lt1070.pdf

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LT1070/LT1071
5A and 2.5A High Efficiency
Switching Regulators
DESCRIPTIO
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FEATURES
s
s
s
s
s
s
s
s
s
s

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 50uA Supply Current
Flyback Regulated Mode Has Fully Floating Outputs
Comes in Standard 5-Pin TO-220 Package
Can be Externally Synchronized (Consult Factory)

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APPLICATIO S
s
s
s
s
s
s
s

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.

The LT (R)1070/LT1071 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward, inverting and "Cuk". A high current, high efficiency
switch is included on the die along with all oscillator,
control and protection circuitry. Integration of all functions allows the 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 50uA 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.

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TYPICAL APPLICATIO

Maximum Output Power*

Boost Converter (5V to 12V)

100

L2
10uH

80

L1**
150uH

OUTPUT
FILTER

C3
100uF

D1
VIN
C3*
100uF

+

+

LT1070
GND

VC

12V
1A

VSW
C2
1000uF

R1
10.7k
1%

POWER (W)**

BOOST

5V

BUCK/BOOST
VO = 30V

60

FLYBACK
40
ISOLATED
20
BUCK/BOOST
VO = 5V

FB
R3
1k
C1
1uF

*REQUIRED IF INPUT LEADS >= 2 "
**PULSE ENGINEERING 92113

R2
1.24k
1%

0

0

10

30
20
INPUT VOLTAGE (V)

40

50
1070/71 TA02

1070/71 TA01

*ROUGH GUIDE ONLY. BUCK MODE POUT = 5A o VOUT.
SPECIAL TOPOLOGIES DELIVER MORE POWER
**DIVIDE VERTICAL POWER SCALE BY 2 FOR LT1071
10701fe

1

LT1070/LT1071

WW

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W

ABSOLUTE MAXIMUM RATINGS

(Note 1)

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

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PACKAGE/ORDER INFORMATION
VSW

VC
1

4

2

CASE
IS GND

3

VIN

ORDER PART
NUMBER

ORDER PART
NUMBER

BOTTOM VIEW

FB
K PACKAGE
4-LEAD TO-3 METAL CAN

TJMAX = 100°C, ?JA = 35°C/ W, QJC = 2°C (LT1070C, I)
TJMAX = 150°C, ?JA = 35°C/ W, QJC = 2°C (LT1070M)
TJMAX = 100°C, ?JA = 35°C/ W, QJC = 4°C (LT1071C, I)
TJMAX = 150°C, ?JA = 35°C/ W, QJC = 4°C (LT1071M)

LT1070CK
LT1070HVCK
LT1070HVMK
LT1070IK
LT1070MK
LT1071CK
LT1071HVCK
LT1071HVMK
LT1071MK

FRONT VIEW
5
4

VSW

3

GND

2

FB

1

LT1070CT
LT1070HVCT
LT1070HVIT
LT1070IT
LT1071CT
LT1071HVCT
LT1071HVIT
LT1071IT

VIN

VC

T PACKAGE
5-LEAD PLASTIC TO-220

TJMAX = 100°C, ?JA = 75°C/ W, QJC = 2°C (LT1070C, I)
TJMAX = 100°C, ?JA = 75°C/ W, QJC = 4°C (LT1071C)

OBSOLETE PACKAGE
Consider the T5 Package for Alternate Source

Consult LTC Marketing for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS The q 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.
SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

VREF

Reference Voltage

Measured at Feedback Pin, VC = 0.8V

1.224
1.214

1.244
1.244

1.264
1.274

V
V

350

750
1100

nA
nA

q

IB

Feedback Input Current

VFB = VREF
q

Error Amplifier Source or Sink Current
Error Amplifier Clamp Voltage

?IC = ? 25uA

umho
umho

150
120

200

350
400

uA
uA

2.30
0.52

V
V

0.03

%/V

Hi Clamp, VFB = 1V
Lo Clamp, VFB = 1.5V
3V <= VIN <= VMAX, VC = 0.8V

Error Amplifier Voltage Gain

1.80
0.25

0.9V <= VC <= 1.4V

Minimum Input Voltage

500

800

V/V

2.6

3.0

6

9

0.8
0.6

0.9

1.08
1.25

V
V

0.4

0.45

0.54

V

3V <= VIN <= VMAX, VC = 0.6V
Duty Cycle = 0
q

Normal/Flyback Threshold on Feedback Pin

0.38

q

q

Supply Current
Control Pin Threshold

IQ

6000
7000

VC = 1.5V

Reference Voltage Line Regulation
AV

3000
2400

q

Error Amplifier Transconductance

4400

q

gm

V
mA

10701fe

2

LT1070/LT1071

ELECTRICAL CHARACTERISTICS

The q 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.
SYMBOL

PARAMETER

CONDITIONS

VFB

Flyback Reference Voltage

MIN

IFB = 50uA

Change in Flyback Reference Voltage

0.05 <= IFB <= 1mA

Flyback Reference Voltage Line Regulation

?IC = ?10uA

Flyback Amplifier Source and Sink Current

VC = 0.6V, IFB = 50uA (Source)
VC = 0.6V, IFB = 50uA (Sink)

Output Switch Breakdown Voltage

UNITS

15
14

16.3

17.6
18.0

V
V

6.8

8.5

V

IFB = 50uA, 3V <= VIN <= VMAX (Note 3)

Flyback Amplifier Transconductance (gm)

MAX

4.5

q

TYP

umho

q
q

15
25

32
40

70
70

uA
uA

3V <= VIN <= VMAX, ISW = 1.5mA
(LT1070/LT1071)
(LT1070HV/LT1071HV)

q
q

65
75

90
90

LT1070
LT1071

q
q

LT1070
LT1071

Switch Current Limit (LT1070)

Duty Cycle <= 50%, TJ >= 25°C
Duty Cycle <= 50%, TJ &amp; lt; 25°C
Duty Cycle = 80% (Note 5)

q
q
q

5
5
4

10
11
10

A
A
A

Switch Current Limit (LT1071)

ILIM

%/V

650

Control Voltage to Switch Current
Transconductance

VSAT

0.03

300

Output Switch "On" Resistance (Note 4)

BV

0.01
150

Duty Cycle <= 50%, TJ >= 25°C
Duty Cycle <= 50%, TJ &amp; lt; 25°C
Duty Cycle = 80% (Note 5)

q
q
q

2.5
2.5
2.0

5.0
5.5
5.0

A
A
A

25

35

mA/A

35
33

40

45
47

kHz
kHz

90

92

97

%

?IIN
?ISW

Switching Frequency
q

DC (Max)

Maximum Switch Duty Cycle
Flyback Sense Delay Time

A/V
A/V

us

1.5

Shutdown Mode Supply Current

3V <= VIN <= VMAX, VC = 0.05V

Shutdown Mode Threshold Voltage

3V <= VIN <= VMAX

100
q

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
?1us. 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 <= 1us, 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=

Ohm
Ohm

0.24
0.50

8
4

Supply Current Increase During
Switch "On" Time

f

0.15
0.30

V
V

100
50

250

uA

150

250
300

mV
mV

t = Minimum "on" time of LT1070/LT1071 in current limit, ? 1us
f = Operating frequency (40kHz)
VF = Forward voltage of external catch diode at ILIMIT
ILIMIT = Current limit of LT1070 (? 8A), LT1071 (? 4A)
RL = Internal series resistance of inductor
Note 3: VMAX = 55V for LT1070HV and LT1071HV to avoid switch
breakdown.
Note 4: Measured with VC in hi clamp, VFB = 0.8V. ISW = 4A for LT1070
and 2A for LT1071.
Note 5: For duty cycles (DC) between 50% and 80%, minimum
guaranteed switch current is given by ILIM = 3.33 (2 - DC) for the
LT1070 and ILIM = 1.67 (2 - DC) for the LT1071.

t o f o VIN - VF
- RL
ILIMIT

10701fe

3

LT1070/LT1071
UW

TYPICAL PERFORMANCE CHARACTERISTICS
Switch Current Limit vs Duty Cycle

Maximum Duty Cycle

16

96

2.2

95

FOR LT1071, DIVIDE
VERTICAL SCALE BY 2

14

2.0

94

1.8

10
- 55°C

8

25°C

125°C

6

TIME (us)

12

DUTY CYCLE (%)

93
92

1.4

91

1.2

90
-75 - 50 - 25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)

2
0
10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)

1.0
-75 - 50 - 25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)

1070/71 G01

1070/71 G02

Switch Saturation Voltage

Minimum Input Voltage
2.9

1.6

SWITCH SATURATION VOLTAGE (V)

MINIMUM INPUT VOLTAGE (V)

SWITCH CURRENT = 5A
2.8
2.7
2.6
SWITCH CURRENT = 0A
2.5
2.4
2.3
-75 - 50 - 25

1.4

22
150°C

1.2
100°C

1.0

25°C

0.8

- 55°C

0.6
0.4
0.2
0

0 25 50 75 100 125 150
TEMPERATURE (°C)

23

FOR LT1071, DIVIDE
CURRENT BY 2

0

1

4
5
2
3
6
SWITCH CURRENT (A)

7

1.248

REFERENCE VOLTAGE (V)

TJ = - 55°C

-1

-5
10

30
40
20
INPUT VOLTAGE (V)

50

60

1070/71 G07

0 25 50 75 100 125 150
TEMPERATURE (°C)

41

1.246

SWITCHING
FREQUENCY

700

40

1.244
1.242

800

39
REFERENCE
V0LTAGE

38

1.240

37

1.238

36
35

-3
-4

RFEEDBACK = 10k

1070/71 G06

42

1.236

-2

0

17

15
- 75 - 50 - 25

8

1.234
- 75 - 50 - 25

34
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G08

SWITCHING FREQUENCY (kHz)

1
0

18

Feedback Bias Current
vs Temperature

1.250

4

TJ = 25°C

RFEEDBACK = 1k

19

Reference Voltage
vs Temperature

5

2

20

1070/71 G05

Line Regulation

TJ = 150°C

RFEEDBACK = 500Ohm

21

16

1070/71 G04

3

1070/71 G03

FLYBACK VOLTAGE (V)

0

REFERENCE VOLTAGE CHANGE (mV)

1.6

4

FEEDBACK BIAS CURRENT (nA)

SWITCH CURRENT (A)

Flyback Blanking Time

600
500
400
300
200
100
0
- 75 - 50 - 25

0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G09

10701fe

4

LT1070/LT1071
UW

TYPICAL PERFORMANCE CHARACTERISTICS

16

140

15

100
80
TJ = - 55°C
TJ >= 25°C

40

ISWITCH <= 10mA

13
12
11

50% DUTY CYCLE

10
9

10% DUTY CYCLE

0
1

0

2
3
4
SWITCH CURRENT (A)

100
VC = 50mV
80
60
40

0

6

5

120

20

0% DUTY CYCLE

7
10

0

1070/71 G10

30
40
20
INPUT VOLTAGE (V)

60

50

Normal/Flyback Mode Threshold
on Feedback Pin

0

10

20
40
30
SUPPLY VOLTAGE (V)

1070/71 G12

Shutdown Mode Supply Current

Error Amplifier Transconductance
5000

490

-22

180

4500

480

-20

470

-18
-16

450

-14

440

-12

430

-10
FEEDBACK PIN CURRENT
(AT THRESHOLD)

-8

140
120

80
60

0

- 55°C <= TJ <= 125°C

40

-6
-4
25 50 75 100 125 150
TEMPERATURE (°C)

0

0

2000
1500
1000

0
-75 - 50 -25

10 20 30 40 50 60 70 80 90 100
VC PIN VOLTAGE (mV)

11

- 400
CURRENT
(OUT OF VC PIN)

10

-300

250

-250
-200
VOLTAGE

150

-150

100

-100
VC VOLTAGE IS REDUCED UNTIL
REGULATOR CURRENT DROPS
BELOW 300uA

- 50

0
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G16

VC PIN CURRENT (uA)

300

IDLE SUPPLY CURRENT (mA)

-350

200

0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G14

1070/71 G14

Shutdown Thresholds

0
- 75 - 50 - 25

2500

Idle Supply Current
vs Temperature

400

50

3000

500

1070/71 G13

350

3500

20

410
400
-50 -25

TJ = 150°C

100

gm = ?I (VC PIN)
?V (FB PIN)

4000

Feedback Pin Clamp Voltage
500

VC = 0.6V

450

9

FEEDBACK VOLTAGE (mV)

420

160

SUPPLY CURRENT (uA)

FEEDBACK PIN VOLTAGE
(AT THRESHOLD)

TRANSCONDUCTANCE (umho)

200

FEEDBACK PIN CURRENT (uA)

-24

460

60

50

1070/71 G11

500

FEEDBACK PIN VOLTAGE (mV)

VC = 0 V

*UNDER VERY LOW OUTPUT CURRENT
CONDITIONS, DUTY CYCLE FOR MOST
CIRCUITS WILL APPROACH 10% OR LESS

*AVERAGE LT1070 POWER SUPPLY CURRENT IS
FOUND BY MULTIPLYING DRIVER CURRENT BY
DUTY CYCLE, THEN ADDING QUIESCENT CURRENT

VC PIN VOLTAGE (mV)

TJ = 25°C

140

90% DUTY CYCLE

8
20

160

TJ = 25°C

14

120

INPUT CURRENT (mA)

DRIVER CURRENT (mA)

160

60

Supply Current vs Supply Voltage
(Shutdown Mode)

Supply Current vs Input Voltage*

SUPPLY CURRENT (uA)

Driver Current* vs Switch Current

8
7
6
5

VSUPPLY = 60V
VSUPPLY = 3V

4

400

- 55°C

350

25°C

300
250

150°C

200
150

3

100

2

50

1
-75 - 50 -25

0
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G14

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

10701fe

5

LT1070/LT1071
UW

TYPICAL PERFORMANCE CHARACTERISTICS
Switch "Off" Characteristics
300

1000
900

7000

TJ = 25°C

500

VSUPPLY =

400
3V

300

15V

40V

55V

TRANSCONDUCTANCE (umho)

600

VFB = 1.5V
(CURRENT INTO
VC PIN)

100
0

0

VFB = 0.8V
(CURRENT OUT OF VC PIN)

- 200
- 300

0

10 20 30 40 50 60 70 80 90 100
SWITCH VOLTAGE (V)

5000

30
gm

4000

60

3000

90

2000

120

1000

150

0

-100

200
100

0

?

180

-1000

- 400
0

0.5

2.0
1.5
1.0
VC PIN VOLTAGE (V)

1070/71 G19

2.5

PHASE (°)

VC PIN CURRENT (uA)

700

- 30

6000

200

800

SWITCH CURRENT (uA)

Transconductance of Error
Amplifier

VC Pin Characteristics

1k

10k

100k
1M
FREQUENCY (Hz)

210
10M
1070/71 G21

1070/71 G20

W

BLOCK DIAGRAM

16V
SWITCH
OUT

VIN
2.3V
REG

FLYBACK
ERROR
AMP

40kHz
OSC

LOGIC

MODE
SELECT

DRIVER

5A, 75V
SWITCH

ANTISAT
COMP

-

FB

ERROR
AMP

VC

+

+
CURRENT
AMP

SHUTDOWN
CIRCUIT
1.24V
REF

0.15V

GAIN ? 6

0.02Ohm
(0.04Ohm LT1071)

-

1070/71 BD

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OPERATION
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

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
10701fe

6

LT1070/LT1071
U

OPERATION
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-pulse current
limiting to provide maximum switch protection under
output overload or short-circuit conditions. A low dropout internal regulator provides a 2.3V supply for all
internal circuitry of the LT1070/LT1071. 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.
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

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TYPICAL APPLICATIONS

transformer coupled flyback topology regulator. By regulating the amplitude of the flyback pulse, the output
voltage can be regulated with no direct connection between input and output. The output is fully floating up to
the breakdown voltage of the transformer windings.
Multiple floating outputs are easily obtained with additional windings. A special delay network inside the 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 (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 LT1070/LT1071 in an idle
mode. Pulling the VC pin below 0.15V causes total
regulator shutdown, with only 50uA supply current for
shutdown circuitry biasing. See AN19 for full application
details.

(Note that maximum output currents are divided by 2 for the LT1071)
Driving High Voltage NPN
C1

Driving High Voltage FET (for Off-Line
Applications, See AN25)

D2

G
D1
VIN

LT1070/LT1071

GND

S

R2**

Q1

R1*
Q1
D1
VIN

VSW

LT1070/LT1071

*SETS IB(ON)
**SETS IB(OFF)

GND

1070/71 TA03
17/0701

+

30AT

10V
TO
20V

VSW

D

1070/71 TA16

10701fe

7

LT1070/LT1071

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TYPICAL APPLICATIONS

(Note that maximum output currents are divided by 2 for the LT1071)
Negative Buck Converter

D1
VIN
C3
100uF

+
L1**
200uH

C2
1000uF

- 5.2V
4.5A

Q1
2N3906

LT1070

GND

LOAD

VSW

+

OPTIONAL INPUT
FILTER

R1
4.64k

VC

FB

L3

OPTIONAL
OUTPUT
FILTER

C1
R2
1.24k

R3
VIN
- 20V

+

C4
200uF

L2
4uH

*REQUIRED IF INPUT LEADS >= 2 &quot;
**PULSE ENGINEERING 92113

1070/71 TA12

Positive Buck Converter
VIN
D3

L2
4uH
VIN

+
C5*

C3
2.2uF

+
LT1070

D2
1N914

R1
3.74k

100uF

GND

VC

C5
200uF

OPTIONAL
OUTPUT
FILTER

VSW

FB
R2
1.24k

R3
470Ohm
C1
1uF

+

C2
1uF

R4
10Ohm

L1**
100uH

r

+

D1

C4
1000uF

*REQUIRED IF INPUT LEADS >=2 &quot;
**PULSE ENGINEERING 92112

5V
4.5A
100mA
MINIMUM
1070/71 TA14

Negative Current Boosted Buck Converter
+
C1

R1
R5

C3

o
VIN

+

VSW

MINIMUM
LOAD = 10mA

T1
1:N
D1

o

Q1
2N3906

R4
12k
R1 =

- VOUT
5V
10A

VOUT - 0.6V
1mA

LT1070

GND

VC

FB
R3

R2
1.24k

C2
- VIN

1070/71 TA13

10701fe

8

LT1070/LT1071

U

TYPICAL APPLICATIONS

(Note that maximum output currents are divided by 2 for the LT1071)
Positive Current Boosted Buck Converter

VIN
28V

470Ohm
2W

R6
470Ohm

C3
0.47uF

C6
0.002uF

D2

VIN

o

1:N

VSW

N ? 0.25

LT1070
R2
1k
GND

R7
1.24k

D1

FB

VC

VIN
7
R3
680Ohm

6

C5*
100uF

-

V+

2
R5
5k

V - LM308
COMP 3
4

+

+

o

C1
0.33uF

8

R4
1.24k

200pF

R1
5k

*REQUIRED IF INPUT LEADS >= 2 &quot;

VOUT
5V
10A

+

C2
5000uF
1070/71 TA19

Positive to Negative Buck/Boost Converter

Negative to Positive Buck/Boost Converter

L1**
150uH

OPTIONAL
OUTPUT
FILTER

C3
VIN

D1
VIN
C4*
100uF

VSW
C2
1000uF

+
LT1070

+

R1
11.3k
Q1

L3
GND
OPTIONAL
INPUT
FILTER
VIN
- 12V
*REQUIRED IF INPUT LEADS >= 2 &quot;
**PULSE ENGINEERING 92113

VC

FB
R3
2.2k
C1
0.22uF

R2
1.24k

R5+
470Ohm
1W

D3+
1N4001

L2

VOUT
12V
2A

+
C4

5uF

VSW

LT1070

GND

VC

+TO AVOID START-UP

PROBLEMS FOR INPUT
VOLTAGES BELOW 10V,
VIN
10V TO 30V CONNECT ANODE OF D3
TO VIN AND REMOVE R5.
C5*
C1 MAY BE REDUCED FOR
100uF
LOWER OUTPUT CURRENTS.
C1 ? (500uF)(IOUT) FOR 5V
OUTPUTS, REDUCE R3 TO
1.5k, INCREASE C2 TO 0.3uF
D2
R1
R4 AND REDUCE R6 TO 100Ohm.
1N914
10.7k
47Ohm

FB
R3
5k
C1
0.1uF

R2
1.24k

+

C1+
C3
2uF 1000uF

+

R6
470Ohm

D1
1070/71 TA09

1070/71 TA05

L1**
200uH

*REQUIRED IF INPUT LEADS >= 2 &quot;
**PULSE ENGINEERING 92113

VOUT
- 12V
2A

10701fe

9

LT1070/LT1071

U

TYPICAL APPLICATIONS

(Note that maximum output currents are divided by 2 for the LT1071)
Current Boosted Boost Converter

Voltage Boosted Boost Converter
R4
680Ohm
1W

C3
0.68uF

R4

D2
VIN

+

VIN
15V

VSW

LT1070

VC

R3
10k
C2
0.047uF

VIN
VIN
16V TO 24V

+

R2
1.24k

D1

VOUT
28V
4A

N

VSW

+

R1
27k
LT1070

+
C1

VOUT
100V
300mA

FB

I

D2

D1

R1
98k
GND

TOTAL
INDUCTANCE = 4mH
INTERLEAVE PRIMARY
AND SECONDARY FOR
LOW LEAKAGE
INDUCTANCE

1
L1
N=5

C3

GND

FB

VC

C1
200uF

R2
1.24k

R3
C2

1070/71 TA10

1070/71 TA11

Negative Input/Negative Output Flyback Converter

Negative Boost Regulator
D2

VSW

C4*
470uF

VIN

+

R1
27k

+
GND

RO
(MINIMUM
LOAD)

+

VIN
-15V

R3
3.3k
C2
0.22uF

o

*REQUIRED IF INPUT LEADS >= 2 &quot;

+

Q1
2N3906

C1

LT1070/LT1071
- VOUT
VC

?V ? - 1.6V
*R1 = OUT
200uA

FB

R4
1.24k

R5
D1

R2
5k

R3
1k

R1*

R2
1.24k
VOUT
-28V
1A

C2
1070/71 TA17

- VIN
1070/71 TA15

External Current Limit

VIN

o

T1
1:N

VSW

C3
10uF

FB

VC

C1
1000uF

GND
L1
200uH

R6

VIN

LT1070

+

C3

External Current Limit

VSW
VX
LT1070/LT1071

LT1070/LT1071

+

R2
VIN

= 2V

FB
GND
R1
1k

Q1
C1
1000pF
RS

VC

D1

GND

VC

R1
500Ohm
R2
1070/71 TA04

C2

NOTE THAT THE LT1070/LT1071
GND PIN IS NO LONGER COMMON
TO VIN-
1070/71 TA06
10701fe

10

LT1070/LT1071

U

TYPICAL APPLICATIONS

(Note that maximum output currents are divided by 2 for the LT1071)
Flyback Converter
CLAMP TURN-ON
SPIKE

VSNUB
L2
10uH
C4
200uF

OPTIONAL
FILTER
D1
VIN
20V TO 30V

C3
0.47uF

R4

VOUT
5V
6A

1N

+

D2

VIN

+

o

VOUT + VF
(N)(VIN) SECONDARY VOLTAGE
AREA "c" = AREA "d" TO MAINTAIN
ZERO DC VOLTS ACROSS SECONDARY

c
0V
d
?I

o

IPRI

VSW
R1
3.74k

LT1070

PRIMARY CURRENT

0
IPRI N

SECONDARY CURRENT

0

FB
GND

b

0V

C1
2000uF

N = 1/3
C4*
100uF

+ VF
V
PRIMARY FLYBACK VOLTAGE = OUT
N
LT1070/LT1071 SWITCH VOLTAGE
AREA "a" = AREA "b" TO MAINTAIN
ZERO DC VOLTS ACROSS PRIMARY

a
VIN

IPRI

VC
R2
1.24k

R3
1.5k
C2
0.15uF

LT1070 SWITCH CURRENT

0
IPRI

SNUBBER DIODE CURRENT

*REQUIRED IF INPUT LEADS >= 2 &quot;

1070/71 TA08

(I )(L )
t = PRI L
VSNUB

U

PACKAGE DESCRIPTION
K Package
4-Lead TO-3 Metal Can

T Package
5-Lead Plastic TO-220 (Standard)

(Reference LTC DWG # 05-08-1311)

(Reference LTC DWG # 05-08-1421)

0.760 - 0.775
(19.30 - 19.69)

0.320 - 0.350
(8.13 - 8.89)

0.060 - 0.135
(1.524 - 3.429)

0.390 - 0.415
(9.906 - 10.541)

0.165 - 0.180
(4.191 - 4.572)

0.147 - 0.155
(3.734 - 3.937)
DIA

0.045 - 0.055
(1.143 - 1.397)

0.230 - 0.270
(5.842 - 6.858)

0.420 - 0.480
(10.67 - 12.19)
0.460 - 0.500
(11.684 - 12.700)

0.038 - 0.043
(0.965 - 1.09)

0.570 - 0.620
(14.478 - 15.748)
0.330 - 0.370
(8.382 - 9.398)

1.177 - 1.197
(29.90 - 30.40)

0.470 TP
P.C.D.

0.655 - 0.675
(16.64 - 19.05)

72°
18°

0.490 - 0.510
(12.45 - 12.95)
R

0.700 - 0.728
(17.78 - 18.491)

SEATING PLANE
0.152 - 0.202
0.260 - 0.320 (3.861 - 5.131)
(6.60 - 8.13)

0.151 - 0.161
(3.84 - 4.09)
DIA 2 PLC
0.167 - 0.177
(4.24 - 4.49)
R

0.620
(15.75)
TYP

0.095 - 0.115
(2.413 - 2.921)
0.155 - 0.195*
(3.937 - 4.953)
0.013 - 0.023
(0.330 - 0.584)

BSC

0.067
(1.70)

0.028 - 0.038
(0.711 - 0.965)

0.135 - 0.165
(3.429 - 4.191)

T5 (TO-220) 0399

* MEASURED AT THE SEATING PLANE

K4(TO-3) 1098

OBSOLETE PACKAGE
10701fe

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

11

LT1070/LT1071

U

TYPICAL APPLICATIONS

(Note that maximum output currents are divided by 2 for the LT1071)
Totally Isolated Converter
OPTIONAL
OUTPUT FILTER
D1
1:N
C3
0.47uF

R4
1.5k

+

o

+V

+

IN

5V

C5*
100uF

+

LT1070/LT1071

COM

C4
500uF

o

VSW

+

C1
500uF

N

N
VIN

L1
10uF

15V

C6
200uF

N = 0.875 = 7:8
FOR VOUT = 15V
? 16V
SWITCH VOLTAGE

FB
GND

+

L2
10uF

-15V

C5
200uF

VC

VIN

500Ohm

tOFF

0V

tON

R2

C2
5k
0.01uF

VF
(DIODE FORWARD VOLTAGE)

VOUT

SECONDARY VOLTAGE

0V
*REQUIRED IF INPUT LEADS >= 2 &quot;

1070/71 TA07

(N)(VIN)

Forward Converter

R4

C2

o

I

L1
70uH

D1

T1
M

N

o

+
D2

D3

VIN

VIN
20V TO 30V

C1
2000uF

o

VSW

LT1070

GND

VOUT
5V
6A

VC

D4

R1
3.74k

FB
Q1
R3
C3

R6
C4 330Ohm

R5
1Ohm

R2
1.24k

1070/71 TA18

RELATED PARTS
PART NUMBER

DESCRIPTION

COMMENTS

LT1074/LT1076

High Voltage Switching Regulators

40V Input (60V for HV Versions), 100kHz, 5A and 2A

LT1170/LT1171/
LT1172

100kHz High Efficiency Switching Regulators

40V Input (65V for HV Versions), 5A/2.5A/1.25A Internal Switch

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
10701fe

12

Linear Technology Corporation

LT/CPI 0202 1.5K REV E o PRINTED IN USA

1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 q FAX: (408) 434-0507

q

www.linear.com

(C) LINEAR TECHNOLOGY CORPORATION 1989


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