LT3582 View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LT3582

I2C Programmable Boost and Single Inductor Inverting DC/DC Converters with OTP

Linear Technology 

LT3582/LT3582-5/LT3582-12

APPLICATIONS INFORMATION

10. Read the OTP data and verify the contents.

11. Write 00h to CMDR. This enables the power switches

and the chip will operate from the OTP configura-

tion.

12. Float the VPP pin. This can be done at any time

after step 8.

Choosing Inductors

Several series of inductors that work well with the LT3582

series are listed in Table 3. This table is not complete, and

there are many other manufacturers and parts that can

be used. Consult each manufacturer for more detailed

information and for their entire selection of related parts,

as many different sizes and shapes are available.

Table 3: Inductor Manufacturers

Coilcraft

LPS3008-LPS4018 Series, www.coilcraft.com

XPL2010 Series

Murata

LQH32C, LQH43C Series www.murata.com

Sumida

CDRH26D09, CDRH26D11, www.sumida.com

CDRH3D14 Series

TDK

VLF and VLCF Series

www.tdk.com

Würth

WE-TPC Series Type T, TH, www.we-online.com

Elektronik XS and S

Inductances of 2.2μH-10μH typically result in a good

tradeoff between inductor size and system performance.

More inductance typically yields an increase in efficiency

at the expense of increased output ripple. Less inductance

may be used in a given application depending on required

efficiency and output current. For higher efficiency, choose

inductors with high frequency core material, such as ferrite,

to reduce core losses. Also to improve efficiency, choose

inductors with more volume for a given inductance. The

inductor should have low DCR (copper-wire resistance)

to reduce I2R losses, and must be able to handle the peak

inductor current without saturating. To minimize radiated

noise, use a toroidal or shielded inductor (note that the

inductance of shielded types will drop more as current

increases, and will saturate more easily).

Peak Current Rating: Real inductors can experience

a drop in inductance as current and temperature

increase. The inductors should have saturation cur-

rent ratings higher than the peak inductor currents.

The peak inductor currents can be calculated as:

IPK

≅ ILIMIT

+

VLSWON

L

• TOS

mA

where:

IPK

ILIMIT

= Peak inductor current

= Typically 350mA for Boost and 600mA for

Inverting

L

= Inductance in μH

VLSWON = Maximum inductor voltage when the

power switch is “on”. Typically max VIN

for the Boost and Inverting converters.

TOS = 100 for Boost and 125 for Inverting

Maximum Load Currents: Use one of the following equa-

tions to estimate the maximum output load current for the

positive and negative output voltages:

IOUTP =

⎛

⎜

⎝

VIN(MIN)

VOUTP

⎞

⎟

⎠

•

⎛

⎜IPK

⎝

–

TOFF _ MIN

• (VOUTP + 0.5

2•L

–

VIN(MIN)

)⎞

⎟

•

0.8η

⎠

or IOUTN =

⎛

⎝⎜⎜

VIN(MIN)

VIN(MIN)+ | VOUTN

⎞

|⎠⎟⎟

•

⎛

⎝⎜IPK

–

TOFF _ MIN

• (|VOUTN

2•L

|

+0.5)⎞

⎟

•

0.8η

⎠

18

3582512f

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