Electronic Components Datasheet Search
  English  ▼

X  

Preview PDF HTML

LM3402 Datasheet(PDF) 9 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor. Click here to check the latest version.
Part # LM3402
Description  LM3402/LM3404 Fast Dimming and True Constant LED Current Evaluation Board
PDF  18 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  NSC [National Semiconductor (TI)]
Direct Link  http://www.national.com
Logo NSC - National Semiconductor (TI)

LM3402 Datasheet(HTML) 9 Page - National Semiconductor (TI)

Back Button LM3402 Datasheet HTML 5Page - National Semiconductor (TI) LM3402 Datasheet HTML 6Page - National Semiconductor (TI) LM3402 Datasheet HTML 7Page - National Semiconductor (TI) LM3402 Datasheet HTML 8Page - National Semiconductor (TI) LM3402 Datasheet HTML 9Page - National Semiconductor (TI) LM3402 Datasheet HTML 10Page - National Semiconductor (TI) LM3402 Datasheet HTML 11Page - National Semiconductor (TI) LM3402 Datasheet HTML 12Page - National Semiconductor (TI) LM3402 Datasheet HTML 13Page - National Semiconductor (TI) Next Button
Zoom Inzoom in Zoom Outzoom out
 9 / 18 page
background image
Example 3 On & Off Times
Three Series LEDs
V
IN (V)
V
OUT (V)
R
ON
t
ON
t
OFF
36
10.4
113 k
Ω
5.92E-07
1.09E-07
48
10.4
113 k
Ω
4.03E-07
1.12E-06
60
10.4
113 k
Ω
3.06E-07
1.14E-06
Four Series LEDs
36
13.8
113 k
Ω
6.83E-07
7.78E-07
48
13.8
113 k
Ω
4.43E-07
8.21E-07
60
13.8
113 k
Ω
3.28E-07
8.41E-07
Five Series LEDs
36
17.2
113 k
Ω
8.06E-07
5.77E-07
48
17.2
113 k
Ω
4.92E-07
6.34E-07
60
17.2
113 k
Ω
3.54E-07
6.59E-07
Calculate Switching Frequency
Example 3 Switching Frequency
V
IN (V)
V
OUT (V)
f
SW (kHz)
Three Series LEDs
36
10.4
595
48
10.4
656
60
10.4
692
Four Series LEDs
36
13.8
685
48
13.8
791
60
13.8
855
Five Series LEDs
36
17.2
723
48
17.2
888
60
17.2
987
Calculate Inductor Value
Therefore:
You can quickly see one benefit of the modified circuit. The
improved circuit eliminates the input and output voltage vari-
ation on RMS current.
•
I
F = 500 mA (typical application)
•
Δi
L = 250 mA (target)
•
R
ON= 113 kΩ
•
L = 59 µH (68 µH standard value)
•
Δi
L = 223 mA (L = 68 µH all combinations)
Calculate R
SNS
Original R
SNS equation:
Substitute improved circuit t
ON calculation:
Simplified:
Typical Application:
•
V
OUT = 13.8V
•
I
F = 500 mA
•
R
ON= 113 kΩ
•
L = 68 µH
•
t
D = 220 ns
R
SNS = 462 mΩ
This equation shows that only variations in V
OUT will affect the
average current over the entire application range. These vari-
ations should be very minor even with large variations in
output voltage.
Calculate Average Current through LED
Modified application circuit average forward current equation.
Simplified:
9
www.national.com



Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18


Datasheet Download

Go To PDF Page


Link URL



Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Contact us   |   Privacy Policy   |   Link to Datasheet    |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com