Data Brief
For further information contact your local STMicroelectronics sales office.
February 2009 Rev 1 1/4
4
STEVAL-ILL023V1
Demonstration board: high-efficiency switching LED driver for
high-current LEDs based on the L6726A
Features
■Input voltage Vin: 8 V to 18 V
■Output voltage (with Vin = 18 V): 2.5 V to 14 V
■Output current ILED: 1 A / 1.5 A / 2.8 A
■Analog dimming (with ILED= 0 A): 0 V to 2.5 V
■Low level PWM signal: 0 V
■High level PWM signal: 2.8 V to 3.8 V
(typ: 3.3 V)
■Duty cycle (at fdim = 200 Hz): 0% to 99 %
■Efficiency (with Vin = 18 V and Vout = 12.6 V):
94.8 %
Description
Rapid advances in LED technology has led to
increases in their output current capabilities in
recent years. 0.350 A LEDs, for example, were
soon followed by 0.7 A LEDs, and then 1 A
devices appeared shortly thereafter. Currently,
LEDs with currents as high as several amps are
present on the market. However, these high
currents increase the requirements of the driving
circuitry of the LEDs, particularly in terms of
efficiency.
The STEVAL-ILL023V1 demonstration board is
based on the L6726A single phase PWM
controller, with two external MOSFETS for
synchronous rectification. Designed for 2.8 A
LEDs (1-3 in a series string), the main benefit of
the solution is its exceptional efficiency. Ease of
dimming and scalability to even higher currents
are additional advantages of the design.
The solution is also much safer with regard to
border conditions, since the current limit is based
solely on the selection of the MOSFETS.
STEVAL-ILL023V1
www.st.com
Circuit schematic STEVAL-ILL023V1
2/4
1 Circuit schematic
Figure 1. STEVAL-ILL023V1 schematic diagram
Boo
oo
t1
Ugate 2
GN
GN
D
3
Lgate 4
Vcc 5
FB
6
COMP
7
Phase8
U2 L6726A
22uF
C1
2R2
R7
2R2
R8
GN
GN
D
10uH
L1
Inductor
22uF
C9
0R56
R9
D1
TS821
4k7
R4
4k7
R3
6k8
R5
82nF
C3
470
70
pF
C2
1k1
R2
100n
0n
F
C7
D3
STPS1L30M
D2
1N4148
10R
R6
10uF
C4
4.7uF
C8
100n
00n
F
C6
IN
3
2
OUT 1
GN
GN
D
U1 L78L06
06
AC
8
2
1
5
4
3
7
6
Q1
STS8DNH3LL
0R56
R10
62k
R1
100n
0n
F
C5
Vcc18V
Comp
Phase
Vcc
cc
6V
Boo
oo
t
OU
OU
T-A
OU
OU
T-K
PWM
Vref
Ugate
Lgate
FB
1
2
3
PWM
1
2
3
4
5
6
OU
OU
T
0R56
R14
0R3
R15
0R3
R16
1
2
3
P1
1
3
2
K375A
CN1
8-18V
STEVAL-ILL023V1 Revision history
3/4
2 Revision history
Table 1. Document revision history
Date Revision Changes
26-Feb-2009 1 Initial release.
STEVAL-ILL023V1
4/4
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