LT1072CT#PBF [Linear]
LT1072 - 1.25A High Efficiency Switching Regulator; Package: TO-220; Pins: 5; Temperature Range: 0°C to 70°C;
| 型号： | LT1072CT#PBF |
| 厂家： | 
Linear |
| 描述： | LT1072 - 1.25A High Efficiency Switching Regulator; Package: TO-220; Pins: 5; Temperature Range: 0°C to 70°C 局域网 开关 |
| 文件： | 总16页 (文件大小：193K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1072
1.25A High Efficiency
Switching Regulator
U
FEATURES
DESCRIPTIO
The LT®1072 is a monolithic high power switching
regulator. It 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
LT1072 to be built in a standard 5-pin TO-3 or TO-220
power package as well as the 8-pin miniDlP. This makes it
extremelyeasytouseandprovides“bustproof”operation
similar to that obtained with 3-pin linear regulators.
■
Available in MiniDiP, TO-220, and TO-3 Packages
■
Wide Input Voltage Range 3V to 60V
■
Low Quiescent Current—6mA
■
Internal 1.25A Switch
■
Very Few External Parts Required
■
Self-Protected Against Overloads
■
Operates in Nearly All Switching Topologies
■
Shutdown Mode Draws Only 50µA Supply Current
■
Flyback-Regulated Mode has Fully Floating Outputs
■
Can be Externally Synchronized
U
TheLT1072operateswithsupplyvoltagesfrom3Vto60V,
and draws only 6mA quiescent current. It can deliver load
power up to 20 watts with no external power devices. By
utilizing current-mode switching techniques, it provides
excellent AC and DC load and line regulation.
APPLICATIO S
■
Logic Supply 5V at 2.5A
5V Logic to ±15V Op Amp Supply
■
■
Offline Converter up to 50W
Battery Upconverter
■
The LT1072 has many unique features not found even on
the vastly more difficult to use low power control chips
presently available. It uses an adaptive anti-sat switch
drive to allow very wide ranging load currents with no loss
in efficiency. An externally activated shutdown mode
reduces total supply current to 50µA typical for standby
operation. Totally isolated and regulated outputs can be
generatedbyusingtheoptional“flybackregulationmode”
builtintotheLT1072, withouttheneedforoptocouplersor
extra transformer windings.
■
Power lnverter (+ to –) or (– to +)
■
Fully Floating Multiple Outputs
■
Driver for High Current Supplies
USER NOTE:
This data sheet is only intended to provide specifications, graphs, and a general functional
description of the LT1072. Application circuits are included to show the capability of the LT1072.
A complete design manual (AN-19) should be obtained to assist in developing new designs. This
manualcontainsacomprehensivediscussionofboththeLT1070andtheexternalcomponentsused
with it, as well as complete formulas for calculating the values of these components. The manual
can also be used for the LT1072 by factoring in the lower switch current rating.
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
TYPICAL APPLICATIO
Boost Converter (5V to 12V)
Maximum Output Power*
25
5V
220µH**
20
V
IN
V
SW
BUCK-BOOST
V
= 30V
O
15
10
5
12V, 0.25A
LT1072
+
–
C3
25µF*
FLYBACK
ISOLATED
10.7k
1.24k
BOOST
FB
GND
V
C
+
–
470µF
1k
+
–
BUCK-BOOST
1µF
V
= 5V
O
0
0
10
20
30
40
50
*REQUIRED IF INPUT LEADS ≥ 2”
**PULSE ENGINEERING 52626
LT1072 • TA01
INPUT VOLTAGE (V)
*ROUGH GUIDE ONLY. BUCK MODE P = 1A x V
.
OUT
OUT
MINIDIP OUTPUT POWER MAY BE LIMITED BY PACKAGE TEMPERATURE
RISE AT HIGH INPUT VOLTAGES OR HIGH DUTY CYCLES
LT1072 • TA02
1072fc
1
LT1072
W W U W
ABSOLUTE AXI U RATI GS
(Note 1)
Note 1: Minimum switch “on” time for the LT1072 in current limit is
≈ 0.7µsec. This limits the maximum input voltage during short-circuit
conditions, in the buck and inverting modes onlyt,o ≈ 40V. Normal
(unshorted) conditions are not affected. If the LT1072 is being operated in
the buck or inverting mode at high input voltages and short-circuit
conditions are expected, a resistor must be placed in series with the
inductor, as follows:
Supply Voltage
LT1072HV (See Note 1)......................................... 60V
LT1072 (See Note 1) ............................................. 40V
Switch Output Voltage
LT1072HV ............................................................. 75V
LT1072 .................................................................. 65V
LT1072S8 .............................................................. 60V
Feedback Pin Voltage (Transient, 1ms) ................. ±15V
Operating Junction Temperature Range
LT1072HVM, LT1072M (OBSOLETE) .... –55°C to 150°C
LT1072HVC, LT1072C (Oper.)*............0°C to 100°C
LT1072HVC, LT1072C (Sh. Ckt.)* ........0°C to 125°C
LT1072HVI ....................................... –40°C to 125°C
Storage Temperature Range ............... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) ...............300°C
*Includes LT1072S8
The value of the resistor is given by:
(t) (f) (V ) – V
IN
f
R =
–R
L
I
(LIMIT)
t = Minimum “on” time of LT1072 in current limit, ≈ 0.7µs
f = Operating frequency (40kHz)
V = Forward voltage of external catch diode at I
f
(LIMIT)
I
= Current limit of LT1072 (2A)
(LIMIT)
R = Internal series resistance of inductor
L
U W
U
PACKAGE/ORDER I FOR ATIO
ORDER PART
ORDER PART
NUMBER
NUMBER
TOP VIEW
TOP VIEW
BOTTOM VIEW
V
V
C
GND
1
2
3
4
E2
V
GND
1
2
3
4
8
7
6
5
E2
V
8
7
6
5
SW
LT1072HVMK
LT1072MK
LT1072HVCK
LT1072CK
LT1072CN8
LT1072CS8
V
V
C
SW
C
SW
1
4
2
3
CASE IS
GND
E1
V
FB
NC
FB
NC
E1
V
IN
IN
V
FB
IN
S8 PART
MARKING
S8 PACKAGE
8-LEAD PLASTIC SO
N PACKAGE
8-LEAD PDIP
K PACKAGE
4-LEAD TO-3 METAL CAN
= 150°C, θ = 8°C/W, θ = 35°C/W
T
= 100°C, θ = 130°C/W
T
= 100°C, θ = 130°C/W
JMAX
JA
JMAX
JA
T
JMAX
JC
JA
T
= 100°C*, θ = 8°C/W, θ = 35°C/W
1072
JMAX
JC JA
J PACKAGE
8-LEAD CERAMIC DIP
= 150°C, θ = 100°C/W
LT1072MJ8
LT1072CJ8
T
JMAX
JA
OBSOLETE PACKAGE
OBSOLETE PACKAGE
Consider the S8 or N8 Packages for Alternate Source
TOP VIEW
ORDER PART
NUMBER
ORDER PART
NUMBER
FRONT VIEW
NC
NC
GND
1
2
3
4
5
6
7
8
16 NC
15
NC
5
VIN
4
LT1072CT
LT1072HVCT
LT1072HVIT
VSW
14
LT1072CSW
E2
3
GND
13
V
V
SW
C
2
FB
12
11
10
9
E1
FB
NC
NC
NC
1
VC
V
IN
T PACKAGE
5-LEAD TO-220
NC
NC
T
= 100°C/W, θ = 8°C/W, θ = 50°C/W
JMAX
JC JA
SW PACKAGE
16-LEAD PLASTIC SO WIDE
= 100°C, θ = 130°C/W
T
JMAX
JC
LT1072 • POI01
Consult LTC Marketing for parts specified with wider operating temperature ranges.
1072fc
2
LT1072
ELECTRICAL CHARACTERISTICS
The ■ denotes specifications which apply over the full operating
temperature range. Unless otherwise specified, VIN = 15V, VC = 0.5V, VFB = VREF, output pin open.
SYMBOL PARAMETER
CONDITlONS
MIN
TYP
MAX
UNITS
V
Reference Voltage
Measured at Feedback Pin
C
1.224 1.244 1.264
1.214 1.244 1.274
V
V
REF
V = 0.8V
■
■
■
■
I
Feedback Input Current
V
= V
REF
350
4400
200
750
nA
nA
B
FB
1100
gm
Error Amplifier
Transconductance
∆I = ±25µA
C
3000
2400
6000
7000
µmho
µmho
Error Amplifier Source or
Sink Current
V = 1.5V
C
150
120
350
400
µA
µA
Error Amplifier Clamp
Voltage
Hi Clamp, V = 1V
1.8
0.25
2.3
0.52
V
V
FB
Lo Clamp, V = 1.5V
0.38
FB
Reference Voltage Line
Regulation
3V ≤ V ≤ V
C
■
■
■
■
0.03
%/V
%/V
IN
MAX
V = 0.8V
A
Error Amplifier Voltage Gain
Minimum Input Voltage
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
MAX
mA
Q
IN
C
Control Pin Threshold
Duty Cycle = 0
0.8
0.6
0.9
1.08
1.25
V
V
Normal/Flyback Threshold on Feedback Pin
Flyback Reference Voltage
0.4
0.45
16.3
0.54
V
V
l
= 50µA
FB
15
14
17.6
18
V
V
FB
Change in Flyback Reference Voltage
0.05 ≤ I ≤ 1mA
4.5
6.8
8.5
V
FB
Flyback Reference Voltage
Line Regulation
l
= 50µA
0.01
0.03
%/V
%/V
FB
3V ≤ V ≤ V
(Note 4)
MAX
IN
Flyback Amplifier Transconductance (gm)
∆I = ±10µA
C
150
300
650
µmho
Flyback Amplifier Source
and Sink Current
V = 0.6V Source
FB
■
■
15
25
32
40
70
70
µA
µA
C
I
= 50µA Sink
BV
Output Switch Breakdown
Voltage
3V ≤ V ≤ V
SW
LT1072
LT1072HV
LT1072S8
■
■
■
65
75
60
90
90
80
V
V
V
IN
MAX
I
= 1.5mA
V
Output Switch ON Resistance (Note 2)
Control Voltage to Switch Current Transconductance
Switch Current Limit
I
= 1.25A
■
0.6
2
1
Ω
SAT
SW
A/V
I
Duty Cycle = 50%
T ≥ 25°C
J
■
■
■
1.25
1.25
1
3
3.5
2.5
A
A
A
LIM
J
Duty Cycle = 50%
T < 25°C
Duty Cycle = 80% (Note 3)
∆I
∆I
Supply Current Increase
During Switch ON Time
25
40
35
mA/A
IN
SW
f
Switching Frequency
35
33
45
47
kHz
kHz
■
DC (max) Maximum Switch Duty Cycle
Flyback Sense Delay Time
90
92
1.5
100
97
%
µs
µA
Shutdown Mode
Supply Current
3V ≤ V ≤ V
C
250
IN
MAX
MAX
V = 0.05V
Shutdown Mode
Threshold Voltage
3V ≤ V ≤ V
100
50
150
250
300
mV
mV
IN
■
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 3: For duty cycles (DC) between 50% and 80%, minimum
guaranteed switch current is given by I = 0.833 (2 – DC).
LIM
Note 2: Measured with V in hi clamp, V = 0.8V.
Note 4: V
= 55V for LT1072HV to avoid switch breakdown.
C
FB
MAX
1072fc
3
LT1072
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Switch Current Limit vs Duty Cycle
Maximum Duty Cycle
Flyback Blanking Time
4
3
2
1
0
96
95
2.2
2.0
94
1.8
–55°C
125°C
25°C
93
92
1.6
1.4
91
90
1.2
1.0
0
10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
–75 –50 –25
0
25 50 75 100 125 150
–75 –50 –25
0
25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
JUNCTION TEMPERATURE (°C)
LT1072 • TPC01
LT1072 • TPC02
LT1072 • TPC03
Isolated Mode Flyback Reference
Voltage
Minimum Input Voltage
Switch Saturation Voltage
2.9
2.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
23
22
21
20
19
18
17
16
15
SWITCH CURRENT = 1.25A
150°C
R
= 500Ω
= 1kΩ
FEEDBACK
FEEDBACK
100°C
2.7
25°C
–55°C
R
2.6
2.5
SWITCH CURRENT = 0A
R
= 10kΩ
FEEDBACK
2.4
2.3
–75 –50 –25
0
25 50 75 100 125 150
1
1.25
25 50
0
0.25 0.5 0.75
1.5 1.75
2
–75 –50 –25
0
75 100 125 150
TEMPERATURE (°C)
SWITCH CURRENT (A)
TEMPERATURE (C°)
LT1072 • TPC04
LT1072 • TPC05
LT1072 • TPC06
Reference Voltage and Switching
Frequency vs Temperature
Feedback Bias Current vs
Temperature
Line Regulation
1.250
1.248
1.246
1.244
42
41
40
39
800
700
600
500
400
300
200
100
0
5
4
3
SWITCHING FREQUENCY
T = 150°C
J
2
1
0
–1
–2
–3
1.242
1.240
1.238
1.236
1.234
38
37
36
35
34
T = –55°C
J
REFERENCE VOLTAGE
–4
–5
25 50
TEMPERATURE (°C)
25 50
–75 –50 –25
0
75 100 125 150
–75 –50 –25
0
75 100 125 150
0
10
30
40
50
60
20
TEMPERATURE (°C)
INPUT VOLTAGE (V)
LT1072 • TPC08
LT1072 • TPC09
LT1072 • TPC07
1072fc
4
LT1072
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
(Shutdown Mode)
Driver Current* vs Switch Current
Supply Current vs Input Voltage*
80
70
60
50
40
30
20
10
0
15
14
13
12
11
10
9
160
140
120
100
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.
90% DUTY CYCLE
V
= 50mV
C
80
60
50% DUTY CYCLE
10% DUTY CYCLE
8
40
20
0
7
V
= 0V
C
6
0% DUTY CYCLE
5
0
0.2 0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
2
0
10
20
40
50
60
0
10
30
40
50
60
30
20
INPUT VOLTAGE (V)
SWITCH CURRENT (A)
SUPPLY VOLTAGE (V)
*AVERAGE LT1072 POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
LT1072 • TPC12
*UNDER VERY LOW OUTPUT CURRENT CONDITIONS,
DUTY CYCLE FOR MOST CIRCUITS WILL APPROACH
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT
10% OR LESS
LT1072 • TPC10
LT1072 • TPC11
Normal/Flyback Mode Threshold
on Feedback Pin
Shutdown Mode Supply Current
Error Amplifier Transconductance
500
–24
–22
–20
–18
–16
–14
–12
–10
–8
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
200
180
160
140
∆I (V PIN)
C
G
=
490
480
470
460
450
440
430
420
410
400
m
∆V (FB PIN)
FEEDBACK PIN VOLTAGE
(AT THRESHOLD)
T = 150°C
120
100
80
60
40
20
0
J
–55°C ≤ T ≤ 125°C
J
FEEDBACK PIN CURRENT
(AT THRESHOLD)
–6
–4
150
0
–50
50
100 125
–75 –50 –25
0
25 50 75 100 125 150
–25
0
25
75
0
10 20 30 40 50 60 70 80 90 100
PIN VOLTAGE (mV)
TEMPERATURE (°C)
TEMPERATURE (C°)
V
C
LT1072 • TPC13
LT1072 • TPC15
LT1072 • TPC14
Idle Supply Current vs
Temperature
Shutdown Thresholds
Feedback Pin Clamp Voltage
11
10
9
500
450
400
350
300
250
200
150
100
50
400
350
300
250
200
150
100
50
–400
–350
–300
–250
–200
–150
–100
–50
V
C
= 0.6V
CURRENT (OUT OF V PIN)
C
–55°C
8
V
V
= 60V
= 3V
7
SUPPLY
SUPPLY
25°C
6
150°C
VOLTAGE
5
4
3
V
VOLTAGE IS REDUCED UNTIL
C
REGULATOR CURRENT DROPS
2
BELOW 300µA
0
0
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 0.7 0.8 0.9
FEEDBACK CURRENT (mA)
1
–75 –50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
TEMPERATURE (°C)
LT1072 • TPC16
LT1072 • TPC18
LT1072 • TPC17
1072fc
5
LT1072
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Transconductance of Error
Amplifier
VC Pin Characteristics
Switch “Off” Characteristics
300
200
7000
6000
5000
4000
3000
2000
1000
0
–30
0
1000
900
800
700
600
500
400
300
200
100
0
V
= 1.5V (CURRENT INTO V PIN)
C
FB
θ
30
100
V
= 55V
SUPPLY
60
V
= 40V
SUPPLY
T = 25°C
0
J
G
V
= 15V
m
SUPPLY
90
V
= 3V
SUPPLY
–100
–200
–300
–400
120
150
180
210
V
= 0.8V (CURRENT OUT OF V PIN)
C
FB
–1000
0
0.5
1.0
1.5
2.0
2.5
1k
10k
100k
1M
10M
0
10 20 30 40 50 60 70 80 90 100
SWITCH VOLTAGE (V)
FREQUENCY (Hz)
V
PIN VOLTAGE (V)
C
LT1072 • TPC19
LT1072 • TPC20
LT1072 • TPC21
W
BLOCK DIAGRA
SWITCH
OUT
V
16V
IN
2.3V
REG
FLYBACK
ERROR
AMP
40kHz
OSC
LOGIC
COMP
DRIVER
ANTI-
SAT
MODE
SELECT
–
FB
ERROR
AMP
V
C
+
+
SHUTDOWN
CIRCUIT
CURRENT
AMP
0.16Ω
0.16Ω
–
GAIN
≈ 6
E1* E2
1.24V
REF
0.15V * ALWAYS CONNECT E1 TO GROUND PIN ON MINIDIP AND SURFACE MOUNT
PACKAGES. EMITTERS TIED TO GROUND ON TO-3 AND TO-220 PACKAGES
GND
LT1072 • BD01
1072fc
6
LT1072
U
LT1072 OPERATIO
The LT1072 is a current mode switcher. 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 fre-
quency 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 LT1072. This low-dropout
design allows input voltage to vary from 3V to 60V with
virtually no change in device performance. A 40kHz
oscillator is the basic clock for all internal timing. It turns
“on” the output switch via the logic and driver circuitry.
Special adaptive antisat 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.
inside the LT1072 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 LT1072 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 AN-19 for full application details.
Extra Pins on the MiniDIP and Surface Mount Packages
The 8 and 16-pin versions of the LT1072 have the emitters
of the power transistor brought out separately from the
ground pin. This eliminates errors due to ground pin
voltagedropsandallowstheusertoreduceswitchcurrent
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
when switch currents exceed 100mA. 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.”
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 LT1072 to disconnect the main error
amplifier output and connects the output of the flyback
amplifier to the comparator input. The LT1072 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
nodirectconnectionbetweeninputandoutput.Theoutput
is fully floating up to the breakdown voltage of the
transformer windings. Multiple floating outputs are easily
obtainedwithadditionalwindings. Aspecialdelaynetwork
Thermal Considerations When Using Small Packages
The low supply current and high switch efficiency of the
LT1072 allow it to be used without a heat sink in most
applicationswhentheTO-220orTO-3packageisselected.
These packages are rated at 50°C/W and 35°C/W
respectively. The small packages, however, are rated at
greater than 100°C/W. Care should be taken with these
packages to ensure that the worse case input voltage and
load current conditions do not cause excessive die
temperatures. The following formulas can be used as a
1072fc
7
LT1072
U
LT1072 OPERATIO
rough guide to calculate LT1072 power dissipation. For
more details, the reader is referred to Application Note 19
(AN19), “Efficiency Calculations” section.
The third approach for lower current applications is to
leave the second switch emitter 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.
Average supply current (including driver current) is:
IIN ≈ 6mA + ISW(0.004 + DC/40)
ThefourthapproachistoclamptheVC pintoavoltageless
than its internal clamp level of 2V. The LT1072 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 AN-19 for details.
ISW = switch current
DC = switch duty cycle
Switch power dissipation is given by:
P
SW = (ISW)2 • RSW • DC
R
SW = LT1072 switch “on” resistance (1Ω maximum)
LT1072 Synchronizing
Total power dissipation is the sum of supply current times
input voltage plus switch power:
TheLT1072canbeexternallysynchronizedinthefrequency
range of 48kHz to 70kHz. 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 1µs. C2 sets the pulse width at ≈ 0.35µs.
The effect of a synchronizing pulse on the LT1072
amplifier offset can be calculated from:
PTOT = (llN)(VIN) + PSW
In a typical example, using a boost converter to generate
12V @ 0.12A from a 5V input, duty cycle is approximately
60%, and switch current is about 0.65A, yielding:
llN = 6mA + 0.65(0.004 + DC/40) = 18mA
PSW = (0.65)2 • 1Ω • (0.6) = 0.25W
PTOT = (5V)(0.018A) + 0.25 = 0.34W
V
KT
C
(t )(f ) I +
S
S
C
(
(
(
(
R3
q
∆V
=
OS
I
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.
C
KT
q
= 26mV at 25°C
tS = pulse width
fS = pulse frequency
IC = LT1072 VC source current (≈ 200µA)
VC = LT1072 operating VC voltage (1V to 2V)
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 LT1072 will
protect the die in most applications by shutting off switch
current. Thermal limit is not a tested parameter, however,
andshouldbeconsideredonlyfornon-criticalapplications
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
conditions must be tolerated for extended periods of time.
R3 = resistor used to set mid-frequency “zero” in LT1072
frequency compensation network.
With tS = 0.35µs, fS = 50kHz, VC = 1.5V, and R3 = 2KΩ,
offset voltage shift is ≈2.2mV. 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
lowvaluesofR3, solargerdrivesmayhavetobeused. The
transistor must be capable of pulling the VC pin to within
200mV of ground to ensure synchronizing.
1072fc
8
LT1072
U
LT1072 OPERATIO
Synchronizing with Bipolar Transistor
Synchronizing with MOS Transistor
V
V
IN
IN
LT1072
LT1072
V
C
V
C
GND
GND
C2
C2
D1
R1
3k
200pF
68pF
1N4158
R3
R3
C1
2N2369
VN2222*
C1
R2
R2
2.2k
D2
1N4158
FROM 5V
LOGIC
FROM 5V
LOGIC
2.2k
*SILICONIX OR EQUIVALENT
LT1072 • OP01
LT1072 • OP02
U
TYPICAL APPLICATIO S
Totally Isolated Converter
OPTIONAL
OUTPUT FILTER
L1
10µH
D1
15V
1:N
+
+
C5
R4
2.7k
C3
0.47µF
C1
N
N
200µF
200µF
COM
–15V
+
+
C6
L2
C4
200µF
200µF
10µH
V
IN
V
SW
+
C5
25µF*
V
IN
5V
LT1072
N = 0.875 = 7:8
FOR V = 15V
OUT
FB
C2
V
GND
C
500Ω
R2
0.01µF
5k
*REQUIRED IF INPUT LEADS ≥ 2”
≈ 16V
V
IN
0
SWITCH VOLTAGE
t
ON
t
OFF
V
+ V (V = DIODE FORWARD VOLTAGE)
f f
OUT
SECONDARY VOLTAGE
0V
N • V
IN
LT1072 • TA03
1072fc
9
LT1072
U
TYPICAL APPLICATIO S
Flyback Converter
CLAMP TURN-ON
SPIKE
L2
10µH
V
SNUB
C4
V
+ V
f
OUT
N
200µF
a
PRIMARY FLYBACK VOLTAGE =
LT1072 SWITCH VOLTAGE
V
IN
OPTIONAL
FILTER
b
d
AREA “a” = AREA “b” TO MAINTAIN
ZERO DC VOLTS ACROSS PRIMARY
0V
V
+ V
f
D1
OUT
V
OUT
V
IN
5V
20 TO 30V
c
SECONDARY VOLTAGE
N • V
IN
1.5A
1
N*
R4
1k
C3
0.47µF
**
AREA “c” = AREA “d” TO MAINTAIN
ZERO DC VOLTS ACROSS SECONDARY
0V
+
C1
500µF
1
3
N* =
∆I
I
PRI
D2
V
R1
3.74k
IN
V
PRIMARY CURRENT
SW
0
0
+
C4
25µF*
LT1072
I
PRI
N
SECONDARY CURRENT
I
PRI
FB
V
GND
C
LT1070 SWITCH CURRENT
SNUBBER DIODE CURRENT
R2
1.24k
R3
1.5k
0
0
I
PRI
C2
0.15µF
*REQUIRED IF INPUT LEADS ≥ 2"
**OPTIONAL TO REPLACE R4 AND C3
(I ) (L )
PRI
L
t =
V
SNUB
LT1072 • TA04
Negative to Positive Buck-Boost Converter
External Current Limit
L2
V
IN
V
SW
FB
OPTIONAL
OUTPUT
FILTER
C3
L1**
220µH
LT1072
D1
V
OUT
12V, 0.5A
V
+
IN
V
V
SW
GND
C
V
IN
R1
11.3k
+
C2
1000µF
–
+
C4
25µF*
LT1072
Q1
R1
1k
R2
C2
NOTE THAT THE LT1072 GND PIN
OPTIONAL
INPUT
FILTER
FB
V
GND
C
Q1
C1
R3
2.2k
R2
1.24k
1000pF
L3
C1
0.22µF
*REQUIRED IF INPUT LEADS ≥ 2"
**PULSE ENGINEERING 52626
IS NO LONGER COMMON TO V (–)
IN
R
S
V
IN
–12V
LT1072 • TA06
LT1072 • TA05
1072fc
10
LT1072
U
TYPICAL APPLICATIO S
Positive to Negative Buck-Boost Converter
†
†
D3
*REQUIRED IF INPUT LEADS ≥ 2"
R5
1N4001
**PULSE ENGINEERING 92113
470Ω, 1W
V
IN
10 TO 30V
†
TO AVOID START-UP PROBLEMS
C5
FOR INPUT VOLTAGES BELOW 10V,
100µF*
CONNECT ANODE OF D3 TO V
AND REMOVE R5. C1 MAY BE
,
IN
V
IN
V
SW
REDUCED FOR LOWER OUTPUT
CURRENTS. C1 ≈ (500µF)(I ).
+
OUT
C4
5µF
LT1072
FOR 5V OUTPUTS, REDUCE R3
TO 1.5k, INCREASE C2 TO 0.3µF,
AND REDUCE R6 TO 100Ω
D2
1N914
R1
10.7k
R4
47Ω
FB
V
GND
C
+
R3
5k
+
†
C3
2µF
C1
R2
1.24k
R6
470Ω
1000µF
C2
0.1µF
D1
V
OUT
–12V AT 2A
L1**
200µH
LT1072 • TA07
External Current Limit
V
X
LT1072
R2
R1
≈ 2V
D1
V
GND
C
500Ω
LT1072 • TA08
Voltage Boosted Boost Converter
R4
1.5k
1/2W
C3
0.68
D2
TOTAL INDUCTANCE = 8mH
INTERLEAVE PRIMARY AND
SECONDARY FOR LOW LEAKAGE
INDUCTANCE
1
L1
N = 5
V
IN
V
SW
+
V
IN
15V
LT1072
D1
R1
98k
V
OUT
100V AT 75mA
FB
V
GND
C
R3
10k
+
R2
1.24k
C1
200µF
C2
0.047µF
LT1072 • TA09
1072fc
11
LT1072
U
TYPICAL APPLICATIO S
Driving High Voltage FET
(for Offline Applications, See AN-25)
G
D
Q1
D1
V
IN
V
SW
+
10 TO 20V
LT1072
GND
LT1072 • TA10
Negative Buck Converter
+
C2
500µF
D1
R1
LOAD
4.64k
V
IN
V
–5.2V AT 1A
SW
L1**
220µH
C3
25µF*
+
Q1
2N3906
LT1072
OPTIONAL
FB
C1
V
INPUT
GND
C
FILTER
OPTIONAL
OUTPUT
FILTER
+
R2
1.24k
C4
200µF
L3
R3
V
IN
–20V
L2
4µH
*REQUIRED IF INPUT LEADS ≥ 2"
**PULSE ENGINEERING 52626
LT1072 • TA11
Positive Buck Converter
V
IN
D3
L2
V
IN
4µH
V
SW
FB
C5
OPTIONAL
OUTPUT
FILTER
200µF
+
C3
2.2µF
LT1072
R1
+
D2
3.74k
C5*
25µF
V
GND
C
1N914
+
R3
470Ω
R2
1.24k
R4
C2
1µF
10Ω
L1**
C1
220µH
1µF
r
5V, 1A
100mA
MINIMUM
+
C4
500µF
D1
*REQUIRED IF INPUT LEADS ≥ 2"
**PULSE ENGINEERING 52626
LT1072 • TA12
1072fc
12
LT1072
U
TYPICAL APPLICATIO S
Negative Boost Regulator
D2
V
IN
V
SW
R1
27k
R
0
LT1072
+
+
C3
10µF
C1
1000µF
(MINIMUM
LOAD)
+
C4
470µF*
FB
V
C
GND
R3
R2
1.24k
3.3k
L1
200µH
C2
0.22µF
D1
V
V
–15V
OUT
IN
–28V AT 0.25A
*REQUIRED IF INPUT LEADS ≥ 2"
LT1072 • TA13
U
PACKAGE DESCRIPTIO
J8 Package
8-Lead CERDIP (Narrow .300 Inch, Hermetic)
(Reference LTC DWG # 05-08-1110)
.405
(10.287)
MAX
CORNER LEADS OPTION
(4 PLCS)
.005
(0.127)
MIN
6
5
4
8
7
.023 – .045
(0.584 – 1.143)
HALF LEAD
OPTION
.025
.220 – .310
(5.588 – 7.874)
.045 – .068
(0.635)
RAD TYP
(1.143 – 1.650)
FULL LEAD
OPTION
1
2
3
.200
(5.080)
MAX
.300 BSC
(7.62 BSC)
.015 – .060
(0.381 – 1.524)
.008 – .018
(0.203 – 0.457)
0° – 15°
.045 – .065
(1.143 – 1.651)
.125
3.175
MIN
NOTE: LEAD DIMENSIONS APPLY TO SOLDER DIP/PLATE
OR TIN PLATE LEADS
.014 – .026
(0.360 – 0.660)
.100
(2.54)
BSC
J8 0801
OBSOLETE PACKAGE
1072fc
13
LT1072
U
PACKAGE DESCRIPTIO
K Package
4-Lead TO-3 Metal Can
(Reference LTC DWG # 05-08-1311)
0.760 – 0.775
(19.30 – 19.69)
0.320 – 0.350
(8.13 – 8.89)
0.060 – 0.135
(1.524 – 3.429)
0.420 – 0.480
(10.67 – 12.19)
0.038 – 0.043
(0.965 – 1.09)
1.177 – 1.197
(29.90 – 30.40)
0.655 – 0.675
(16.64 – 19.05)
0.470 TP
P.C.D.
0.151 – 0.161
(3.84 – 4.09)
DIA 2 PLC
0.167 – 0.177
(4.24 – 4.49)
R
0.490 – 0.510
(12.45 – 12.95)
R
72°
18°
K4(TO-3) 1098
OBSOLETE PACKAGE
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.400*
(10.160)
MAX
8
7
6
5
4
.255 ± .015*
(6.477 ± 0.381)
1
2
3
.130 ± .005
.300 – .325
.045 – .065
(3.302 ± 0.127)
(1.143 – 1.651)
(7.620 – 8.255)
.065
(1.651)
TYP
.008 – .015
(0.203 – 0.381)
.120
.020
(0.508)
MIN
(3.048)
MIN
+.035
.325
–.015
.018 ± .003
(0.457 ± 0.076)
.100
(2.54)
BSC
+0.889
8.255
(
)
N8 1002
–0.381
NOTE:
INCHES
1. DIMENSIONS ARE
MILLIMETERS
*THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
1072fc
14
LT1072
U
PACKAGE DESCRIPTIO
S8 Package
8-Lead Plastic Small Outline (Narrow .150 Inch)
(Reference LTC DWG # 05-08-1610)
.189 – .197
(4.801 – 5.004)
NOTE 3
.045 ±.005
.050 BSC
7
5
8
6
N
N
.245
MIN
.160 ±.005
.150 – .157
(3.810 – 3.988)
NOTE 3
.228 – .244
(5.791 – 6.197)
1
2
3
N/2
N/2
4
.030 ±.005
TYP
RECOMMENDED SOLDER PAD LAYOUT
1
2
3
.010 – .020
(0.254 – 0.508)
× 45°
.053 – .069
(1.346 – 1.752)
.004 – .010
(0.101 – 0.254)
.008 – .010
(0.203 – 0.254)
0°– 8° TYP
.016 – .050
(0.406 – 1.270)
.050
(1.270)
BSC
.014 – .019
(0.355 – 0.483)
TYP
NOTE:
INCHES
1. DIMENSIONS IN
(MILLIMETERS)
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)
SO8 0502
SW Package
16-Lead Plastic Small Outline (Wide .300 Inch)
(Reference LTC DWG # 05-08-1620)
.050 BSC .045 ±.005
.030 ±.005
.398 – .413
(10.109 – 10.490)
NOTE 4
TYP
15 14
12
10
9
N
16
N
13
11
.325 ±.005
.420
MIN
.394 – .419
(10.007 – 10.643)
NOTE 3
N/2
8
1
2
3
N/2
RECOMMENDED SOLDER PAD LAYOUT
2
3
5
7
1
4
6
.291 – .299
(7.391 – 7.595)
NOTE 4
.037 – .045
(0.940 – 1.143)
.093 – .104
(2.362 – 2.642)
.010 – .029
× 45°
(0.254 – 0.737)
.005
(0.127)
RAD MIN
0° – 8° TYP
.050
(1.270)
BSC
.004 – .012
.009 – .013
(0.102 – 0.305)
NOTE 3
(0.229 – 0.330)
.014 – .019
.016 – .050
(0.356 – 0.482)
TYP
(0.406 – 1.270)
NOTE:
1. DIMENSIONS IN
INCHES
(MILLIMETERS)
S16 (WIDE) 0502
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)
1072fc
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LT1072
U
PACKAGE DESCRIPTIO
T Package
5-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1421)
.165 – .180
(4.191 – 4.572)
.147 – .155
(3.734 – 3.937)
DIA
.390 – .415
(9.906 – 10.541)
.045 – .055
(1.143 – 1.397)
.230 – .270
(5.842 – 6.858)
.570 – .620
(14.478 – 15.748)
.620
(15.75)
TYP
.460 – .500
(11.684 – 12.700)
.330 – .370
(8.382 – 9.398)
.700 – .728
(17.78 – 18.491)
.095 – .115
(2.413 – 2.921)
SEATING PLANE
.152 – .202
(3.861 – 5.131)
.155 – .195*
(3.937 – 4.953)
.260 – .320
(6.60 – 8.13)
.013 – .023
(0.330 – 0.584)
.067
BSC
.135 – .165
(3.429 – 4.191)
.028 – .038
(0.711 – 0.965)
(1.70)
* MEASURED AT THE SEATING PLANE
T5 (TO-220) 0801
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1070/HV
5A I , 40kHz, High Efficiency Switching Regulator
V =3V to 40/60V, V
Package
up to 65/75V, I =6mA, I <50µA, TO220-5
OUT Q SD
SW
IN
LT1071/HV
LT1082
2.5A I , 40kHz, High Efficiency Switching Regulator V =3V to 40/60V, V
up to 65/75V, I =6mA, I <50µA,TO220-5 Package
SW
IN
OUT Q SD
1A I , 60kHz, High Efficiency Switching Regulator
V =3V to 75V, V
Packages
up to 100V, I =4.5mA, I <120µA, DD, N8, TO220-5
SW
IN
OUT Q SD
LT1170/HV
5A I , 100kHz, High Efficiency Switching Regulator V =3V to 40/60V, V
up to 65/75V, I =6mA, I <50µA, DD, N8, S16,
OUT Q SD
SW
IN
TO220-5 Packages
LT1171/HV
2.5A I , 100kHz, High Efficiency Switching
Regulator
V =3V to 40/60V, V
TO220-5 Packages
up to 65/75V, I =6mA, I <50µA, DD, N8, S16,
Q SD
SW
IN
OUT
LT1172/HV
1.25A I , 100kHz, High Efficiency Switching
Regulator
V =3V to 40/60V, V
TO220-5 Packages
up to 65/75V, I =6mA, I <50µA, DD, N8, S16,
Q SD
SW
IN
OUT
LT1307/LT1307B
LT1317/LT1317B
LT1370/HV
600mA I , 600kHz, High Efficiency Switching
Regulator
V =1V to 12V, V
Packages
up to 28V, I =50µA/1mA, I <1µA, MS8, N8, S8
SW
IN
OUT Q SD
600mA I , 600kHz, High Efficiency Switching
V =1.5V to 12V, V
up to 28V, I =100µA/4.8mA, I <30µA/28µA, MS8,
OUT Q SD
SW
IN
Regulator
S8 Packages
6A ISW, 500kHz, High Efficiency Switching Regulator V =2.7V to 30V, V
up to 35/42V, I =4.5mA, I <12µA, DD, T0220-7
Q SD
IN
OUT
Packages
LT1371/HV
3A ISW, 500kHz, High Efficiency Switching Regulator V =2.7V to 30V, V
up to 35/42V, I =4mA, I <12µA, DD, S20,
OUT Q SD
IN
T0220-7 Packages
1072fc
LW/TP 1102 1K REV C • PRINTED IN USA
16 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
■
■
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
LINEAR TECHNOLOGY CORPORATION 1988
相关型号：
LT1072HVCT#PBF
LT1072 - 1.25A High Efficiency Switching Regulator; Package: TO-220; Pins: 5; Temperature Range: 0°C to 70°C
Linear
LT1072HVIK
IC 1.25 A SWITCHING REGULATOR, 40 kHz SWITCHING FREQ-MAX, MBFM2, METAL, TO-3, 2 PIN, Switching Regulator or Controller
Linear
©2020 ICPDF网 联系我们和版权申明