LINER LT1172CN8 100khz, 5a, 2.5a and 1.25a high efficiency switching regulator Datasheet

LT1170/LT1171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
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FEATURES
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DESCRIPTIO
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
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APPLICATIO S
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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 SwitcherCADTM is also available.
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, 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 voltages 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 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
SwitcherCAD is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATIO
Boost Converter (5V to 12V)
5V
Maximum Output Power*
L1**
50µH
L2
10µH
OUTPUT
FILTER
100
* 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.
LT1170
VSW
+
LT1170
C3*
100µF
+
C2
1000µF
80
R1
10.7k
1%
12V
1A
FB
GND
VC
R3
1k
C1
1µF
*REQUIRED IF INPUT LEADS ≥ 2"
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
R2
1.24k
1%
POWER (W) **
D1
MBR330
VIN
C3
100µF
BOOST
LT1170/1/2 TA02
FLYBACK
40
20
BUCK-BOOST
VO = 5V
0
1170/1/2 TA01
BUCK-BOOST
VO = 30V
60
0
10
30
20
INPUT VOLTAGE (V)
40
50
1
LT1170/LT1171/LT1172
W W
W
AXI U
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ABSOLUTE
RATI GS
(Note 1)
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
Operating Junction Temperature Range
LT1170/71/72M ......................... – 55°C to 150°C
LT1170/71/72HVC,
LT1170/71/72C (Oper.) .............. 0°C to 100°C
LT1170/71/72HVC
C
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,
I
LT1170/71/72I (Sh. Ckt.) ...... – 40°C to 125°C
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PACKAGE/ORDER I FOR ATIO
ORDER PART
NUMBER
TOP VIEW
GND 1
8
E2
VC 2
7
VSW
FB 3
6
E1
NC* 4
5
VIN
J8 PACKAGE
8-LEAD CERDIP
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
* Do not connect Pin 4 of the LT1172 DIP or SO to external
circuitry. This pin may be active in future revisions.
TJMAX = 150°C, θJA = 100°C/W (J)
TJMAX = 100°C, θJA = 100°C/W (N)
TJMAX = 100°C, θJA = 120°C/W to 150°C/W
depending on board layout (S)
BOTTOM VIEW
VSW
VC
1
4
2
3
VIN
CASE
IS GND
FB
K PACKAGE
4-LEAD TO-3 METAL CAN
TJMAX
θJC
LT1170MK
150°C 2°C/W
LT1170CK
100°C 2°C/W
LT1171MK
150°C 4°C/W
LT1171CK
100°C 4°C/W
LT1172MK
150°C 8°C/W
LT1172CK
150°C 8°C/W
Based on continuous operation.
TJMAX = 125°C for intermittent fault conditions.
*θ will vary from
approximately
25°C/W with 2.8
VIN
5
sq. in. of 1oz.
VSW
4
copper to 45°C/W
GND
3
with 0.20 sq. in. of
FB
2
1oz. copper.
VC
1
Somewhat lower
Q PACKAGE
values can be
5-LEAD DD
obtained with
TJMAX = 100°C, θJA = *°C/W additional copper
layers in multilayer
boards.
FRONT VIEW
2
θJA
35°C/W
35°C/W
35°C/W
35°C/W
35°C/W
35°C/W
LT1172MJ8
LT1172CJ8
LT1172CN8
LT1172IN8
LT1172CS8
LT1172IS8
ORDER PART
NUMBER
TOP VIEW
NC 1
16 NC
NC 2
15 NC
GND 3
14 E2
VC 4
13 VSW
FB 5
12 E1
NC 6
11 VIN
NC 7
10 NC
NC 8
9
LT1172CSW
NC
SW PACKAGE
16-LEAD PLASTIC SO WIDE
TJMAX = 100°C, θJA = 150°C/W
S8 PART MARKING
1172 1172I
Based on continuous operation.
TJMAX = 125°C for intermittent fault conditions.
ORDER PART
NUMBER
FRONT VIEW
LT1170MK
LT1170CK
LT1171MK
LT1171CK
LT1172MK
LT1172CK
ORDER PART
NUMBER
LT1170CQ LT1171HVCQ
LT1170IQ LT1172CQ
LT1171CQ LT1172HVIQ
LT1171IQ
5
VIN
4
VSW
3
GND
2
FB
1
VC
T PACKAGE
5-LEAD PLASTIC TO-220
TJMAX
θJC
θJA
LT1170CT/LT1170HVCT
100°C 2°C/W 75°C/W
LT1171CT/LT1171HVCT
100°C 4°C/W 75°C/W
LT1172CT/LT1172HVCT
100°C 8°C/W 75°C/W
Based on continuous operation.
TJMAX = 125°C for intermittent fault conditions.
ORDER PART
NUMBER
LT1170CT
LT1170IT
LT1170HVCT
LT1170HVIT
LT1171CT
LT1171IT
LT1171HVCT
LT1172CT
LT1172HVCT
LT1170/LT1171/LT1172
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
VREF
Measured at Feedback Pin
VC = 0.8V
1.224
1.214
1.244
1.244
1.264
1.274
V
V
350
750
1100
nA
nA
IB
Reference Voltage
Feedback Input Current
●
VFB = VREF
●
gm
AV
Error Amplifier
Transconductance
∆IC = ±25µA
Error Amplifier Source or
Sink Current
VC = 1.5V
Error Amplifier Clamp
Voltage
Hi Clamp, VFB = 1V
Lo Clamp, VFB = 1.5V
Reference Voltage Line
Regulation
3V ≤ VIN ≤ VMAX
VC = 0.8V
Error Amplifier Voltage Gain
0.9V ≤ VC ≤ 1.4V
6000
7000
µmho
µmho
150
120
200
●
350
400
µA
µA
2.30
0.52
V
V
0.03
%/V
1.80
0.25
500
3V ≤ VIN ≤ VMAX, VC = 0.6V
Control Pin Threshold
Duty Cycle = 0
Normal/Flyback Threshold
on Feedback Pin
800
V/V
2.6
3.0
6
9
0.8
0.6
0.9
1.08
1.25
V
V
0.4
0.45
0.54
V
15.0
14.0
16.3
17.6
18.0
V
V
4.5
6.8
9
V
0.01
0.03
%/V
150
300
650
µmho
70
70
µA
µA
●
Supply Current
●
VFB
0.38
●
Minimum Input Voltage (Note 5)
IQ
3000
2400
4400
●
V
mA
Flyback Reference Voltage
(Note 5)
IFB = 50µA
Change in Flyback Reference
Voltage
0.05 ≤ IFB ≤ 1mA
Flyback Reference Voltage
Line Regulation (Note 5)
IFB = 50µA
7V ≤ VIN ≤ VMAX
Flyback Amplifier
Transconductance (gm)
∆IC = ±10µA
Flyback Amplifier Source
and Sink Current
VC = 0.6V
IFB = 50µA
Source
Sink
●
●
15
25
32
40
BV
Output Switch Breakdown
Voltage
3V ≤ VIN ≤ VMAX,
ISW = 1.5mA
LT1170/LT1171/LT1172
LT1170HV/LT1171HV/LT1172HV
LT1172S8
●
●
●
65
75
60
90
90
80
VSAT
Output Switch
“On” Resistance (Note 3)
LT1170
LT1171
LT1172
Control Voltage to Switch
Current Transconductance
LT1170
LT1171
LT1172
Switch Current Limit
(LT1170)
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
TJ ≥ 25°C
TJ < 25°C
●
●
●
5
5
4
10
11
10
A
A
A
(LT1171)
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
TJ ≥ 25°C
TJ < 25°C
●
●
●
2.5
2.5
2.0
5.0
5.5
5.0
A
A
A
(LT1172)
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
TJ ≥ 25°C
TJ < 25°C
●
●
●
1.25
1.25
1.00
3.0
3.5
2.5
A
A
A
ILIM
●
0.15
0.30
0.60
●
●
●
V
V
V
0.24
0.50
1.00
8
4
2
Ω
Ω
Ω
A/V
A/V
A/V
3
LT1170/LT1171/LT1172
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VIN = 15V, VC = 0.5V, VFB = VREF, output pin open, unless otherwise noted.
SYMBOL PARAMETER
∆IIN
Supply Current Increase
During Switch On-Time
∆ISW
f
CONDITIONS
MIN
Switching Frequency
DCMAX
Maximum Switch Duty Cycle
Shutdown Mode
Supply Current
3V ≤ VIN ≤ VMAX
VC = 0.05V
Shutdown Mode
Threshold Voltage
3V ≤ VIN ≤ VMAX
TYP
MAX
UNITS
25
35
mA/A
88
85
100
●
112
115
kHz
kHz
●
85
92
97
%
100
250
µA
150
250
300
mV
mV
100
50
●
Flyback Sense Delay Time (Note 5)
µs
1.5
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:
(R)(IL) + Vf
VIN (max, output shorted) = 15V +
(t)(f)
buck and inverting mode
R = Inductor DC resistance
IL = 10A for LT1170, 5A for LT1171, and 2.5A for LT1172
Vf = Output catch diode forward voltage at IL
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 VC in hi clamp, VFB = 0.8V. ISW = 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 ILIM = 3.33 (2 – DC) for the LT1170,
ILIM = 1.67 (2 – DC) for the LT1171, and ILIM = 0.833 (2 – DC) for the
LT1172.
Note 5: Minimum input voltage for isolated flyback mode is 7V. VMAX =
55V for HV grade in fully isolated mode to avoid switch breakdown.
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TYPICAL PERFOR A CE CHARACTERISTICS
Switch Current Limit vs Duty Cycle*
Minimum Input Voltage
16
Switch Saturation Voltage
2.9
12
–55°C
8
25°C
125°C
4
* DIVIDE VERTICAL SCALE BY TWO FOR
LT1171, BY FOUR FOR LT1172.
0
0
10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
1170/1/2 G01
4
MINIMUM INPUT VOLTAGE (V)
SWITCH CURRENT (A)
SWITCH CURRENT = IMAX
2.8
2.7
2.6
SWITCH CURRENT = 0A
2.5
2.4
2.3
–75 –50 –25
SWITCH SATURATION VOLTAGE (V)
1.6
1.4
150°C
1.2
100°C
1.0
25°C
0.8
–55°C
0.6
0.4
* DIVIDE CURRENT BY TWO FOR
LT1171, BY FOUR FOR LT1172.
0.2
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
1170/1/2 G02
0
1
2
4
5
6
3
SWITCH CURRENT (A)*
7
8
1170/1/2 G03
LT1170/LT1171/LT1172
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TYPICAL PERFOR A CE CHARACTERISTICS
TJ = 150°C
2
1
0
TJ = –55°C
TJ = 25°C
–1
–2
1.250
800
1.248
700
FEEDBACK BIAS CURRENT (nA)
4
REFERENCE VOLTAGE (V)
REFERENCE VOLTAGE CHANGE (mV)
5
3
Feedback Bias Current vs
Temperature
Reference Voltage vs Temperature
Line Regulation
1.246
1.244
1.242
1.240
1.238
–3
1.234
–75 –50 –25
–5
0
10
30
40
20
INPUT VOLTAGE (V)
50
60
500
400
300
200
100
1.236
–4
600
0
–75 –50 –25
25 50 75 100 125 150
TEMPERATURE (°C)
0
1170/1/2 G04
1170/1/2 G06
1170/1/2 G05
Supply Current vs Supply Voltage
(Shutdown Mode)
Supply Current vs Input Voltage*
Driver Current* vs Switch Current
15
160
160
TJ = 25°C
140
140
120
120
TJ = 25°C
14
NOTE THAT THIS CURRENT DOES NOT
INCLUDE DRIVER CURRENT, WHICH IS
A FUNCTION OF LOAD CURRENT AND
DUTY CYCLE.
VC = 50mV
80
60
40
SUPPLY CURRENT (mA)
DRIVER CURRENT (mA)
SUPPLY CURRENT (µA)
13
100
0 25 50 75 100 125 150
TEMPERATURE (°C)
100
TJ = –55°C
80
60
TJ = ≥ 25°C
40
12
11
10
90% DUTY CYCLE
9
50% DUTY CYCLE
8
10% DUTY CYCLE
7
20
20
VC = 0V
10
30
20
40
SUPPLY VOLTAGE (V)
50
0
60
1170/1/2 G07
4500
TJ = 150°C
120
100
80
60
–55°C ≤ TJ ≤ 125°C
40
20
TRANSCONDUCTANCE (µmho)
5000
180
140
2
3
SWITCH CURRENT (A)
4
0
10 20 30 40 50 60 70 80 90 100
VC PIN VOLTAGE (mV)
1170/1/2 G10
10
30
40
20
INPUT VOLTAGE (V)
50
60
1170/1/2 G09
* UNDER VERY LOW OUTPUT CURRENT CONDITIONS,
DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH
10% OR LESS.
VC Pin Characteristics
300
gm =
∆I (VC PIN)
∆V (FB PIN)
VFB = 1.5V (CURRENT INTO VC PIN)
200
4000
3500
3000
2500
2000
1500
100
0
TJ = 25°C
–100
–200
VFB = 0.8V (CURRENT OUT OF VC PIN)
1000
–300
500
0
0
5
1170/1/2 G08
Error Amplifier Transconductance
200
160
1
* AVERAGE LT1170 POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT.
Shutdown Mode Supply Current
0% DUTY CYCLE
5
VC PIN CURRENT (µA)
0
SUPPLY CURRENT (µA)
6
0
0
0
–75 –50 –25
–400
0 25 50 75 100 125 150
TEMPERATURE (°C)
1170/1/2 G11
0
0.5
1.5
2.0
1.0
VC PIN VOLTAGE (V)
2.5
1170/1/2 G12
5
LT1170/LT1171/LT1172
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TYPICAL PERFOR A CE CHARACTERISTICS
Idle Supply Current vs
Temperature
Feedback Pin Clamp Voltage
IDLE SUPPLY CURRENT (mA)
10
VC = 0.6V
FEEDBACK VOLTAGE (mV)
9
8
7
VSUPPLY = 60V
6
VSUPPLY = 3V
5
4
3
2
1
–75 –50 –25
500
1000
450
900
400
800
–55°C
350
300
SWITCH CURRENT (µA)
11
25°C
250
150°C
200
150
150
– 150
100
–100
VC VOLTAGE IS REDUCED UNTIL
REGULATOR CURRENT DROPS
BELOW 300µA
22
– 50
0
25 50 75 100 125 150
TEMPERATURE (°C)
0
FLYBACK VOLTAGE (V)
– 200
VOLTAGE
23
1.8
TIME (µs)
VC PIN VOLTAGE (mV)
– 250
200
1.6
1.4
1.2
1.0
–75 –50 –25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
18
17
RFB = 10k
15
–75 –50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1170/1/2 G18
–24
0
490
–22
480
–20
60
gm
90
3000
120
2000
150
1000
0
180
–1000
210
10M
1170/1/2 G19
FEEDBACK PIN VOLTAGE (mV)
500
PHASE (DEG)
TRANSCONDUCTANCE (µmho)
RFB = 1k
–30
30
5000
1M
100k
FREQUENCY (Hz)
19
–18
470
460
FEEDBACK PIN VOLTAGE
(AT THRESHOLD)
–16
–14
450
–12
440
430
FEEDBACK PIN CURRENT
(AT THRESHOLD)
–10
420
–8
410
–6
400
–50 –25
0
–4
25 50 75 100 125 150
TEMPERATURE (°C)
1170/1/2 G20
FEEDBACK PIN CURRENT (µA)
θ
10k
20
Normal/Flyback Mode Threshold on
Feedback Pin
7000
4000
RFB = 500Ω
1170/1/2 G17
Transconductance of Error
Amplifier
6000
21
16
1170/1/2 G16
6
Isolated Mode Flyback
Reference Voltage
2.0
VC PIN CURRENT (µA)
250
10 20 30 40 50 60 70 80 90 100
SWITCH VOLTAGE (V)
1170/1/2 G15
2.2
– 350
– 300
1k
0
1170/1/2 G14
– 400
300
VSUPPLY
= 55V
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
FEEDBACK CURRENT (mA)
Flyback Blanking Time
CURRENT (OUT OF VC PIN)
VSUPPLY
= 15V
300
100
0
400
0
–75 –50 –25
500 VSUPPLY
= 3V
400
200
Shutdown Thresholds
50
600
50
0 25 50 75 100 125 150
TEMPERATURE (°C)
VSUPPLY
= 40V
700
100
1170/1/2 G13
350
Switch “Off” Characteristics
LT1170/LT1171/LT1172
W
BLOCK DIAGRA
VIN
16V
2.3V
REG
SWITCH
OUT
FLYBACK
ERROR
AMP
LT1172
5A, 75V
SWITCH
100kHz
OSC
LOGIC
DRIVER
ANTISAT
MODE
SELECT
COMP
–
FB
ERROR
AMP
VC
+
+
SHUTDOWN
CIRCUIT
1.24V
REF
CURRENT
AMP
GAIN ≈ 6
–
0.02 Ω
(0.04 Ω LT1171)
(0.16 Ω LT1172)
0.16 Ω
0.15V
(LT1170 AND LT1171 ONLY)
E1†
E2
† 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.
1170/1/2 BD
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OPERATIO
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 closedloop 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 turnoff 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
7
LT1170/LT1171/LT1172
U
OPERATIO
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 regulator. 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. Multiple floating outputs are easily obtained with additional
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 (VC) has four different
functions. It is used for frequency compensation, current
limit adjustment, soft starting, and total regulator shutdown. 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
(gm) 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 VC pin is pulled to ground through a
diode, placing the LT1170/LT1171/LT1172 in an idle mode.
Pulling the VC 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) disconnected. 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
*See note under block diagram.
8
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 selected. 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).
Care should be taken for miniDIP applications to ensure
that the worst case input voltage and load current conditions do not cause excessive die temperatures. The following 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 Calculations” section.
Average supply current (including driver current) is:
IIN ≈ 6mA + ISW (0.004 + DC/40)
ISW = switch current
DC = switch duty cycle
Switch power dissipation is given by:
PSW = (ISW)2 • (RSW)(DC)
RSW = LT1172 switch “on” resistance (1Ω maximum)
Total power dissipation is the sum of supply current times
input voltage plus switch power:
PD(TOT) = (IIN)(VIN) + PSW
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:
IIN = 6mA + 0.65(0.004 + DC/40) = 18mA
PSW = (0.65)2 • (1Ω)(0.6) = 0.25W
PD(TOT) = (5V)(0.018A) + 0.25 = 0.34W
LT1170/LT1171/LT1172
U
OPERATIO
Temperature rise in a plastic miniDIP would be 130°C/W
times 0.34W, or approximately 44°C. The maximum ambient 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 conditions 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 I2R switch dissipation under current limit
conditions.
The fourth approach is to clamp the VC pin to a voltage less
than its internal clamp level of 2V. The LT1172 switch
current limit is zero at approximately 1V on the VC pin and
2A at 2V on the VC 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 synchronized in the frequency range of 120kHz to 160kHz. This is
accomplished as shown in the accompanying figures.
Synchronizing occurs when the VC 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 

VC 
+
t
f
I
S
S
C
 q

R3 
 

∆VOS =
IC
KT = 26mV at 25°C
q
tS = pulse width
fS = pulse frequency
IC = VC source current (≈ 200µA)
VC = operating VC voltage (1V to 2V)
R3 = resistor used to set mid-frequency “zero” in
frequency compensation network.
( )( )
With tS = 0.2µs, fS = 150kHz, VC = 1.5V, and R3 = 2k, offset
voltage shift is ≈ 3.8mV. This is not particularly bothersome, 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 VC pin to within 200mV of ground
to ensure synchronizing.
Synchronizing with Bipolar Transistor
Synchronizing with MOS Transistor
VIN
VIN
LT1170
GND
LT1170
VC
GND
C2
39pF
R3
C1
R1
3k
R3
2N2369
R2
2.2k
VC
FROM 5V
LOGIC
1170/1/2 OP01
C1
D1
1N4158
C2
100pF
VN2222*
R2
2.2k
* SILICONIX OR EQUIVALENT
D2
1N4158
FROM 5V
LOGIC
1170/1/2 OP02
9
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
Flyback Converter
L2 OPTIONAL
FILTER
5µH
CLAMP TURN-ON
SPIKE
VSNUB
C4
100µF
a
VIN
N* = 1/3
VIN
20V TO 30V
D3
25V
1W
VOUT
5V
6A
1 N*
+
D2
MUR110
VIN
C4*
100µF
D1
b
0V
VOUT + Vf
c
C1
2000µF
N • VIN
0V
d
R1
3.74k
∆I
PRIMARY CURRENT
0
LT1170
IPRI/N
FB
GND
SECONDARY VOLTAGE
AREA “c” = AREA “d” TO MAINTAIN
ZERO DC VOLTS ACROSS SECONDARY
IPRI
VSW
+
+ Vf
V
PRIMARY FLYBACK VOLTAGE = OUT
N
LT1170 SWITCH VOLTAGE
AREA “a” = AREA “b” TO MAINTAIN
ZERO DC VOLTS ACROSS PRIMARY
SECONDARY CURRENT
VC
0
IPRI
R3
1.5k
R2
1.24k
LT1170 SWITCH CURRENT
0
C2
0.15µF
IPRI
SNUBBER DIODE CURRENT
*REQUIRED IF INPUT LEADS ≥ 2"
0
(I )(L )
t = PRI L
VSNUB
1170/1/2 TA03
LCD Contrast Supply
5V*
L1**
50µH
VIN
VSW
E2
LT1172
R1
200k
D1
1N914
C1
1µF
TANTALUM
VOUT
–10V TO –26V
FB
VC
D2
C4
0.047µF
R3
15k
C3
0.0047µF
D3
+
GND
VN2222
+
R2
100k
E1
OPTIONAL
SHUTDOWN
VBAT*
3V TO 20V
C2***
2µF
TANTALUM
D2, D3 = ER82.004 600mA SCHOTTKY. OTHER FAST SWITCHING TYPES MAY BE USED.
* VIN AND BATTERY MAY BE TIED TOGETHER. MAXIMUM VALUE FOR VBAT IS EQUAL TO THE NEGATIVE OUTPUT + 1V. WITH HIGHER
BATTERY VOLTAGES, HIGHEST EFFICIENCY IS OBTAINED BY RUNNING THE LT1172 VIN PIN FROM 5V. SHUTTING OFF THE 5V SUPPLY
WILL AUTOMATICALLY TURN OFF THE LT1172. EFFICIENCY IS ABOUT 80% AT IOUT = 25mA.
R1, R2, R3 ARE MADE LARGE TO MINIMIZE BATTERY DRAIN IN SHUTDOWN, WHICH IS APPROXIMATELY VBAT /(R1 + R2 + R3).
** FOR HIGH EFFICIENCY, L1 SHOULD BE MADE ON A FERRITE OR MOLYPERMALLOY CORE. PEAK INDUCTOR CURRENTS ARE ABOUT
600mA AT POUT = 0.7Ω. INDUCTOR SERIES RESISTANCE SHOULD BE LESS THAN 0.4Ω FOR HIGH EFFICIENCY.
*** OUTPUT RIPPLE IS ABOUT 200mVP-P TO 400mVP-P WITH C2 = 2µF TANTALUM. IF LOWER RIPPLE IS DESIRED, INCREASE C2, OR ADD
A 10Ω , 1µF TANTALUM OUTPUT FILTER.
1170/1/2 TA04
10
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
(Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.)
Driving High Voltage FET
(for Off-Line Applications, See AN25)
External Current Limit
D
Q1
G
VX
D1
VIN
LT1170
VSW
R2
+
10V TO
20V
≈ 2V
LT1170
VC
GND
D1
R1
500Ω
GND
1170/1/2 TA05
1170/1/2 TA06
Negative-to-Positive Buck-Boost Converter†
L1**
50µH
External Current Limit
L2
VIN
OPTIONAL
OUTPUT
FILTER
LT1170
+
D1
VIN
C4*
100µF
VSW
+
+
LT1170
R1
11.3k
C2
1000µF
VOUT
12V
2A
–
VIN
VC
GND
L3
R1
1k
FB
R2
Q1
FB
C1
1000pF
R3
2.2k
C1
0.22µF
VIN
–20V
VC
GND
Q1
OPTIONAL
INPUT FILTER
VSW
C3
R2
1.24k
C2
RS
NOTE THAT THE LT1170
GND PIN IS NO LONGER
COMMON TO VIN–.
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114, COILTRONICS 50-2-52
† 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
1170/1/2 TA07
Negative Buck Converter
+
D1
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114
COILTRONICS 50-2-52
VIN
L3
+
Q1
2N3906
LT1170
LOAD
R1
4.64k
–5.2V
4.5A
R4
12k
FB
GND
VC
OPTIONAL
OUTPUT
FILTER
C1
R3
VIN
–20V
C2
1000µF
VSW
C3*
100µF
OPTIONAL
INPUT FILTER
L1**
50µH
R2
1.24k
+
C4
200µF
L2
4µH
1170/1/2 TA09
11
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
Positive-to-Negative Buck-Boost Converter
D3†
1N4001
R5†
470Ω, 1W
+
VIN
C4
1µF
VSW
VIN
10V TO
30V
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114, COILTRONICS 50-2-52
† 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 100Ω.
C5
100µF*
+
LT1170
D2
1N914
R1
10.7k
FB
VC
GND
R4
47Ω
R3
5k
C2
0.1µF
+
R2
1.24k
+
C3
2µF
C1†
1000µF
R6
470Ω
D1
VOUT
–12V
2A
L1**
50µH
1170/1/2 TA10
High Efficiency Constant Current Charger
INPUT VOLTAGE
> VBAT + 2V < 35V
R3
25k
VSW
D1
1N5819
LT1171
VIN
C2
2.2µF
35V
TANTALUM
C1 +
200µF
35V
+
RUN = 0V
SHUTDOWN = 5V
C3
0.47µF
C4
0.01µF
R7
22k
R8
1k
–
V–
R4
1k
+
L2*
10µH, 1A
L1
100µH, 1A
R5
0.05Ω
2N3904
R6
78k
* L2 REDUCES RIPPLE CURRENT INTO
THE BATTERY BY ABOUT 20 :1.
IT MAY BE OMITTED IF DESIRED.
LT1006
FB
VC
GND
+
V
R2
1k
+
1.244V • R4
= 1A AS SHOWN
R3 • R5
ICHRG =
+
D2
MBR340
C4
200µF
25V
1A
+
BATTERY
2V TO 25V
1170/1/2 TA11
Backlight CCFL Supply (see AN45 for details)
INPUT VOLTAGE†
4.5V TO 20V
L2***
1k
L1**
300µH
1N5818
A
33pF
3kV
LAMP
Q1*
V IN
E2
10µF
TANT
VSW
0.02µF
+
LT1172
VC
+
2µF
12
D2
1N914
Q2*
B
E1 GND
D1
1N914
FB
C6
1µ F
R3
10k
50k
INTENSITY
ADJUST
R1
560Ω
* Q1,Q2 = BCP56 OR MPS650/561
1170/1/2 TA12
** COILTRONICS CTX300-4
*** SUMIDA 6345-020 OR COILTRONICS 110092-1
† A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY.
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
Positive Buck Converter
VIN
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114
COILTRONICS 50-2-52
D3
C3
2.2µF
L2
4µH
VIN
+
VSW
LT1170
+
D2
1N914
R1
3.74k
C5*
100µF
VC
GND
OPTIONAL
OUTPUT
FILTER
C5
200µF
FB
+
R2
1.24k
R3
470Ω
C1
1µF
C2
1µF
R4
10Ω
L1**
50µH
r
C4
1000µF
D1
5V, 4.5A
+
100mA
MINIMUM
1170/1/2 TA13
Negative Boost Regulator
D2
VIN
VSW
R1
27k
LT1170
C4*
470µF
VIN
–15V
+
+
C3
10µF
+
C1
1000µF
RO
(MINIMUM
LOAD)
FB
GND
L1
50µH
VC
R3
3.3k
C2
0.22µF
R2
1.24k
D1
VOUT
–28V, 1A
1170/1/2 TA14
* REQUIRED IF INPUT LEADS ≥ 2"
Driving High Voltage NPN
C1
D2
R2**
R1*
Q1
D1
VIN
VSW
LT1170
* SETS IB (ON)
** SETS IB (OFF)
GND
1170/1/2 TA15
13
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
Forward Converter
D1
L1
25µH
VOUT
5V, 6A
T1
C2
R4
1
M
N
D2
C1
2000µF
+
R1
3.74k
D3
VIN
VSW
VIN
20V TO 30V
D4
LT1170
FB
R6
330Ω
VC
GND
Q1
R3
R2
1.24k
R5
1Ω
C4
C3
1170/1/2 TA16
High Efficiency 5V Buck Converter
VIN
+
C1
330µF
35V
10µH
3A
VIN
VSW
LT1170
FB
VC
GND
C6
0.02µF
R1
680Ω
C5
0.03µF
C4
0.1µF
D1
MBR330p
C3
4.7µF
TANT
DIODE
LT1432
<0.3V = NORMAL MODE
>2.5V = SHUTDOWN
OPEN = BURST MODE
+
OPTIONAL
OUTPUT
FILTER
+
L1
50µH
R2*
0.013Ω
+
VC
VIN
MODE LOGIC
220pF
100µF
16V
D2
1N4148
V+
×
C2
390µF
16V
VOUT
5V
3A**
VLIM
VOUT
MODE
GND
* R2 IS MADE FROM PC BOARD
COPPER TRACES.
** MAXIMUM CURRENT IS DETERMINED
BY THE CHOICE OF LT1070 FAMILY.
SEE APPLICATION SECTION.
1170/1/2 TA17
14
LT1170/LT1171/LT1172
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
J8 Package
8-Lead CERDIP (Narrow 0.300, Hermetic)
(LTC DWG # 05-08-1110)
CORNER LEADS OPTION
(4 PLCS)
0.023 – 0.045
(0.584 – 1.143)
HALF LEAD
OPTION
0.045 – 0.068
(1.143 – 1.727)
FULL LEAD
OPTION
0.005
(0.127)
MIN
0.405
(10.287)
MAX
8
7
6
5
0.025
(0.635)
RAD TYP
0.220 – 0.310
(5.588 – 7.874)
1
0.300 BSC
(0.762 BSC)
2
3
4
0.200
(5.080)
MAX
0.015 – 0.060
(0.381 – 1.524)
0.008 – 0.018
(0.203 – 0.457)
0° – 15°
NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE
OR TIN PLATE LEADS
0.045 – 0.065
(1.143 – 1.651)
0.014 – 0.026
(0.360 – 0.660)
0.100
(2.54)
BSC
0.125
3.175
MIN
J8 1298
15
LT1170/LT1171/LT1172
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
K Package
4-Lead TO-3 Metal Can
(LTC DWG # 05-08-1311)
1.177 – 1.197
(29.90 – 30.40)
0.760 – 0.775
(19.30 – 19.69)
0.320 – 0.350
(8.13 – 8.89)
0.470 TP
P.C.D.
0.060 – 0.135
(1.524 – 3.429)
0.655 – 0.675
(16.64 – 19.05)
0.151 – 0.161
(3.84 – 4.09)
DIA 2 PLC
0.420 – 0.480
(10.67 – 12.19)
0.167 – 0.177
(4.24 – 4.49)
R
0.038 – 0.043
(0.965 – 1.09)
72°
18°
0.490 – 0.510
(12.45 – 12.95)
R
K4(TO-3) 1098
N8 Package
8-Lead PDIP (Narrow 0.300)
(LTC DWG # 05-08-1510)
0.400*
(10.160)
MAX
8
7
6
5
1
2
3
4
0.255 ± 0.015*
(6.477 ± 0.381)
0.300 – 0.325
(7.620 – 8.255)
0.009 – 0.015
(0.229 – 0.381)
(
+0.035
0.325 –0.015
8.255
+0.889
–0.381
)
0.045 – 0.065
(1.143 – 1.651)
0.065
(1.651)
TYP
0.100
(2.54)
BSC
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
16
0.130 ± 0.005
(3.302 ± 0.127)
0.125
(3.175) 0.020
MIN (0.508)
MIN
0.018 ± 0.003
(0.457 ± 0.076)
N8 1098
LT1170/LT1171/LT1172
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
Q Package
5-Lead Plastic DD Pak
(LTC DWG # 05-08-1461)
0.256
(6.502)
0.060
(1.524)
TYP
0.060
(1.524)
0.390 – 0.415
(9.906 – 10.541)
0.165 – 0.180
(4.191 – 4.572)
15° TYP
0.060
(1.524)
0.183
(4.648)
0.059
(1.499)
TYP
0.330 – 0.370
(8.382 – 9.398)
0.045 – 0.055
(1.143 – 1.397)
(
+0.008
0.004 –0.004
+0.203
0.102 –0.102
)
0.095 – 0.115
(2.413 – 2.921)
0.075
(1.905)
0.300
(7.620)
(
+0.012
0.143 –0.020
+0.305
3.632 –0.508
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
0.067
(1.70)
0.028 – 0.038 BSC
(0.711 – 0.965)
)
0.013 – 0.023
(0.330 – 0.584)
0.050 ± 0.012
(1.270 ± 0.305)
Q(DD5) 1098
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
8
7
6
5
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
0.010 – 0.020
× 45°
(0.254 – 0.508)
0.008 – 0.010
(0.203 – 0.254)
0.053 – 0.069
(1.346 – 1.752)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.014 – 0.019
(0.355 – 0.483)
TYP
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
2
3
4
0.004 – 0.010
(0.101 – 0.254)
0.050
(1.270)
BSC
SO8 1298
17
LT1170/LT1171/LT1172
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
SW Package
16-Lead Plastic Small Outline (Wide 0.300)
(LTC DWG # 05-08-1620)
0.398 – 0.413*
(10.109 – 10.490)
16
15
14
13
12
11
10
9
0.394 – 0.419
(10.007 – 10.643)
NOTE 1
1
0.291 – 0.299**
(7.391 – 7.595)
2
3
4
5
6
7
0.093 – 0.104
(2.362 – 2.642)
0.010 – 0.029 × 45°
(0.254 – 0.737)
8
0.037 – 0.045
(0.940 – 1.143)
0° – 8° TYP
0.009 – 0.013
(0.229 – 0.330)
NOTE 1
0.016 – 0.050
(0.406 – 1.270)
0.050
(1.270)
BSC
0.014 – 0.019
(0.356 – 0.482)
TYP
NOTE:
1. 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
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
18
0.004 – 0.012
(0.102 – 0.305)
S16 (WIDE) 1098
LT1170/LT1171/LT1172
U
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
T Package
5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1421)
0.390 – 0.415
(9.906 – 10.541)
0.165 – 0.180
(4.191 – 4.572)
0.147 – 0.155
(3.734 – 3.937)
DIA
0.045 – 0.055
(1.143 – 1.397)
0.230 – 0.270
(5.842 – 6.858)
0.460 – 0.500
(11.684 – 12.700)
0.570 – 0.620
(14.478 – 15.748)
0.330 – 0.370
(8.382 – 9.398)
0.620
(15.75)
TYP
0.700 – 0.728
(17.78 – 18.491)
0.095 – 0.115
(2.413 – 2.921)
SEATING PLANE
0.152 – 0.202
0.260 – 0.320 (3.861 – 5.131)
(6.60 – 8.13)
0.155 – 0.195*
(3.937 – 4.953)
0.013 – 0.023
(0.330 – 0.584)
BSC
0.067
(1.70)
0.028 – 0.038
(0.711 – 0.965)
0.135 – 0.165
(3.429 – 4.191)
* MEASURED AT THE SEATING PLANE
T5 (TO-220) 0399
Information 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 representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO
Positive Current Boosted Buck Converter
VIN
28V
470Ω
2W
C3
0.47µF
C6
0.002µF
D2
VIN
R6
470Ω
1: N
VSW
LT1170
R2
1.24k
R7
1k
N ≈ 0.25
D1
FB
GND
VIN
VC
7
C5*
100µF
+
R3
680Ω
C4
0.01µF
6
–
2
+
3
LM308
C1
0.33µF
4
R5
5k
8
200pF
R4
1.24k
R1
5k
+
* REQUIRED IF INPUT LEADS ≥ 2"
VOUT
5V, 10A
C2
5000µF
1170/1/2 TA18
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1070/LT1071/LT1072
5A/2.5A/1.25A High Efficiency Switching Regulators
40kHz, VIN to 60V, VSW 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
VIN to 75V, VSW to 100V, Telecom
LT1268/LT1268B
7.5A, 150kHz Switching Regulators
VIN to 30V, VSW to 60V
LT1269/LT1271
4A High Efficiency Switching Regulators
100kHz/60kHz, VIN to 30V, VSW to 60V
LT1270/LT1270A
8A and 10A High Efficiency Switching Regulators
60kHz, VIN to 30V, VSW 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 ±VOUT
LT1373
250kHz Low Supply Current High Efficiency 1.5A Switching Regulator
Low 1mA Quiescent Current
LT1374
4A, 500kHz Step-Down Switching Regulator
Synchronizable, VIN 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, <100µVP-P Output Noise
20
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● (408) 432-1900
FAX: (408) 434-0507● TELEX: 499-3977 ● www.linear-tech.com
117012fe LT/TP 1299 2K REV E • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 1991