数据搜索系统,热门电子元器件搜索
  Chinese  ▼

Delete All
ON OFF
ALLDATASHEETCN.COM

X  

预览 PDF Download HTML

LTC3542IS6 数据表(PDF) 12 Page - Linear Integrated Systems

部件名 LTC3542IS6
功能描述  500mA, 2.25MHz Synchronous Step-Down
Download  16 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
制造商  LINEAR [Linear Integrated Systems]
网页  http://www.linearsystems.com
标志 LINEAR - Linear Integrated Systems

LTC3542IS6 数据表(HTML) 12 Page - Linear Integrated Systems

Back Button LTC3542IS6 Datasheet HTML 8Page - Linear Integrated Systems LTC3542IS6 Datasheet HTML 9Page - Linear Integrated Systems LTC3542IS6 Datasheet HTML 10Page - Linear Integrated Systems LTC3542IS6 Datasheet HTML 11Page - Linear Integrated Systems LTC3542IS6 Datasheet HTML 12Page - Linear Integrated Systems LTC3542IS6 Datasheet HTML 13Page - Linear Integrated Systems LTC3542IS6 Datasheet HTML 14Page - Linear Integrated Systems LTC3542IS6 Datasheet HTML 15Page - Linear Integrated Systems LTC3542IS6 Datasheet HTML 16Page - Linear Integrated Systems  
Zoom Inzoom in Zoom Outzoom out
 12 / 16 page
background image
LTC3542
12
3542fa
parallel with COUT, causing a rapid drop in VOUT. No regula-
tor can deliver enough current to prevent this problem, if
the switch connecting the load has low resistance and is
driven quickly. The solution is to limit the turn-on speed of
the load switch driver. A Hot SwapTM controller is designed
specifically for this purpose and usually incorporates cur-
rent limit, short circuit protection and soft-start.
Design Example
As a design example, assume the LTC3542 is used in a single
lithium-ion battery-powered cellular phone application. The
VIN will be operating from a maximum of 4.2V down to
about 2.7V. The load current requirement is a maximum
of 0.5A, but most of the time it will be in standby mode,
requiring only 2mA. Efficiency at both low and high load
currents is important. Output voltage is 1.8V.
With this information we can calculate L using:
L
fI
V
V
V
L
OUT
OUT
IN
=
⎝⎜
⎠⎟
1
1
••
Δ
Substituting VOUT = 1.8V, VIN = 4.2V, ΔIL = 200mA and
f = 2.25MHz gives:
L
V
MHz
mA
V
V
μH
=
⎝⎜
⎠⎟
=
18
2 25
200
1
18
42
228
.
.•
•–
.
.
.
Choosing a vendor’s closest inductor value of 2.2μH results
in a maximum ripple current of:
ΔI
V
MHz
μH
V
V
L =
⎝⎜
⎠⎟
=
18
225
2 2
1
18
42
207
.
.• .
•–
.
.
.8
8mA
Hot Swap is a trademark of Linear Technology Corporation.
CIN will require an RMS current rating of at least
0.25A
≅ ILOAD(MAX)/2 at temperature and COUT will require
ESR of less than 0.2
Ω. In most cases, ceramic capacitors
will satisfy these requirements. Select COUT = 10μF and
CIN = 10μF.
For the feedback resistors, choose R1 = 75k, R2 can be
calculated from:
R
V
V
R
V
V
k
OUT
2
06
11
18
06
175
= ⎛
⎝⎜
⎠⎟
= ⎛
⎝⎜
⎠⎟
.
–•
.
.
–•
== 150k
Figure 3 shows the complete circuit along with its efficiency
curve, load step response and recommended layout
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3542. These items are also illustrated graphically
in Figure 3b. Check the following in your layout:
1. The power traces, consisting of the GND trace, the SW
trace and the VIN trace should be kept short, direct and
wide.
2. Does the VFB pin connect directly to the feedback re-
sistors? The resistive divider R1/R2 must be connected
between the (+) plate of COUT and ground.
3. Does the (+) plate of CIN connect to VIN as closely as
possible? This capacitor provides the AC current to the
internal power MOSFETs.
4. Keep the (–) plates of CIN and COUT as close as pos-
sible.
5. Keep the switching node, SW, away from the sensitive
VFB node.
APPLICATIONS INFORMATION


Html Pages

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


数据表 下载

Go To PDF Page


链接网址




隐私政策
ALLDATASHEETCN.COM
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   |   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