数据搜索系统，热门电子元器件搜索
  Chinese  ▼
ALLDATASHEETCN.COM

X  

预览 PDF HTML

LED5000 数据表(PDF) 39 Page - STMicroelectronics

部件名 LED5000
功能描述  3 A monolithic step-down current source with dimming capability
PDF  52 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
制造商  STMICROELECTRONICS [STMicroelectronics]
网页  http://www.st.com
标志 STMICROELECTRONICS - STMicroelectronics

LED5000 数据表(HTML) 39 Page - STMicroelectronics

Back Button LED5000 Datasheet HTML 35Page - STMicroelectronics LED5000 Datasheet HTML 36Page - STMicroelectronics LED5000 Datasheet HTML 37Page - STMicroelectronics LED5000 Datasheet HTML 38Page - STMicroelectronics LED5000 Datasheet HTML 39Page - STMicroelectronics LED5000 Datasheet HTML 40Page - STMicroelectronics LED5000 Datasheet HTML 41Page - STMicroelectronics LED5000 Datasheet HTML 42Page - STMicroelectronics LED5000 Datasheet HTML 43Page - STMicroelectronics Next Button
Zoom Inzoom in Zoom Outzoom out
 39 / 52 page
background image
LED5000
Application notes - alternative topologies
Doc ID 023951 Rev 1
39/51
Equation 61
This is due to the fact that the current flowing through the internal power switch is delivered
to the output only during the OFF phase.
The switch peak current must be lower than the minimum current limit of the overcurrent
protection (see
Section Table 5.: Electrical characteristics for details) while the average
current must be lower than the rated DC current of the device.
As a consequence, the maximum output current is:
Equation 62
where ISW MAX represents the rated current of the device.
The current capability is reduced by the term (1-DREAL) and so, for example, with a duty
cycle of 0.5, and considering an average current through the switch of 3 A, the maximum
output current deliverable to the load is 1.5 A.
Figure 29 shows the circuit schematic for an LED current source based on positive buck-
boost topology. The input voltage ranges from 18 to 30 V and it can drive a string composed
of 7 LEDs with 0.7 A DC (VFW_LED = 3.75 V so VOUT=26.4 V).
The network D5, R4, RS implements an inexpensive overvoltage protection. R4 effect can
be neglected during the normal operation since the FB biasing current is negligible (tens of
nA, see
Table 5: Electrical characteristics) but it limits the current flowing in the zener diode
D5. In case the load is disconnected or in case of open LED:
Equation 63
R4 must be dimensioned to limit the D5 rated power so it is an inexpensive small signal
Zener diode.
Figure 29.
LED current source based on positive BB+ topology
I
SW
I
LOAD
1D
REAL
–
---------------------------
=
I
LOAD MAX
I
SW MAX
1D
REAL
–
()
⋅
≅
V
OUT
V
FB
V
ZENER_DIODE
+
=
I
ZENER_DIODE
V
FB
R
S
R
4
+
---------------------
=
small signal
power plane
L1
XAL6060-22uH
D3STPS3L60U
2
1
D5
R4
10k
R3
10K
R1
10k
C9
1nF
TP1
DIM
RS
0.28R
C6
100nF
R5
NM
JP1
C10
NM
C7
NM
TP4
INH
C5
15pF
C4
1.5nF
TP5
VLED-
TP6
GND
C1
10uF
C8
2.2uF
50V
JP2
TP3
VLED+
R6
100
TP2
VIN
R8
10k
R7
NM
Q1
STN3NF06L
U1
LED5000
SW
8
VIN
7
BOOT
1
EP
EP
DIM
2
INH
3
GND
6
COMP
4
FB
5
TP7
GND
R2
NM
C2
10uF
C3
100nF
AM13513v1



Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52


数据表 下载

Go To PDF Page


链接网址



ALLDATASHEET是否为您带来帮助?  [ DONATE ] 

关于 Alldatasheet   |   广告服务   |   联系我们   |   隐私政策   |   数据表链接    |   链接交换   |   制造商名单
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