1
LT1170/LT1171/LT1172
117012ff
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
Wide Input Voltage Range: 3V to 60V
Low Quiescent Current: 6mA
I
nternal 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
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 effi-
ciency switch is included on the die along with all oscilla-
tor, control 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 volt-
ages from 3V to 60V, and draw only 6mA quiescent
current. They can deliver load power up to 100W with no
external power devices. By utilizing current-mode switch-
ing 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 cur-
rents with no loss in efficiency. An externally activated
shutdown mode reduces total supply current to 50µA
typically for standby operation.
Boost Converter (5V to 12V) Maximum Output Power*
, LTC and LT are registered trademarks of Linear Technology Corporation.
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
TM
is also available.
SwitcherCAD is a trademark of Linear Technology Corporation.
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
1170/1/2 TA01
D1
MBR330
C2
1000µF
C1
1µF
R1
10.7k
1%
R2
1.24k
1%
LT1170
GND
V
IN
5V
R3
1k
*REQUIRED IF INPUT LEADS 2" ** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
V
SW
FB
V
C
OUTPUT
FILTER
L2
10µH
L1**
50µH
C3
100µF
12V
1A
C3*
100µF
+
+
INPUT VOLTAGE (V)
0
POWER (W) **
100
80
60
40
20
040
LT1170/1/2 TA02
10 20 30 50
*ROUGH GUIDE ONLY. BUCK MODE
POUT = (5A)(VOUT)
SPECIAL TOPOLOGIES DELIVER
MORE POWER.
** DIVIDE VERTICAL POWER SCALE
BY TWO FOR LT1171, BY FOUR
FOR LT1172.
BOOST
BUCK-BOOST
VO = 30V
FLYBACK
BUCK-BOOST
VO = 5V
LT1170
2
LT1170/LT1171/LT1172
117012ff
*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.
LT1172CN8
LT1172IN8
LT1172CS8
LT1172IS8
S8 PART MARKING
Supply Voltage
LT1170/71/72HV (Note 2) .................................. 60V
LT1170/71/72 (Note 2)....................................... 40V
Switch Output Voltage
LT1170/71/72HV ................................................ 75V
LT1170/71/72..................................................... 65V
LT1172S8........................................................... 60V
Feedback Pin Voltage (Transient, 1ms) ................ ±15V
Storage Temperature Range ............... 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
T
JMAX
= 100°C, θ
JA
= *°C/W
LT1170CQ
LT1170IQ
LT1170HVCQ
LT1171CQ
LT1171IQ
LT1171HVCQ
LT1171HVIQ
LT1172CQ
LT1172HVCQ
LT1172HVIQ
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) 1172
1172I
* Do not connect Pin 4 of the LT1172 DIP or SO to external
circuitry. This pin may be active in future revisions.
Operating Junction Temperature Range
LT1170/71/72M (OBSOLETE) .. –55°C to 150°C
LT1170/71/72HVC,
LT1170/71/72C (Oper.) .............. 0°C to 100°C
LT1170/71/72HVC
LT1170/71/72C (Sh. Ckt.) .......... 0°C to 125°C
LT1170/71/72HVI,
LT1170/71/72I (Oper.) .......... 40°C to 100°C
LT1170/71/72HVI,
LT1170/71/72I (Sh. Ckt.) ...... 40°C to 125°C
(Note 1)
T
JMAX
θ
JC
θ
JA
LT1170CT/LT1170HVCT 100°C2°C/W 75°C/W
LT1171CT/LT1171HVCT 100°C4°C/W 75°C/W
LT1172CT/LT1172HVCT 100°C8°C/W 75°C/W
Based on continuous operation.
T
JMAX
= 125°C for intermittent fault conditions.
LT1170CT
LT1170IT
LT1170HVCT
LT1170HVIT
LT1171CT
LT1171IT
LT1171HVCT
LT1171HVIT
LT1172CT
LT1172HVCT
T
JMAX
= 100°C, θ
JA
= 150°C/W
Based on continuous operation.
T
JMAX
= 125°C for intermittent fault conditions.
LT1172CSW
ORDER PART
NUMBER
Q PACKAGE
5-LEAD DD
V
IN
V
SW
GND
FB
V
C
FRONT VIEW
5
4
3
2
1
ORDER PART
NUMBER
TOP VIEW
SW PACKAGE
16-LEAD PLASTIC SO WIDE
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
NC
NC
GND
VC
FB
NC
NC
NC
NC
NC
E2
VSW
E1
VIN
NC
NC
T PACKAGE
5-LEAD PLASTIC TO-220
V
IN
V
SW
GND
FB
V
C
FRONT VIEW
5
4
3
2
1
C
I
PACKAGE/ORDER I FOR ATIO
UU
W
ABSOLUTE AXI U RATI GS
WWWU
ORDER PART
NUMBER
N8 PACKAGE
8-LEAD PDIP
1
2
3
4
8
7
6
5
TOP VIEW
GND
V
C
FB
NC*
E2
V
SW
E1
V
IN
S8 PACKAGE
8-LEAD PLASTIC SO
3
LT1170/LT1171/LT1172
117012ff
T
JMAX
θ
JC
θ
JA
LT1170MK 150°C2°C/W 35°C/W
LT1170CK 100°C2°C/W 35°C/W
LT1171MK 150°C4°C/W 35°C/W
LT1171CK 100°C4°C/W 35°C/W
LT1172MK 150°C8°C/W 35°C/W
LT1172CK 150°C8°C/W 35°C/W
Based on continuous operation.
T
JMAX
= 125°C for intermittent fault conditions.
LT1170MK
LT1170CK
LT1171MK
LT1171CK
LT1172MK
LT1172CK
ORDER PART
NUMBER
2
4
1
3
VSW VC
FB
CASE
IS GND
VIN
K PACKAGE
4-LEAD TO-3 METAL CAN
BOTTOM VIEW
PACKAGE/ORDER I FOR ATIO
UU
W
ORDER PART
NUMBER
LT1172MJ8
LT1172CJ8
T
JMAX
= 150°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.
1
2
3
4
8
7
6
5
TOP VIEW
GND
V
C
FB
NC*
E2
V
SW
E1
V
IN
J8 PACKAGE
8-LEAD CERDIP
OBSOLETE PACKAGES
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
REF
Reference Voltage Measured at Feedback Pin 1.224 1.244 1.264 V
V
C
= 0.8V 1.214 1.244 1.274 V
I
B
Feedback Input Current V
FB
= V
REF
350 750 nA
1100 nA
g
m
Error Amplifier I
C
= ±25µA 3000 4400 6000 µmho
Transconductance 2400 7000 µmho
Error Amplifier Source or V
C
= 1.5V 150 200 350 µA
Sink Current 120 400 µA
Error Amplifier Clamp Hi Clamp, V
FB
= 1V 1.80 2.30 V
Voltage Lo Clamp, V
FB
= 1.5V 0.25 0.38 0.52 V
Reference Voltage Line 3V V
IN
V
MAX
0.03 %/V
Regulation V
C
= 0.8V
A
V
Error Amplifier Voltage Gain 0.9V V
C
1.4V 500 800 V/V
Minimum Input Voltage (Note 5) 2.6 3.0 V
I
Q
Supply Current 3V V
IN
V
MAX
, V
C
= 0.6V 6 9 mA
Control Pin Threshold Duty Cycle = 0 0.8 0.9 1.08 V
0.6 1.25 V
Normal/Flyback Threshold 0.4 0.45 0.54 V
on Feedback Pin
V
FB
Flyback Reference Voltage I
FB
= 50µA 15.0 16.3 17.6 V
(Note 5) 14.0 18.0 V
Change in Flyback Reference 0.05 I
FB
1mA 4.5 6.8 9 V
Voltage
Flyback Reference Voltage I
FB
= 50µA 0.01 0.03 %/V
Line Regulation (Note 5) 7V V
IN
V
MAX
Flyback Amplifier I
C
= ±10µA 150 300 650 µmho
Transconductance (g
m
)
The denotes the specifications which apply over the full operating tem-
perature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
4
LT1170/LT1171/LT1172
117012ff
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Flyback Amplifier Source V
C
= 0.6V Source 15 32 70 µA
and Sink Current I
FB
= 50µASink 25 40 70 µA
BV Output Switch Breakdown 3V V
IN
V
MAX
, LT1170/LT1171/LT1172 65 90 V
Voltage I
SW
= 1.5mA LT1170HV/LT1171HV/LT1172HV 75 90 V
LT1172S8 60 80 V
V
SAT
Output Switch LT1170 0.15 0.24
“On” Resistance (Note 3) LT1171 0.30 0.50
LT1172 0.60 1.00
Control Voltage to Switch LT1170 8 A/V
Current Transconductance LT1171 4 A/V
LT1172 2 A/V
I
LIM
Switch Current Limit (LT1170) Duty Cycle = 50% T
J
25°C510A
Duty Cycle = 50% T
J
< 25°C511A
Duty Cycle = 80% (Note 4) 410A
(LT1171) Duty Cycle = 50% T
J
25°C2.5 5.0 A
Duty Cycle = 50% T
J
< 25°C2.5 5.5 A
Duty Cycle = 80% (Note 4) 2.0 5.0 A
(LT1172) Duty Cycle = 50% T
J
25°C1.25 3.0 A
Duty Cycle = 50% T
J
< 25°C1.25 3.5 A
Duty Cycle = 80% (Note 4) 1.00 2.5 A
I
IN
Supply Current Increase 25 35 mA/A
I
SW
During Switch On-Time
f Switching Frequency 88 100 112 kHz
85 115 kHz
DC
MAX
Maximum Switch Duty Cycle 85 92 97 %
Shutdown Mode 3V V
IN
V
MAX
100 250 µA
Supply Current V
C
= 0.05V
Shutdown Mode 3V V
IN
V
MAX
100 150 250 mV
Threshold Voltage 50 300 mV
Flyback Sense Delay Time (Note 5) 1.5 µs
The denotes the specifications which apply over the full operating tem-
perature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.
ELECTRICAL CHARACTERISTICS
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.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of the device may be impaired.
Note 2: Minimum effective switch “on” time for the LT1170/71/72 (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:
V
IN
(max, output shorted) = 15V +
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.
(R)(I
L
) + Vf
(t)(f)
5
LT1170/LT1171/LT1172
117012ff
Switch Current Limit vs Duty Cycle*
TEMPERATURE (°C)
–75
MINIMUM INPUT VOLTAGE (V)
–25 25 50 150
1170/1/2 G02
–50 0 75 100 125
2.9
2.8
2.7
2.6
2.5
2.4
2.3
SWITCH CURRENT = 0A
SWITCH CURRENT = I
MAX
Minimum Input Voltage Switch Saturation Voltage
DUTY CYCLE (%)
0
SWITCH CURRENT (A)
16
12
8
4
040
1170/1/2 G01
20 30 50 60 70 80 90 100
25°C
125°C
–55°C
10
* DIVIDE VERTICAL SCALE BY TWO FOR
LT1171, BY FOUR FOR LT1172.
SWITCH CURRENT (A)*
0
SWITCH SATURATION VOLTAGE (V)
8
1170/1/2 G03
123
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
04567
25°C
150°C
–55°C
100°C
* DIVIDE CURRENT BY TWO FOR
LT1171, BY FOUR FOR LT1172.
TYPICAL PERFOR A CE CHARACTERISTICS
UW
INPUT VOLTAGE (V)
0
SUPPLY CURRENT (mA)
10 20 30 40
1170/1/2 G09
50
15
14
13
12
11
10
9
8
7
6
560
TJ = 25°C
NOTE THAT THIS CURRENT DOES NOT
INCLUDE DRIVER CURRENT, WHICH IS
A FUNCTION OF LOAD CURRENT AND
DUTY CYCLE.
90% DUTY CYCLE
50% DUTY CYCLE
10% DUTY CYCLE
0% DUTY CYCLE
* UNDER VERY LOW OUTPUT CURRENT CONDITIONS,
DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH
10% OR LESS.
Supply Current vs Input Voltage*
SUPPLY VOLTAGE (V)
0
SUPPLY CURRENT (µA)
10 20 30 40
160
140
120
100
80
60
40
20
050 60
1170/1/2 G07
VC = 50mV
VC = 0V
TJ = 25°C
Supply Current vs Supply Voltage
(Shutdown Mode) Driver Current* vs Switch Current
SWITCH CURRENT (A)
0
DRIVER CURRENT (mA)
123
160
140
120
100
80
60
40
20
045
1170/1/2 G08
T
J
= –55°C
T
J
= 25°C
* AVERAGE LT1170 POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT.
Reference Voltage vs Temperature
INPUT VOLTAGE (V)
0
REFERENCE VOLTAGE CHANGE (mV)
10 20 30 40
1170/1/2 G04
50
5
4
3
2
1
0
–1
–2
–3
–4
–5 60
T
J
= 150°C
T
J
= –55°CT
J
= 25°C
Line Regulation
TEMPERATURE (°C)
REFERENCE VOLTAGE (V)
1170/1/2 G05
1.250
1.248
1.246
1.244
1.242
1.240
1.238
1.236
1.234
–75 –25 25 50 150
–50 0 75 100 125
TEMPERATURE (°C)
FEEDBACK BIAS CURRENT (nA)
1170/1/2 G06
800
700
600
500
400
300
200
100
0
–75 –25 25 50 150
–50 0 75 100 125
Feedback Bias Current vs
Temperature
6
LT1170/LT1171/LT1172
117012ff
V
C
PIN VOLTAGE (mV)
0
SUPPLY CURRENT (µA)
200
180
160
140
120
100
80
60
40
20
040
1170/1/2 G10
10 20 30 50 60 70 80 90 100
T
J
= 150°C
–55°C T
J
125°C
Shutdown Mode Supply Current
TEMPERATURE (°C)
TRANSCONDUCTANCE (µmho)
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
1170/1/2 G11
–75 –25 25 50 150
–50 0 75 100 125
g
m
= I (V
C
PIN)
V (FB PIN)
Error Amplifier Transconductance VC Pin Characteristics
V
C
PIN VOLTAGE (V)
300
200
100
0
100
200
300
400
1170/1/2 G12
V
C
PIN CURRENT (µA)
0 2.0
0.5 1.0 1.5 2.5
V
FB
= 1.5V (CURRENT INTO V
C
PIN)
V
FB
= 0.8V (CURRENT OUT OF V
C
PIN)
T
J
= 25°C
TYPICAL PERFOR A CE CHARACTERISTICS
UW
TEMPERATURE (°C)
V
C
PIN VOLTAGE (mV)
1170/1/2 G16
400
350
300
250
200
150
100
50
0
–75 –25 25 50 150
–50 0 75 100 125
400
350
300
250
200
150
100
–50
0
V
C
PIN CURRENT (µA)
CURRENT (OUT OF V
C
PIN)
VOLTAGE
V
C
VOLTAGE IS REDUCED UNTIL
REGULATOR CURRENT DROPS
BELOW 300µA
JUNCTION TEMPERATURE (°C)
–75
TIME (µs)
–25 25 50 150
1170/1/2 G17
–50 0 75 100 125
2.2
2.0
1.8
1.6
1.4
1.2
1.0
Isolated Mode Flyback
Reference Voltage
TEMPERATURE (°C)
FLYBACK VOLTAGE (V)
1170/1/2 G18
23
22
21
20
19
18
17
16
15
–75 –25 25 50 150
–50 0 75 100 125
R
FB
= 500
R
FB
= 1k
R
FB
= 10k
Flyback Blanking TimeShutdown Thresholds
TEMPERATURE (°C)
IDLE SUPPLY CURRENT (mA)
11
10
9
8
7
6
5
4
3
2
1
1170/1/2 G13
–75 –25 25 50 150
–50 0 75 100 125
V
SUPPLY
= 60V
V
SUPPLY
= 3V
V
C
= 0.6V
Feedback Pin Clamp Voltage Switch “Off” Characteristics
Idle Supply Current vs
Temperature
FEEDBACK CURRENT (mA)
0
FEEDBACK VOLTAGE (mV)
500
450
400
350
300
250
200
150
100
50
00.4
1170/1/2 G14
0.1 0.2 0.3 0.5 0.6 0.7 0.8 0.9 1.0
–55°C
25°C
150°C
SWITCH VOLTAGE (V)
0
SWITCH CURRENT (µA)
1000
900
800
700
600
500
400
300
200
100
040
1170/1/2 G15
10 20 30 50 60 70 80 90 100
V
SUPPLY
= 55V
V
SUPPLY
= 3V
V
SUPPLY
= 15V
V
SUPPLY
= 40V
7
LT1170/LT1171/LT1172
117012ff
Normal/Flyback Mode Threshold on
Feedback Pin
TEMPERATURE (°C)
–50
FEEDBACK PIN VOLTAGE (mV)
500
490
480
470
460
450
440
430
420
410
400 050 75
1170/1/2 G20
–25 25 100 125 150
–24
–22
–20
–18
–16
–14
–12
–10
–8
–6
–4
FEEDBACK PIN CURRENT (µA)
FEEDBACK PIN CURRENT
(AT THRESHOLD)
FEEDBACK PIN VOLTAGE
(AT THRESHOLD)
Transconductance of Error
Amplifier
FREQUENCY (Hz)
1k
TRANSCONDUCTANCE (µmho)
7000
6000
5000
4000
3000
2000
1000
0
1000 10k 100k
1170/1/2 G19
1M 10M
–30
0
30
60
90
120
150
180
210
PHASE (DEG)
θ
g
m
TYPICAL PERFOR A CE CHARACTERISTICS
UW
1.24V
REF
1170/1/2 BD
ERROR
AMP
100kHz
OSC
2.3V
REG
V
IN
FB
+
+
SHUTDOWN
CIRCUIT
V
C
COMP
LOGIC DRIVER
ANTI-
SAT
FLYBACK
ERROR
AMP
16V
SWITCH
OUT
5A, 75V
SWITCH
0.02
(0.04
(0.16
LT1171)
LT1172) 0.16
CURRENT
AMP
GAIN 6
0.15V
ALWAYS CONNECT E1 TO THE GROUND PIN ON MINIDIP, 8- AND 16-PIN SURFACE MOUNT PACKAGES.
E1 AND E2 INTERNALLY TIED TO GROUND ON TO-3 AND TO-220 PACKAGES.
MODE
SELECT
E1
E2
(LT1170 AND LT1171 ONLY)
LT1172
BLOCK DIAGRA
W
8
LT1170/LT1171/LT1172
117012ff
The LT1170/LT1171/LT1172 are current mode switchers.
This means that switch duty cycle is directly controlled by
switch current rather than by output voltage. Referring to
the block diagram, the switch is turned “on” at the start of
each oscillator cycle. It is turned “off” when switch current
reaches a predetermined level. Control of output voltage is
obtained by using the output of a voltage sensing error
amplifier to set current trip level. This technique has
several advantages. First, it has immediate response to
input voltage variations, unlike ordinary switchers which
have notoriously poor line transient response. Second, it
reduces the 90° phase shift at midfrequencies in the
energy storage inductor. This greatly simplifies closed-
loop frequency compensation under widely varying input
voltage or output load conditions. Finally, it allows simple
pulse-by-pulse current limiting to provide maximum switch
protection under output overload or short conditions. A
low dropout internal regulator provides a 2.3V supply for
all internal circuitry on the LT1170/LT1171/LT1172. This
low dropout design allows input voltage to vary from 3V to
60V with virtually no change in device performance. A
100kHz oscillator is the basic clock for all internal timing.
It turns “on” the output switch via the logic and driver
circuitry. Special adaptive anti-sat circuitry detects onset
of saturation in the power switch and adjusts driver
current instantaneously to limit switch saturation. This
minimizes driver dissipation and provides very rapid turn-
off of the switch.
A 1.2V bandgap reference biases the positive input of the
error amplifier. The negative input is brought out for
output voltage sensing. This feedback pin has a second
function; when pulled low with an external resistor, it
programs the LT1170/LT1171/LT1172 to disconnect the
main error amplifier output and connects the output of the
flyback amplifier to the comparator input. The LT1170/
LT1171/LT1172 will then regulate the value of the flyback
pulse with respect to the supply voltage.* This flyback
pulse is directly proportional to output voltage in the
traditional transformer coupled flyback topology regula-
tor. By regulating the amplitude of the flyback pulse, the
output voltage can be regulated with no direct connection
between input and output. The output is fully floating up to
the breakdown voltage of the transformer windings. Mul-
tiple floating outputs are easily obtained with additional
OPERATIO
U
windings. A special delay network inside the LT1170/
LT1171/LT1172 ignores the leakage inductance spike at
the leading edge of the flyback pulse to improve output
regulation.
The error signal developed at the comparator input is
brought out externally. This pin (V
C
) has four different
functions. It is used for frequency compensation, current
limit adjustment, soft starting, and total regulator shut-
down. During normal regulator operation this pin sits at a
voltage between 0.9V (low output current) and 2.0V (high
output current). The error amplifiers are current output
(g
m
) types, so this voltage can be externally clamped for
adjusting current limit. Likewise, a capacitor coupled
external clamp will provide soft start. Switch duty cycle
goes to zero if the V
C
pin is pulled to ground through a
diode, placing the LT1170/LT1171/LT1172 in an idle mode.
Pulling the V
C
pin below 0.15V causes total regulator
shutdown, with only 50µA supply current for shutdown
circuitry biasing. See AN19 for full application details.
Extra Pins on the MiniDIP and Surface Mount Packages
The 8- and 16-pin versions of the LT1172 have the
emitters of the power transistor brought out separately
from the ground pin. This eliminates errors due to ground
pin voltage drops and allows the user to reduce switch
current limit 2:1 by leaving the second emitter (E2) discon-
nected. The first emitter (E1) should always be connected
to the ground pin. Note that switch “on” resistance doubles
when E2 is left open, so efficiency will suffer somewhat
when switch currents exceed 300mA. Also, note that chip
dissipation will actually
increase
with E2 open during
normal load operation, even though dissipation in current
limit mode will
decrease
. See “Thermal Considerations”
next.
Thermal Considerations When Using the MiniDIP and
SW Packages
The low supply current and high switch efficiency of the
LT1172 allow it to be used without a heat sink in most
applications when the TO-220 or TO-3 package is se-
lected. These packages are rated at 50°C/W and 35°C/W
respectively. The miniDIPs, however, are rated at 100°C/W
in ceramic (J) and 130°C/W in plastic (N).
*See note under block diagram.
9
LT1170/LT1171/LT1172
117012ff
OPERATIO
U
Care should be taken for miniDIP applications to ensure
that the worst case input voltage and load current condi-
tions do not cause excessive die temperatures. The follow-
ing formulas can be used as a rough guide to calculate
LT1172 power dissipation. For more details, the reader is
referred to Application Note 19 (AN19), “Efficiency Calcu-
lations” section.
Average supply current (including driver current) is:
I
IN
6mA + I
SW
(0.004 + DC/40)
I
SW
= switch current
DC = switch duty cycle
Switch power dissipation is given by:
P
SW
= (I
SW
)
2
• (R
SW
)(DC)
R
SW
= LT1172 switch “on” resistance (1 maximum)
Total power dissipation is the sum of supply current times
input voltage plus switch power:
P
D(TOT)
= (I
IN
)(V
IN
) + P
SW
In a typical example, using a boost converter to generate
12V at 0.12A from a 5V input, duty cycle is approximately
60%, and switch current is about 0.65A, yielding:
I
IN
= 6mA + 0.65(0.004 + DC/40) = 18mA
P
SW
= (0.65)
2
• (1)(0.6) = 0.25W
P
D(TOT)
= (5V)(0.018A) + 0.25 = 0.34W
Temperature rise in a plastic miniDIP would be 130°C/W
times 0.34W, or approximately 44°C. The maximum am-
bient temperature would be limited to 100°C (commercial
temperature limit) minus 44°C, or 56°C.
In most applications, full load current is used to calculate
die temperature. However, if overload conditions must
also be accounted for, four approaches are possible. First,
if loss of regulated output is acceptable under overload
conditions, the internal
thermal limit
of the LT1172 will
protect the die in most applications by shutting off switch
current.
Thermal limit is not a tested parameter
, however,
and should be considered only for noncritical applications
with temporary overloads. A second approach is to use the
larger TO-220 (T) or TO-3 (K) package which, even without
a heat sink, may limit die temperatures to safe levels under
overload conditions. In critical situations, heat sinking of
these packages is required; especially if overload condi-
tions must be tolerated for extended periods of time.
The third approach for lower current applications is to
leave the second switch emitter (miniDIP only) open. This
increases switch “on” resistance by 2:1, but reduces
switch current limit by 2:1 also, resulting in a net 2:1
reduction in I
2
R switch dissipation under current limit
conditions.
The fourth approach is to clamp the V
C
pin to a voltage less
than its internal clamp level of 2V. The LT1172 switch
current limit is zero at approximately 1V on the V
C
pin and
2A at 2V on the V
C
pin. Peak switch current can be
externally clamped between these two levels with a diode.
See AN19 for details.
LT1170/LT1171/LT1172 Synchronizing
The LT1170/LT1171/LT1172 can be externally synchro-
nized in the frequency range of 120kHz to 160kHz. This is
accomplished as shown in the accompanying figures.
Synchronizing occurs when the V
C
pin is pulled to ground
with an external transistor. To avoid disturbing the DC
characteristics of the internal error amplifier, the width of
the synchronizing pulse should be under 0.3µs. C2 sets
the pulse width at 0.2µs. The effect of a synchronizing
pulse on the LT1170/LT1171/LT1172 amplifier offset can
be calculated from:
KT = 26mV at 25°C
q
t
S
= pulse width
f
S
= pulse frequency
I
C
=V
C
source current (200µA)
V
C
= operating V
C
voltage (1V to 2V)
R3 = resistor used to set mid-frequency “zero” in
frequency compensation network.
V
KT
qtfI V
R
I
OS
SSC C
C
=
()()
+
3
10
LT1170/LT1171/LT1172
117012ff
Synchronizing with MOS Transistor
Synchronizing with Bipolar Transistor
1170/1/2 OP01
C2
39pF R1
3k
R2
2.2k
LT1170
GND
V
IN
V
C
C1
R3 2N2369
FROM 5V
LOGIC
1170/1/2 OP02
D1
1N4158
R2
2.2k
LT1170
GND
V
IN
V
C
C1
R3
FROM 5V
LOGIC
C2
100pF
D2
1N4158
* SILICONIX OR EQUIVALENT
VN2222*
OPERATIO
U
With t
S
= 0.2µs, f
S
= 150kHz, V
C
= 1.5V, and R3 = 2k, offset
voltage shift is 3.8mV. This is not particularly bother-
some, but note that high offsets could result if R3 were
reduced to a much lower value. Also, the synchronizing
transistor must sink higher currents with low values of R3,
so larger drives may have to be used. The transistor must
be capable of pulling the V
C
pin to within 200mV of ground
to ensure synchronizing.
TYPICAL APPLICATIO S
U
Flyback Converter
1170/1/2 TA03
D1
C1
2000µF
C4*
100µF
C2
0.15µF
R1
3.74k
R2
1.24k
V
IN
20V TO 30V
R3
1.5k
*REQUIRED IF INPUT LEADS 2"
LT1170
V
IN
V
SW
FB
V
C
OPTIONAL
FILTER
L2
5µH
C4
100µF
V
OUT
5V
6A
V
SNUB
CLAMP TURN-ON
SPIKE
PRIMARY FLYBACK VOLTAGE =
LT1170 SWITCH VOLTAGE
AREA “a” = AREA “b” TO MAINTAIN
ZERO DC VOLTS ACROSS PRIMARY
SECONDARY VOLTAGE
AREA “c” = AREA “d” TO MAINTAIN
ZERO DC VOLTS ACROSS SECONDARY
PRIMARY CURRENT
SECONDARY CURRENT
LT1170 SWITCH CURRENT
SNUBBER DIODE CURRENT
V
OUT
+ Vf
N
0V
V
IN
a
b
0V
c
d
V
OUT
+ V
f
N • V
IN
II
PRI
0I
PRI
/N
I
PRI
I
PRI
t =
(I
PRI
)(L
L
)
V
SNUB
0
0
0
1
N* = 1/3
N*
D3
25V
1W
D2
MUR110
GND
+
+
11
LT1170/LT1171/LT1172
117012ff
LCD Contrast Supply
C4
0.047µF
V
OUT
10V TO –26V
1170/1/2 TA04
R3
15k
OPTIONAL
SHUTDOWN
R2
100k R1
200k
C1
1µF
TANTALUM
D1
1N914
C3
0.0047µF
C2***
2µF
TANTALUM
D2
VN2222
5V* L1**
50µHV
BAT
*
3V TO 20V
V
IN
V
C
FB
V
SW
LT1172
E2
E1
GND
D3
*
**
***
D2, D3 = ER82.004 600mA SCHOTTKY. OTHER FAST SWITCHING TYPES MAY BE USED.
V
IN
AND BATTERY MAY BE TIED TOGETHER. MAXIMUM VALUE FOR V
BAT
IS EQUAL TO THE NEGATIVE OUTPUT+ 1V. WITH HIGHER
BATTERY VOLTAGES, HIGHEST EFFICIENCY IS OBTAINED BY RUNNING THE LT1172 V
IN
PIN FROM 5V. SHUTTING OFF THE 5V SUPPLY
WILL AUTOMATICALLY TURN OFF THE LT1172. EFFICIENCY IS ABOUT 80% AT I
OUT
= 25mA.
R1, R2, R3 ARE MADE LARGE TO MINIMIZE BATTERY DRAIN IN SHUTDOWN, WHICH IS APPROXIMATELY V
BAT
/(R1 + R2 + R3).
FOR HIGH EFFICIENCY, L1 SHOULD BE MADE ON A FERRITE OR MOLYPERMALLOY CORE. PEAK INDUCTOR CURRENTS ARE ABOUT
600mA AT P
OUT
= 0.7. INDUCTOR SERIES RESISTANCE SHOULD BE LESS THAN 0.4 FOR HIGH EFFICIENCY.
OUTPUT RIPPLE IS ABOUT 200mV
P-P
TO 400mV
P-P
WITH C2 = 2µF TANTALUM. IF LOWER RIPPLE IS DESIRED, INCREASE C2, OR ADD
A 10 , 1µF TANTALUM OUTPUT FILTER.
+
+
Driving High Voltage FET
(for Off-Line Applications, See AN25) External Current Limit
1170/1/2 TA05
V
IN
V
SW
LT1170
GND
10V TO
20V
D1
+
D
GQ1
1170/1/2 TA06
V
X
D1
LT1170
GND
R2
2V V
C
R1
500
(Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.)
TYPICAL APPLICATIO S
U
12
LT1170/LT1171/LT1172
117012ff
Negative-to-Positive Buck-Boost Converter
(Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.)
Negative Buck Converter
External Current Limit
C4*
100µF
V
OUT
12V
2A
1170/1/2 TA07
R3
2.2k
C2
1000µF
D1
C1
0.22µF
Q1
V
IN
V
C
FB
V
SW
LT1170
GND
OPTIONAL
INPUT FILTER
L3
V
IN
20V
REQUIRED IF INPUT LEADS 2"
PULSE ENGINEERING 92114, COILTRONICS 50-2-52
*
**
R2
1.24k
L1**
50µH
OPTIONAL
OUTPUT
FILTER
C3
L2
R1
11.3k
THIS CIRCUIT IS OFTEN USED TO CONVERT –48V TO 5V. TO GUARANTEE
FULL SHORT-CIRCUIT PROTECTION, THE CURRENT LIMIT CIRCUIT SHOWN
IN AN19, FIGURE 39, SHOULD BE ADDED WITH C1 REDUCED TO 200pF.
++
1170/1/2 TA08
R2
C2
VIN
VCFB
VSW
LT1170
GND
VIN
NOTE THAT THE LT1170
GND PIN IS NO LONGER
COMMON TO VIN.
R1
1k
+
C1
1000pF
Q1
RS
C3*
100µF
5.2V
4.5A
1170/1/2 TA09
R3
L1**
50µH
R1
4.64k
C2
1000µF
D1
C1
Q1
2N3906
VIN
VC
FB
VSW
LT1170
GND
OPTIONAL
INPUT FILTER
L3
VIN
20V
LOAD
REQUIRED IF INPUT LEADS 2"
PULSE ENGINEERING 92114
COILTRONICS 50-2-52
*
**
R2
1.24k
R4
12k
L2
4µH
OPTIONAL
OUTPUT
FILTER
C4
200µF
+
+
+
TYPICAL APPLICATIO S
U
13
LT1170/LT1171/LT1172
117012ff
High Efficiency Constant Current Charger
Backlight CCFL Supply (see AN45 for details)
D2
MBR340
1170/1/2 TA11
INPUT VOLTAGE
> V
BAT
+ 2V < 35V
C2
2.2µF
35V
TANTALUM
R7
22k R8
1k
C3
0.47µF
V
+
V
R4
1k
C4
200µF
25V BATTERY
2V TO 25V
L2*
10µH, 1A
L1
100µH, 1A
R5
0.05
R3
25k
R2
1k
RUN = 0V
SHUTDOWN = 5V
* L2 REDUCES RIPPLE CURRENT INTO
THE BATTERY BY ABOUT 20:1.
IT MAY BE OMITTED IF DESIRED.
I = 1.244V • R4
R3 • R5 = 1A AS SHOWN
CHRG
R6
78k
V
IN
C
VFB
V
SW
GND
D1
1N5819
C4
0.01µF
LT1006
+
+
LT1171
C1
200µF
35V
1A
2N3904
+ + +
+
GND
2µF
1170/1/2 TA12
D1
1N914
33pF
3kV
10µF
TANT
R3
10k
50k
INTENSITY
ADJUST
1N5818 L1**
300µH
INPUT VOLTAGE
4.5V TO 20V
Q1,Q2 = BCP56 OR MPS650/561
COILTRONICS CTX300-4
SUMIDA 6345-020 OR COILTRONICS 110092-1
A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY.
*
**
***
C6
1 F
µ
R1
560
1k
LT1172
IN
V
V
C
V
SW
E2
E1
D2
1N914
LAMP
FB
L2***
0.02µF
A
B
Q1*
Q2*
+
+
TYPICAL APPLICATIO S
U
Positive-to-Negative Buck-Boost Converter
C4
1µF
VIN
10V TO
30V
1170/1/2 TA10
R3
5k
C5
100µF*
D3
1N4001
C2
0.1µF
VIN
VCFB
VSW
LT1170
GND
VOUT
–12V
2A
REQUIRED IF INPUT LEADS 2"
PULSE ENGINEERING 92114, COILTRONICS 50-2-52
*
**
R2
1.24k
L1**
50µH
R5
470, 1W
TO AVOID STARTUP PROBLEMS FOR INPUT VOLTAGES
BELOW 10V, CONNECT ANODE OF D3 TO VIN, AND
REMOVE R5. C1 MAY BE REDUCED FOR LOWER OUTPUT
CURRENTS. C1 (500µF)(IOUT).
FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO
0.3µF, AND REDUCE R6 TO 100.
C3
2µF
D2
1N914 R4
47
C1
1000µF
D1
R6
470
R1
10.7k
+
+
+ +
14
LT1170/LT1171/LT1172
117012ff
Positive Buck Converter
Negative Boost Regulator
Driving High Voltage NPN
C5*
100µF
V
IN
1170/1/2 TA13
R3
470
5V, 4.5A
D2
1N914
C1
1µF
V
IN
V
C
FB
V
SW
LT1170
GND
REQUIRED IF INPUT LEADS 2"
PULSE ENGINEERING 92114
COILTRONICS 50-2-52
*
**
R1
3.74k
L1**
50µH
R4
10
C3
2.2µF
D1
r
R2
1.24k
C2
1µF
C4
1000µF100mA
MINIMUM
D3
OPTIONAL
OUTPUT
FILTER
C5
200µF
L2
4µH
+
+
+
+
C4*
470µF
1170/1/2 TA14
R3
3.3k
C3
10µF
D1
C2
0.22µF
V
IN
V
C
FB
LT1170
GND
V
IN
–15V
REQUIRED IF INPUT LEADS 2"
*
R2
1.24k
D2
R1
27k
V
SW
L1
50µH
C1
1000µF
R
O
(MINIMUM
LOAD)
V
OUT
28V, 1A
+
+ +
1170/1/2 TA15
D2
C1
SETS I
B
(ON)
SETS I
B
(OFF)
*
**
R2**
V
IN
V
SW
LT1170
GND
D1
Q1
R1*
TYPICAL APPLICATIO S
U
15
LT1170/LT1171/LT1172
117012ff
High Efficiency 5V Buck Converter
Forward Converter
1170/1/2 TA16
C1
2000µF
C3
R4
R2
1.24k
V
IN
20V TO 30V
R3
LT1170
V
IN
V
SW
FB
V
C
1N
D3
L1
25µH
C4
R6
330
R5
1
C2 M
D2
D1 V
OUT
5V, 6A
T1
Q1
D4
R1
3.74k
GND
+
+
VSW
FB GND
VIN
VC
LT1170
+
C1
330µF
35V
C6
0.02µF
C4
0.1µF
R1
680C5
0.03µF
D1
MBR330p
C3
4.7µF
TANT
D2
1N4148
L1
50µHR2*
0.013
C2
390µF
16V
VOUT
5V
3A**
+
×
MODE LOGIC
220pF
<0.3V = NORMAL MODE
>2.5V = SHUTDOWN
OPEN = BURST MODE
* R2 IS MADE FROM PC BOARD
COPPER TRACES.
** MAXIMUM CURRENT IS DETERMINED
BY THE CHOICE OF LT1070 FAMILY.
SEE APPLICATION SECTION.
VIN
1170/1/2 TA17
OPTIONAL
OUTPUT
FILTER
100µF
16V
10µH
3A
+
VC
GND
MODE
DIODE
VOUT
VLIM
V+
LT1432
VIN
TYPICAL APPLICATIO S
U
16
LT1170/LT1171/LT1172
117012ff
U
PACKAGE DESCRIPTIO
J8 Package
8-Lead CERDIP (Narrow .300 Inch, Hermetic)
(Reference LTC DWG # 05-08-1110)
K Package
4-Lead TO-3 Metal Can
(Reference LTC DWG # 05-08-1311)
J8 0801
.014 – .026
(0.360 – 0.660)
.200
(5.080)
MAX
.015 – .060
(0.381 – 1.524)
.125
3.175
MIN
.100
(2.54)
BSC
.300 BSC
(7.62 BSC)
.008 – .018
(0.203 – 0.457) 0° – 15°
.005
(0.127)
MIN
.405
(10.287)
MAX
.220 – .310
(5.588 – 7.874)
1234
8765
.025
(0.635)
RAD TYP
.045 – .068
(1.143 – 1.650)
FULL LEAD
OPTION
.023 – .045
(0.584 – 1.143)
HALF LEAD
OPTION
CORNER LEADS OPTION
(4 PLCS)
.045 – .065
(1.143 – 1.651)
NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE
OR TIN PLATE LEADS
K4(TO-3) 0801
72°
18°
.490 – .510
(12.45 – 12.95)
R
.470 TP
P.C.D.
.167 – .177
(4.24 – 4.49)
R
.151 – .161
(3.84 – 4.09)
DIA 2 PLC
.655 – .675
(16.64 – 19.05)
1.177 – 1.197
(29.90 – 30.40)
.038 – .043
(0.965 – 1.09)
.060 – .135
(1.524 – 3.429)
.320 – .350
(8.13 – 8.89)
.420 – .480
(10.67 – 12.19)
.760 – .775
(19.30 – 19.69)
OBSOLETE PACKAGES
17
LT1170/LT1171/LT1172
117012ff
U
PACKAGE DESCRIPTIO
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
Q Package
5-Lead Plastic DD Pak
(Reference LTC DWG # 05-08-1461)
N8 0502
.100
(2.54)
BSC
.065
(1.651)
TYP
.045 – .065
(1.143 – 1.651)
.130 ± .005
(3.302 ± 0.127)
.020
(0.508)
MIN
.018 ± .003
(0.457 ± 0.076)
.125
(3.175)
MIN
.009 – .015
(0.229 – 0.381)
.300 – .325
(7.620 – 8.255)
.325 +.035
–.015
+0.889
–0.381
8.255
()
12 34
8765
.255 ± .015*
(6.477 ± 0.381)
.400*
(10.160)
MAX
NOTE:
1. DIMENSIONS ARE INCHES
MILLIMETERS
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
Q(DD5) 0502
.028 – .038
(0.711 – 0.965)
TYP
.143 +.012
–.020
()
3.632+0.305
0.508
.067
(1.702)
BSC
.013 – .023
(0.330 – 0.584)
.095 – .115
(2.413 – 2.921)
.004 +.008
–.004
()
0.102+0.203
0.102
.050 ± .012
(1.270 ± 0.305)
.059
(1.499)
TYP
.045 – .055
(1.143 – 1.397)
.165 – .180
(4.191 – 4.572)
.330 – .370
(8.382 – 9.398)
.060
(1.524)
TYP
.390 – .415
(9.906 – 10.541)
15° TYP
.420
.350
.565
.090
.042
.067
RECOMMENDED SOLDER PAD LAYOUT
.325
.205
.080
.565
.090
RECOMMENDED SOLDER PAD LAYOUT
FOR THICKER SOLDER PASTE APPLICATIONS
.042
.067
.420
.276
.320
NOTE:
1. DIMENSIONS IN INCH/(MILLIMETER)
2. DRAWING NOT TO SCALE
.300
(7.620)
.075
(1.905)
.183
(4.648)
.060
(1.524)
.060
(1.524)
.256
(6.502)
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
18
LT1170/LT1171/LT1172
117012ff
U
PACKAGE DESCRIPTIO
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
SW Package
16-Lead Plastic Small Outline (Wide .300 Inch)
(Reference LTC DWG # 05-08-1620)
.016 – .050
(0.406 – 1.270)
.010 – .020
(0.254 – 0.508)× 45°
0°– 8° TYP
.008 – .010
(0.203 – 0.254)
SO8 0502
.053 – .069
(1.346 – 1.752)
.014 – .019
(0.355 – 0.483)
TYP
.004 – .010
(0.101 – 0.254)
.050
(1.270)
BSC
1
N
234
N/2
.150 – .157
(3.810 – 3.988)
NOTE 3
8765
.189 – .197
(4.801 – 5.004)
NOTE 3
.228 – .244
(5.791 – 6.197)
.245
MIN
N
1 2 3 N/2
.160 ±.005
RECOMMENDED SOLDER PAD LAYOUT
.045 ±.005
.050 BSC
.030 ±.005
TYP
INCHES
(MILLIMETERS)
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
S16 (WIDE) 0502
NOTE 3
.398 – .413
(10.109 – 10.490)
NOTE 4
16 15 14 13 12 11 10 9
1
N
2345678
N/2
.394 – .419
(10.007 – 10.643)
.037 – .045
(0.940 – 1.143)
.004 – .012
(0.102 – 0.305)
.093 – .104
(2.362 – 2.642)
.050
(1.270)
BSC .014 – .019
(0.356 – 0.482)
TYP
0° – 8° TYP
NOTE 3
.009 – .013
(0.229 – 0.330)
.005
(0.127)
RAD MIN
.016 – .050
(0.406 – 1.270)
.291 – .299
(7.391 – 7.595)
NOTE 4
× 45°
.010 – .029
(0.254 – 0.737)
INCHES
(MILLIMETERS)
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS
4. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
.420
MIN
.325 ±.005
RECOMMENDED SOLDER PAD LAYOUT
.045 ±.005
N
123 N/2
.050 BSC
.030 ±.005
TYP
19
LT1170/LT1171/LT1172
117012ff
I
nformation furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
PACKAGE DESCRIPTIO
T Package
5-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1421)
T5 (TO-220) 0399
0.028 – 0.038
(0.711 – 0.965)
0.067
(1.70) 0.135 – 0.165
(3.429 – 4.191)
0.700 – 0.728
(17.78 – 18.491)
0.045 – 0.055
(1.143 – 1.397)
0.095 – 0.115
(2.413 – 2.921)
0.013 – 0.023
(0.330 – 0.584)
0.620
(15.75)
TYP
0.155 – 0.195*
(3.937 – 4.953)
0.152 – 0.202
(3.861 – 5.131)
0.260 – 0.320
(6.60 – 8.13)
0.165 – 0.180
(4.191 – 4.572)
0.147 – 0.155
(3.734 – 3.937)
DIA
0.390 – 0.415
(9.906 – 10.541)
0.330 – 0.370
(8.382 – 9.398)
0.460 – 0.500
(11.684 – 12.700)
0.570 – 0.620
(14.478 – 15.748)
0.230 – 0.270
(5.842 – 6.858)
BSC
SEATING PLANE
* MEASURED AT THE SEATING PLANE
20
LT1170/LT1171/LT1172
117012ff
LINEAR T ECHNOLOGY CORPORATION 1991
LT/TP 1002 1K REV F • PRINTED IN USA
PART NUMBER DESCRIPTION COMMENTS
LT1070/LT1071/LT1072 5A/2.5A/1.25A High Efficiency Switching Regulators 40kHz, V
IN
to 60V, V
SW
to 75V
LT1074/LT1076 5.5A/2A Step-Down Switching Regulators 100kHz, Also for Positive-to-Negative Conversion
LT1082 1A, High Voltage, High Efficiency Switching Regulator V
IN
to 75V, V
SW
to 100V, Telecom
LT1268/LT1268B 7.5A, 150kHz Switching Regulators V
IN
to 30V, V
SW
to 60V
LT1269/LT1271 4A High Efficiency Switching Regulators 100kHz/60kHz, V
IN
to 30V, V
SW
to 60V
LT1270/LT1270A 8A and 10A High Efficiency Switching Regulators 60kHz, V
IN
to 30V, V
SW
to 60V
LT1370 500kHz High Efficiency 6A Switching Regulator High Power Boost, Flyback, SEPIC
LT1371 500kHz High Efficiency 3A Switching Regulator Good for Boost, Flyback, Inverting, SEPIC
LT1372/LT1377 500kHz and 1MHz High Efficiency 1.5A Switching Regulators Directly Regulates ±V
OUT
LT1373 250kHz Low Supply Current High Efficiency 1.5A Switching Regulator Low 1mA Quiescent Current
LT1374 4A, 500kHz Step-Down Switching Regulator Synchronizable, V
IN
to 25V
LT1375/LT1376 1.5A, 500kHz Step-Down Switching Regulators Up to 1.25A Out from an SO-8
LT1425 Isolated Flyback Switching Regulator 6W Output, ±5% Regulation,
No Optocoupler Needed
LT1507 500kHz Monolithic Buck Mode Switching Regulator 1.5A Switch, Good for 5V to 3.3V
LT1533 Ultralow Noise 1A Switching Regulator Push-Pull, <100µV
P-P
Output Noise
RELATED PARTS
Positive Current Boosted Buck Converter
1170/1/2 TA18
C1
0.33µF
470
2W
R7
1k
V
IN
28V
R3
680
LT1170
V
IN
V
SW
FB
V
C
1: N
D2
R2
1.24k
C3
0.47µF
D1
V
OUT
5V, 10
A
N 0.25
R4
1.24k
GND
C5*
100µF
R6
470
C6
0.002µF
+
C4
0.01µF
7
V
IN
6
4
8
200pF
2
3
R5
5k
R1
5k C2
5000µF
* REQUIRED IF INPUT LEADS 2"
LM308
+
+
U
TYPICAL APPLICATIO
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
FAX: (408) 434-0507
www.linear.com