LT3581 LINER [Linear Technology], LT3581 Datasheet - Page 20

• Manufacturer Part Number: LT3581
• Description: 3.3A Boost/Inverting DC/DC Converter with Fault Protection
• Manufacturer: LINER [Linear Technology]

LT3581
applicaTions inForMaTion
• The slave switch, by not performing a current sense
• The master switch, immune from the capacitor current
• Since the slave switch can sustain large current spikes,
High V
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
V
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.
0
IN
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).
spike (seen only by the slave switch) can sense the
inductor current more accurately.
the diodes that feed current into the flying capacitors do
not need current limiting resistors, leading to efficiency
and thermal improvements.
, the single inductor inverting topology (shown in Figure
OUT
Charge Pump Topology
2.2µF
12V
V
V
C
IN
Figure 12. High V
Build VFD Bias Supplies
ENABLE
IN
IN
43.2k
Figure 13. Single Inductor Inverting Topology
100k
R
T
100k
L1
10µH
GATE
V
FAULT
SHDN
RT
IN
V
FAULT
SHDN
RT
SYNC
SW1
IN
OUT
LT3581
SYNC
SW1 SW2
D1
LT3581
Charge Pump Topology Can Be Used to
GND
SW2
CLKOUT
CLKOUT
GND
SS
C1
FB
V
GATE
0.47µF
C
SS
FB
V
C
2.2µF
2.2µF
2.2µF
D2
370k
D3
C
100pF
SS
R
C
VC
C
OUT
VC1
3579 F13
24k
1nF
8.06k
R
FB
V
AND |V
C
2.2µF
2.2µF
2.2µF
OUT
VC2
3581 F12
< 0V
OUT
| > |V
V
97V
140mA
V
65V
70mA
OUT2
OUT1
IN
3581f
|