STEVAL-ILL008V1 STMicroelectronics, STEVAL-ILL008V1 Datasheet - Page 6

• Manufacturer Part Number: STEVAL-ILL008V1
• Description: EVAL BOARD CREE LED FLASHLIGHT
• Manufacturer: STMicroelectronics

Specifications of STEVAL-ILL008V1

• Mfg Application Notes: Low Voltage LED Driver AppNote
• Design Resources: STEVAL-ILL008V1 Gerber Files STEVAL-ILL008V1 Schematic STEVAL-ILL008V1 Bill of Materials
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3.5V
• Features: 1V Start up Input Voltage
• Voltage - Input: 1 ~ 5.5 V
• Utilized Ic / Part: L6920
• Product: Display Modules
• Core Chip: L6920DA
• Output Voltage: 3.5V
• Kit Contents: L6920D, L4971, L6902D Reference Board
• Development Tool Type: Hardware - Eval/Demo Board
• Tool / Board Applications: LED Flashlight
• Mcu Supported Families: L6920DA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output / Channel: -
• Lead Free Status / Rohs Status: Details
• Other names: 497-5516

AN1941 APPLICATION NOTE
Figure 9. Size of the demo board
3 L4971 BUCK LED DRIVER:
For applications that use multiple LEDs it is better to drive LEDs in series rather than parallel.
3.1 LED parameters;
As shown below, the LED voltage drop tolerance varies by ±16.6% for the white LED. Different
colors will have different typical voltage drop. For this reason, it is recommended that the LEDs
be connected in series rather than parallel. If connected in parallel, the current would not be
shared equally between the multiple LEDs due to the differences in forward voltage drop. Dif-
ferent brightness would result depending on individual voltage drop of the string of LEDs. With
the LEDs connected in series the same current flows through each LED and the output will be
better matched.
Below is the forward voltage drop spec sheet from Luxeon Star Technical Data Sheet DS23
Table 2.
6/15
Royal Blue
Amber
Green
Color
White
Cyan
Blue
Red
Min.
2.79
2.79
2.79
2.79
2.79
2.31
2.31
Forward Voltage
V
Typ.
3.42
3.42
3.42
3.42
3.42
2.85
2.85
F
(V)
Max.
3.99
3.99
3.99
3.99
3.99
3.27
3.27
Resistance
Dynamic
( ) R
1.0
1.0
1.0
1.0
1.0
2.4
2.4
D
Temperature Coefficient
of Forward Voltage
(mV/°C)
V
-2.0
-2.0
-2.0
-2.0
-2.0
-2.0
-2.0
F
/ T
J