Datasheet

1
LT1268B/LT1268
7.5A, 150kHz
Switching Regulators
S
F
EA
T
U
RE
D
U
ESCRIPTIO
■
Wide Input Voltage Range: 3.5V to 30V
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Low Quiescent Current: 7mA
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Internal 7.5A Switch
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Very Few External Parts Required
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Self-Protected Against Overloads
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Available in Standard and Surface Mount
5-Pin Packages
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Can Be Externally Synchronized
(See LT1072 Data Sheet)
The LT1268B and LT1268 are monolithic high power
switching regulators. Identical to the popular LT1070,
except for switching frequency (150kHz) and higher
switch current, they can be operated in all standard
switching configurations including buck, boost, flyback,
and inverting. A high current, high efficiency switch is
included on the die along with all oscillator, control, and
protection circuitry. Integration of all functions allows
the LT1268 to be built in standard 5-pin power packages.
This makes it extremely easy to use and provides “bust
proof” operations similar to that obtained with 3-pin
linear regulators.
The LT1268 operate with supply voltages from 3.5V to
30V and draw only 7mA quiescent current. By utilizing
current mode switching techniques, it provides excellent
AC and DC load and line regulation.
The LT1268 use an adaptive anti-sat switch drive to allow
very wide ranging load currents with no loss in efficiency.
An externally activated shutdown mode reduces total
supply current to 100µA typical for standby operation.
USER NOTE:
This data sheet is only intended to provide specifications, graphs, and a general functional
description of the LT1268B/LT1268. Application circuits are included to show the capability of the
LT1268B/LT1268. A complete design manual (AN19) should be obtained to assist in developing new
designs. This manual contains a comprehensive discussion of both the LT1070 and the external
components used with it, as well as complete formulas for calculating the values of these
components. The manual can also be used for the LT1268B/LT1268 factoring in the higher switch
current rating and higher operating frequency.
U
A
O
PP
L
IC
AT
ITY
P
I
CA
L
Boost Regulator with 5.3V ±1% Output
LOAD CURRENT (A)
0
EFFICIENCY (%)
80
90
4
LT1268 • TA02
70
60
1
2
3
100
V
IN
= 5.3V
V
IN
= 4.7V
V
IN
= 5V
Efficiency of 5.3V Boost Converter
V
IN
V
SW
LT1268B
L1
8µH, 5A*
D1
MBR1035
D2, D3
†
1N4001
C2
0.068
C3
390µF
16V
R1
4.043k
0.1%
R2
1.24k
0.1%
R3
220Ω
FB
GND V
C
CASE
L2
2µH, 5A**
C1
220µF
16V
+
+
C4
390µF
16V
V
OUT
5.3V ±1%
3.75A
V
IN
4.7V TO
5.3V
LT1268 • TA01
COILTRONICS CTX8-5-52
COILTRONICS CTX2-5-52
OPTIONAL. D2 AND D3 ARE USED TO INCREASE
UNDERVOLTAGE LOCKOUT FROM 2.7V TO ≈4V.
*
**
†
+
C5
0.02
U
S
A
O
PP
L
IC
AT
I
■
High Efficiency Boost Converter
■
PC Power Supply with Multiple Outputs
■
Battery Upconverter
■
Negative-to-Positive Converter