전자부품 데이터시트 검색엔진
  Korean  ▼
ALLDATASHEET.CO.KR

X  

Preview PDF HTML

LM3402 데이터시트(PDF) 11 Page - National Semiconductor (TI)

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

LM3402 데이터시트(HTML) 11 Page - National Semiconductor (TI)

Back Button 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) LM3402 Datasheet HTML 14Page - National Semiconductor (TI) LM3402 Datasheet HTML 15Page - National Semiconductor (TI) Next Button
Zoom Inzoom in Zoom Outzoom out
 11 / 18 page
background image
Modified Application Circuit Design
Example 4
•
V
IN = 48V (±20%)
•
Driving 3, 4, or 5 HB LEDs with V
F = 3.4V
•
I
F = 500 mA (typical application)
•
Estimated efficiency = 82%
•
f
SW = 500 kHz (typ app)
The inductor, R
ON resistor, and the RSNS resistor are calcu-
lated for a typical or average design.
• V
OUT = 3 x 3.4V + 200 mV = 10.4V
• V
OUT = 4 x 3.4V + 200 mV = 13.8V
• V
OUT = 5 x 3.4V + 200 mV = 17.2V
Reduce switching frequency for the typical application to
about 500 kHz to increase efficiency.
Calculate t
ON, tOFF & RON
•
V
OUT = 13.8V
•
V
IN = 48V
•
I
F = 500 mA
•
t
D = 220 ns
•
η = 0.85
•
f
SW = 500 kHz
t
ON ≊ 705 ns
R
ON ≊ 179 kΩ (use standard value of 182 kΩ)
Calculate Inductor Value
•
I
F = 500 mA
•
Δi
L = 250 mA (target)
•
R
ON = 182 kΩ
•
L = 100 µH
Calculate
Δi
L with L = 100 µH (VIN = 48V, VOUT = 13.8V)
Δi
L = 241 mA (all combinations)
Calculate Switching Frequency
Example 4 Switching Frequency
V
IN (V)
V
OUT (V)
f
SW (kHz)
Three Series LEDs
36
10.4
374
48
10.4
412
V
IN (V)
V
OUT (V)
f
SW (kHz)
Three Series LEDs
60
10.4
435
Four Series LEDs
36
13.8
430
48
13.8
497
60
13.8
537
Five Series LEDs
36
17.2
454
48
17.2
558
60
17.2
620
Calculate R
SNS
•
V
OUT = 13.8V
•
V
IN = 48V
•
I
F = 500 mA
•
t
D = 220 ns
•
η = 0.85
•
L = 100 µH
R
SNS = 488 mΩ
Calculate Average Current through LED
Example 4 Average LED Current
V
IN (V)
V
OUT (V)
I
F (A)
Three Series LEDs
36
10.4
0.507
48
10.4
0.507
60
10.4
0.507
Four Series LEDs
36
13.8
0.500
48
13.8
0.500
60
13.8
0.500
Five Series LEDs
36
17.2
0.493
48
17.2
0.493
60
17.2
0.493
In the reduced frequency application you can see that there
is a difference of 14 mA between the low and high of the av-
erage current.
If the original t
ON circuit was used (no PNP transistor) with the
switching frequency centered around 500 kHz the difference
between the high and low values would be about 67 mA.
11
www.national.com



Html Pages

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


데이터시트 다운로드

Go To PDF Page


링크 URL



ALLDATASHEET 가 귀하에 도움이 되셨나요?  [ DONATE ] 

Alldatasheet는?   |   광고문의   |   운영자에게 연락하기   |   개인정보취급방침   |   링크 투 데이터시트    |   링크교환   |   제조사별 검색
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