Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.NET

X  

Preview PDF Download HTML

LT8331 Datasheet(HTML) 13 Page - Analog Devices

Part No. LT8331
Description  Low IQ Boost/SEPIC/Flyback/Inverting Converter with 0.5A, 140V Switch
Download  30 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  AD [Analog Devices]
Homepage  http://www.analog.com
Logo 

LT8331 Datasheet(HTML) 13 Page - Analog Devices

Back Button LT8331 Datasheet HTML 13Page - Analog Devices Next Button
Zoom Inzoom in Zoom Outzoom out
Go To Page :
/ 30 page
background image
LT8331
13
Rev. C
For more information www.analog.com
APPLICATIONS INFORMATION
Discontinuous conduction mode (DCM) provides higher
conversion ratios at a given frequency at the cost of
reduced efficiencies, higher switching currents, and lower
available output power.
Boost Converter: Maximum Output Current Capability
and Inductor Selection
For the boost topology, the maximum average inductor
current is:
IL(MAX)(AVE)= IO(MAX)
1
1 − DMAX
1
η
where η (< 1.0) is the converter efficiency.
Due to the current limit of its internal power switch, the
LT8331 should be used in a boost converter whose maxi-
mum output current (IO(MAX)) is:
I O(MAX)
VIN(MIN)
VOUT
• 0.5A − 0.5 • ΔISW
(
) • η
Minimum possible inductor value and switching frequency
should also be considered since they will increase inductor
ripple current ∆ISW.
The inductor ripple current ∆ISW has a direct effect on the
choice of the inductor value and the converter’s maximum
output current capability. Choosing smaller values of
∆ISW increases output current capability, but requires
large inductances and reduces the current loop gain
(the converter will approach voltage mode). Accepting
larger values of ∆ISW provides fast transient response and
allows the use of low inductances, but results in higher
input current ripple and greater core losses, and reduces
output current capability. It is recommended to choose a
∆ISW of approximately 0.2A to 0.3A.
Given an operating input voltage range, and having cho-
sen the operating frequency and ripple current in the
inductor, the inductor value of the boost converter can
be determined using the following equation:
L =
VIN(MIN)
ΔISW • fOSC
• DMAX
The peak inductor current is the switch current limit (max-
imum 0.7A), and the RMS inductor current is approxi-
mately equal to IL(MAX)(AVE).
Choose an inductor that can handle at least 0.7A without
saturating, and ensure that the inductor has a low DCR
(copper-wire resistance) to minimize I2R power losses.
Note that in some applications, the current handling
requirements of the inductor can be lower, such as in the
SEPIC topology where each inductor only carries one-
half of the total switch current. For better efficiency, use
similar valued inductors with a larger volume. Many dif-
ferent sizes and shapes are available from various manu-
facturers (see Table 2). Choose a core material that has
low losses at the programmed switching frequency, such
as a ferrite core. The final value chosen for the inductor
should not allow peak inductor currents to exceed 0.5A
in steady state at maximum load. Due to tolerances, be
sure to account for minimum possible inductance value,
switching frequency and converter efficiency.
Table 2. Inductor Manufacturers
Sumida
(847) 956-0666
www.sumida.com
TDK
(847) 803-6100
www.tdk.com
Murata
(714) 852-2001
www.murata.com
Coilcraft
(847) 639-6400
www.coilcraft.com
Wurth
(605) 886-4385
www.we-online.com
BOOST CONVERTER: INPUT CAPACITOR SELECTION
Bypass the input of the LT8331 circuit with a ceramic
capacitor of X7R or X5R type placed as close as possible
to the VIN and GND pins. Y5V types have poor performance
over temperature and applied voltage, and should not be
used. A 4.7µF to 10µF ceramic capacitor is adequate to
bypass the LT8331 and will easily handle the ripple cur-
rent. If the input power source has high impedance, or
there is significant inductance due to long wires or cables,
additional bulk capacitance may be necessary. This can
be provided with a low performance electrolytic capacitor.
A precaution regarding the ceramic input capacitor con-
cerns the maximum input voltage rating of the LT8331.
A ceramic input capacitor combined with trace or cable


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 


Datasheet Download

Go To PDF Page


Link URL



Privacy Policy
ALLDATASHEET.NET
Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Contact us   |   Privacy Policy   |   Bookmark   |   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