LT3581IMSE-TRPBF View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

LT3581IMSE-TRPBF

3.3A Boost/Inverting DC/DC Converter with Fault Protection

Linear Technology 

LT3581

APPLICATIONS INFORMATION

• The slave switch, by not performing a current sense

operation like the master switch, can sustain fairly large

current spikes when the flying capacitors charge up.

Since this current spike flows through SW2, it does

not affect the operation of the current comparator (A4

in Block Diagram).

• The master switch, immune from the capacitor current

spike (seen only by the slave switch) can sense the

inductor current more accurately.

• Since the slave switch can sustain large current spikes,

the diodes that feed current into the flying capacitors do

not need current limiting resistors, leading to efficiency

and thermal improvements.

High VOUT Charge Pump Topology

The LT3581 can be used in a charge-pump topology as

shown in Figure 12, multiplying the output of an inductive

boost converter. The master switch (SW1) can be used to

drive the inductive boost converter (first stage of charge

pump), while the slave switch (SW2) can be used to drive

one or more other charge pump stages. This topology is

useful for high voltage applications including VFD bias

supplies.

Single Inductor Inverting Topology

If there is a need to use just one inductor to generate a

negative output voltage whose magnitude is greater than

VIN, the single inductor inverting topology (shown in Figure

13) can be used. Since the master and slave switches are

isolated by a Schottky diode, the current spike through C1

will flow only through the slave switch, thereby preventing

the current comparator, (A4 in the Block Diagram), from

falsely tripping. Output disconnect is inherently built into

the single inductor topology.

2.2µF

2.2µF

2.2µF

VOUT2

97V

140mA

2.2µF

VOUT1

65V

70mA

VIN

12V

2.2µF

43.2k

10µH

2.2µF

SW1 SW2

100k VIN

FAULT

FB

370k

GATE

SHDN

CLKOUT

RT LT3581 VC

SYNC

SS

GND

100pF

0.47µF

8.06k

2.2µF

24k

1nF

3581 F12

Figure 12. High VOUT Charge Pump Topology Can Be Used to

Build VFD Bias Supplies

VIN

CIN

ENABLE

L1

D1

C1

SW1 SW2

GATE

FB

VIN

CLKOUT

100k

LT3581

FAULT

VC

SHDN

SS

RT SYNC GND

RT

D3

D2

COUT

VOUT < 0V

AND |VOUT| > |VIN|

RFB

CSS

RVC

CVC2

CVC1

3579 F13

Figure 13. Single Inductor Inverting Topology

20

For more information www.linear.com/LT3581

3581fb

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