Prema PR4401, PR4402 Schematic [ru]
LED DRIVER PR4401/PR4402
Vcc
Gnd
Vout
PR4401/02
Vbat =1.2V or 1.5V
L1
White
LED
Vcc
Vout
Gnd
top view
U
I
x
x
0.9V Boost Driver for White LEDs PR4401/4402
Requires Only One External Component
The PR4401 and PR4402* are single cell step-up converters for white LEDs operating
from a supply voltage of less than 0.9V. Only one external inductor is needed for operation
of a white LED. PR4401 is recommended for mean LED currents of up to 20mA, PR4402
for up to 40mA. This makes PR4401 and PR4402 ideal for use in low-cost or small-sized
applications such as LED flashlights or LCD backlighting for portable devices.
Features Applications
• minimum startup voltage 0.9V • Small-sized LED torches
• 200/250mA peak output current • LCD backlighting
• only one external component required • LED indicator lights
• battery deep discharge protection
Typical Application
For output currents higher than 20mA an additional
blocking capacitor at Vcc is recommended.
Pin Description
The inductance L1 determines the LED
current:
Inductance L1 Mean current for
47µH 6.5 mA PR4401
32µH 8.3 mA PR4401
26.7µH 10.8 mA PR4401
22 µH 11 mA PR4401
14.7 µH 14 mA PR4401
10 µH 22 mA PR4401/4402
6.8 µH * 32 mA * PR4402
4.7 µH * 40 mA * PR4402
* PR4402 only measured with inductor Murata type
LQH32C series
10-22µH: one white LED
4.7-6.8µH: two white LEDs in parallel
PIN Name PIN Function Description
Vcc Supply voltage
Vout Output voltage, LED connection
Gnd Ground connection
Topside marking: "UI" (PR4401) or "UJ" (PR4402) with a two-digit lot code
Package SOT23-3 or COB on request
© PREMA Semiconductor GmbH 2006-2008
Page 1/12 Rev 0908
Ref.
Vcc
Gnd
Vout
Comp.
Control
Logic
LED DRIVER PR4401/PR4402
Absolute Maximum Ratings (PR4401 and PR4402)
Parameter Min Typ Max Units
VCC (no damage) -0.3 8 V
Operating Temperature Range -20 85 °C
Storage Temperature Range -55 150 °C
Electrostatic Discharge (ESD) Protection 2 kV
Electrical Characteristics
Vcc=1.5V, Ta = 25°C, 10-22µH: one white LED / 4.7-6.8µH: two white LEDs in parallel, unless otherwise noted.
Parameter Conditions Min Typ Max Min Typ Max Units
PR4401 PR4402
Supply Voltage, min. operating
min. startup
max. operating
Supply Voltage, min. operating
min. startup
max. operating
LED Mean Current
measured with L1 type LQH32C Murata
Switching Current at Vout Vout = 0.4V 200 250 mA
Switching Frequency 500 500 kHz
Quiescent supply current Vcc > 950mV
Efficiency 80 80 %
Vout Vcc 15 15 V
L1 = 10...22µH
Ta = 25°C
L1 = 10...22µH
Ta = 0...60°C
L1 = 47µH
L1 = 32µH
L1 = 26.7µH
L1 = 22µH
L1 = 14.7µH
L1 = 10µH
L1 = 6.8µH
L1 = 4.7µH
Vcc = 600mV
Vcc = 400mV
1.90
1.90
0.70
0.90
0.80
1.00
6.5
8.3
10.8
12
15
23
--
--
4
50
10
0.80
0.95
1.90
0.90
1.05
1.90
5 8
0.70
0.90
0.80
1.00
--
--
-12
15
23
32
40
100
20
0.80
0.95
0.90
1.05
mA
mA
mA
mA
mA
10 mA
µA
µA
V
V
V
V
V
V
Block Diagram
© PREMA Semiconductor GmbH 2006-2008
Page 2/12 Rev 0908
LED DRIVER PR4401/PR4402
Efficiency % =
1
T
∫
0
T
V
LED⋅ILED
dt
1
T
∫
0
T
Vin⋅I
in
dt
⋅100
Vcc
Gnd
Vout
PR4401
L1
0.5Ω
or 1Ω
470nF
0.5Ω
or 1Ω
Typical Characteristics
Test circuit
Measurement and Calculation of Efficiency
Depending on test setup and measuring method, efficiency values can vary by approx. ±5%, and peak
current values can vary by up to ±20%, Accuracy of mean currents: ±1mA.
Measuring conditions for all diagrams, unless otherwise noted:
● Ta = 25°C
● one LED connected (peak voltage 4.2...5.8V)
A LQH32C from Murata has been used as reference inductor, the DC resistance is specified as 0.44 Ω ±
30% for 10 µH (max current 300 mA), 0.71 Ω ± 30% for 22 µH (max. current 250 mA) and 1.30 Ω ± 30% for a
47 µH inductor (max. current 170 mA).
Oscilloscope Displays
PR4401; LED voltage (CH1) and LED current (CH2, over 0.5 Ohm resistor)
with L1 = 22 µH L1 = 10 µH
© PREMA Semiconductor GmbH 2006-2008
Page 3/12 Rev 0908
LED DRIVER PR4401/PR4402
0,8 1 1,2 1,4 1,6 1,8 2
0
10
20
30
40
50
60
70
80
90
100
Efficiency vs. Supply Voltage
22 µH
14,7 µH
10 µH
Supply Voltage (V)
Efficiency (%)
0,8 1 1,2 1,4 1,6 1,8 2
0
10
20
30
40
50
60
70
80
90
100
110
120
Mean Supply Current vs. Supply Voltage
22 µH
10 µH
Supply Voltage (V)
Supply Current (mA)
0,8 1 1,2 1,4 1,6 1,8 2
0
5
10
15
20
25
Mean LED Current vs. Supply Voltage
22 µH
14.7 µH
10 µH
Supply Voltage (V)
LED Mean Current (mA)
0,8 1 1,2 1,4 1,6 1,8 2
0
25
50
75
100
125
150
175
200
225
250
Peak LED Current vs. Supply Voltage
22 µH
10 µH
Supply Voltage (V)
LED Peak Current (mA)
-20 -10 0 10 20 30 40 50 60 70
0,7
0,8
0,9
1
1,1
Startup Voltage vs. Temperature
22 µH
10 µH
Temperature (°C)
Startup Voltage (V))
0,75 1 1,25 1,5 1,75 2
0
100
200
300
400
500
600
700
800
Oscillation Frequency vs. Supply Voltage
22 µH
10 µH
Supply Voltage (V)
Frequency (kHz)
-20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
10
15
20
25
30
Mean LED Current vs. Temp. @ L1=10µH
1.0V
1,25V
1,50V
1,75V
Temperature (°C)
Mean LED current (mA)
PR4401 data
© PREMA Semiconductor GmbH 2006-2008
Page 4/12 Rev 0908
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