STEVAL-ILL010V1
High intensity LED dimming driver evaluation board based on the L6902
Data Brief
Features
Input voltage Vin= 8 V to 30 Vdc Dimming interface Analog current control Average current control by PWM
Description
Thanks to their high efficiency and reliability, super high-brightness LEDs are becoming more and more popular as a subsitute for conventional light sources. Although LEDs can be supplied directly from a simple voltage source (like a battery with resistor), for most applications it is better to use a switching current source to achieve not only higher efficiency but also better light output. This evaluation board is designed around an L6902D-based DC-DC converter with dimming interface. It board implements both of two well known dimming methods:
STEVAL-ILL010V1 The second dimming method implemented on this board is PWM control of average LED current. This control requires a digital PWM signal (with an amplitude of either 3.3 V or 5 V) between the dimming pin and the ground pin. Varying the dutycycle on the board will then change the brightness of the LED (100% = LED off, and 0% = LED fully on).
Analog current control Average current control by PWM
While there is only a single dimming input connector on the board, it can be used for both dimming methods. A signal between 0 and 3.3 V should be used for analog (peak current) dimming. When the dimming pin is grounded (0 V), the 350 mA maximum output current is provided. Likewise, when 3.3 V is applied to the pin, the current provided is zero and the LED is off.
Februar y 2008
Rev 1
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For further information contact your local STMicroelectronics sales office.
1
GN D
VREF
7
6
1
1
STEVAL-ILL010V1
J3 3.3V Vref
J4 Dimming Input
J6
1
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Circuit schematic
Figure 1.
L1 100uH
J1
U1
L6902D
J2
Schematic
2 1
VCC
8
OUT
1
D1 STPS34OU
R1 9k1
+
C2 10uF 35V
1 2
Output
8 - 24V
4 COMP
C3 22nF
CS+ CS-
2 3
R4 1k R4
Circuit schematic
+
C1 10uF 25V CERAMIC
C4 220pF
R3 1k
FB
5
R2 5k1
R6 27k
R5 8k2
Rsense 0.33
GND
STEVAL-ILL010V1
Revision history
2
Revision history
Table 1.
Date 11-Feb-2008
Document revision history
Revision 1 Initial release. Changes
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STEVAL-ILL010V1
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