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R1218X SERIES
Step-up DC/DC converter for Whilte LED Backlight
NO.EA-006-1025
OUTLINE
The R1218X Series are PWM control type step-up DC/DC converter ICs with low supply current. The R1218X is fully dedicated to drive White LED with constant current. Each of these ICs consists of an NMOS FET, an oscillator, a PWM comparator, a voltage reference unit, an error amplifier, an under voltage lockout circuit (UVLO), an over-voltage protection circuit (OVP), and so on. The R1218X can drive white LEDs with high efficiency with low supply current. A diode is built-in the R1218XXX1A, therefore it is possible to drive up to 4LEDs without an external diode. The R1218XXX2A, an external diode is necessary, however, up to 6 serial LEDs can be driven with the R1218XXX2A. Constant current can be set with an external resistance value. Dimming control is possible by PWM signal for CE pin. Feedback voltage is 0.2V, therefore power loss by current setting resistance is small and efficiency is good. Maximum duty cycle is internally fixed, Typ. 91%. LEDs can be driven from low voltage. Protection circuits are the current limit of Lx peak current, the over voltage limit of output, and the under voltage lockout function. Packages are standard SOT23-6 and very tiny PLP1820-6.
FEATURES
* * * * * * * * * Operating voltage ............................................. 1.8V to 5.5V Built-in 400mA, 1.5, 20V Nch MOSFET (R1218XXX1A) Built-in 400mA, 1.5, 29V Nch MOSFET (R1218XXX2A) High Frequency PWM control .......................... Oscillator Frequency 1.2MHz Maximum Duty Cycle ....................................... Typ. 91% Low Feedback Voltage ..................................... Typ. 0.2V UVLO Threshold Voltage.................................. Typ. 1.6V (Hysteresis Typ. 0.1V) Lx Current limit Protection ................................ Typ. 700mA Over Voltage Protection (OVP) Threshold ....... Typ. 9.5V(R1218X02XA) .......................................................................... Typ. 14.0V(R1218X03XA) .......................................................................... Typ. 18.5V(R1218X04XA) .......................................................................... Typ. 23.0V(R1218X052A) .......................................................................... Typ. 27.5V(R1218X062A) * LED dimming control .....................................by external PWM signal (Frequency 500Hz to 5kHz) to CE pin .......................................................................by feedback voltage and filtered PWM signal (high frequency) * Packages.......................................................... SOT23-6 or PLP1820-6
APPLICATION
* White LED Backlight for portable equipment
1
R1218X
BLOCK DIAGRAMS
*
R1218XXX1A
V FB V IN LX V OUT
Err. Amp
UVLO PWM Comp
+ -
Vref
+ -
R S
Q
Switch Control
OVP
Oscillator Slope Compensation Compensation Current Protect Current sense
Shu tdown delay CE
CE
GND
*
R1218XXX2A V FB V IN LX V OUT
Err. Amp PWM Comp
UVLO
+ -
Vref
+ -
R S
Q
Switch Control
OVP
Oscillator Slope Compensation Compensation Current Protect Current sense
Shutdown delay CE
CE
GND
2
R1218X
SELECTION GUIDE
The OVP threshold voltage and the package for the ICs can be selected at the user's request. The selection can be available by designating the part number as shown below;
R1218Xxxxx-xx
ab Code a c
Part Number
Descriptions Designation of the package N: SOT23-6 K: PLP1820-6 Designation of OVP threshold and with/without of built-in diode 021A: 9.5V with built-in diode 031A: 14.0V with built-in diode 041A: 18.5V with built-in diode 052A: 23.0V without built-in diode 062A: 27.5V without built-in diode Taping type (SOT23-6: TR-F, PLP1820-6: TR)
b
c
PIN CONFIGURATIONS
z SOT23-6
*
4
LX
PLP1820-6 VOUT VIN GND
6
VFB
5
GND
6
5
4
CE
VOUT
VIN
CE
1
VFB
2
LX
3
1
2
3
PIN DESCRIPTION
*
SOT23-6
Pin No 1 2 3 4 5 6 Symbol CE VOUT VIN Lx GND VFB Chip Enable Pin Output Voltage Power Supply Input Pin Switching Pin (Open Drain Output) Ground Pin Feedback Pin Pin Description
3
R1218X
*
PLP1820-6
Pin No 1 2 3 4 5 6 Symbol CE VFB Lx GND VIN VOUT Chip Enable Pin Feedback Pin Switching Pin (Open Drain Output) Ground Pin Power Supply Input Pin Output Voltage Pin Description
ABSOLUTE MAXIMUM RATINGS
Symbol VIN VCE VFB VOUT VLX ILX PD Topt Tstg Item VIN Pin Voltage CE Pin Voltage VFB Pin Voltage VOUT Pin Voltage Lx Pin Voltage Lx Pin Current Power Dissipation Operating Temperature Range Storage Temperature Range Rating 6.5 -0.3 to VIN+0.3 -0.3 to VIN+0.3 R1218XXX1A R1218XXX2A R1218XXX1A R1218XXX2A 1000 R1218NXXXA suspended in air R1218KXXXA*Note1 -40 to +85 -55 to 125 250 880 -0.3 to 22.0 -0.3 to 32.0 -0.3 to 22.0 -0.3 to 32.0 Unit V V V V V mA mW C C
(*Note 1) Mounted on board. Conditions: Board material: FR4 Board Dimensions: 40*40*1.6(mm), Double layer, Wiring Ratio=50%(Both sides), Thermal via: 0.54mm*30pcs, Wind velocity: 0m/s
ELECTRICAL CHARACTERISTICS
*
Common
Symbol VIN IIN ISTB VUVLO2 VCEH VCEL RCE Tshudn Item Operating Input Voltage Supply Current Standby Current UVLO Released Voltage CE "H" Input Voltage CE "L" Input Voltage CE Pull Down Resistance CE Shutdown Delay VIN=5.5V, VFB=0V, Lx at no load VIN=5.5V, VCE=0V VIN falling VIN rising VIN=5.5V VIN=1.8V VIN=3.6V VIN=3.6V 600 1200 10 1.5 0.5 1600 1.5 Conditions MIN. 1.8 0.5 0.0 1.6 VUVLO1+0.1 TYP. (Topt=25C) MAX. 5.5 1.0 3.0 1.7 1.8 Unit V mA A V V V V k ms
VUVLO1 UVLO Detector Threshold
4
R1218X
Symbol VFB VFB/T IFB RON IOFF ILIM fOSC Maxduty Item VFB Voltage Tolerance VFB Voltage Temperature Coefficient VFB Input Current Switch On Resistance Switch Leakage Current Switch Current Limit Oscillator Frequency Maximum Duty Cycle VIN=3.6V VIN=3.6V, -40CTopt85C VIN=5.5V, VFB=0V or 5.5V VIN=3.6V, ISW=100mA R1218XXX1A R1218XXX2A VIN=3.6V VIN=3.6V, VOUT=VFB=0V VIN=3.6V, VOUT=VFB=0V R1218X021A VOVP1 OVP Detector Threshold VIN=3.6V VOUT rising R1218X031A R1218X041A R1218X052A R1218X062A R1218X021A VOVP2 OVP Released Voltage VIN=3.6V VOUT falling R1218X031A R1218X041A R1218X052A R1218X062A VLX=20V VLX=29V 400 1000 86 8.5 13.0 17.0 21.5 26.0 -0.1 1.5 0.0 0.0 700 1200 91 9.5 14.0 18.5 23.0 27.5 VOVP1-0.5 VOVP1-0.75 VOVP1-1.0 VOVP1-1.25 VOVP1-1.5 10.5 15.0 20.0 24.5 29.0 3.0 3.0 1000 1400 Conditions MIN. 0.19 TYP. 0.20 150 0.1 MAX. 0.21 Unit V ppm /C A mA kHz % V V V V V V V V V V
*
R1218XXX1A
Symbol VF IR Item Diode Forward Voltage Diode Leakage Current Conditions IDIODE=100mA VOUT=20V, VLX=0V MIN. TYP. 0.8 10 MAX. Unit V A
TEST CIRCUITS
Supply Current Test Circuit UVLO Detector Threshold/ UVLO Released Voltage
VIN CE GND V FB
VIN CE GND
LX
V FB
5
R1218X
VFB Voltage, Oscillator Frequency, Maximum Duty OVP Detector Threshold, OVP Released Voltage Test Circuit Test Circuit
VIN
LX
VIN CE
LX
CE
V OUT V FB
GND
V
FB
GND
TYPICAL APPLICATIONS
R1218X041A R1218X062A
L1 22uH C1 1uF C1 1uF
L1 22uH C2 0.22uF
VIN CE GND
LX V
C2 0.22uF
VIN CE GND
LX VOUT VFB
OUT
VFB
R1 10
R1 10
* *
LED Current setting
LED current can be set with feedback resister(R1) ILED=VFB/R1
LED Dimming Control, Softstart
(1) LED dimming control by PWM signal to CE pin LED dimming control is possible by forcing PWM signal to CE pin. When the power-on or start up with CE pin, softstart function works, however, after that, if the CE pin is set as "L" and set CE pin "H" again during the shutdown delay time, softstart function is disabled and starts up fast to normal mode, therefore 200Hz to 5kHz PWM signal is standard. By the CE pin input, LED turns on and off. Average LED current varies depending on the duty cycle of CE input. Too high frequency PWM signal is not effective because of its delay. (2)Dimming control by DC voltage LED dimming control is also possible by using the DC voltage to VFB pin. LED current is adjustable by DC voltage and resisters, R1 and R2 in the figure 4. ILED=(DC-0.2)/R2-0.2/R1 (3)Dimming control by feedback voltage and filtered PWM signal LED dimming control is also possible by using the feedback voltage and filtered PWM signal. LED current is adjustable according to the "H" level (VH) and "L" level(VL) of PWM signal and resisters, R1, R2, R3, and R4 in the figure5.Duty 6
R1218X
=0% to 100% PWM signal duty cycle can be used up to the maximum LED current and minimum LED current as in the next formulas. ILEDMIN=(0.2-R2*(VH-0.2)/(R3+R4))/R1 ILEDMAX=(0.2-R2*(VL-0.2)/(R3+R4))/R1 For example, supposed that the PWM signal level is set as 2.5V/0V, to adjust the LED current range from 0mA to 20mA by the duty cycle, our recommendation external components values are, R1=10, R2=5.1k, R3=51k, R4=5.1k or around. C3 should be set large enough to regard the PWM signal as adjustable DC voltage by the filter. In this method, higher frequency control than the frequency against the CE pin can be used for dimming control. For example, if the frequency is 40kHz, 0.1uF or more capacitor is our recommendation value as C3. Figure 3. Dimming controle by CE pin input Figure 4. Dimming control by DC voltage
CE VFB
R2 R1
VFB
R1
DC
Figure 5. Dimming controle by filtered PWM signal
R2
VFB
R3 R4
R1
VH VL
C3
*
Selection of Inductors
*
The peak current of the inductor at normal mode can be calculated as next formula: ILxpeak=1.25xILEDxVOUT/VIN+0.5xVINx(VOUT-VIN)/(LxVOUTxfOSC) When the start-up or dimming control by CE pin, transient current flows, the peak current must be equal or less than the current limit of the IC. The peak current should not beyond the rating current of the inductor. For example, for 4 serial LED drive from VIN=3.6V, recommendation value of the inductor is 10uH or more.
Selection of Capacitors
Set 1F or more value bypass capacitor between VIN pin and the GND like C1 as in the figure above as close as posible to the IC. Set 0.22F or more capacitor between VOUT and the GND like C2 as in the figure above.
7
R1218X
TYPICAL CHARACTERISTICS
1) Efficiency vs. ILED( 2LED) L:LQH32CN220 Topt=25C
100 90 80 Efficiency (%) Efficiency (%) 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA) 16 20 R1218X021A VIN=1.8V 100 90 80 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA) 16 20 R1218X021A VIN=3.6V
100 90 80 Efficiency (%) 70 60 50 40 30 20 10 0 0 4
R1218X021A
VIN=4.2V
8 12 LED Current ILED (mA)
16
20
2. Efficiency vs. ILED (3LED) L: LQH32CN220, Topt=25C
100 90 80 Efficiency (%) 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA) 16 20 Efficiency (%) R1218X031A VIN=2.7V 100 90 80 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA) 16 20 R1218X031A VIN=3.6V
8
R1218X
R1218X031A VIN=4.2V
100 90 80 70 60 Efficiency 50 40 30 20 10 0 0
4
8
12
16
20
LED ILED (mA)
3. Efficiency vs. ILED (4 LED ) L: LQH32CN220, Topt=25C
100 90 80 Efficiency (%) Efficiency (%) 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA) 16 20 R1218X041A VIN=2.7V 100 90 80 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA) 16 20 R1218X041A VIN=3.6V
R1218X041A 100 90 80 Efficiency (%) 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA)
VIN=4.2V
16
20
9
R1218X
4. Efficiency vs. ILED (6LED) L: LQH32CN220, Diode: CRS02
R1218X062A 100 90 80 Efficiency (%) Efficiency (%) 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA) 16 20 VIN=2.7V 100 90 80 70 60 50 40 30 20 10 0 0 4 8 12 LED Current ILED (mA) 16 20 R1218X062A VIN=3.6V
L LQH32CN220 Diode CRS02
100 90 80 Efficiency (%) 70 60 50 40 30 20 10 0 0 4
R1218X062A
VIN=4.2V
L LQH32CN220 Diode CRS02
25
8 12 LED Current ILED (mA)
16
20
5. PWM Dimming Control (2 LED) VIN=3.6V, R1=10 5-1. Duty vs. LED current
R1218X021A 25 22.5
LED Current ILED (mA)
Topt=25
20 17.5 15 12.5 10 7.5 5 2.5 0 0 20 40 60 DUTY (%) 80 5kHz 1kHz 200Hz 100
10
R1218X
5-2. Output Voltage Waveform (Topt=25C)
25 20 Output Voltage VOUT (V) 15 10 5 0 Output Voltage R1218X021A Fosc=200Hz 10 5 CE Input Voltage VCE (V) 0 25 20 15 10 5 0 Output Voltage R1218X021A CE Input Voltage Output Voltage VOUT (V) 5 0 CE Input Voltage VCE (V)
CE Input Voltage VCE (V)
Fosc=5kHz 10
CE Input Voltage
0
0.8
1.6 2.4 Time (ms)
3.2
4
0
0.04
0.08 0.12 Time (ms)
0.16
0.2
6. PWM Dimming Control (4 LED) VIN=3.6V, R1=10 6-1. Duty vs. LED Current (Topt=25C)
25 22.5
LED Current ILED (mA)
R1218X041A
20 17.5 15 12.5 10 7.5 5 2.5 0 0 20 40 60 DUTY (%) 80 100 5kHz 1kHz 200Hz
6-2. Output Voltage Waveform
50 40 30 20 10 0 Output Voltage R1218X041A CE Input Voltage Fosc=200Hz 10 5 0 50 40
Output Voltage VOUT (V)
R1218X041A CE Input Voltage
Fosc=5kH
10 5 0
CE Input Voltage VCE (V)
Output Voltage VOUT (V)
30 20 10 0 Output Voltage
0
0.8
1.6 2.4 Time (ms)
3.2
4
0
0.04
0.08 0.12 Time (ms)
0.16
0.2
11
R1218X
7. PWM Dimming Control (6 LED) VIN=3.6V,R1=10
7-1. Duty vs. LED Current (Topt=25C)
R1218X062A 25 22.5
LED Current ILED (mA)
20 17.5 15 12.5 10 7.5 5 2.5 0 0 20 40 60 DUTY (%) 80 100 5kHz 1kHz 200Hz
7-2. Output Voltage Waveform (Topt=25C)
50
Output Voltage VOUT (V)
R1218X062A CE Input Voltage
Fosc=200Hz 10
CE Input Voltage VCE (V)
50
Output Voltage VOUT (V)
R1218X062A CE Input Voltage
Fosc=5kHz 10
CE Input Voltage VCE (V)
40 30
5 0
40 30 20 10 0
5 0
Output Voltage 20 10 0
Output Voltage
0
0.8
1.6 2.4 Time (ms)
3.2
4
0
0.04
0.08 0.12 Time (ms)
0.16
0.2
8. VFB Voltage vs. Temperature
0.215 0.21
VFB Voltage VFB (V)
9. UVLO Detector Threshold/Released Voltage vs. Temperature VIN=3.6V
UVLO Detector Threshold UVLO1(V)
R1218X041A
R1218X041A 1.7 1.66 1.62 1.58 1.54 1.5
VIN=3.6V
0.205 0.2 0.195 0.19 0.185 -50 -25 0 25 50 Temperature Topt (C) 75 100
UVLO Released
UVLO Detector
-50
-25
0
25
50
75
100
Temperature Topt (C)
12
R1218X
10. Oscillator Frequency vs. Temperature
Oscillator Frequency1 FOSC1 (kHz)
11. Maximum duty cycle vs. Temperature
99 97
Maxduty Maxduty (%)
1400 1350 1300 1250 1200 1150 1100 1050 1000 -50 -25
R1218X041A
Vin=3.6V
R1218X041A
Vin=3.6V
95 93 91 89 87 85 -50 -25 0 25 50 75 100
0 25 50 Temperature Topt (C)
75
100
Temperature Topt (C)
12. OVP Detector Threshold/Released Voltage vs. Temperature 20.5
OVP Detector Threshold OVP1(V)
13. Supply Current vs. Temperature
360 320 Supply Current1 ICC1 (uA)
R1218X041A Vin=3.6V
R1218X041A
Vin=3.6V
20 19.5 19 18.5 18 17.5 17 16.5 -50 -25 0 25 50 Temperature Topt (C) 75 100 OVP Released Voltage OVP Detector Threshold
280 240 200 160 120 80 40 0 -50 -25 0 25 50 Temperature Topt (C) 75 100
14. LX Current Limit vs. Temperature
1000 900 Lx Current Limit ILIM(mA) 800 700 600 500 400 300 -50 -25 0 25 50 Temperature Topt (C) 75 100
R1218X041A Vin=3.6V
13
R1218X
15. OVP Transient Response (Topt=25C)
15 12.5
OVP Voltage VOVP (V)
R1218X021A
25
R1218X041A OVP Voltage
10 7.5 5 2.5 0 0 20 40 60 Time (ms) 80 100
OVP Voltage VOVP (V)
OVP Voltage
20
15
10
5
0 0 20 40 60 Time (ms) 80 100
35 30 OVP Voltage VOVP (V) 25 20 15 10 5 0 0 20
R1218X062A OVP Voltage
40
60 Time (ms)
80
100
16. Efficiency dependence on inductors
90 85 80 Efficiency [%] 75 70 65 60 55 50 0 5 10 15 LED Current ILED[m A] 20
LQH 32CN 220K53 LQH 32CN 100K53 GLF2012T220K GLF2012T100K R1218X041A [Internal D iode Type] VIN=3.6V
14

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