10701fe
1
LT1070/LT1071
FEATURES
APPLICATIO S
U
DESCRIPTIO
U
TYPICAL APPLICATIO
U
5A and 2.5A High Efficiency
Switching Regulators
■
Wide Input Voltage Range: 3V to 60V
■
Low Quiescent Current: 6mA
■
Internal 5A Switch (2.5A for LT1071)
■
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
■
Comes in Standard 5-Pin TO-220 Package
■
Can be Externally Synchronized (Consult Factory)
The LT
®
1070/LT1071 are monolithic high power switch-
ing regulators. They can be operated in all standard switch-
ing configurations including buck, boost, flyback, for-
ward, 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 func-
tions allows the LT1070/LT1071 to be built in a standard
5-pin T0-220 power package. This makes it extremely
easy to use and provides “bust proof” operation similar to
that obtained with 3-pin linear regulators.
The LT1070/LT1071 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 LT1070/LT1071 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 typical for standby
operation. Totally isolated and regulated outputs can be
generated by using the optional “flyback regulation mode”
built into the LT1070/LT1071, without the need for
optocouplers or extra transformer windings.
USER NOTE:
This data sheet is only intended to provide specifications, graphs and a general functional
description of the LT1070/LT1071. Application circuits are included to show the capability of the
LT1070/LT1071. 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 LT1071 by factoring in the lower switch current
rating. A second Application Note, AN25, which details off-line applications is available.
+
R1
10.7k
1%
R2
1.24k
1%
1070/71 TA01
12V
1A
R3
1k
C1
1µF
C2
1000µF
+
C3*
100µF
L1**
150µH
D1
5V
V
SW
V
C
V
IN
LT1070
GND FB
C3
100µF
L2
10µH
OUTPUT
FILTER
*
**REQUIRED IF INPUT LEADS ≥ 2"
PULSE ENGINEERING 92113
INPUT VOLTAGE (V)
0
POWER (W)**
60
80
100
40
1070/71 TA02
40
20
010 20 30 50
BOOST
BUCK/BOOST
V
O
= 30V
FLYBACK
ISOLATED
BUCK/BOOST
V
O
= 5V
ROUGH GUIDE ONLY. BUCK MODE P
OUT
= 5A • V
OUT
.
SPECIAL TOPOLOGIES DELIVER MORE POWER
DIVIDE VERTICAL POWER SCALE BY 2 FOR LT1071
*
**
Maximum Output Power*
Boost Converter (5V to 12V)
■
Logic Supply 5V at 10A
■
5V Logic to ±15V Op Amp Supply
■
Off-Line Converter Up to 200W
■
Battery Upconverter
■
Power Inverter (+ to –) or (– to +)
■
Fully Floating Multiple Outputs
■
For Lower Current Applications, See the LT1072
, LTC and LT are registered trademarks of Linear Technology Corporation.
2
LT1070/LT1071
10701fe
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
REF
Reference Voltage Measured at Feedback Pin, V
C
= 0.8V 1.224 1.244 1.264 V
●1.214 1.244 1.274 V
I
B
Feedback Input Current V
FB
= V
REF
350 750 nA
●1100 nA
g
m
Error Amplifier Transconductance ∆I
C
= ±25µA 3000 4400 6000 µmho
●2400 7000 µmho
Error Amplifier Source or Sink Current V
C
= 1.5V 150 200 350 µA
●120 400 µA
Error Amplifier Clamp Voltage Hi Clamp, V
FB
= 1V 1.80 2.30 V
Lo Clamp, V
FB
= 1.5V 0.25 0.38 0.52 V
Reference Voltage Line Regulation 3V ≤ V
IN
≤ V
MAX
, V
C
= 0.8V ●0.03 %/V
A
V
Error Amplifier Voltage Gain 0.9V ≤ V
C
≤ 1.4V 500 800 V/V
Minimum Input Voltage ●2.6 3.0 V
I
Q
Supply Current 3V ≤ V
IN
≤ V
MAX
, V
C
= 0.6V 6 9 mA
Control Pin Threshold Duty Cycle = 0 0.8 0.9 1.08 V
●0.6 1.25 V
Normal/Flyback Threshold on Feedback Pin 0.4 0.45 0.54 V
ABSOLUTE MAXIMUM RATINGS
W
WW
U
Supply Voltage
LT1070/LT1071 (Note 2) .................................... 40V
LT1070HV/LT1071HV (Note 2) .......................... 60V
Switch Output Voltage
LT1070/LT1071 .................................................. 65V
LT1070HV/LT1071HV ........................................ 75V
Feedback Pin Voltage (Transient, 1ms) ................ ±15V
Operating Junction Temperature Range
Commercial (Operating) ....................... 0°C to 100°C
Commercial (Short Circuit)................... 0°C to 125°C
Industrial ......................................... –40°C to 125°C
Military (OBSOLETE) ................. –55°C to 150°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
PACKAGE/ORDER INFORMATION
W
UU
ORDER PART
NUMBER
LT1070CK
LT1070HVCK
LT1070HVMK
LT1070IK
LT1070MK
LT1071CK
LT1071HVCK
LT1071HVMK
LT1071MK
ORDER PART
NUMBER
LT1070CT
LT1070HVCT
LT1070HVIT
LT1070IT
LT1071CT
LT1071HVCT
LT1071HVIT
LT1071IT
T
JMAX
= 100°C, θ
JA
= 35°C/ W, Q
JC
= 2°C (LT1070C, I)
T
JMAX
= 150°C, θ
JA
= 35°C/ W, Q
JC
= 2°C (LT1070M)
T
JMAX
= 100°C, θ
JA
= 35°C/ W, Q
JC
= 4°C (LT1071C, I)
T
JMAX
= 150°C, θ
JA
= 35°C/ W, Q
JC
= 4°C (LT1071M)
2
4
1
3
VSW VC
FB
CASE
IS GND
VIN
K PACKAGE
4-LEAD TO-3 METAL CAN
BOTTOM VIEW
T
JMAX
= 100°C, θ
JA
= 75°C/ W, Q
JC
= 2°C (LT1070C, I)
T
JMAX
= 100°C, θ
JA
= 75°C/ W, Q
JC
= 4°C (LT1071C)
T PACKAGE
5-LEAD PLASTIC TO-220
V
IN
V
SW
GND
FB
V
C
FRONT VIEW
5
4
3
2
1
ELECTRICAL CHARACTERISTICS
(Note 1)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
OBSOLETE PACKAGE
Consider the T5 Package for Alternate Source
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 specified.
10701fe
3
LT1070/LT1071
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V
FB
Flyback Reference Voltage I
FB
= 50µA 15 16.3 17.6 V
●14 18.0 V
Change in Flyback Reference Voltage 0.05 ≤ I
FB
≤ 1mA 4.5 6.8 8.5 V
Flyback Reference Voltage Line Regulation I
FB
= 50µA, 3V ≤ V
IN
≤ V
MAX
(Note 3) 0.01 0.03 %/V
Flyback Amplifier Transconductance (g
m
)∆I
C
= ±10µA 150 300 650 µmho
Flyback Amplifier Source and Sink Current V
C
= 0.6V, I
FB
= 50µA (Source) ●15 32 70 µA
V
C
= 0.6V, I
FB
= 50µA (Sink) ●25 40 70 µA
B
V
Output Switch Breakdown Voltage 3V ≤ V
IN
≤ V
MAX
,
I
SW
= 1.5mA
(LT1070/LT1071) ●65 90 V
(LT1070HV/LT1071HV) ●75 90 V
V
SAT
Output Switch “On” Resistance (Note 4) LT1070 ●0.15 0.24 Ω
LT1071 ●0.30 0.50 Ω
Control Voltage to Switch Current LT1070 8 A/V
Transconductance LT1071 4 A/V
I
LIM
Switch Current Limit (LT1070) Duty Cycle ≤ 50%, T
J
≥ 25°C●510A
Duty Cycle ≤ 50%, T
J
< 25°C●511A
Duty Cycle = 80% (Note 5) ●410A
Switch Current Limit (LT1071) Duty Cycle ≤ 50%, T
J
≥ 25°C●2.5 5.0 A
Duty Cycle ≤ 50%, T
J
< 25°C●2.5 5.5 A
Duty Cycle = 80% (Note 5) ●2.0 5.0 A
∆I
IN
Supply Current Increase During 25 35 mA/A
∆I
SW
Switch “On” Time
f Switching Frequency 35 40 45 kHz
●33 47 kHz
DC (Max) Maximum Switch Duty Cycle 90 92 97 %
Flyback Sense Delay Time 1.5 µs
Shutdown Mode Supply Current 3V ≤ V
IN
≤ V
MAX
, V
C
= 0.05V 100 250 µA
Shutdown Mode Threshold Voltage 3V ≤ V
IN
≤ V
MAX
100 150 250 mV
●50 300 mV
Note 1: Absolute Maximum Ratings are those values beyond which the life of
a device may be impaired.
Note 2: Minimum switch “on” time for the LT1070/LT1071 in current limit is
≈1µs. This limits the maximum input voltage during short-circuit conditions,
in the buck and inverting modes only
, to ≈35V. Normal (unshorted) conditions
are not affected. Mask changes are being implemented which will reduce
minimum “on” time to ≤1µs, increasing maximum short-circuit input voltage
above 40V. If the present LT1070/LT1071 (contact factory for package date
code) 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:
The value of the resistor is given by:
R = – R
L
t • f • V
IN
– V
F
I
LIMIT
t = Minimum “on” time of LT1070/LT1071 in current limit, ≈1µs
f = Operating frequency (40kHz)
V
F
= Forward voltage of external catch diode at I
LIMIT
I
LIMIT
= Current limit of LT1070 (≈8A), LT1071 (≈4A)
R
L
= Internal series resistance of inductor
Note 3: V
MAX
= 55V for LT1070HV and LT1071HV to avoid switch
breakdown.
Note 4: Measured with V
C
in hi clamp, V
FB
= 0.8V. I
SW
= 4A for LT1070
and 2A for LT1071.
Note 5: For duty cycles (DC) between 50% and 80%, minimum
guaranteed switch current is given by I
LIM
= 3.33 (2 – DC) for the
LT1070 and I
LIM
= 1.67 (2 – DC) for the LT1071.
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 specified.
4
LT1070/LT1071
10701fe
TYPICAL PERFORMANCE CHARACTERISTICS
UW
Switch Current Limit vs Duty Cycle
DUTY CYCLE (%)
0
SWITCH CURRENT (A)
16
14
12
10
8
6
4
2
080
1070/71 G01
20 40 60 1007010 30 50 90
FOR LT1071, DIVIDE
VERTICAL SCALE BY 2
–55°C
125°C
25°C
Flyback Blanking Time
JUNCTION TEMPERATURE (°C)
–75
1.0
TIME (µs)
1.2
1.6
1.8
2.0
–25 25 50 150
1070/71 G03
1.4
–50 0 75 100 125
2.2
JUNCTION TEMPERATURE (°C)
–75
90
DUTY CYCLE (%)
91
93
94
95
–25 25 50 150
1070/71 G02
92
–50 0 75 100 125
96
Maximum Duty Cycle
Minimum Input Voltage
TEMPERATURE (°C)
–75
2.3
MINIMUM INPUT VOLTAGE (V)
2.4
2.6
2.7
2.8
–25 25 50 150
1070/71 G04
2.5
–50 0 75 100 125
2.9
SWITCH CURRENT = 5A
SWITCH CURRENT = 0A
Switch Saturation Voltage
SWITCH CURRENT (A)
0
SWITCH SATURATION VOLTAGE (V)
0.8
1.2
8
1070/71 G05
0.4
0
1.0
25°C
1.4
0.6
0.2
246
1357
1.6 FOR LT1071, DIVIDE
CURRENT BY 2
100°C
–55°C
150°C
TEMPERATURE (°C)
–75
FLYBACK VOLTAGE (V)
19
20
21
125
1070/71 G06
18
17
15 –25 25 75–50 1500 50 100
16
23
22
R
FEEDBACK
= 500Ω
R
FEEDBACK
= 1k
R
FEEDBACK
= 10k
Line Regulation Feedback Bias Current
vs Temperature
INPUT VOLTAGE (V)
0
–5
REFERENCE VOLTAGE CHANGE (mV)
–3
–1
1
10 20 30 40
1070/71 G07
50
3
5
–4
–2
0
2
4
60
TJ = 150°C
TJ = 25°C
TJ = –55°C
TEMPERATURE (°C)
–75
FEEDBACK BIAS CURRENT (nA)
600
500
400
300
200
100
0125
1070/71 G09
–25 25 75–50 1500 50 100
800
700
Reference Voltage
vs Temperature
TEMPERATURE (°C)
–75
REFERENCE VOLTAGE (V)
SWITCHING FREQUENCY (kHz)
1.246
1.244
1.242
1.240
1.238
1.236
1.234 125
1070/71 G08
–25 25 75–50 1500 50 100
1.250
1.248
40
39
38
37
36
35
34
42
41
SWITCHING
FREQUENCY
REFERENCE
V0LTAGE
10701fe
5
LT1070/LT1071
TYPICAL PERFORMANCE CHARACTERISTICS
UW
Supply Current vs Supply Voltage
(Shutdown Mode)Driver Current* vs Switch Current
SWITCH CURRENT (A)
0
DRIVER CURRENT (mA)
160
140
120
100
80
60
40
20
0 4
1070/71 G10
1
*
23 5
T
J
≥ 25°C
AVERAGE LT1070 POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT
T
J
= –55°C
SUPPLY VOLTAGE (V)
0
SUPPLY CURRENT (µA)
60
80
100
30 50
1070/71 G12
40
20
010 20 40
120
140
160
60
T
J
= 25°C
V
C
= 50mV
V
C
= 0V
Supply Current vs Input Voltage*
INPUT VOLTAGE (V)
0
6
INPUT CURRENT (mA)
8
10
12
10 20 30
*
40
1070/71 G11
50
14
UNDER VERY LOW OUTPUT CURRENT
CONDITIONS, DUTY CYCLE FOR MOST
CIRCUITS WILL APPROACH 10% OR LESS
16
7
9
11
13
15
60
T
J
= 25°C
I
SWITCH
≤ 10mA
90% DUTY CYCLE
50% DUTY CYCLE
0% DUTY CYCLE
10% DUTY CYCLE
Feedback Pin Clamp Voltage
Shutdown Thresholds
TEMPERATURE (°C)
–75
V
C
PIN VOLTAGE (mV)
V
C
PIN CURRENT (µA)
300
250
200
150
100
50
0125
1070/71 G16
–25 25 75–50 1500 50 100
400
350
–300
–250
–200
–150
–100
–50
0
–400
–350
V
C
VOLTAGE IS REDUCED UNTIL
REGULATOR CURRENT DROPS
BELOW 300µA
VOLTAGE
CURRENT
(OUT OF V
C
PIN)
FEEDBACK CURRENT (mA)
0
FEEDBACK VOLTAGE (mV)
300
400
500
0.8
1070/71 G18
200
100
250
350
450
150
50
00.2 0.4 0.6
0.1 0.9
0.3 0.5 0.7 1.0
–55°C
25°C
150°C
TEMPERATURE (°C)
–75
IDLE SUPPLY CURRENT (mA)
7
9
11
125
1070/71 G14
5
3
6
8
10
4
2
1–25 25 75
–50 150
050 100
V
C
= 0.6V
V
SUPPLY
= 60V
V
SUPPLY
= 3V
Idle Supply Current
vs Temperature
Normal/Flyback Mode Threshold
on Feedback Pin
TEMPERATURE (°C)
–50
400
FEEDBACK PIN VOLTAGE (mV)
FEEDBACK PIN CURRENT (µA)
410
430
440
450
500
470
050 75
1070/71 G13
420
480
490
460
–4
–6
–10
–12
–14
–24
–18
–8
–20
–22
–16
–25 25 100 125 150
FEEDBACK PIN VOLTAGE
(AT THRESHOLD)
FEEDBACK PIN CURRENT
(AT THRESHOLD)
Error Amplifier Transconductance
TEMPERATURE (°C)
–75
TRANSCONDUCTANCE (µmho)
3000
4000
5000
125
1070/71 G14
2000
1000
2500
3500
4500
1500
500
0–25 25 75
–50 150
050 100
g
m
= (V
C
PIN)
(FB PIN)
∆I
∆V
Shutdown Mode Supply Current
V
C
PIN VOLTAGE (mV)
0
SUPPLY CURRENT (µA)
120
160
200
80
1070/71 G14
80
40
100
140
180
60
20
020 40 60
10 90
30 50 70 100
T
J
= 150°C
–55°C ≤ T
J
≤ 125°C
6
LT1070/LT1071
10701fe
TYPICAL PERFORMANCE CHARACTERISTICS
UW
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
The LT1070/LT1071 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 reaches a predetermined level. Control of output
OPERATION
U
Switch “Off” Characteristics
SWITCH VOLTAGE (V)
0
SWITCH CURRENT (µA)
600
800
1000
80
1070/71 G19
400
200
500
700
900
300
100
020 40 60
10 90
30 50 70 100
V
SUPPLY
=
3V 15V 40V 55V
FREQUENCY (Hz)
1000
TRANSCONDUCTANCE (µmho)
PHASE (°)
3000
4000
6000
7000
1k 100k 1M 10M
1070/71 G21
–1000 10k
5000
2000
0
150
90
θ
60
0
–30
210
30
120
180
g
m
Transconductance of Error
Amplifier
VC Pin Characteristics
VC PIN VOLTAGE (V)
0
–400
VC PIN CURRENT (µA)
–300
–200
–100
300
100
0.5 1.0
200
0
1.5 2.0 2.5
1070/71 G20
VFB = 1.5V
(CURRENT INTO
VC PIN)
VFB = 0.8V
(CURRENT OUT OF VC PIN)
TJ = 25°C
BLOCK DIAGRAM
W
–
+
–
+
ERROR
AMP
CURRENT
AMP 0.02Ω
(0.04Ω LT1071)
SHUTDOWN
CIRCUIT
MODE
SELECT
40kHz
OSC LOGIC DRIVER
ANTISAT
16V
5A, 75V
SWITCH
V
IN
FB
V
C
COMP
GAIN ≈ 6
0.15V
1070/71 BD
1.24V
REF
2.3V
REG FLYBACK
ERROR
AMP
SWITCH
OUT
10701fe
7
LT1070/LT1071
OPERATION
U
midfrequencies in the energy storage inductor. This
greatly simplifies closed-loop frequency compensation
under widely varying input voltage or output load condi-
tions. Finally, it allows simple pulse-by-pulse current
limiting to provide maximum switch protection under
output overload or short-circuit conditions. A low drop-
out internal regulator provides a 2.3V supply for all
internal circuitry of the LT1070/LT1071. This low drop-
out 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 satura-
tion in the power switch and adjusts driver current
instantaneously to limit switch saturation. This mini-
mizes driver dissipation and provides very rapid turn-off
of the switch.
A 1.2V bandgap reference biases the positive input of the
error amplifier. The negative input is brought out for
output voltage sensing. This feedback pin has a second
function; when pulled low with an external resistor, it
programs the LT1070/LT1071 to disconnect the main
error amplifier output and connects the output of the
flyback amplifier to the comparator input. The LT1070/
LT1071 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 regu-
lating the amplitude of the flyback pulse, the output
voltage can be regulated with no direct connection be-
tween input and output. The output is fully floating up to
the breakdown voltage of the transformer windings.
Multiple floating outputs are easily obtained with addi-
tional windings. A special delay network inside the LT1070/
LT1071 ignores the leakage inductance spike at the
leading edge of the flyback pulse to improve output
regulation.
The error signal developed at the comparator input is
brought out externally. This pin (V
C
) has four different
functions. It is used for frequency compensation, current
limit adjustment, soft starting and total regulator shut-
down. During normal regulator operation this pin sits at
a voltage between 0.9V (low output current) and 2.0V
(high output current). The error amplifiers are current
output (g
m
) types, so this voltage can be externally
clamped for adjusting current limit. Likewise, a capacitor
coupled external clamp will provide soft start. Switch
duty cycle goes to zero if the V
C
pin is pulled to ground
through a diode, placing the LT1070/LT1071 in an idle
mode. Pulling the V
C
pin below 0.15V causes total
regulator shutdown, with only 50µA supply current for
shutdown circuitry biasing. See AN19 for full application
details.
TYPICAL APPLICATIONS
U
(Note that maximum output currents are divided by 2 for the LT1071)
R1*
R2**
1070/71 TA16
D1
SETS I
B(ON)
SETS I
B(OFF)
*
**
D2
C1
V
SW
V
IN
LT1070/LT1071
GND
Q1
Driving High Voltage NPN
Driving High Voltage FET (for Off-Line
Applications, See AN25)
1070/71 TA03
1070/71 TA03
10V
TO
20V
D1
VSW
GD
SQ1
VIN
LT1070/LT1071
GND
+
8
LT1070/LT1071
10701fe
TYPICAL APPLICATIONS
U
(Note that maximum output currents are divided by 2 for the LT1071)
Negative Current Boosted Buck Converter
1070/71 TA13
R3 R2
1.24k
Q1
2N3906
R4
12k
C2
C3
R1 MINIMUM
LOAD = 10mA –V
OUT
5V
10A
D1
T1
1:N
R5 •
•
C1
V
SW
V
C
V
IN
–V
IN
LT1070
GND FB
+
+
V
OUT
– 0.6V
1mA
R1 =
1070/71 TA12
R3 R2
1.24k
*
**REQUIRED IF INPUT LEADS ≥ 2"
PULSE ENGINEERING 92113
Q1
2N3906
R1
4.64k
C1
C2
1000µF
C3
100µF
V
IN
–20V
–5.2V
4.5A
D1 L1**
200µH
V
SW
V
C
V
IN
LT1070
GND
OPTIONAL INPUT
FILTER FB
LOAD
C4
200µF
L2
4µH
OPTIONAL
OUTPUT
FILTER
+
+
+
L3
Negative Buck Converter
Positive Buck Converter
R2
1.24k R4
10Ω
100mA
MINIMUM
1070/71 TA14
5V
4.5A
R3
470Ω
C1
1µF
D1
r
+
C3
2.2µF
+
C5*
100µF
+
C2
1µF
+
C4
1000µF
L1**
100µH
V
SW
V
C
V
IN
V
IN
LT1070
R1
3.74k
D2
1N914
GND FB
D3 L2
4µH
C5
200µF
OPTIONAL
OUTPUT
FILTER
*
**REQUIRED IF INPUT LEADS ≥2"
PULSE ENGINEERING 92112
10701fe
9
LT1070/LT1071
TYPICAL APPLICATIONS
U
(Note that maximum output currents are divided by 2 for the LT1071)
Positive Current Boosted Buck Converter
R3
680Ω
C1
0.33µF200pF
*REQUIRED IF INPUT LEADS ≥ 2"
R4
1.24k
C2
5000µF
V
OUT
5V
10A
V
IN
28V
R1
5k
V
SW
•
•
V
IN
C3
0.47µF
C6
0.002µF
D2
470Ω
2W
1:N
N ≈ 0.25
LT1070
GND V
C
FB
1070/71 TA19
R6
470Ω
–
+
COMP
LM308
V
IN
R2
1k R7
1.24k
R5
5k
V
–
7
D1
2
3
8
4
6V
+
+
C5*
100µF
+
Positive to Negative Buck/Boost Converter
+
R1
11.3k
1070/71 TA05
V
OUT
12V
2A
V
IN
–12V
R3
2.2k
C1
0.22µF
R2
1.24k
*
**REQUIRED IF INPUT LEADS ≥ 2"
PULSE ENGINEERING 92113
C2
1000µF
+
C4*
100µF
L1**
150µH
Q1
D1
V
SW
V
C
V
IN
LT1070
GND FB
C3
L2
OPTIONAL
OUTPUT
FILTER
L3
OPTIONAL
INPUT
FILTER
+R6
470Ω
1070/71 TA09
V
IN
10V TO 30V
*
**REQUIRED IF INPUT LEADS ≥ 2"
PULSE ENGINEERING 92113
†
TO AVOID START-UP
PROBLEMS FOR INPUT
VOLTAGES BELOW 10V,
CONNECT ANODE OF D3
TO V
IN
AND REMOVE R5.
C1 MAY BE REDUCED FOR
LOWER OUTPUT CURRENTS.
C1 ≈ (500µF)(I
OUT
) FOR 5V
OUTPUTS, REDUCE R3 TO
1.5k, INCREASE C2 TO 0.3µF
AND REDUCE R6 TO 100Ω.
V
OUT
–12V
2A
R3
5k R2
1.24k
C1
0.1µF
C5*
100µF
C3
2µF
+
C4
5µF
+
C1
†
1000µF
L1**
200µH
V
SW
V
C
V
IN
LT1070
R5
†
470Ω
1W
D3
†
1N4001
R1
10.7k R4
47Ω
D2
1N914
D1
GND FB
Negative to Positive Buck/Boost Converter
10
LT1070/LT1071
10701fe
TYPICAL APPLICATIONS
U
(Note that maximum output currents are divided by 2 for the LT1071)
Current Boosted Boost Converter
+
R4
1070/71 TA11
R3 R2
1.24k
R1
27k
C2
C3 I
N
C1
V
OUT
28V
4A
D2
D1
V
SW
V
C
V
IN
LT1070
GND
V
IN
16V TO 24V
FB
+
R1
27k
R
O
(MINIMUM
LOAD)
R2
1.24k
1070/71 TA15
R3
3.3k
C2
0.22µF
C3
10µF
++
C1
1000µF
+
C4*
470µF
V
IN
–15V
V
OUT
–28V
1A
L1
200µH
D2
D1
V
SW
V
C
V
IN
LT1070
GND FB
*REQUIRED IF INPUT LEADS ≥ 2"
+
R4
680Ω
1W
1070/71 TA10
1
L1
N = 5
TOTAL
INDUCTANCE = 4mH
INTERLEAVE PRIMARY
AND SECONDARY FOR
LOW LEAKAGE
INDUCTANCE
R3
10k R2
1.24k
R1
98k
C2
0.047µF
C3
0.68µF
C1
200µF
V
OUT
100V
300mA
D2
D1
V
SW
V
C
V
IN
LT1070
GND
V
IN
15V
FB
+
Voltage Boosted Boost Converter
Negative Boost Regulator Negative Input/Negative Output Flyback Converter
+
R5 R4
1.24k
C2
V
SW
Q1
2N3906
•
•
V
IN
C3
C1
–V
OUT
1070/71 TA17
R6
R1*
T1
1:N
LT1070/LT1071
GND V
C
FB
–V
IN
R3
1k
R2
5k
+
*R1 = V
OUT
– 1.6V
200µA
External Current Limit External Current Limit
1070/71 TA04
LT1070/LT1071
VC
GND
D1
VX
R1
500Ω
R2
= 2V
1070/71 TA06
R2
V
IN
R1
1k
C2
C1
1000pF
NOTE THAT THE LT1070/LT1071
GND PIN IS NO LONGER COMMON
TO V
IN–
V
SW
V
C
R
S
V
IN
LT1070/LT1071
GND FB
+
Q1
10701fe
11
LT1070/LT1071
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-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
TYPICAL APPLICATIONS
U
(Note that maximum output currents are divided by 2 for the LT1071)
T5 (TO-220) 0399
0.028 – 0.038
(0.711 – 0.965)
0.067
(1.70) 0.135 – 0.165
(3.429 – 4.191)
0.700 – 0.728
(17.78 – 18.491)
0.045 – 0.055
(1.143 – 1.397)
0.095 – 0.115
(2.413 – 2.921)
0.013 – 0.023
(0.330 – 0.584)
0.620
(15.75)
TYP
0.155 – 0.195*
(3.937 – 4.953)
0.152 – 0.202
(3.861 – 5.131)
0.260 – 0.320
(6.60 – 8.13)
0.165 – 0.180
(4.191 – 4.572)
0.147 – 0.155
(3.734 – 3.937)
DIA
0.390 – 0.415
(9.906 – 10.541)
0.330 – 0.370
(8.382 – 9.398)
0.460 – 0.500
(11.684 – 12.700)
0.570 – 0.620
(14.478 – 15.748)
0.230 – 0.270
(5.842 – 6.858)
BSC
SEATING PLANE
* MEASURED AT THE SEATING PLANE
K4(TO-3) 1098
72°
18°
0.490 – 0.510
(12.45 – 12.95)
R
0.470 TP
P.C.D.
0.167 – 0.177
(4.24 – 4.49)
R
0.151 – 0.161
(3.84 – 4.09)
DIA 2 PLC
0.655 – 0.675
(16.64 – 19.05)
1.177 – 1.197
(29.90 – 30.40)
0.038 – 0.043
(0.965 – 1.09)
0.060 – 0.135
(1.524 – 3.429)
0.320 – 0.350
(8.13 – 8.89)
0.420 – 0.480
(10.67 – 12.19)
0.760 – 0.775
(19.30 – 19.69)
Flyback Converter
1070/71 TA08
*REQUIRED IF INPUT LEADS ≥ 2"
a
b
V
SNUB
C2
0.15µF
R3
1.5k
R1
3.74k
R2
1.24k
C4*
100µF
V
IN
20V TO 30V
V
OUT
5V
6A
V
SW
V
C
V
IN
LT1070
GND FB
C3
0.47µFC1
2000µF
D2
D1
R4 1N
•
•
+
+
PRIMARY FLYBACK VOLTAGE =
LT1070/LT1071 SWITCH VOLTAGE
AREA “a” = AREA “b” TO MAINTAIN
ZERO DC VOLTS ACROSS PRIMARY
SECONDARY VOLTAGE
AREA “c” = AREA “d” TO MAINTAIN
ZERO DC VOLTS ACROSS SECONDARY
PRIMARY CURRENT
V
OUT
+ V
F
N
0V
V
IN
CLAMP TURN-ON
SPIKE
C4
200µF
L2
10µH
OPTIONAL
FILTER
c
∆I
d
V
OUT
+ V
F
(N)(V
IN
)
I
PRI
0V
0
LT1070 SWITCH CURRENT
SNUBBER DIODE CURRENT
I
PRI
I
PRI
t = (I
PRI
)(L
L
)
V
SNUB
SECONDARY CURRENT
I
PRI
N
0
0
N = 1/3
PACKAGE DESCRIPTION
U
OBSOLETE PACKAGE
T Package
5-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1421)
K Package
4-Lead TO-3 Metal Can
(Reference LTC DWG # 05-08-1311)
12
LT1070/LT1071
10701fe
LT/CPI 0202 1.5K REV E • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 1989
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
RELATED PARTS
PART NUMBER DESCRIPTION COMMENTS
LT1074/LT1076 High Voltage Switching Regulators 40V Input (60V for HV Versions), 100kHz, 5A and 2A
LT1170/LT1171/ 100kHz High Efficiency Switching Regulators 40V Input (65V for HV Versions), 5A/2.5A/1.25A Internal Switch
LT1172
LT1370/LT1371 500kHz High Efficiency Switching Regulators 35V, 6A/3A Internal Switch
LT1374/LT1376 100kHz High Efficiency Switching Regulators 25V Input, 4.5A/1.5A Internal Switch
LT1765 1.25MHz, 3A, Step-Down Regulator 25V Input, TSSOP-16E, SO8 Package
Forward Converter
Totally Isolated Converter
1070/71 TA07
R4
1.5k
5k
500Ω
N = 0.875 = 7:8
FOR VOUT = 15V
*REQUIRED IF INPUT LEADS ≥ 2"
R2
SECONDARY VOLTAGE
0V
VOUT
tOFF tON
≈16V
(N)(VIN)
C2
0.01µF
C5*
100µF
VIN
5V
VSW
VC
VIN
LT1070/LT1071
GND FB
+
C3
0.47µFN
D1
1:N
•
•
N
+
L1
10µF
L2
10µF
15V
COM
+
C4
500µF
C1
500µF
+
+
C6
200µF
C5
200µF
OPTIONAL
OUTPUT FILTER
+
–15V
SWITCH VOLTAGE
VF
(DIODE FORWARD VOLTAGE)
0V
VIN
+
R3 R6
330ΩR5
1Ω
Q1
C3
C4
V
SW
L1
70µH
•
••
V
IN
C2
D3
C1
2000µF
D1 V
OUT
5V
6A
R4
T1
LT1070
GND V
C
FB
V
IN
20V TO 30V D4
IMN
D2
1070/71 TA18
R1
3.74k
R2
1.24k
TYPICAL APPLICATIONS
U
(Note that maximum output currents are divided by 2 for the LT1071)
