LT1172I [Linear]
100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators; 为100kHz ，5A ， 2.5A和1.25A的高效率开关稳压器
| 型号： | LT1172I |
| 厂家： | 
Linear |
| 描述： | 100kHz, 5A, 2.5A and 1.25A High Efficiency Switching Regulators |
| 文件： | 总20页 (文件大小：269K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1170/LT1171/LT1172
100kHz, 5A, 2.5A and 1.25A
High Efficiency Switching Regulators
U
FEATURES
DESCRIPTIO
■
Wide Input Voltage Range: 3V to 60V
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-
■
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
ciency switch is included on the die along with all oscilla-
tor, control and protection circuitry. Integration of all
functionsallowstheLT1170/LT1171/LT1172tobebuiltin
astandard5-pinTO-3orTO-220powerpackageaswellas
the 8-pin packages (LT1172). This makes them extremely
easy to use and provides “bust proof” operation similar to
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 that obtained with 3-pin linear regulators.
Packages
Can Be Externally Synchronized
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.
U
APPLICATIO S
■
Logic Supply 5V at 10A
■
5V Logic to ±15V Op Amp Supply
The LT1170/LT1171/LT1172 have many unique features
not found even on the vastly more difficult to use low
powercontrolchipspresentlyavailable. Theyuseadaptive
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.
■
Battery Upconverter
■
Power Inverter (+ to –) or (– to +)
■
Fully Floating Multiple Outputs
USER NOTE:
Thisdatasheetisonlyintendedtoprovidespecifications,graphs,andageneralfunctionaldescription
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. ThemanualcanalsobeusedfortheLT1170/LT1171/LT1172byfactoringinthehigher
frequency. A CAD design program called SwitcherCADTM is also available.
, LTC and LT are registered trademarks of Linear Technology Corporation.
SwitcherCAD is a trademark of Linear Technology Corporation.
U
TYPICAL APPLICATIO
Boost Converter (5V to 12V)
Maximum Output Power*
L1**
5V
L2
OUTPUT
FILTER
50µH
100
10µH
* ROUGH GUIDE ONLY. BUCK MODE
LT1170
P
= (5A)(V
)
OUT
OUT
C3
100µF
SPECIAL TOPOLOGIES DELIVER
MORE POWER.
80
60
40
20
0
D1
** DIVIDE VERTICAL POWER SCALE
BY TWO FOR LT1171, BY FOUR
FOR LT1172.
V
IN
MBR330
BUCK-BOOST
= 30V
12V
1A
V
SW
V
O
+
R1
BOOST
C2
1000µF
10.7k
LT1170/1/2 TA02
LT1170
FLYBACK
+
1%
C3*
100µF
FB
V
GND
C
R2
1.24k
1%
R3
1k
C1
1µF
BUCK-BOOST
V
O
= 5V
0
10
20
30
40
50
*REQUIRED IF INPUT LEADS ≥ 2"
** COILTRONICS 50-2-52
PULSE ENGINEERING 92114
INPUT VOLTAGE (V)
1170/1/2 TA01
1
LT1170/LT1171/LT1172
W W U W
ABSOLUTE AXI U RATI GS
(Note 1)
Supply Voltage
Operating Junction Temperature Range
LT1170/71/72M......................... –55°C to 150°C
LT1170/71/72HVC,
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
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,
C
I
LT1170/71/72I (Oper.) .......... –40°C to 100°C
LT1170/71/72HVI,
LT1170/71/72I (Sh. Ckt.) ...... –40°C to 125°C
U W
U
PACKAGE/ORDER I FOR ATIO
TOP VIEW
TOP VIEW
ORDER PART
NUMBER
ORDER PART
NC
NC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
NC
NC
E2
V
GND
1
2
3
4
E2
V
8
7
6
5
NUMBER
V
C
SW
GND
FB
E1
V
LT1172MJ8
LT1172CJ8
LT1172CN8
LT1172IN8
LT1172CS8
LT1172IS8
LT1172CSW
V
C
SW
NC*
IN
FB
NC
NC
NC
E1
J8 PACKAGE
8-LEAD CERDIP
N8 PACKAGE
8-LEAD PDIP
V
IN
NC
NC
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.
SW PACKAGE
16-LEAD PLASTIC SO WIDE
TJMAX = 150°C, θJA = 100°C/W (J)
TJMAX = 100°C, θJA = 100°C/W (N)
JMAX = 100°C, θJA = 120°C/W to 150°C/W
depending on board layout (S)
TJMAX = 100°C, θJA = 150°C/W
S8 PART MARKING
1172 1172I
Based on continuous operation.
TJMAX = 125°C for intermittent fault conditions.
T
ORDER PART
NUMBER
ORDER PART
NUMBER
BOTTOM VIEW
FRONT VIEW
V
V
C
SW
5
4
3
2
1
V
V
IN
1
4
2
3
CASE
IS GND
SW
LT1170MK
LT1170CK
LT1171MK
LT1171CK
LT1172MK
LT1172CK
LT1170CT
LT1170IT
GND
FB
V
FB
IN
K PACKAGE
4-LEAD TO-3 METAL CAN
V
C
LT1170HVCT
LT1170HVIT
LT1171CT
T PACKAGE
5-LEAD PLASTIC TO-220
TJMAX
θJC
θJA
LT1170MK
LT1170CK
LT1171MK
LT1171CK
LT1172MK
LT1172CK
150°C 2°C/W 35°C/W
100°C 2°C/W 35°C/W
150°C 4°C/W 35°C/W
100°C 4°C/W 35°C/W
150°C 8°C/W 35°C/W
150°C 8°C/W 35°C/W
TJMAX
θJC
θJA
LT1170CT/LT1170HVCT
LT1171CT/LT1171HVCT
LT1172CT/LT1172HVCT
100°C 2°C/W 75°C/W
100°C 4°C/W 75°C/W
100°C 8°C/W 75°C/W
LT1171IT
LT1171HVCT
LT1172CT
Based on continuous operation.
TJMAX = 125°C for intermittent fault conditions.
Based on continuous operation.
TJMAX = 125°C for intermittent fault conditions.
LT1172HVCT
*θ will vary from
ORDER PART
NUMBER
approximately
FRONT VIEW
25°C/W with 2.8
sq. in. of 1oz.
5
4
3
2
1
V
V
GND
FB
IN
SW
copper to 45°C/W
with 0.20 sq. in. of
1oz. copper.
Somewhat lower
values can be
obtained with
LT1170CQ
LT1170IQ
LT1171CQ
LT1171HVCQ
LT1172CQ
LT1172HVIQ
V
C
Q PACKAGE
5-LEAD DD
additional copper LT1171IQ
TJMAX = 100°C, θJA = *°C/W
layers in multilayer
boards.
2
LT1170/LT1171/LT1172
ELECTRICAL CHARACTERISTICS
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.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
Reference Voltage
Measured at Feedback Pin
V = 0.8V
C
1.224 1.244 1.264
1.214 1.244 1.274
V
V
REF
●
●
●
●
I
Feedback Input Current
V
= V
REF
350
4400
200
750
1100
nA
nA
B
FB
g
Error Amplifier
Transconductance
∆I = ±25µA
C
3000
2400
6000
7000
µmho
µmho
m
Error Amplifier Source or
Sink Current
V = 1.5V
C
150
120
350
400
µA
µA
Error Amplifier Clamp
Voltage
Hi Clamp, V = 1V
1.80
0.25
2.30
0.52
V
V
FB
Lo Clamp, V = 1.5V
0.38
FB
Reference Voltage Line
Regulation
3V ≤ V ≤ V
V = 0.8V
C
●
●
●
0.03
%/V
IN
MAX
A
Error Amplifier Voltage Gain
Minimum Input Voltage (Note 5)
Supply Current
0.9V ≤ V ≤ 1.4V
500
800
2.6
6
V/V
V
V
C
3.0
9
I
3V ≤ V ≤ V
, V = 0.6V
C
mA
Q
IN
MAX
Control Pin Threshold
Duty Cycle = 0
0.8
0.6
0.9
1.08
1.25
V
V
Normal/Flyback Threshold
on Feedback Pin
0.4
0.45
16.3
6.8
0.54
V
V
Flyback Reference Voltage
(Note 5)
I
= 50µA
FB
15.0
14.0
17.6
18.0
V
V
FB
●
Change in Flyback Reference
Voltage
0.05 ≤ I ≤ 1mA
4.5
9
V
FB
Flyback Reference Voltage
Line Regulation (Note 5)
I
= 50µA
0.01
300
0.03
650
%/V
FB
7V ≤ V ≤ V
IN
MAX
Flyback Amplifier
∆I = ±10µA
150
µmho
C
Transconductance (g )
m
Flyback Amplifier Source
and Sink Current
V = 0.6V
Source
Sink
●
●
15
25
32
40
70
70
µA
µA
C
I
= 50µA
FB
BV
Output Switch Breakdown
Voltage
3V ≤ V ≤ V
,
MAX
LT1170/LT1171/LT1172
LT1170HV/LT1171HV/LT1172HV
LT1172S8
●
●
●
65
75
60
90
90
80
V
V
V
IN
I
= 1.5mA
SW
V
Output Switch
“On” Resistance (Note 3)
LT1170
LT1171
LT1172
●
●
●
0.15
0.30
0.60
0.24
0.50
1.00
Ω
Ω
Ω
SAT
Control Voltage to Switch
Current Transconductance
LT1170
LT1171
LT1172
8
4
2
A/V
A/V
A/V
I
Switch Current Limit (LT1170)
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
T ≥ 25°C
T < 25°C
J
●
●
●
5
5
4
10
11
10
A
A
A
LIM
J
(LT1171)
(LT1172)
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
T ≥ 25°C
T < 25°C
J
●
●
●
2.5
2.5
2.0
5.0
5.5
5.0
A
A
A
J
Duty Cycle = 50%
Duty Cycle = 50%
Duty Cycle = 80% (Note 4)
T ≥ 25°C
●
●
●
1.25
1.25
1.00
3.0
3.5
2.5
A
A
A
J
T < 25°C
J
3
LT1170/LT1171/LT1172
ELECTRICAL CHARACTERISTICS
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.
SYMBOL PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
∆I
∆I
Supply Current Increase
During Switch On-Time
25
35
mA/A
IN
SW
f
Switching Frequency
88
85
100
112
115
kHz
kHz
●
●
DC
Maximum Switch Duty Cycle
85
92
97
%
MAX
Shutdown Mode
Supply Current
3V ≤ V ≤ V
V = 0.05V
C
100
250
µA
IN
MAX
Shutdown Mode
Threshold Voltage
3V ≤ V ≤ V
100
50
150
250
300
mV
mV
IN
MAX
●
Flyback Sense Delay Time (Note 5)
1.5
µs
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
outputshortedcondition.Buckmodeandinvertingmodeinputvoltageduring
an output shorted condition is limited to:
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.
(R)(I ) + Vf
Note 3: Measured with V in hi clamp, V = 0.8V. I = 4A for LT1170,
2A for LT1171, and 1A for LT1172.
L
C
FB
SW
V
(max, output shorted) = 15V +
IN
(t)(f)
buck and inverting mode
R = Inductor DC resistance
Note 4: For duty cycles (DC) between 50% and 80%, minimum
guaranteed switch current is given by I = 3.33 (2 – DC) for the LT1170,
LIM
I = 10A for LT1170, 5A for LT1171, and 2.5A for LT1172
L
I
= 1.67 (2 – DC) for the LT1171, and I = 0.833 (2 – DC) for the
LIM
LIM
Vf = Output catch diode forward voltage at I
LT1172.
L
t = 0.6µs, f = 100kHz switching frequency
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.
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.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Current Limit vs Duty Cycle*
Minimum Input Voltage
Switch Saturation Voltage
16
12
8
2.9
2.8
2.7
2.6
2.5
2.4
2.3
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
SWITCH CURRENT = I
MAX
150°C
100°C
25°C
–55°C
25°C
–55°C
125°C
SWITCH CURRENT = 0A
4
* DIVIDE VERTICAL SCALE BY TWO FOR
LT1171, BY FOUR FOR LT1172.
* DIVIDE CURRENT BY TWO FOR
LT1171, BY FOUR FOR LT1172.
0
70
0
10 20 30 40 50 60
80 90 100
2
4
5
6
7
0
1
3
8
–75 –50 –25
0
25 50 75 100 125 150
DUTY CYCLE (%)
SWITCH CURRENT (A)*
TEMPERATURE (°C)
1170/1/2 G01
1170/1/2 G02
1170/1/2 G03
4
LT1170/LT1171/LT1172
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Feedback Bias Current vs
Temperature
Line Regulation
Reference Voltage vs Temperature
5
4
800
700
600
500
400
300
200
100
0
1.250
1.248
1.246
1.244
1.242
1.240
1.238
1.236
1.234
3
T = 150°C
J
2
1
0
T = –55°C
J
T = 25°C
J
–1
–2
–3
–4
–5
–75 –50 –25
0
25 50 75
100 125
150
–75 –50 –25
0
25 50 75 100 125 150
0
10
30
40
50
60
20
INPUT VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
1170/1/2 G04
1170/1/2 G05
1170/1/2 G06
Supply Current vs Supply Voltage
(Shutdown Mode)
Supply Current vs Input Voltage*
Driver Current* vs Switch Current
15
14
13
12
11
10
9
160
140
120
100
80
160
140
120
100
80
T = 25°C
T = 25°C
J
J
NOTE THAT THIS CURRENT DOES NOT
INCLUDE DRIVER CURRENT, WHICH IS
A FUNCTION OF LOAD CURRENT AND
DUTY CYCLE.
T = –55°C
V
= 50mV
J
C
90% DUTY CYCLE
50% DUTY CYCLE
60
60
T = ≥ 25°C
J
8
40
40
10% DUTY CYCLE
0% DUTY CYCLE
7
20
20
V
= 0V
C
6
0
0
5
30
SUPPLY VOLTAGE (V)
0
1
2
3
4
0
10
30
40
50
1170/1/2 G09
60
0
10
20
40
50
5
20
60
SWITCH CURRENT (A)
INPUT VOLTAGE (V)
1170/1/2 G08
1170/1/2 G07
* UNDER VERY LOW OUTPUT CURRENT CONDITIONS,
DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH
10% OR LESS.
* AVERAGE LT1170 POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT.
Shutdown Mode Supply Current
Error Amplifier Transconductance
VC Pin Characteristics
200
180
160
140
120
100
80
5000
300
∆I (V PIN)
∆V (FB PIN)
C
4500
4000
3500
3000
2500
2000
1500
1000
500
g =
m
V
FB
= 1.5V (CURRENT INTO V PIN)
C
200
100
T = 150°C
J
0
T
J
= 25°C
–100
–200
–300
–400
60
–55°C ≤ T ≤ 125°C
J
V
FB
= 0.8V (CURRENT OUT OF V PIN)
C
40
20
0
0
100 125
150
0
10 20 30 40 50 60
80
–75 –50 –25
0
25 50 75
0
0.5
1.0
V PIN VOLTAGE (V)
C
1.5
2.0
2.5
70
90 100
V
C
PIN VOLTAGE (mV)
TEMPERATURE (°C)
1170/1/2 G10
1170/1/2 G11
1170/1/2 G12
5
LT1170/LT1171/LT1172
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Idle Supply Current vs
Temperature
Feedback Pin Clamp Voltage
Switch “Off” Characteristics
11
10
9
500
450
400
350
300
250
200
150
100
50
1000
900
800
700
600
500
400
300
200
100
0
V
C
= 0.6V
–55°C
V
8
SUPPLY
= 40V
V
7
V
= 60V
= 3V
SUPPLY
= 15V
25°C
SUPPLY
V
6
SUPPLY
= 3V
V
SUPPLY
150°C
V
SUPPLY
5
= 55V
4
3
2
1
0
–75 –50 –25
0
25 50 75 100 125 150
0
0.1 0.2 0.3 0.4 0.5 0.6
0.8
0
10 20 30 40 50 60
80
90 100
0.7
0.9 1.0
70
TEMPERATURE (°C)
FEEDBACK CURRENT (mA)
SWITCH VOLTAGE (V)
1170/1/2 G13
1170/1/2 G14
1170/1/2 G15
Isolated Mode Flyback
Reference Voltage
Shutdown Thresholds
Flyback Blanking Time
2.2
2.0
1.8
1.6
1.4
1.2
1.0
400
350
300
250
200
150
100
50
–400
–350
–300
–250
–200
–150
–100
–50
23
22
21
20
19
18
17
16
15
CURRENT (OUT OF V PIN)
C
R
FB
= 500Ω
R
= 1k
FB
FB
VOLTAGE
R
= 10k
V
VOLTAGE IS REDUCED UNTIL
C
REGULATOR CURRENT DROPS
BELOW 300µA
0
0
–75 –50 –25
0
25 50 75 100 125 150
100
125 150
–75 –50 –25
0
25 50 75
–75 –50 –25
0
25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
1170/1/2 G16
1170/1/2 G18
1170/1/2 G17
Transconductance of Error
Amplifier
Normal/Flyback Mode Threshold on
Feedback Pin
–24
7000
6000
5000
4000
3000
2000
1000
0
–30
0
500
490
480
470
460
450
440
430
420
410
400
–22
–20
–18
–16
–14
–12
–10
–8
θ
30
FEEDBACK PIN VOLTAGE
(AT THRESHOLD)
60
g
m
90
120
150
180
210
FEEDBACK PIN CURRENT
(AT THRESHOLD)
–6
–1000
–4
150
1k
10k
100k
1M
10M
–50
50
100 125
–25
0
25
75
FREQUENCY (Hz)
TEMPERATURE (°C)
1170/1/2 G19
1170/1/2 G20
6
LT1170/LT1171/LT1172
W
BLOCK DIAGRA
SWITCH
OUT
V
IN
16V
2.3V
REG
FLYBACK
ERROR
AMP
LT1172
5A, 75V
SWITCH
100kHz
OSC
LOGIC
COMP
DRIVER
ANTI-
SAT
MODE
SELECT
FB
–
ERROR
AMP
V
C
+
+
0.02Ω
(0.04Ω LT1171)
(0.16Ω LT1172)
SHUTDOWN
CIRCUIT
CURRENT
0.16Ω
AMP
–
≈
GAIN
6
1.24V
REF
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
U
OPERATIO
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.
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
reachesapredeterminedlevel. Controlofoutputvoltageis
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-pulsecurrentlimitingtoprovidemaximumswitch
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 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
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.
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.TheminiDIPs,however,areratedat100°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 condi-
tionsdonotcauseexcessivedietemperatures.Thefollow-
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.
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 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
(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,placingtheLT1170/LT1171/LT1172inanidlemode.
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.
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:
Extra Pins on the MiniDIP and Surface Mount Packages
PD(TOT) = (IIN)(VIN) + PSW
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
currentlimit2:1byleavingthesecondemitter(E2)discon-
nected. The first emitter (E1) should always be connected
tothegroundpin.Notethatswitch“on”resistancedoubles
when E2 is left open, so efficiency will suffer somewhat
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
*See note under block diagram.
8
LT1170/LT1171/LT1172
U
OPERATIO
LT1170/LT1171/LT1172 Synchronizing
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.
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 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:
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
withtemporaryoverloads.Asecondapproachistousethe
largerTO-220(T)orTO-3(K)packagewhich,evenwithout
aheatsink, maylimitdietemperaturestosafelevelsunder
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.
VC
R3
KT
q
t
f
I +
C
( S)( S)
∆VOS =
IC
KT
= 26mV at 25°C
q
tS = pulse width
fS = pulse frequency
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.
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 bother-
some, but note that high offsets could result if R3 were
reduced to a much lower value. Also, the synchronizing
transistormustsinkhighercurrentswithlowvaluesofR3,
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.
ThefourthapproachistoclamptheVC pintoavoltageless
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.
Synchronizing with Bipolar Transistor
Synchronizing with MOS Transistor
V
IN
V
IN
LT1170
LT1170
GND
V
C
GND
V
C
C2
C2
D1
R1
3k
39pF
100pF
1N4158
R3
C1
R3
C1
2N2369
VN2222*
R2
2.2k
D2
1N4158
R2
2.2k
FROM 5V
LOGIC
FROM 5V
LOGIC
1170/1/2 OP01
* SILICONIX OR EQUIVALENT
1170/1/2 OP02
9
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
Flyback Converter
CLAMP TURN-ON
SPIKE
OPTIONAL
FILTER
L2
5µH
V
SNUB
C4
100µF
V
+ Vf
N
OUT
a
PRIMARY FLYBACK VOLTAGE =
LT1170 SWITCH VOLTAGE
V
IN
N* = 1/3
D1
b
d
V
5V
6A
OUT
AREA “a” = AREA “b” TO MAINTAIN
ZERO DC VOLTS ACROSS PRIMARY
V
IN
0V
V
OUT
+ V
f
20V TO 30V
D3
25V
1W
N*
1
c
SECONDARY VOLTAGE
N • V
+
IN
C1
2000µF
AREA “c” = AREA “d” TO MAINTAIN
ZERO DC VOLTS ACROSS SECONDARY
0V
D2
MUR110
R1
3.74k
∆I
V
I
IN
PRI
V
SW
FB
PRIMARY CURRENT
+
C4*
100µF
0
0
LT1170
I
/N
PRI
SECONDARY CURRENT
V
GND
C
I
PRI
R3
1.5k
R2
1.24k
LT1170 SWITCH CURRENT
0
0
C2
I
PRI
0.15µF
SNUBBER DIODE CURRENT
*REQUIRED IF INPUT LEADS ≥ 2"
(I )(L )
PRI
L
t =
V
SNUB
1170/1/2 TA03
LCD Contrast Supply
5V*
L1**
50µH
V
*
BAT
3V TO 20V
V
IN
V
E2
E1
SW
+
C1
D1
1N914
1µF
LT1172
TANTALUM
R1
200k
R2
100k
V
OUT
FB
–10V TO –26V
V
GND
C
D2
C2***
R3
15k
C3
0.0047µF
D3
2µF
+
TANTALUM
OPTIONAL
SHUTDOWN
C4
0.047µF
VN2222
D2, D3 = ER82.004 600mA SCHOTTKY. OTHER FAST SWITCHING TYPES MAY BE USED.
* V AND BATTERY MAY BE TIED TOGETHER. MAXIMUM VALUE FOR V IS EQUAL TO THE NEGATIVE OUTPUT + 1V. WITH HIGHER
BAT
IN
BATTERY VOLTAGES, HIGHEST EFFICIENCY IS OBTAINED BY RUNNING THE LT1172 V PIN FROM 5V. SHUTTING OFF THE 5V SUPPLY
IN
WILL AUTOMATICALLY TURN OFF THE LT1172. EFFICIENCY IS ABOUT 80% AT I
= 25mA.
OUT
R1, R2, R3 ARE MADE LARGE TO MINIMIZE BATTERY DRAIN IN SHUTDOWN, WHICH IS APPROXIMATELY V
/(R1 + R2 + R3).
BAT
** FOR HIGH EFFICIENCY, L1 SHOULD BE MADE ON A FERRITE OR MOLYPERMALLOY CORE. PEAK INDUCTOR CURRENTS ARE ABOUT
600mA AT P = 0.7Ω. INDUCTOR SERIES RESISTANCE SHOULD BE LESS THAN 0.4Ω FOR HIGH EFFICIENCY.
OUT
*** OUTPUT RIPPLE IS ABOUT 200mV TO 400mV WITH C2 = 2µF TANTALUM. IF LOWER RIPPLE IS DESIRED, INCREASE C2, OR ADD
P-P
P-P
A 10Ω , 1µF TANTALUM OUTPUT FILTER.
1170/1/2 TA04
10
LT1170/LT1171/LT1172
U
(Note that maximum output currents are divided by 2 for LT1171, by 4 for LT1172.)
TYPICAL APPLICATIO S
Driving High Voltage FET
(for Off-Line Applications, See AN25)
External Current Limit
D
Q1
G
V
X
D1
V
IN
LT1170
V
SW
R2
+
≈
2V
D1
10V TO
20V
LT1170
GND
V
GND
C
R1
500Ω
1170/1/2 TA05
1170/1/2 TA06
Negative-to-Positive Buck-Boost Converter†
External Current Limit
L1**
50µH
L2
V
IN
V
SW
FB
OPTIONAL
OUTPUT
FILTER
C3
LT1170
+
–
D1
V
12V
2A
OUT
V
IN
V
IN
V
SW
V
GND
C
+
R1
11.3k
C2
1000µF
+
C4*
100µF
LT1170
R1
1k
R2
C2
Q1
Q1
OPTIONAL
INPUT FILTER
FB
C1
1000pF
V
GND
C
L3
R2
1.24k
R3
2.2k
R
S
1170/1/2 TA08
C1
0.22µF
NOTE THAT THE LT1170
GND PIN IS NO LONGER
V
IN
–20V
–
COMMON TO V
.
IN
* 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 TA07
Negative Buck Converter
+
C2
1000µF
D1
LOAD
R1
4.64k
L1**
50µH
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114
COILTRONICS 50-2-52
V
IN
–5.2V
4.5A
V
SW
FB
R4
12k
+
C3*
100µF
Q1
2N3906
LT1170
OPTIONAL
INPUT FILTER
V
C
OPTIONAL
OUTPUT
FILTER
GND
+
C4
200µF
L3
C1
R3
R2
1.24k
V
IN
–20V
1170/1/2 TA09
11
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
Positive-to-Negative Buck-Boost Converter
†
D3
1N4001
†
R5
V
470Ω, 1W
IN
10V TO
30V
* REQUIRED IF INPUT LEADS ≥ 2"
+
+
** PULSE ENGINEERING 92114, COILTRONICS 50-2-52
C5
†
TO AVOID STARTUP PROBLEMS FOR INPUT VOLTAGES
V
IN
100µF*
V
SW
BELOW 10V, CONNECT ANODE OF D3 TO V , AND
IN
REMOVE R5. C1 MAY BE REDUCED FOR LOWER OUTPUT
+
CURRENTS. C1 ≈ (500µF)(I ).
OUT
C4
1µF
LT1170
FOR 5V OUTPUTS, REDUCE R3 TO 1.5k, INCREASE C2 TO
D2
R1
R4
47Ω
0.3µF, AND REDUCE R6 TO 100Ω.
1N914
10.7k
FB
V
C
GND
+
†
R3
5k
R2
1.24k
C3
2µF
C1
1000µF
R6
470Ω
C2
0.1µF
D1
V
–12V
2A
OUT
L1**
50µH
1170/1/2 TA10
High Efficiency Constant Current Charger
1.244V • R4
R3 • R5
R3
25k
I
=
= 1A AS SHOWN
CHRG
INPUT VOLTAGE
> V + 2V < 35V
V
SW
BAT
* L2 REDUCES RIPPLE CURRENT INTO
THE BATTERY BY ABOUT 20:1.
D1
+
LT1171
V
IT MAY BE OMITTED IF DESIRED.
1N5819
R2
1k
–
+
V
LT1006
–
FB
IN
V
R4
1k
GND
C
C2
2.2µF
35V
+
+
C1
C4
0.01µF
V
200µF
+
L1
100µH, 1A
L2*
C3
0.47µF
35V
TANTALUM
10µH, 1A
R5
0.05Ω
1A
RUN = 0V
SHUTDOWN = 5V
2N3904
+
C4
+
R6
78k
200µF
BATTERY
2V TO 25V
D2
MBR340
R8
1k
R7
22k
25V
1170/1/2 TA11
Backlight CCFL Supply (see AN45 for details)
†
INPUT VOLTAGE
4.5V TO 20V
L2***
1k
33pF
3kV
L1**
300µH
LAMP
1N5818
A
Q1*
V
IN
V
SW
E2
D1
1N914
D2
1N914
0.02µF
+
50k
INTENSITY
ADJUST
10µF
TANT
LT1172
Q2*
B
R1
560Ω
R3
10k
E1
FB
GND
V
C
Q1,Q2 = BCP56 OR MPS650/561
COILTRONICS CTX300-4
SUMIDA 6345-020 OR COILTRONICS 110092-1
*
C6
1µF
1170/1/2 TA12
**
***
†
A MODIFICATION WILL ALLOW OPERATION DOWN TO 4.5V. CONSULT FACTORY.
2µF
12
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
Positive Buck Converter
V
IN
* REQUIRED IF INPUT LEADS ≥ 2"
** PULSE ENGINEERING 92114
COILTRONICS 50-2-52
D3
L2
4µH
V
IN
V
SW
+
C3
OPTIONAL
OUTPUT
FILTER
C5
200µF
2.2µF
LT1170
D2
R1
+
1N914
3.74k
C5*
100µF
FB
V
GND
C
+
C2
1µF
R2
1.24k
R3
R4
10Ω
470Ω
L1**
50µH
C1
1µF
r
5V, 4.5A
+
C4
1000µF
100mA
MINIMUM
D1
1170/1/2 TA13
Negative Boost Regulator
D2
V
IN
V
SW
R1
27k
R
+
+
O
C1
1000µF
C3
10µF
LT1170
(MINIMUM
LOAD)
+
C4*
470µF
FB
V
GND
C
R2
1.24k
R3
3.3k
C2
0.22µF
L1
50µH
D1
V
V
IN
OUT
–15V
–28V, 1A
1170/1/2 TA14
* REQUIRED IF INPUT LEADS ≥ 2"
Driving High Voltage NPN
C1
D2
R2**
R1*
Q1
D1
V
IN
V
SW
LT1170
GND
* SETS I (ON)
B
** SETS I (OFF)
B
1170/1/2 TA15
13
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO S
Forward Converter
L1
25µH
D1
V
OUT
T1
5V, 6A
1
M
N
C2
R4
+
C1
2000µF
D2
R1
3.74k
D3
V
IN
V
SW
FB
V
IN
D4
LT1170
20V TO 30V
R6
330Ω
V
GND
C
Q1
R2
1.24k
R3
C3
R5
1Ω
C4
1170/1/2 TA16
High Efficiency 5V Buck Converter
V
IN
10µH
3A
V
SW
V
IN
+
C1
330µF
35V
LT1170
+
OPTIONAL
OUTPUT
FILTER
FB
100µF
16V
V
C
GND
D2
1N4148
C6
0.02µF
C3
+
R1
680Ω
C5
0.03µF
4.7µF
TANT
L1
50µH
R2*
0.013Ω
C4
0.1µF
V
OUT
5V
×
3A**
+
D1
MBR330p
C2
+
390µF
16V
V
V
C
DIODE
V
V
V
IN
LIM
LT1432
GND
MODE
OUT
MODE LOGIC
220pF
* R2 IS MADE FROM PC BOARD
COPPER TRACES.
<0.3V = NORMAL MODE
>2.5V = SHUTDOWN
OPEN = BURST MODE
** 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)
0.405
(10.287)
MAX
CORNER LEADS OPTION
(4 PLCS)
0.005
(0.127)
MIN
6
5
4
8
7
2
0.023 – 0.045
(0.584 – 1.143)
HALF LEAD
OPTION
0.025
(0.635)
RAD TYP
0.220 – 0.310
(5.588 – 7.874)
0.045 – 0.068
(1.143 – 1.727)
FULL LEAD
OPTION
1
3
0.200
0.300 BSC
(5.080)
MAX
(0.762 BSC)
0.015 – 0.060
(0.381 – 1.524)
0.008 – 0.018
(0.203 – 0.457)
0° – 15°
0.045 – 0.065
(1.143 – 1.651)
0.125
3.175
MIN
NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE
OR TIN PLATE LEADS
0.014 – 0.026
(0.360 – 0.660)
0.100
(2.54)
BSC
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)
0.655 – 0.675
(16.64 – 19.05)
0.320 – 0.350
(8.13 – 8.89)
0.470 TP
P.C.D.
0.060 – 0.135
(1.524 – 3.429)
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)
0.490 – 0.510
(12.45 – 12.95)
R
72°
18°
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
4
0.255 ± 0.015*
(6.477 ± 0.381)
1
2
3
0.130 ± 0.005
0.300 – 0.325
0.045 – 0.065
(3.302 ± 0.127)
(1.143 – 1.651)
(7.620 – 8.255)
0.065
(1.651)
TYP
0.009 – 0.015
(0.229 – 0.381)
0.125
0.020
(0.508)
MIN
(3.175)
MIN
+0.035
0.325
–0.015
0.018 ± 0.003
(0.457 ± 0.076)
0.100
(2.54)
BSC
+0.889
8.255
(
)
N8 1098
–0.381
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.010 INCH (0.254mm)
16
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)
0.060
(1.524)
TYP
0.390 – 0.415
(9.906 – 10.541)
0.060
0.256
0.165 – 0.180
(4.191 – 4.572)
(1.524)
(6.502)
0.045 – 0.055
(1.143 – 1.397)
15° TYP
+0.008
0.004
–0.004
0.060
(1.524)
0.183
(4.648)
0.059
(1.499)
TYP
0.330 – 0.370
(8.382 – 9.398)
+0.203
–0.102
0.102
(
)
0.095 – 0.115
(2.413 – 2.921)
0.075
(1.905)
0.067
(1.70)
BSC
0.050 ± 0.012
(1.270 ± 0.305)
0.300
(7.620)
0.013 – 0.023
(0.330 – 0.584)
+0.012
0.143
–0.020
0.028 – 0.038
(0.711 – 0.965)
+0.305
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
3.632
Q(DD5) 1098
(
)
–0.508
S8 Package
8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.189 – 0.197*
(4.801 – 5.004)
7
5
8
6
0.150 – 0.157**
(3.810 – 3.988)
0.228 – 0.244
(5.791 – 6.197)
1
3
4
2
0.010 – 0.020
(0.254 – 0.508)
× 45°
0.053 – 0.069
(1.346 – 1.752)
0.004 – 0.010
(0.101 – 0.254)
0.008 – 0.010
(0.203 – 0.254)
0°– 8° TYP
0.016 – 0.050
(0.406 – 1.270)
0.050
(1.270)
BSC
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
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)
15 14 12
10
9
16
13
11
0.394 – 0.419
(10.007 – 10.643)
NOTE 1
2
3
5
7
8
1
4
6
0.291 – 0.299**
(7.391 – 7.595)
0.037 – 0.045
(0.940 – 1.143)
0.093 – 0.104
(2.362 – 2.642)
0.010 – 0.029
(0.254 – 0.737)
× 45°
0° – 8° TYP
0.050
(1.270)
BSC
0.004 – 0.012
(0.102 – 0.305)
0.009 – 0.013
NOTE 1
(0.229 – 0.330)
0.014 – 0.019
0.016 – 0.050
(0.356 – 0.482)
TYP
(0.406 – 1.270)
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
S16 (WIDE) 1098
*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
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)
0.165 – 0.180
(4.191 – 4.572)
0.147 – 0.155
(3.734 – 3.937)
DIA
0.390 – 0.415
(9.906 – 10.541)
0.045 – 0.055
(1.143 – 1.397)
0.230 – 0.270
(5.842 – 6.858)
0.570 – 0.620
(14.478 – 15.748)
0.620
(15.75)
TYP
0.460 – 0.500
(11.684 – 12.700)
0.330 – 0.370
(8.382 – 9.398)
0.700 – 0.728
(17.78 – 18.491)
0.095 – 0.115
(2.413 – 2.921)
SEATING PLANE
0.152 – 0.202
(3.861 – 5.131)
0.155 – 0.195*
(3.937 – 4.953)
0.260 – 0.320
(6.60 – 8.13)
0.013 – 0.023
(0.330 – 0.584)
0.067
BSC
0.135 – 0.165
(3.429 – 4.191)
0.028 – 0.038
(0.711 – 0.965)
(1.70)
* MEASURED AT THE SEATING PLANE
T5 (TO-220) 0399
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-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
19
LT1170/LT1171/LT1172
U
TYPICAL APPLICATIO
Positive Current Boosted Buck Converter
V
IN
28V
470Ω
2W
C3
0.47µF
R6
470Ω
C6
0.002µF
D2
V
IN
1: N
V
SW
FB
N ≈ 0.25
LT1170
R2
R7
1k
1.24k
D1
V
IN
V
GND
C
7
2
–
C4
0.01µF
R3
+
6
C5*
100µF
R5
5k
680Ω
LM308
3
+
C1
0.33µF
4
8
R4
1.24k
200pF
V
OUT
5V, 10A
R1
5k
+
C2
5000µF
* REQUIRED IF INPUT LEADS ≥ 2"
1170/1/2 TA18
RELATED PARTS
PART NUMBER
LT1070/LT1071/LT1072
LT1074/LT1076
LT1082
DESCRIPTION
COMMENTS
40kHz, V to 60V, V to 75V
5A/2.5A/1.25A High Efficiency Switching Regulators
5.5A/2A Step-Down Switching Regulators
1A, High Voltage, High Efficiency Switching Regulator
7.5A, 150kHz Switching Regulators
IN
SW
100kHz, Also for Positive-to-Negative Conversion
V
IN
V
IN
to 75V, V to 100V, Telecom
SW
LT1268/LT1268B
LT1269/LT1271
LT1270/LT1270A
LT1370
to 30V, V to 60V
SW
4A High Efficiency Switching Regulators
100kHz/60kHz, V to 30V, V to 60V
IN SW
8A and 10A High Efficiency Switching Regulators
500kHz High Efficiency 6A Switching Regulator
500kHz High Efficiency 3A Switching Regulator
60kHz, V to 30V, V to 60V
IN SW
High Power Boost, Flyback, SEPIC
LT1371
Good for Boost, Flyback, Inverting, SEPIC
LT1372/LT1377
LT1373
500kHz and 1MHz High Efficiency 1.5A Switching Regulators
250kHz Low Supply Current High Efficiency 1.5A Switching Regulator
4A, 500kHz Step-Down Switching Regulator
Directly Regulates ±V
OUT
Low 1mA Quiescent Current
LT1374
Synchronizable, V to 25V
IN
LT1375/LT1376
LT1425
1.5A, 500kHz Step-Down Switching Regulators
Isolated Flyback Switching Regulator
Up to 1.25A Out from an SO-8
6W Output, ±5% Regulation,
No Optocoupler Needed
LT1507
LT1533
500kHz Monolithic Buck Mode Switching Regulator
Ultralow Noise 1A Switching Regulator
1.5A Switch, Good for 5V to 3.3V
Push-Pull, <100µV Output Noise
P-P
117012fe LT/TP 1299 2K REV E • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1991
Linear Technology Corporation
●
1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900
20
●
●
FAX: (408) 434-0507 TELEX: 499-3977 www.linear-tech.com
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