
76.2 mm × 114.3 mm × 0.8 mm
Copper Ratio
Outer Layer (First Layer): Less than 95% of 50 mm Square
Inner Layers (Second and Third Layers): Approx. 100% of 50 mm Square
Outer Layer (Fourth Layer): Approx. 100% of 50 mm Square
Through-holes
0.3 mm × 23 pcs
Measurement Result
Item
(Ta = 25°C, Tjmax = 125°C)
Measurement Result
Power Dissipation
3100 mW
Thermal Resistance (ja)
ja = 32°C/W
Thermal Characterization Parameter (ψjt)
ψjt = 8°C/W
ja: Junction-to-Ambient Thermal Resistance
ψjt: Junction-to-Top Thermal Characterization Parameter
Power Dissipation vs. Ambient Temperature
Measurement Board Pattern
i
PACKAGE DIMENSIONS
DFN(PLP)2730-12
DM-DFN(PNP)2730-12-JE-B
DFN(PLP)2730-12 Package Dimensions (Unit: mm)
i
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