FEATURES
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LT1070/LT1071
5A and 2.5A High Efficiency
Switching Regulators
DESCRIPTION
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 TO-3 or T0-220 power package. This makes it ex-
tremely 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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 Packages
Can be Externally Synchronized (Consult Factory)
APPLICATIONS
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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
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.
TYPICAL APPLICATION
Boost Converter (5V to 12V)
L2
10µH
5V
L1**
150µH
D1
V
IN
C3*
100µF
V
SW
OUTPUT
FILTER
C3
100µF
POWER (W)**
100
80
Maximum Output Power*
60
+
LT1070
GND
V
C
FB
R3
1k
C1
1µF
*REQUIRED IF INPUT LEADS
≥
2"
**PULSE ENGINEERING 92113
+
12V
1A
C2
1000µF
R1
10.7k
1%
40
ISOLATED
20
BUCK/BOOST
V
O
= 5V
0
0
10
30
20
INPUT VOLTAGE (V)
40
50
1070/71 TA02
R2
1.24k
1%
1070/71 TA01
*ROUGH GUIDE ONLY. BUCK MODE P
OUT
= 5A • V
OUT
.
SPECIAL TOPOLOGIES DELIVER MORE POWER
**DIVIDE VERTICAL POWER SCALE BY 2 FOR LT1071
U
U
U
BOOST
BUCK/BOOST
V
O
= 30V
FLYBACK
1
LT1070/LT1071
ABSOLUTE
MAXIMUM
RATINGS
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
PACKAGE/ORDER INFORMATION
BOTTOM VIEW
V
SW
1
2
3
V
C
ORDER PART
NUMBER
CASE
IS GND
4
V
IN
FB
K PACKAGE
4-LEAD TO-3 METAL CAN
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)
LT1070CK
LT1070HVCK
LT1070HVMK
LT1070IK
LT1070MK
LT1071CK
LT1071HVCK
LT1071HVMK
LT1071MK
ELECTRICAL CHARACTERISTICS
SYMBOL
V
REF
I
B
g
m
PARAMETER
Reference Voltage
Feedback Input Current
Error Amplifier Transconductance
Error Amplifier Source or Sink Current
Error Amplifier Clamp Voltage
Reference Voltage Line Regulation
A
V
I
Q
Error Amplifier Voltage Gain
Minimum Input Voltage
Supply Current
Control Pin Threshold
Normal/Flyback Threshold on Feedback Pin
V
IN
= 15V, V
C
= 0.5V, V
FB
= V
REF
, output pin open unless otherwise specified.
MIN
q
CONDITIONS
Measured at Feedback Pin, V
C
= 0.8V
V
FB
= V
REF
q
∆I
C
=
±25µA
q
V
C
= 1.5V
q
Hi Clamp, V
FB
= 1V
Lo Clamp, V
FB
= 1.5V
3V
≤
V
IN
≤
V
MAX
, V
C
= 0.8V
0.9V
≤
V
C
≤
1.4V
q
q
3V
≤
V
IN
≤
V
MAX
, V
C
= 0.6V
Duty Cycle = 0
q
2
U
U
W
W W
U
W
(Note 1)
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 ............................................ – 55°C to 150°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
FRONT VIEW
5
4
3
2
1
T PACKAGE
5-LEAD PLASTIC TO-220
V
IN
V
SW
GND
FB
V
C
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)
LT1070CT
LT1070HVCT
LT1070HVIT
LT1070IT
LT1071CT
LT1071HVCT
LT1071HVIT
LT1071IT
TYP
1.244
1.244
350
MAX
1.264
1.274
750
1100
6000
7000
350
400
2.30
0.52
0.03
UNITS
V
V
nA
nA
µmho
µmho
µA
µA
V
V
%/V
V/V
V
mA
V
V
V
1.224
1.214
3000
2400
150
120
1.80
0.25
500
4400
200
0.38
800
2.6
6
3.0
9
1.08
1.25
0.54
0.8
0.6
0.4
0.9
0.45
LT1070/LT1071
ELECTRICAL CHARACTERISTICS
SYMBOL
V
FB
PARAMETER
Flyback Reference Voltage
Change in Flyback Reference Voltage
Flyback Reference Voltage Line Regulation
Flyback Amplifier Transconductance (g
m
)
Flyback Amplifier Source and Sink Current
B
V
Output Switch Breakdown Voltage
V
IN
= 15V, V
C
= 0.5V, V
FB
= V
REF
, output pin open unless otherwise specified.
MIN
q
CONDITIONS
I
FB
= 50µA
0.05
≤
I
FB
≤
1mA
I
FB
= 50µA, 3V
≤
V
IN
≤
V
MAX
(Note 3)
∆I
C
=
±10µA
V
C
= 0.6V, I
FB
= 50µA (Source)
V
C
= 0.6V, I
FB
= 50µA (Sink)
3V
≤
V
IN
≤
V
MAX
, I
SW
= 1.5mA
(LT1070/LT1071)
(LT1070HV/LT1071HV)
LT1070
LT1071
LT1070
LT1071
Duty Cycle
≤
50%, T
J
≥
25°C
Duty Cycle
≤
50%, T
J
< 25°C
Duty Cycle = 80% (Note 5)
Duty Cycle
≤
50%, T
J
≥
25°C
Duty Cycle
≤
50%, T
J
< 25°C
Duty Cycle = 80% (Note 5)
q
q
q
q
q
q
q
q
q
q
q
q
TYP
16.3
6.8
0.01
300
32
40
90
90
0.15
0.30
8
4
MAX
17.6
18.0
8.5
0.03
650
70
70
UNITS
V
V
V
%/V
µmho
µA
µA
V
V
15
14
4.5
150
15
25
65
75
V
SAT
Output Switch “On” Resistance (Note 4)
Control Voltage to Switch Current
Transconductance
0.24
0.50
Ω
Ω
A/V
A/V
I
LIM
Switch Current Limit (LT1070)
5
5
4
2.5
2.5
2.0
25
35
33
90
40
92
1.5
100
10
11
10
5.0
5.5
5.0
35
45
47
97
250
250
300
A
A
A
A
A
A
mA/A
kHz
kHz
%
µs
µA
mV
mV
Switch Current Limit (LT1071)
∆I
IN
∆I
SW
f
DC (Max)
Supply Current Increase During
Switch “On” Time
Switching Frequency
q
Maximum Switch Duty Cycle
Flyback Sense Delay Time
Shutdown Mode Supply Current
Shutdown Mode Threshold Voltage
3V
≤
V
IN
≤
V
MAX
, V
C
= 0.05V
3V
≤
V
IN
≤
V
MAX
q
100
50
150
The
q
denotes the specifications which apply over the full operating
temperature range.
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=
t • f • V
IN
– V
F
– R
L
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.
3
LT1070/LT1071
TYPICAL PERFORMANCE CHARACTERISTICS
Switch Current Limit vs Duty Cycle
16
14
SWITCH CURRENT (A)
FOR LT1071, DIVIDE
VERTICAL SCALE BY 2
12
TIME (µs)
1070/71 G02
10
– 55°C
8
6
4
2
0
0
10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
1070/71 G01
25°C
DUTY CYCLE (%)
125°C
Minimum Input Voltage
2.9
SWITCH SATURATION VOLTAGE (V)
SWITCH CURRENT = 5A
2.8
2.7
2.6
SWITCH CURRENT = 0A
2.5
2.4
2.3
–75 – 50 – 25
MINIMUM INPUT VOLTAGE (V)
100°C
1.0
0.8
0.6
0.4
0.2
0
0
1
4
5
2
3
6
SWITCH CURRENT (A)
7
8
25°C
– 55°C
FLYBACK VOLTAGE (V)
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G04
Line Regulation
5
REFERENCE VOLTAGE CHANGE (mV)
4
REFERENCE VOLTAGE (V)
3
2
1
0
–1
–2
–3
–4
–5
0
10
30
40
20
INPUT VOLTAGE (V)
50
60
T
J
= – 55°C
T
J
= 150°C
T
J
= 25°C
1.246
1.244
1.242
1.240
1.238
1.236
1.234
– 75 – 50 – 25
40
39
FEEDBACK BIAS CURRENT (nA)
4
U W
1070/71 G07
Maximum Duty Cycle
96
95
94
93
92
91
90
–75 – 50 – 25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
2.2
2.0
1.8
1.6
1.4
1.2
Flyback Blanking Time
1.0
–75 – 50 – 25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
1070/71 G03
Switch Saturation Voltage
1.6
1.4
1.2
FOR LT1071, DIVIDE
CURRENT BY 2
150°C
21
20
19
18
17
16
23
22
Isolated Mode Flyback
Reference Voltage
R
FEEDBACK
= 500Ω
R
FEEDBACK
= 1k
R
FEEDBACK
= 10k
15
– 75 – 50 – 25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G06
1070/71 G05
Reference Voltage
vs Temperature
1.250
1.248
SWITCHING
FREQUENCY
42
41
SWITCHING FREQUENCY (kHz)
800
700
600
500
400
300
200
100
Feedback Bias Current
vs Temperature
REFERENCE
V0LTAGE
38
37
36
35
34
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G08
0
– 75 – 50 – 25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G09
LT1070/LT1071
TYPICAL PERFORMANCE CHARACTERISTICS
Driver Current* vs Switch Current
160
140
16
15
14
DRIVER CURRENT (mA)
13
12
11
10
9
8
I
SWITCH
≤
10mA
100
80
T
J
= – 55°C
60
40
20
0
0
1
4
2
3
SWITCH CURRENT (A)
5
1070/71 G10
SUPPLY CURRENT (µA)
INPUT CURRENT (mA)
120
T
J
≥
25°C
*AVERAGE LT1070 POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT
Normal/Flyback Mode Threshold
on Feedback Pin
500
490
FEEDBACK PIN VOLTAGE (mV)
480
470
460
450
440
430
420
410
400
–50 –25
0
FEEDBACK PIN CURRENT
(AT THRESHOLD)
FEEDBACK PIN VOLTAGE
(AT THRESHOLD)
–24
–22
FEEDBACK PIN CURRENT (µA)
–20
–18
–16
–14
–12
–10
–8
–6
–4
25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G13
TRANSCONDUCTANCE (µmho)
SUPPLY CURRENT (µA)
Shutdown Thresholds
400
350
V
C
PIN VOLTAGE (mV)
IDLE SUPPLY CURRENT (mA)
FEEDBACK VOLTAGE (mV)
CURRENT
(OUT OF V
C
PIN)
300
250
200
VOLTAGE
150
100
50
V
C
VOLTAGE IS REDUCED UNTIL
REGULATOR CURRENT DROPS
BELOW 300µA
0
– 75 – 50 – 25
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G16
U W
Supply Current vs Input Voltage*
T
J
= 25°C
90% DUTY CYCLE
160
140
120
100
Supply Current vs Supply Voltage
(Shutdown Mode)
T
J
= 25°C
V
C
= 50mV
80
60
40
20
0
0
10
20
V
C
= 0V
40
30
SUPPLY VOLTAGE (V)
50
60
50% DUTY CYCLE
10% DUTY CYCLE
0% DUTY CYCLE
0
10
30
40
20
INPUT VOLTAGE (V)
50
60
7
6
1070/71 G11
1070/71 G12
*UNDER VERY LOW OUTPUT CURRENT
CONDITIONS, DUTY CYCLE FOR MOST
CIRCUITS WILL APPROACH 10% OR LESS
Shutdown Mode Supply Current
200
180
160
140
120
100
80
60
40
20
0
0
10 20 30 40 50 60 70 80 90 100
V
C
PIN VOLTAGE (mV)
1070/71 G14
Error Amplifier Transconductance
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
–75 – 50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G14
g
m
=
∆I
(V
C
PIN)
∆V
(FB PIN)
T
J
= 150°C
– 55°C
≤
T
J
≤
125°C
Idle Supply Current
vs Temperature
– 400
–350
–300
–250
–200
–150
–100
– 50
V
C
PIN CURRENT (µA)
11
10
9
8
7
6
5
4
3
2
1
–75 – 50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G14
Feedback Pin Clamp Voltage
500
450
400
350
300
250
200
150
100
50
0
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
FEEDBACK CURRENT (mA)
1070/71 G18
V
C
= 0.6V
– 55°C
25°C
150°C
V
SUPPLY
= 60V
V
SUPPLY
= 3V
5
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