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Электронный компонент: R1218XXX2A

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R1218x SERIES
Step-up DC/DC converter for Whilte LED Backlight
NO.EA-006-1025
1
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
R1218X
2
BLOCK DIAGRAMS
R1218XXX1A
R1218XXX2A
Slope
Slope
Slope
Slope
Com
Com
Com
Compensation
pensation
pensation
pensation
L
X
V
V
V
V
FB
FB
FB
FB
GND
V
V
V
V
IN
IN
IN
IN
CE
CE
V
V
V
Vref
ref
ref
ref
Oscillator
+
+
UVLO
Current
Current
Current
Current
sense
sense
sense
sense
Current
Current
Current
Current
Protect
Protect
Protect
Protect
Switch
Switch
Switch
Switch
Control
Control
Control
Control
S
R
Q
Err. Amp
PWM Comp
V
OUT
OVP
Shu
tdown
delay
Slope
Slope
Slope
Slope
Com
Com
Com
Compensation
pensation
pensation
pensation
L
X
V
V
V
V
FB
FB
FB
FB
GND
V
V
V
V
IN
IN
IN
IN
CE
CE
Vref
Vref
Vref
Vref
Oscillator
+
+
UVLO
Current
Current
Current
Current
s
s
s
sense
ense
ense
ense
Current
Current
Current
Current
Protect
Protect
Protect
Protect
Switch
Switch
Switch
Switch
Control
Control
Control
Control
S
R
Q
Err. Amp
PWM Comp
V
OUT
OVP
Shutdown
delay
R1218X
3
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
Part Number
a b c
Code Descriptions
a
Designation of the package
N: SOT23-6
K: PLP1820-6
b
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
c
Taping type (SOT23-6: TR-F, PLP1820-6: TR)
PIN CONFIGURATIONS
z
SOT23-6
PLP1820-6
PIN DESCRIPTION
SOT23-6
Pin No
Symbol
Pin Description
1 CE
Chip
Enable
Pin
2 V
OUT
Output
Voltage
3 V
IN
Power Supply Input Pin
4
Lx
Switching Pin (Open Drain Output)
5 GND
Ground
Pin
6 V
FB
Feedback
Pin
CE
CE
CE
CE
V
V
V
V
OUT
OUT
OUT
OUT



V
V
V
V
IN
IN
IN
IN



V
V
V
V
FB
FB
FB
FB



LX
LX
LX
LX
GND
GND
GND
GND
1
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
5
5
5
5
6
6
6
6
CE
CE
CE
CE V
V
V
V
FB
FB
FB
FB

LX
LX
LX
LX
V
V
V
V
OUT
OUT
OUT
OUT

GND
GND
GND
GND
V
V
V
V
IN
IN
IN
IN

1
1
1
1
2
2
2
2
3
3
3
3
4
4
4
4
5
5
5
5
6
6
6
6
R1218X
4
PLP1820-6
Pin No
Symbol
Pin Description
1 CE
Chip
Enable
Pin
2 V
FB
Feedback
Pin
3
Lx
Switching Pin (Open Drain Output)
4 GND
Ground
Pin
5 V
IN
Power Supply Input Pin
6 V
OUT
Output
Voltage
ABSOLUTE MAXIMUM RATINGS
Symbol Item
Rating
Unit
V
IN
V
IN
Pin Voltage
6.5
V
V
CE
CE Pin Voltage
-0.3 to V
IN
+0.3 V
V
FB
V
FB
Pin Voltage
-0.3 to V
IN
+0.3 V
R1218XXX1A -0.3
to
22.0
V
OUT
V
OUT
Pin Voltage
R1218XXX2A -0.3
to
32.0
V
R1218XXX1A -0.3
to
22.0
V
LX
Lx Pin Voltage
R1218XXX2A -0.3
to
32.0
V
I
LX
Lx Pin Current
1000
mA
R1218NXXXA suspended in air
250
P
D
Power
Dissipation
R1218KXXXA*Note1 880
mW
Topt
Operating Temperature Range
-40 to +85
C
Tstg
Storage Temperature Range
-55 to 125
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
(Topt=25
C)
Symbol Item
Conditions MIN.
TYP.
MAX.
Unit
V
IN
Operating Input Voltage
1.8
5.5
V
I
IN
Supply
Current
V
IN
=5.5V, V
FB
=0V, Lx at no load
0.5
1.0
mA
I
STB
Standby
Current
V
IN
=5.5V, V
CE
=0V
0.0
3.0
A
V
UVLO1
UVLO Detector Threshold
V
IN
falling
1.5
1.6
1.7
V
V
UVLO2
UVLO
Released
Voltage V
IN
rising
V
UVLO1
+0.1 1.8 V
V
CEH
CE "H" Input Voltage
V
IN
=5.5V 1.5
V
V
CEL
CE "L" Input Voltage
V
IN
=1.8V
0.5
V
R
CE
CE Pull Down Resistance V
IN
=3.6V 600
1200
1600
k
Tshudn CE
Shutdown
Delay
V
IN
=3.6V
10
ms
R1218X
5
Symbol Item
Conditions MIN.
TYP.
MAX.
Unit
V
FB
V
FB
Voltage Tolerance
V
IN
=3.6V 0.19
0.20
0.21
V
V
FB
/
T
V
FB
Voltage Temperature
Coefficient
V
IN
=3.6V, -40
C
Topt
85
C
150
ppm
/
C
I
FB
V
FB
Input Current
V
IN
=5.5V, V
FB
=0V or 5.5V
-0.1
0.1
A
R
ON
Switch On Resistance
V
IN
=3.6V, I
SW
=100mA
1.5
R1218XXX1A V
LX
=20V
0.0
3.0
I
OFF
Switch Leakage Current
R1218XXX2A V
LX
=29V
0.0
3.0
I
LIM
Switch Current Limit
V
IN
=3.6V 400
700
1000
mA
f
OSC
Oscillator
Frequency
V
IN
=3.6V, V
OUT
=V
FB
=0V 1000
1200
1400
kHz
Maxduty Maximum Duty Cycle
V
IN
=3.6V, V
OUT
=V
FB
=0V 86
91
%
R1218X021A 8.5
9.5
10.5
V
R1218X031A 13.0
14.0
15.0
V
R1218X041A 17.0
18.5
20.0
V
R1218X052A 21.5
23.0
24.5
V
V
OVP1
OVP Detector Threshold
V
IN
=3.6V
V
OUT
rising
R1218X062A 26.0
27.5
29.0
V
R1218X021A V
OVP1
-0.5
V
R1218X031A V
OVP1
-0.75
V
R1218X041A V
OVP1
-1.0
V
R1218X052A V
OVP1
-1.25
V
V
OVP2
OVP
Released
Voltage
V
IN
=3.6V
V
OUT
falling
R1218X062A V
OVP1
-1.5
V
R1218XXX1A
Symbol Item
Conditions
MIN.
TYP.
MAX.
Unit
V
F
Diode Forward Voltage
I
DIODE
=100mA
0.8
V
I
R
Diode Leakage Current
V
OUT
=20V, V
LX
=0V
10
A
TEST CIRCUITS
Supply Current Test Circuit
UVLO Detector Threshold/ UVLO Released Voltage
V
V
V
V
IN
IN
IN
IN
CE
CE
CE
CE
GND
GND
GND
GND V
V
V
V
FB
FB
FB
FB
V
V
V
V
IN
IN
IN
IN
L
L
L
L
X
X
X
X
CE
CE
CE
CE
GND
GND
GND
GND V
V
V
V
FB
FB
FB
FB
R1218X
6
VFB Voltage, Oscillator Frequency, Maximum Duty
Test Circuit
OVP Detector Threshold, OVP Released Voltage
Test Circuit
TYPICAL APPLICATIONS
R1218X041A R1218X062A
LED Current setting
LED current can be set with feedback resister(R1)
I
LED
=V
FB
/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 V
FB
pin. LED current is adjustable by DC voltage and
resisters, R1 and R2 in the figure 4.
I
LED
=(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
V
V
V
V
IN
IN
IN
IN
L
L
L
L
X
X
X
X
V
V
V
V
FB
FB
FB
FB
V
V
V
V
OUT
OUT
OUT
OUT
GND
GND
GND
GND
CE
CE
CE
CE
C2
0.22uF
C1
1uF
R1
10
L1
22uH
V
V
V
V
IN
IN
IN
IN
L
L
L
L
X
X
X
X
CE
GND
GND
GND
GND V
V
V
V
FB
FB
FB
FB
V
V
V
V
IN
IN
IN
IN
L
L
L
L
X
X
X
X
CE
CE
CE
CE V
V
V
V
OUT
OUT
OUT
OUT
GND
GND
GND
GND V
V
V
V
FB
FB
FB
FB
V
V
V
V
IN
IN
IN
IN
L
L
L
L
X
X
X
X
V
V
V
V
FB
FB
FB
FB
V
V
V
V
OUT
OUT
OUT
OUT
GND
GND
GND
GND
CE
CE
CE
CE
C2
0.22uF
C1
1uF
R1
10
L1
22
uH
R1218X
7
=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.
I
LEDMIN
=(0.2-R2*(VH-0.2)/(R3+R4))/R1
I
LEDMAX
=(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
Figure 5. Dimming controle by filtered PWM signal
Selection of Inductors
The peak current of the inductor at normal mode can be calculated as next formula:
ILxpeak=1.25
I
LED
V
OUT
/V
IN
+0.5
V
IN
(V
OUT
-V
IN
)/(L
V
OUT
f
OSC
)
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 V
IN
=3.6V, recommendation value of the inductor is 10uH or more.
Selection of Capacitors
Set 1
F 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 0.22
F or more capacitor between V
OUT
and the GND like C2 as in the figure above.
V
FB
CE
R1
V
FB
R1
R2
DC
V
FB
R1
R2
R3
R4
C3
VH
VL
R1218X
8
TYPICAL CHARACTERISTICS
1) Efficiency vs. I
LED
( 2LED) L:LQH32CN220 Topt=25



C
2. Efficiency vs. I
LED
(3LED) L: LQH32CN220, Topt=25



C
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=1.8V
R1218X021A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=3.6V
R1218X021A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=4.2V
R1218X021A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=2.7V
R1218X031A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(
%)
V
IN
=3.6V
R1218X031A
R1218X
9
3. Efficiency vs. ILED (4 LED )
L: LQH32CN220, Topt=25
C
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED I
LED
(mA)
E
fficiency
V
IN
=4.2V
R1218X031A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=2.7V
R1218X041A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=3.6V
R1218X041A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=4.2V
R1218X041A
R1218X
10
4. Efficiency vs. I
LED
(6LED) L: LQH32CN220, Diode: CRS02
5. PWM Dimming Control (2 LED)
V
IN
=3.6V, R1=10

5-1. Duty vs. LED current
L
LQH32CN220
Diode
CRS02
L
LQH32CN220
Diode
CRS02
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=2.7V
R1218X062A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
V
IN
=3.6V
R1218X062A
0
10
20
30
40
50
60
70
80
90
100
0
4
8
12
16
20
LED Current I
LED
(mA)
Effi
ci
e
n
cy
(%
)
25
V
IN
=4.2V
R1218X062A
0
2.5
5
7.5
10
12.5
15
17.5
20
22.5
25
0
20
40
60
80
100
DUTY (%)
LE
D Current
I
LE
D
(m
A
)
5kHz
1kHz
200Hz
R1218X021A
Topt=25
R1218X
11
5-2. Output Voltage Waveform (Topt=25



C)
6. PWM Dimming Control (4 LED)
V
IN
=3.6V, R1=10
6-1. Duty vs. LED Current (Topt=25



C)
6-2. Output Voltage Waveform
R1218X021A
0
5
10
15
20
25
0
0.8
1.6
2.4
3.2
4
Time (ms)
Out
put
V
o
l
t
age V
OU
T
(V
)
0
5
10
CE
I
nput
V
o
l
t
age
V
CE
(V
)
CE Input Voltage
Fosc=200Hz
Output Voltage
R1218X021A
0
5
10
15
20
25
0
0.04
0.08
0.12
0.16
0.2
Time (ms)
Out
put
V
o
l
t
age
V
OU
T
(
V
)
0
5
10
CE
I
nput
V
o
l
t
age
V
CE
(V
)
CE Input Voltage
Fosc=5kHz
Output Voltage
0
2.5
5
7.5
10
12.5
15
17.5
20
22.5
25
0
20
40
60
80
100
DUTY (%)
LE
D Current
I
LE
D
(m
A
)
5kHz
1kHz
200Hz
R1218X041A
R1218X041A
0
10
20
30
40
50
0
0.8
1.6
2.4
3.2
4
Time (ms)
Out
put
V
o
l
t
age
V
OU
T
(V
)
0
5
10
CE
I
nput
V
o
l
t
age
V
CE
(V
)
CE Input Voltage
Fosc=200Hz
Output Voltage
R1218X041A
0
10
20
30
40
50
0
0.04
0.08
0.12
0.16
0.2
Time (ms)
Out
put
V
o
l
t
age
V
OU
T
(V
)
0
5
10
CE
I
nput
V
o
l
t
age
V
CE
(V
)
CE Input Voltage
Fosc=5kH
Output Voltage
R1218X
12
7.
PWM Dimming Control (6 LED)
VIN=3.6V,R1=10
7-1. Duty vs. LED Current (Topt=25



C)
7-2. Output Voltage Waveform (Topt=25



C)
8. VFB Voltage vs. Temperature
9. UVLO Detector Threshold/Released Voltage vs. Temperature
0
2.5
5
7.5
10
12.5
15
17.5
20
22.5
25
0
20
40
60
80
100
DUTY (%)
LE
D Current
I
LE
D
(m
A
)
5kHz
1kHz
200Hz
R1218X062A
R1218X062A
0
10
20
30
40
50
0
0.04
0.08
0.12
0.16
0.2
Time (ms)
Out
put
V
o
l
t
age
V
OU
T
(
V
)
0
5
10
CE
I
nput
V
o
l
t
age
V
CE
(V
)
CE Input Voltage
Fosc=5kHz
Output Voltage
R1218X062A
0
10
20
30
40
50
0
0.8
1.6
2.4
3.2
4
Time (ms)
Out
put
V
o
l
t
age
V
OU
T
(V
)
0
5
10
CE
I
nput
V
o
l
t
age
V
CE
(V
)
CE Input Voltage
Fosc=200Hz
Output Voltage
0.185
0.19
0.195
0.2
0.205
0.21
0.215
-50
-25
0
25
50
75
100
Temperature Topt (C)
V
F
B
V
o
l
t
age V
FB
(V
)
R1218x041A
V
IN
=3.6V
1.5
1.54
1.58
1.62
1.66
1.7
-50
-25
0
25
50
75
100
Temperature
Topt (
C)
UV
LO Det
e
c
t
or Thres
hol
d
UV
LO1(V
)
R1218x041A
V
IN
=3.6V
UVLO Detector
UVLO Released
R1218X
13
10. Oscillator Frequency vs. Temperature
11. Maximum duty cycle vs. Temperature
12. OVP Detector Threshold/Released Voltage vs. Temperature
13. Supply Current vs. Temperature
14. LX Current Limit vs. Temperature
1000
1050
1100
1150
1200
1250
1300
1350
1400
-50
-25
0
25
50
75
100
Temperature Topt (C)
Os
c
illat
o
r Frequenc
y
1
F
OSC
1
(k
Hz
)
Vin=3.6V
R1218x041A
85
87
89
91
93
95
97
99
-50
-25
0
25
50
75
100
Temperature Topt (
C)
M
a
x
dut
y
M
a
x
dut
y
(%
)
R1218x041A
Vin=3.6V
16.5
17
17.5
18
18.5
19
19.5
20
20.5
-50
-25
0
25
50
75
100
Temperature Topt (
C)
O
VP D
e
te
cto
r
Th
r
e
sh
o
l
d
O
VP1
(
V
)
R1218x041A
Vin=3.6V
OVP Detector
Threshold
OVP Released
Voltage
0
40
80
120
160
200
240
280
320
360
-50
-25
0
25
50
75
100
Temperature Topt (
C)
S
upply
C
u
r
r
ent1 I
CC1
(u
A)
R1218x041A
Vin=3.6V
300
400
500
600
700
800
900
1000
-50
-25
0
25
50
75
100
Temperature Topt (
C)
Lx
C
u
r
r
ent Lim
i
t I
LIM
(m
A)
R1218x041A
Vin=3.6V
R1218X
14
15. OVP Transient Response (Topt=25



C)
16. Efficiency dependence on inductors
R1218X041A [Internal Diode Type]
50
55
60
65
70
75
80
85
90
0
5
10
15
20
LED Current I
LED
[m A]
Ef
f
i
cie
n
cy [
%
]
LQH32CN220K53
LQH32CN100K53
GLF2012T220K
GLF2012T100K
V
IN
=3.6V
R1218X021A
0
2.5
5
7.5
10
12.5
15
0
20
40
60
80
100
Time (ms)
OV
P
V
o
l
t
age V
OV
P
(V
)
OVP Voltage
R1218X041A
0
5
10
15
20
25
0
20
40
60
80
100
Time (ms)
O
VP Vo
lta
g
e
V
OV
P
(V
)
OVP Voltage
R1218X062A
0
5
10
15
20
25
30
35
0
20
40
60
80
100
Time (ms)
OV
P
V
o
l
t
age V
OV
P
(V
)
OVP Voltage