LRC LR256

LESHAN RADIO COMPANY, LTD.
LR256 White LED Step-Up Converter
LR256 is a step-up DC/DC converter
specifically designed to drive white LED with a
constant current. It can drive two,three,or four
LEDS. It switches at 1.2MHz and use tiny
external components. The output capacitor can
be as small as 0.22uF,which can save space
and cost versus alternative solutions. Feedback
¾
¾
¾
¾
¾
¾
¾
¾
Fast 1.2MHz Switching Frequency
Requires Only 0.22uF Output Capacitor
Inherently Matched LED Current
High Efficiency: 85% Typical
2.5V to 10V VIN ranges
Drives Up to Four series LEDs with a Li-lon cell
Uses Very Tiny Inductors
SOT-25 Package
voltage is as low as 95mV.
Absolute maximum ratings
Parameter
symbol
value
unit
Supply Voltage
VIN
10
V
Feedback Voltage
FB
10
V
Switch Voltage
SW
20
V
CE Voltage
VCE
10
V
Operating temperature range
Topr
-25 to +70
℃
Storage temperature range
Rstg
-55 to +150
℃
Junction temperature
Tj
125
℃
Pin name
Description
1
Symbol
Description
Symbol
5
5:Supply
2
3
1:Switch
SW
VIN
Voltage
4
2:GND
GND
3:Feedback
FB
4:Start-Up
CE
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LESHAN RADIO COMPANY, LTD.
LR256
Block Diagram
PIN1(SW)
PWM
CONTROL
2
Fosc
CURRENT SENSE
+
1
SLOPE COMP
+
0
-
PIN5(Vin)
2
0
2
VREF
1
1
2
PIN2(GND)
+
1
2
PIN4
1
SHUTDOWN
gm
D256
PIN3(FB)
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LESHAN RADIO COMPANY, LTD.
LR256
Electrical Characteristics
Tamb = 25℃, VIN=3V,VCE=3V,unless otherwise specified.
Parameter
Test Conditions / Pins
Min
Minimum Operating Voltage
Type
Max
2.5
Unit
V
Maximum Operating Voltage
10
V
ISW=100mA,
Feedback Voltage
86
95
104
mV
50
100
200
nA
1.9
2.5
mA
0.1
1
uA
1.6
MHz
Duty Cycle=66%
FB Pin Bias Current
Supply Current
VCE=0V
Switching Frequency
0.8
1.2
Maximum Duty Cycle
85
90
%
320
mA
mV
Switch Current Limit
Switch VCESAT
ISW =250mA
350
Switch Leakage Current
VSW=5V
0.01
CE Voltage High
5
uA
1.5
V
CE Voltage Low
0.4
CE Pin Bias Current
V
65
uA
Typical Application
L1
1
HI
2
22uH
VCC
PIN1(SW)
D4
1
2
D1
PWM
CONTROL
C1
2
C2
Fosc
0.22u
CURRENT SENSE
+
0
0
-
PIN5(Vin)
2
D1
1
SLOPE COMP
+
2
VREF
1
1
2
PIN2(GND)
1
2
D1
+
-
1u
gm
1
SHUTDOWN
PIN3(FB)
1k
R1
R
PIN4(CE)
3/8
LESHAN RADIO COMPANY, LTD.
LR256
Analog Voltage Light Control
L1
1
HI
2
22uH
VCC
PIN1(SW)
D4
1
2
D1
PWM
CONTROL
C1
2
1u
C2
Fosc
0.22u
CURRENT SENSE
+
0
0
-
PIN5(Vin)
2
D1
1
SLOPE COMP
+
2
VREF
1
1
2
PIN2(GND)
D1
+
1
2
gm
1
5K
SHUTDOWN
R1
R
PIN3(FB)
PIN4(CE)
90K
HI
VDC
Logic Voltage Light Control
L1
1
HI
2
22uH
VCC
PIN1(SW)
D4
1
2
D1
PWM
CONTROL
C1
1u
2
C2
Fosc
0.22u
CURRENT SENSE
+
0
0
-
PIN5(Vin)
2
D1
1
SLOPE COMP
+
2
VREF
1
1
2
PIN2(GND)
D1
+
1
2
gm
1
HI
SHUTDOWN
PWM
PIN3(FB)
1k
R1
R
PIN4(CE)
4/8
LESHAN RADIO COMPANY, LTD.
LR256
Figure
Iq(mA)
Iq
Vs T
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-50
100
25
0
2
4
6
8
10
Vin(V)
Swich Frequency
Vs
T
Swich Frequency(MHz)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-25
0
25
50
75
100
T(°C)
5/8
LESHAN RADIO COMPANY, LTD.
LR256
η(%)
η VS T
84.5
84
83.5
83
82.5
82
81.5
81
80.5
80
ILED=10mA
ILED=15mA
ILED=20mA
-25
0
25
50
75
100
T(°C)
η(%)
Drive 2LED
86
84
82
80
78
76
74
72
70
Vin=3.6V
Vin=3V
0
10
20
ILED(mA)
30
40
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LESHAN RADIO COMPANY, LTD.
LR256
Drive 3LED
90
η(%)
85
80
Vin=3V
Vin=3.6V
75
70
65
60
0
5
10
ILED(mA)
15
20
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LESHAN RADIO COMPANY, LTD.
LR256
SOT25
Diagram
Symbol
A
A1
B
b
C
D
E
H
L
min
0.787
1.397
0.250
2.591
2.692
0.838
0.080
0.300
Dimension(in mm)
max
1.450
0.152
1.803
0.559
2.997
3.099
1.041
0.254
0.610
Dimension(in Inch)
min
max
0.031
0.057
0.006
0.055
0.071
0.010
0.022
0.102
0.118
0.106
0.122
0.033
0.041
0.003
0.010
0.012
0.024
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