LT1170/LT1171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
FEATURES
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DESCRIPTION
The LT
®
1170/LT1171/LT1172 are monolithic high power-
switching regulators. They can be operated in all standard
switching configurations including buck, boost, flyback,
forward, inverting and “Cuk.” A high current, high efficiency
switch is included on the die along with all oscillator, con-
trol and protection circuitry. Integration of all functions
allows the LT1170/LT1171/LT1172 to be built in a standard
5-pin TO-3 or TO-220 power package as well as the 8-pin
packages (LT1172). This makes them extremely easy to
use and provides “bust proof” operation similar to that
obtained with 3-pin linear regulators.
The LT1170/LT1171/LT1172 operate with supply voltages
from 3V to 60V, and draw only 6mA quiescent current.
They can deliver load power up to 100W with no exter-
nal power devices. By utilizing current-mode switching
techniques, they provide excellent AC and DC load and
line regulation.
The LT1170/LT1171/LT1172 have many unique features not
found even on the vastly more difficult to use low power
control chips presently available. They use adaptive antisat
switch drive to allow very wide ranging load currents with
no loss in efficiency. An externally activated shutdown
mode reduces total supply current to 50μA typically for
standby operation.
L,
LT, LTC, LTM, Linear Technology, the Linear logo and SwitcherCAD are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
Wide Input Voltage Range: 3V to 60V
Low Quiescent Current: 6mA
Internal 5A Switch
(2.5A for LT1171, 1.25A for LT1172)
Shutdown Mode Draws Only 50μA Supply Current
Very Few External Parts Required
Self-Protected Against Overloads
Operates in Nearly All Switching Topologies
Flyback-Regulated Mode Has Fully Floating Outputs
Comes in Standard 5-Pin Packages
LT1172 Available in 8-Pin MiniDIP and
Surface Mount Packages
Can Be Externally Synchronized
APPLICATIONS
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Logic Supply 5V at 10A
5V Logic to ±15V Op Amp Supply
Battery Upconverter
Power Inverter (+ to –) or (– to +)
Fully Floating Multiple Outputs
USER NOTE:
This data sheet is only intended to provide specifications, graphs, and a general functional
description of the LT1170/LT1171/LT1172. Application circuits are included to show the capability
of the LT1170/LT1171/LT1172. 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 LT1170/LT1171/LT1172 by factoring in
the higher frequency. A CAD design program called SwitcherCAD
®
is also available.
TYPICAL APPLICATION
Boost Converter (5V to 12V)
5V
L1**
50μH
100
Maximum Output Power*
OUTPUT
FILTER
80
POWER (W)
**
BUCK-BOOST
V
O
= 30V
BOOST
FLYBACK
40
LT1170
*
ROUGH GUIDE ONLY. BUCK MODE
P
OUT
= (5A)(V
OUT
)
SPECIAL TOPOLOGIES DELIVER
MORE POWER.
** DIVIDE VERTICAL POWER SCALE
BY TWO FOR LT1171, BY FOUR
FOR LT1172.
LT1170/1/2 TA02
L2
10μH
C3
100μF
V
IN
V
SW
D1
MBR330
+
+
LT1170
C3*
100μF
GND
V
C
R3
1k
C1
1μF
*REQUIRED IF INPUT LEADS
2"
FB
C2
1000μF
R1
10.7k
1%
12V
1A
60
20
R2
1.24k
1%
BUCK-BOOST
V
O
= 5V
0
0
10
30
20
INPUT VOLTAGE (V)
40
50
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
1170/1/2 TA01
117012fg
1
LT1170/LT1171/LT1172
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Supply Voltage
LT1170/LT1171/LT1172HV (Note 2) .......................60V
LT1170/LT1171/LT1172 (Note 2)............................40V
Switch Output Voltage
LT1170/LT1171/LT1172HV .....................................75V
LT1170/LT1171/LT1172 .........................................65V
LT1172S8 ..............................................................60V
Feedback Pin Voltage (Transient, 1ms) ................... ±15V
Storage Temperature Range .................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec .................... 300°C
Operating Junction Temperature Range
LT1170M/LT1171M
(OBSOLETE)
....... –55°C to 150°C
LT1172M ............................................ –55°C to 125°C
LT1170/LT1171/LT1172HVC,
LT1170/LT1171/LT1172C (Oper.)............. 0°C to 100°C
LT1170/LT1171/LT1172HVC
LT1170/LT1171/LT1172C (Sh. Ckt.) ........ 0°C to 125°C
LT1170/LT1171/LT1172HVI,
LT1170/LT1171/LT1172I (Oper.) .......... –40°C to 100°C
LT1170/LT1171/LT1172HVI,
LT1170/LT1171/LT1172I (Sh. Ckt.)...... –40°C to 125°C
PIN CONFIGURATION
BOTTOM VIEW
V
SW
TOP VIEW
GND 1
V
C
2
FB 3
NC* 4
J8 PACKAGE
8-LEAD CERDIP
T
JMAX
= 125°C,
θ
JA
= 100°C/W
* Do not connect Pin 4 of the LT1172 DIP or SO to external
circuitry. This pin may be active in future revisions.
8
7
6
5
E2
V
SW
E1
V
IN
V
IN
K PACKAGE
4-LEAD TO-3 METAL CAN
LT1170MK: T
JMAX
= 150°C,
θ
JC
= 2°C/W,
θ
JA
= 35°C/W
LT1170CK: T
JMAX
= 100°C,
θ
JC
= 2°C/W,
θ
JA
= 35°C/W
LT1171MK: T
JMAX
= 150°C,
θ
JC
= 4°C/W,
θ
JA
= 35°C/W
LT1171CK: T
JMAX
= 100°C,
θ
JC
= 4°C/W,
θ
JA
= 35°C/W
LT1172MK: T
JMAX
= 150°C,
θ
JC
= 8°C/W,
θ
JA
= 35°C/W
LT1172CK: T
JMAX
= 100°C,
θ
JC
= 8°C/W,
θ
JA
= 35°C/W
Based on continuous operation.
T
JMAX
= 125°C for intermittent fault conditions.
1
4
2
3
V
C
CASE
IS GND
FB
GND 1
V
C
2
FB 3
NC* 4
N8 PACKAGE
8-LEAD PDIP
TOP VIEW
8
7
6
5
E2
V
SW
E1
V
IN
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 100°C,
θ
JA
= 100°C/W (N)
T
JMAX
= 100°C,
θ
JA
= 120°C/W to 150°C/W
depending on board layout (S)
* Do not connect Pin 4 of the LT1172 DIP or SO to external
circuitry. This pin may be active in future revisions.
OBSOLETE
TOP VIEW
FRONT VIEW
5
4
3
2
1
Q PACKAGE
5-LEAD DD
T
JMAX
= 100°C,
θ
JA
= *°C/W
*
θ
will vary from approximately 25°C/W with 2.8 sq.
in. of 1oz. copper to 45°C/W with 0.20 sq. in. of 1oz.
copper. Somewhat lower values can be obtained with
additional copper layers in multilayer boards.
V
IN
V
SW
GND
FB
V
C
NC 1
NC 2
GND 3
V
C
4
FB 5
NC 6
NC 7
NC 8
16 NC
15 NC
14 E2
13 V
SW
12 E1
11 V
IN
10 NC
9
NC
FRONT VIEW
5
4
3
2
1
T PACKAGE
5-LEAD PLASTIC TO-220
LT1170CT/LT1170HVCT: T
JMAX
=100°C,
θ
JC
= 2°C/W,
θ
JA
= 75°C/W
LT1171CT/LT1171HVCT: T
JMAX
=100°C,
θ
JC
= 4°C/W,
θ
JA
= 75°C/W
LT1172CT/LT1172HVCT: T
JMAX
=100°C,
θ
JC
= 8°C/W,
θ
JA
= 75°C/W
Based on continuous operation.
T
JMAX
= 125°C for intermittent fault conditions.
V
IN
V
SW
GND
FB
V
C
SW PACKAGE
16-LEAD PLASTIC SO WIDE
T
JMAX
= 100°C,
θ
JA
= 150°C/W
Based on continuous operation.
T
JMAX
= 125°C for intermittent fault conditions.
117012fg
2
LT1170/LT1171/LT1172
ORDER INFORMATION
LEAD FREE FINISH
LT1172MJ8#PBF
LT1172CJ8#PBF
(OBSOLETE)
LT1170MK#PBF
(OBSOLETE)
LT1170CK#PBF
(OBSOLETE)
LT1171MK#PBF
(OBSOLETE)
LT1171CK#PBF
(OBSOLETE)
LT1172MK#PBF
(OBSOLETE)
LT1172CK#PBF
(OBSOLETE)
LT1172CN8#PBF
LT1172IN8#PBF
LT1172CS8#PBF
LT1172IS8#PBF
LT1170CQ#PBF
LT1170IQ#PBF
LT1170HVCQ#PBF
LT1171CQ#PBF
LT1171IQ#PBF
LT1171HVCQ#PBF
LT1171HVIQ#PBF
LT1172CQ#PBF
LT1172HVCQ#PBF
LT1172HVIQ#PBF
LT1172CSW#PBF
LT1170CT#PBF
LT1170IT#PBF
LT1170HVCT#PBF
LT1170HVIT#PBF
LT1171CT#PBF
LT1171IT#PBF
LT1171HVCT#PBF
LT1171HVIT#PBF
LT1172CT#PBF
LT1172HVCT#PBF
TAPE AND REEL
LT1172MJ8#TRPBF
LT1172CJ8#TRPBF
LT1170MK#TRPBF
LT1170CK#TRPBF
LT1171MK#TRPBF
LT1171CK#TRPBF
LT1172MK#TRPBF
LT1172CK#TRPBF
LT1172CN8#TRPBF
LT1172IN8#TRPBF
LT1172CS8#TRPBF
LT1172IS8#TRPBF
LT1170CQ#TRPBF
LT1170IQ#TRPBF
LT1170HVCQ#TRPBF
LT1171CQ#TRPBF
LT1171IQ#TRPBF
LT1171HVCQ#TRPBF
LT1171HVIQ#TRPBF
LT1172CQ#TRPBF
LT1172HVCQ#TRPBF
LT1172HVIQ#TRPBF
LT1172CSW#TRPBF
LT1170CQ#TRPBF
LT1170IT#TRPBF
LT1170HVCT#TRPBF
LT1170HVIT#TRPBF
LT1171CT#TRPBF
LT1171IT#TRPBF
LT1171HVCT#TRPBF
LT1171HVIT#TRPBF
LT1172CT#TRPBF
LT1172HVCT#TRPBF
1172
1172I
PART MARKING
PACKAGE DESCRIPTION
8-Lead CERDIP
8-Lead CERDIP
4-Lead TO-3 Metal Can
4-Lead TO-3 Metal Can
4-Lead TO-3 Metal Can
4-Lead TO-3 Metal Can
4-Lead TO-3 Metal Can
4-Lead TO-3 Metal Can
8-Lead PDIP or 8-Lead Plastic SO
8-Lead PDIP or 8-Lead Plastic SO
8-Lead PDIP or 8-Lead Plastic SO
8-Lead PDIP or 8-Lead Plastic SO
5-Lead DD
5-Lead DD
5-Lead DD
5-Lead DD
5-Lead DD
5-Lead DD
5-Lead DD
5-Lead DD
5-Lead DD
5-Lead DD
16-Lead Plastic SO Wide
5-Lead Plastic TO-220
5-Lead Plastic TO-220
5-Lead Plastic TO-220
5-Lead Plastic TO-220
5-Lead Plastic TO-220
5-Lead Plastic TO-220
5-Lead Plastic TO-220
5-Lead Plastic TO-220
5-Lead Plastic TO-220
5-Lead Plastic TO-220
TEMPERATURE RANGE
–55°C to 125°C
0°C to 100°C
–55°C to 125°C
0°C to 100°C
–55°C to 125°C
0°C to 100°C
–55°C to 125°C
0°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
–40°C to 100°C
0°C to 100°C
0°C to 100°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
117012fg
3
LT1170/LT1171/LT1172
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
V
REF
I
B
g
m
Reference Voltage
Feedback Input Current
Error Amplifier Transconductance
Error Amplifier Source or Sink Current
Error Amplifier Clamp Voltage
Reference Voltage Line Regulation
A
V
I
Q
Error Amplifier Voltage Gain
Minimum Input Voltage (Note 5)
Supply Current
Control Pin Threshold
Normal/Flyback Threshold on Feedback Pin
V
FB
Flyback Reference Voltage (Note 5)
Change in Flyback Reference Voltage
Flyback Reference Voltage Line Regulation
(Note 5)
Flyback Amplifier Transconductance (g
m
)
Flyback Amplifier Source and Sink Current
BV
Output Switch Breakdown Voltage
I
FB
= 50μA
0.05 ≤ I
FB
≤ 1mA
I
FB
= 50μA
7V ≤ V
IN
≤ V
MAX
ΔI
C
= ±10μA
V
C
= 0.6V
I
FB
= 50μA
3V ≤ V
IN
≤ V
MAX
,
I
SW
= 1.5mA
LT1170
LT1171
LT1172
LT1170
LT1171
LT1172
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
T
J
≥ 25°C
T
J
< 25°C
T
J
≥ 25°C
T
J
< 25°C
T
J
≥ 25°C
T
J
< 25°C
l
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l
l
l
l
l
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
C
= 0.5V, V
FB
= V
REF
, output pin open, unless otherwise noted.
CONDITIONS
Measured at Feedback Pin
V
C
= 0.8V
V
FB
= V
REF
ΔI
C
= ±25μA
V
C
= 1.5V
Hi Clamp, V
FB
= 1V
Lo Clamp, V
FB
= 1.5V
3V ≤ V
IN
≤ V
MAX
V
C
= 0.8V
0.9V ≤ V
C
≤ 1.4V
l
l
l
l
l
l
MIN
1.224
1.214
TYP
1.244
1.244
350
MAX
1.264
1.274
750
1100
6000
7000
350
400
2.30
0.52
0.03
UNITS
V
V
nA
nA
μmho
μmho
μA
μA
V
V
%/V
V/V
3000
2400
150
120
1.80
0.25
4400
200
0.38
500
800
2.6
6
3.0
9
1.08
1.25
0.54
17.6
18.0
9
0.03
650
70
70
V
mA
V
V
V
V
V
V
%/V
μmho
mA
mA
V
V
V
3V ≤ V
IN
≤ V
MAX
, V
C
= 0.6V
Duty Cycle = 0
l
0.8
0.6
0.4
15.0
14.0
4.5
0.9
0.45
16.3
6.8
0.01
150
Source
Sink
LT1170/LT1171/LT1172
LT1170HV/LT1171HV/LT1172HV
LT1172S8
l
l
l
l
l
l
l
l
300
32
40
90
90
80
0.15
0.30
0.60
8
4
2
15
25
65
75
60
V
SAT
Output Switch “On” Resistance (Note 3)
0.24
0.50
1.00
Ω
Ω
Ω
A/V
A/V
A/V
Control Voltage to Switch Current
Transconductance
I
LIM
Switch Current Limit (LT1170)
5
5
4
2.5
2.5
2.0
1.25
1.25
1.00
25
88
85
100
10
11
10
5.0
5.5
5.0
3.0
3.5
2.5
35
112
115
A
A
A
A
A
A
A
A
A
mA/A
kHz
kHz
117012fg
(LT1171)
(LT1172)
ΔI
IN
ΔI
SW
f
Supply Current Increase During Switch
On-Time
Switching Frequency
l
4
LT1170/LT1171/LT1172
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
DC
MAX
Maximum Switch Duty Cycle
Shutdown Mode
Supply Current
Shutdown Mode
Threshold Voltage
Flyback Sense Delay Time (Note 5)
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
Minimum effective switch “on” time for the LT1170/LT1171/
LT1172 (in current limit only) is ≈ 0.6μs. This limits the maximum safe
input voltage during an output shorted condition. Buck mode and inverting
mode input voltage during an output shorted condition is limited to:
3V ≤ V
IN
≤ V
MAX
V
C
= 0.05V
3V ≤ V
IN
≤ V
MAX
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 15V, V
C
= 0.5V, V
FB
= V
REF
, output pin open, unless otherwise noted.
CONDITIONS
l
MIN
85
TYP
92
100
MAX
97
250
250
300
UNITS
%
μA
mV
mV
μs
100
50
150
1.5
(
R
)
I
L
+
Vf
V
IN
(max, output shorted) =
15V
+
(
t
)
(
f
)
buck and inverting mode
R = Inductor DC resistance
I
L
= 10A for LT1170, 5A for LT1171, and 2.5A for LT1172
Vf = Output catch diode forward voltage at I
L
t = 0.6μs, f = 100kHz switching frequency
Maximum input voltage can be increased by increasing R or Vf.
External current limiting such as that shown in AN19, Figure 39, will
provide protection up to the full supply voltage rating. C1 in Figure 39
should be reduced to 200pF
.
(
)
Transformer designs will tolerate much higher input voltages because
leakage inductance limits rate of rise of current in the switch. These
designs must be evaluated individually to assure that current limit is well
controlled up to maximum input voltage.
Boost mode designs are never protected against output shorts because
the external catch diode and inductor connect input to output.
Note 3:
Measured with V
C
in hi clamp, V
FB
= 0.8V. I
SW
= 4A for LT1170,
2A for LT1171, and 1A for LT1172.
Note 4:
For duty cycles (DC) between 50% and 80%, minimum guaranteed
switch current is given by I
LIM
= 3.33 (2 – DC) for the LT1170, I
LIM
= 1.67
(2 – DC) for the LT1171, and I
LIM
= 0.833 (2 – DC) for the LT1172.
Note 5:
Minimum input voltage for isolated flyback mode is 7V. V
MAX
= 55V
for HV grade in fully isolated mode to avoid switch breakdown.
117012fg
5
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