Zetex DN85 Zxsc400 1w/3w buck led driver Datasheet

DN85
ZXSC400 1W/3W buck LED drivers
Ray Liu, Applications Engineer, Zetex Semiconductors
Description
In Figure 1, ZXSC400 is configured as a high efficiency buck LED driver. The target applications
are either 1W (350mA) or 3W (700mA) drivers for white LED driven from a 4 cell battery, or a 2
alkaline cell input for flashlights. The supply voltage for ZXSC400 reference design is:
VIN = 3.8V to 6V.
Parts lists for 1W and 3W design are shown in Table 1 and Table 2 respectively. Performance data
is measured based on two different LED's VF binning with 0.3V VF difference.
C3
L1
VIN = 4V to 6V
D1
C2
U1
VCC
C1
Q1
VDRIVE
Stdn
VFB
GND
ISENSE
R3
R2
ZXSC400
R1
Figure 1
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
Schematic diagram
1
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DN85
Ref. Value
Package Part number
Manufacturer Contact details
Notes
U1
N/A
SOT23-6 ZXSC400E6
Zetex
www.zetex.com
LED Driver
Q1
N/A
SOT23
ZXTN25012EFL Zetex
www.zetex.com
Low sat NPN
transistor
D1
40V/0.75A SOT23
BAT750
Zetex
www.zetex.com
40V/0.75A
Schottky diode
L1
47␮H
N/A
744052470
Wurth
Elektronik
www.we-online.com ISAT = 520mA
R1
62m⍀
0805
Generic
N/A
0805 1%
R2
10⍀
0805
Generic
N/A
0805 5%
R3
47⍀
0805
Generic
N/A
0805 5%
C1
4.7␮F/10V 1206
Generic
N/A
X7R/X5R
C2
100pF/10V 0805
Generic
N/A
COG/NPO
C3
1uF/10V
Generic
N/A
X7R/X5R optional
0805
Table 1
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Bill of materials for 1W LED
2
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
DN85
Performance
90
0.4
Output Current (A)
0.5
Efficiency (%)
100
80
70
60
VF~3.3
5.8
5.4
5
4.6
0.2
0.1
VF~3.6
VF~3.3
50
6.2
0.3
4.2
3.8
6.2
5.8
Input Voltage (V)
5.4
5
4.6
4.2
3.8
Input Voltage (V)
Input Voltage vs Efficiency
Input Voltage vs Output Current
0.4
4
0.3
3
Output Voltage (V)
Input Current (A)
VF~3.6
0.0
0.2
2
0.1
1
VF~3.3
VF~3.6
VF~3.3
0.0
6.2
5.8
5.4
5
4.6
4.2
3.8
6.2
Input Voltage (V)
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
5.8
5.4
5
4.6
Input Voltage (V)
4.2
3.8
Input Voltage vs Output Voltage
Input Voltage vs Input Current
Figure 2
VF~3.6
0
Performance graphs for 1W design
3
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DN85
Ref. Value
Package Part number
Manufacturer Contact details
Notes
U1
N/A
SOT23-6 ZXSC400E6
Zetex
www.zetex.com
LED Driver
Q1
N/A
SOT23
ZXTN25012EFL Zetex
www.zetex.com
Low sat NPN
transistor
D1
40V/1A
SOT23
ZHCS1000
Zetex
www.zetex.com
40V/1A Schottky
diode
L1
33␮H
N/A
722065330
Wurth
Elektronik
www.we-online.com Isat=1.6A
R1
30m⍀
0805
Generic
N/A
0805 1%
R2
10⍀
0805
Generic
N/A
0805 5%
R3
47⍀
0805
Generic
N/A
0805 5%
C1
10␮F/10V 1210
Generic
N/A
X7R/X5R
C2
100pF/10V 0805
Generic
N/A
COG/NPO
C3
2.2uF/10V 1206
Generic
N/A
X7R/X5R optional
Table 2
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Bill of materials for 3W LED
4
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
DN85
Performance
0.8
100
0.7
Output Current (A)
Efficiency (%)
90
80
70
60
VF~3.2
6
5.6
5.2
4.8
4.4
0.5
0.4
0.3
0.2
0.1
VF~3.5
50
6.4
0.6
VF~3.2
VF~3.5
0.0
4
6.4
6
Input Voltage (V)
5.6
5.2
4.8
4.4
4
Input Voltage (V)
Input Voltage vs Efficiency
Input Voltage vs Output Current
0.8
4
0.6
3
Output Voltage (V)
Input Current (A)
0.7
0.5
0.4
2
0.3
0.2
1
VF~3.2
0.1
VF~3.5
VF~3.2
0.0
6.4
6
5.6
5.2
4.8
4.4
4
6.4
Input Voltage (V)
Issue 1 - August 2007
© Zetex Semiconductors plc 2007
6
5.6
5.2
4.8
Input Voltage (V)
4.4
4
Input Voltage vs Output Voltage
Input Voltage vs Input Current
Figure 3
VF~3.5
0
Performance graphs for 3W design
5
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DN85
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© Zetex Semiconductors plc 2007
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