LINER LT1070 5a and 2.5a high efficiency switching regulator Datasheet

LT1070/LT1071
5A and 2.5A High Efficiency
Switching Regulators
DESCRIPTION
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FEATURES
■
■
■
■
■
■
■
■
■
■
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)
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APPLICATIONS
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■
■
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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.
The LT ®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 TO-3 or 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.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATION
Maximum Output Power*
Boost Converter (5V to 12V)
100
L2
10µH
80
L1**
150µH
OUTPUT
FILTER
C3
100µF
D1
VIN
C3*
100µF
+
+
LT1070
GND
VC
12V
1A
VSW
C2
1000µF
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
1µF
*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 • VOUT.
SPECIAL TOPOLOGIES DELIVER MORE POWER
**DIVIDE VERTICAL POWER SCALE BY 2 FOR LT1071
1
LT1070/LT1071
W W
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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 ............................................ – 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, θJA = 35°C/ W, QJC = 2°C (LT1070C, I)
TJMAX = 150°C, θJA = 35°C/ W, QJC = 2°C (LT1070M)
TJMAX = 100°C, θJA = 35°C/ W, QJC = 4°C (LT1071C, I)
TJMAX = 150°C, θJA = 35°C/ W, QJC = 4°C (LT1071M)
LT1070CK
LT1070HVCK
LT1070HVMK
LT1070IK
LT1070MK
LT1071CK
LT1071HVCK
LT1071HVMK
LT1071MK
ELECTRICAL CHARACTERISTICS
FRONT VIEW
5
VIN
4
VSW
3
GND
2
FB
1
VC
LT1070CT
LT1070HVCT
LT1070HVIT
LT1070IT
LT1071CT
LT1071HVCT
LT1071HVIT
LT1071IT
T PACKAGE
5-LEAD PLASTIC TO-220
TJMAX = 100°C, θJA = 75°C/ W, QJC = 2°C (LT1070C, I)
TJMAX = 100°C, θJA = 75°C/ W, QJC = 4°C (LT1071C)
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
●
IB
Feedback Input Current
VFB = VREF
●
gm
Error Amplifier Transconductance
Error Amplifier Source or Sink Current
Error Amplifier Clamp Voltage
AV
∆IC = ±25µA
6000
7000
µmho
µmho
150
120
200
●
350
400
µA
µA
2.30
0.52
V
V
0.03
%/V
VC = 1.5V
Hi Clamp, VFB = 1V
Lo Clamp, VFB = 1.5V
Reference Voltage Line Regulation
3V ≤ VIN ≤ VMAX, VC = 0.8V
Error Amplifier Voltage Gain
0.9V ≤ VC ≤ 1.4V
Minimum Input Voltage
IQ
3000
2400
4400
●
1.80
0.25
●
500
3V ≤ VIN ≤ VMAX, VC = 0.6V
Control Pin Threshold
Duty Cycle = 0
●
Normal/Flyback Threshold on Feedback Pin
2
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
●
Supply Current
0.38
V
mA
LT1070/LT1071
ELECTRICAL CHARACTERISTICS
VIN = 15V, VC = 0.5V, VFB = VREF, output pin open unless otherwise specified.
SYMBOL
PARAMETER
CONDITIONS
VFB
Flyback Reference Voltage
IFB = 50µA
●
Change in Flyback Reference Voltage
BV
VSAT
ILIM
0.05 ≤ IFB ≤ 1mA
Flyback Reference Voltage Line Regulation
IFB = 50µA, 3V ≤ VIN ≤ VMAX (Note 3)
Flyback Amplifier Transconductance (gm)
∆IC = ±10µA
Flyback Amplifier Source and Sink Current
VC = 0.6V, IFB = 50µA (Source)
VC = 0.6V, IFB = 50µA (Sink)
Output Switch Breakdown Voltage
TYP
MAX
UNITS
15
14
16.3
17.6
18.0
V
V
4.5
6.8
8.5
V
0.01
0.03
%/V
150
300
650
µmho
●
●
15
25
32
40
70
70
µA
µA
3V ≤ VIN ≤ VMAX, ISW = 1.5mA
(LT1070/LT1071)
(LT1070HV/LT1071HV)
●
●
65
75
90
90
Output Switch “On” Resistance (Note 4)
LT1070
LT1071
●
●
Control Voltage to Switch Current
Transconductance
LT1070
LT1071
Switch Current Limit (LT1070)
Duty Cycle ≤ 50%, TJ ≥ 25°C
Duty Cycle ≤ 50%, TJ < 25°C
Duty Cycle = 80% (Note 5)
●
●
●
5
5
4
10
11
10
A
A
A
Switch Current Limit (LT1071)
Duty Cycle ≤ 50%, TJ ≥ 25°C
Duty Cycle ≤ 50%, TJ < 25°C
Duty Cycle = 80% (Note 5)
●
●
●
2.5
2.5
2.0
5.0
5.5
5.0
A
A
A
25
35
mA/A
40
45
47
kHz
kHz
92
97
∆IIN
∆ISW
Supply Current Increase During
Switch “On” Time
f
Switching Frequency
0.15
0.30
Maximum Switch Duty Cycle
35
33
90
Flyback Sense Delay Time
Ω
Ω
0.24
0.50
A/V
A/V
%
µs
1.5
Shutdown Mode Supply Current
3V ≤ VIN ≤ VMAX, VC = 0.05V
Shutdown Mode Threshold Voltage
3V ≤ VIN ≤ VMAX
●
The ● 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=
V
V
8
4
●
DC (Max)
MIN
100
50
100
250
µA
150
250
300
mV
mV
t = Minimum “on” time of LT1070/LT1071 in current limit, ≈1µs
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 • f • VIN – VF
– RL
ILIMIT
3
LT1070/LT1071
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TYPICAL PERFORMANCE CHARACTERISTICS
Switch Current Limit vs Duty Cycle
Maximum Duty Cycle
16
FOR LT1071, DIVIDE
VERTICAL SCALE BY 2
96
2.2
95
2.0
94
1.8
10
– 55°C
25°C
8
125°C
6
TIME (µs)
12
DUTY CYCLE (%)
93
2
0
92
1.4
91
1.2
10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
90
–75 – 50 – 25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
1.0
–75 – 50 – 25 0 25 50 75 100 125 150
JUNCTION TEMPERATURE (°C)
1070/71 G01
1070/71 G02
1.6
2.9
SWITCH SATURATION VOLTAGE (V)
SWITCH CURRENT = 5A
MINIMUM INPUT VOLTAGE (V)
Isolated Mode Flyback
Reference Voltage
Switch Saturation Voltage
Minimum Input Voltage
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
–2
–4
–5
10
30
40
20
INPUT VOLTAGE (V)
50
60
1070/71 G07
4
RFEEDBACK = 10k
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G06
1.246
SWITCHING
FREQUENCY
800
41
700
40
1.244
1.242
42
39
REFERENCE
V0LTAGE
38
1.240
37
1.238
36
1.236
35
–3
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 = 500Ω
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)
14
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
LT1070/LT1071
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TYPICAL PERFORMANCE CHARACTERISTICS
160
16
INPUT CURRENT (mA)
80
TJ = – 55°C
TJ ≥ 25°C
40
12
11
50% DUTY CYCLE
10
9
10% DUTY CYCLE
8
20
0
1
0
4
2
3
SWITCH CURRENT (A)
0
10
1070/71 G10
Normal/Flyback Mode Threshold
on Feedback Pin
60
40
30
40
20
INPUT VOLTAGE (V)
50
60
Shutdown Mode Supply Current
490
–22
180
4500
480
–20
470
–18
–14
440
–12
430
–10
FEEDBACK PIN CURRENT
(AT THRESHOLD)
420
140
120
TJ = 150°C
100
80
60
– 55°C ≤ TJ ≤ 125°C
40
–6
20
–4
25 50 75 100 125 150
0
TEMPERATURE (°C)
0
410
400
–50 –25
–8
160
SUPPLY CURRENT (µA)
450
0
–250
200
–200
VOLTAGE
150
–150
100
–100
VC VOLTAGE IS REDUCED UNTIL
REGULATOR CURRENT DROPS
BELOW 300µA
– 50
0
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G16
IDLE SUPPLY CURRENT (mA)
250
VC PIN CURRENT (µA)
–300
0
– 75 – 50 – 25
10
–350
300
50
11
– 400
60
gm = ∆I (VC PIN)
∆V (FB PIN)
3500
3000
2500
2000
1500
1000
0
–75 – 50 –25
10 20 30 40 50 60 70 80 90 100
VC PIN VOLTAGE (mV)
0 25 50 75 100 125 150
TEMPERATURE (°C)
1070/71 G14
1070/71 G14
Shutdown Thresholds
CURRENT
(OUT OF VC PIN)
50
4000
Idle Supply Current
vs Temperature
400
20
40
30
SUPPLY VOLTAGE (V)
500
1070/71 G13
350
TRANSCONDUCTANCE (µmho)
5000
–16
10
Error Amplifier Transconductance
200
FEEDBACK PIN VOLTAGE
(AT THRESHOLD)
0
1070/71 G12
–24
460
VC = 0V
1070/71 G11
500
FEEDBACK PIN CURRENT (µA)
FEEDBACK PIN VOLTAGE (mV)
VC = 50mV
80
*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)
100
0
6
5
120
20
0% DUTY CYCLE
7
Feedback Pin Clamp Voltage
500
VC = 0.6V
450
9
FEEDBACK VOLTAGE (mV)
DRIVER CURRENT (mA)
100
ISWITCH ≤ 10mA
13
TJ = 25°C
140
90% DUTY CYCLE
14
120
160
TJ = 25°C
15
140
60
Supply Current vs Supply Voltage
(Shutdown Mode)
Supply Current vs Input Voltage*
SUPPLY CURRENT (µA)
Driver Current* vs Switch Current
8
7
6
5
VSUPPLY = 60V
VSUPPLY = 3V
4
400
250
150
2
50
0
1070/71 G14
150°C
200
100
0 25 50 75 100 125 150
TEMPERATURE (°C)
25°C
300
3
1
–75 – 50 –25
– 55°C
350
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
5
LT1070/LT1071
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TYPICAL PERFORMANCE CHARACTERISTICS
Switch “Off” Characteristics
Transconductance of Error
Amplifier
VC Pin Characteristics
300
1000
900
6000
VC PIN CURRENT (µA)
SWITCH CURRENT (µA)
600
500
VSUPPLY =
400
3V
300
15V
40V
55V
VFB = 1.5V
(CURRENT INTO
VC PIN)
100
0
–100
VFB = 0.8V
(CURRENT OUT OF VC PIN)
– 200
200
– 300
100
0
10 20 30 40 50 60 70 80 90 100
SWITCH VOLTAGE (V)
30
5000
gm
4000
0
0.5
2.0
1.5
1.0
VC PIN VOLTAGE (V)
1070/71 G19
2.5
60
3000
90
2000
120
1000
150
0
180
–1000
– 400
0
0
θ
1k
10k
100k
1M
FREQUENCY (Hz)
PHASE (°)
TRANSCONDUCTANCE (µmho)
200
800
700
– 30
7000
TJ = 25°C
210
10M
1070/71 G21
1070/71 G20
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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
VC
+ AMP
+
CURRENT
AMP
SHUTDOWN
CIRCUIT
1.24V
REF
0.15V
GAIN ≈ 6
0.02Ω
(0.04Ω 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
6
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
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 50µA 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)
VIN
10V
TO
20V
+
VSW
LT1070/LT1071
GND
1070/71 TA03
G
D
D1
S
D2
R2**
R1*
Q1
Q1
D1
VIN
VSW
LT1070/LT1071
*SETS IB(ON)
**SETS IB(OFF)
GND
1070/71 TA16
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
100µF
+
L1**
200µH
C2
1000µF
– 5.2V
4.5A
Q1
2N3906
LT1070
FB
VC
GND
LOAD
VSW
+
OPTIONAL INPUT
FILTER
R1
4.64k
L3
OPTIONAL
OUTPUT
FILTER
C1
R2
1.24k
R3
VIN
– 20V
+
C4
200µF
L2
4µH
*REQUIRED IF INPUT LEADS ≥ 2"
**PULSE ENGINEERING 92113
1070/71 TA12
Positive Buck Converter
VIN
D3
L2
4µH
VIN
+
C5*
C3
2.2µF
OPTIONAL
OUTPUT
FILTER
VSW
+
LT1070
D2
1N914
R1
3.74k
100µF
VC
GND
C5
200µF
FB
R2
1.24k
R3
470Ω
C1
1µF
+
C2
1µF
R4
10Ω
L1**
100µH
r
+
D1
C4
1000µF
*REQUIRED IF INPUT LEADS ≥2"
**PULSE ENGINEERING 92112
5V
4.5A
100mA
MINIMUM
1070/71 TA14
Negative Current Boosted Buck Converter
+
C1
R1
R5
C3
•
VIN
+
VSW
T1
1:N
D1
•
Q1
2N3906
R4
12k
R1 =
LT1070
GND
VC
FB
R3
R2
1.24k
C2
– VIN
8
MINIMUM
LOAD = 10mA
1070/71 TA13
VOUT – 0.6V
1mA
– VOUT
5V
10A
LT1070/LT1071
U
TYPICAL APPLICATIONS
(Note that maximum output currents are divided by 2 for the LT1071)
Positive Current Boosted Buck Converter
VIN
28V
470Ω
2W
R6
470Ω
C3
0.47µF
C6
0.002µF
D2
VIN
•
1:N
VSW
N ≈ 0.25
LT1070
R2
1k
GND
R7
1.24k
D1
FB
VC
VIN
7
6
C5*
100µF
–
R3
680Ω
+
•
+
2
V
V – LM308
COMP 3
4
R5
5k
+
C1
0.33µF
8
R4
1.24k
200pF
R1
5k
*REQUIRED IF INPUT LEADS ≥ 2"
VOUT
5V
10A
+
C2
5000µF
1070/71 TA19
Positive to Negative Buck/Boost Converter
Negative to Positive Buck/Boost Converter
L1**
150µH
OPTIONAL
OUTPUT
FILTER
C3
VIN
D1
VIN
C4*
100µF
VSW
C2
1000µF
+
LT1070
+
R1
11.3k
Q1
L3
GND
OPTIONAL
INPUT
FILTER
VIN
– 12V
VC
FB
R3
2.2k
C1
0.22µF
R2
1.24k
R5†
470Ω
1W
D3†
1N4001
L2
VOUT
12V
2A
C4
5µF
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
100µF
LOWER OUTPUT CURRENTS.
C1 ≈ (500µF)(IOUT) FOR 5V
OUTPUTS, REDUCE R3 TO
1.5k, INCREASE C2 TO 0.3µF
D2
R1
R4
1N914 47Ω AND REDUCE R6 TO 100Ω.
10.7k
FB
R3
5k
C1
0.1µF
R2
1.24k
+
C3
C1†
2µF 1000µF
+
R6
470Ω
D1
1070/71 TA09
1070/71 TA05
L1**
200µH
*REQUIRED IF INPUT LEADS ≥ 2"
**PULSE ENGINEERING 92113
VOUT
– 12V
2A
*REQUIRED IF INPUT LEADS ≥ 2"
**PULSE ENGINEERING 92113
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
680Ω
1W
C3
0.68µF
R4
D2
VIN
+
VIN
15V
VSW
LT1070
VC
R3
10k
C2
0.047µF
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
VC
GND
C1
200µF
FB
R2
1.24k
R3
C2
1070/71 TA10
1070/71 TA11
Negative Input/Negative Output Flyback Converter
Negative Boost Regulator
D2
VSW
C4*
470µF
VIN
–15V
VIN
+
R1
27k
+
GND
L1
200µH
R6
•
VIN
LT1070
+
C3
R3
3.3k
C2
0.22µF
RO
(MINIMUM
LOAD)
+
VC
FB
*R1 =
R4
1.24k
R5
*REQUIRED IF INPUT LEADS ≥ 2"
VOUT
–28V
1A
C2
1070/71 TA17
– VIN
1070/71 TA15
External Current Limit
External Current Limit
VSW
VX
LT1070/LT1071
LT1070/LT1071
R2
+
= 2V
VIN
FB
GND
R1
1k
Q1
C1
1000pF
RS
10
D1
VC
GND
VC
R1
500Ω
R2
1070/71 TA04
C2
C1
– VOUT
GND
D1
+
Q1
2N3906
LT1070/LT1071
R2
1.24k
VIN
•
R1*
C3
10µF
FB
VC
C1
1000µF
T1
1:N
VSW
R2
5k
R3
1k
NOTE THAT THE LT1070/LT1071
GND PIN IS NO LONGER COMMON
TO VIN–
1070/71 TA06
VOUT – 1.6V
200µA
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
10µH
C4
200µF
OPTIONAL
FILTER
D1
VIN
20V TO 30V
C3
0.47µF
R4
+
(N)(VIN) SECONDARY VOLTAGE
AREA “c” = AREA “d” TO MAINTAIN
ZERO DC VOLTS ACROSS SECONDARY
c
0V
d
C1
2000µF
∆I
IPRI
R1
3.74k
PRIMARY CURRENT
0
IPRI N
SECONDARY CURRENT
0
FB
IPRI
VC
R2
1.24k
R3
1.5k
C2
0.15µF
LT1070 SWITCH CURRENT
0
IPRI
SNUBBER DIODE CURRENT
*REQUIRED IF INPUT LEADS ≥ 2"
1070/71 TA08
(I )(L )
t = PRI L
VSNUB
U
PACKAGE DESCRIPTION
0.320 – 0.350
(8.13 – 8.89)
VOUT + VF
VSW
LT1070
GND
b
0V
•
N = 1/3
C4*
100µF
VOUT
5V
6A
1 N
D2
VIN
+
•
+ VF
V
PRIMARY FLYBACK VOLTAGE = OUT
N
LT1070/LT1071 SWITCH VOLTAGE
AREA “a” = AREA “b” TO MAINTAIN
ZERO DC VOLTS ACROSS PRIMARY
a
VIN
Dimensions in inches (millimeters) unless otherwise noted.
K Package
4-Lead TO-3 Metal Can
T Package
5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1311)
(LTC DWG # 05-08-1421)
0.760 – 0.775
(19.30 – 19.69)
0.390 – 0.415
(9.906 – 10.541)
0.060 – 0.135
(1.524 – 3.429)
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)
0.620
(15.75)
TYP
0.700 – 0.728
(17.78 – 18.491)
1.177 – 1.197
(29.90 – 30.40)
0.470 TP
P.C.D.
0.655 – 0.675
(16.64 – 19.05)
0.151 – 0.161
(3.84 – 4.09)
DIA 2 PLC
0.167 – 0.177
(4.24 – 4.49)
R
72°
18°
0.152 – 0.202
0.260 – 0.320 (3.861 – 5.131)
(6.60 – 8.13)
0.095 – 0.115
(2.413 – 2.921)
0.013 – 0.023
(0.330 – 0.584)
0.057 – 0.077
(1.448 – 1.956)
0.028 – 0.038
(0.711 – 0.965)
0.135 – 0.165
(3.429 – 4.191)
0.155 – 0.195
(3.937 – 4.953)
T5 (TO-220) 0398
0.495 – 0.525
(12.57 – 13.34)
R
K4(TO-3) 0695
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
15V
1:N
C3
0.47µF
R4
1.5k
+
•
+
N
VIN
+V
+
IN
5V
C5*
100µF
LT1070/LT1071
COM
C4
500µF
•
VSW
+
C1
500µF
N
L1
10µF
–15V
C6
200µF
N = 0.875 = 7:8
FOR VOUT = 15V
≈16V
SWITCH VOLTAGE
FB
VC
GND
+
L2
10µF
C5
200µF
VIN
500Ω
tOFF
0V
tON
R2
C2
5k
0.01µF
VF
(DIODE FORWARD VOLTAGE)
VOUT
SECONDARY VOLTAGE
0V
*REQUIRED IF INPUT LEADS ≥ 2"
1070/71 TA07
(N)(VIN)
Forward Converter
R4
C2
•
I
L1
70µH
D1
T1
M
N
•
+
D2
VIN
VIN
20V TO 30V
D3
VC
C1
2000µF
•
VSW
LT1070
GND
VOUT
5V
6A
D4
R1
3.74k
FB
Q1
R3
C3
R6
C4 330Ω
R5
1Ω
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
12
Linear Technology Corporation
10701fd LT/TP 1098 2K REV D • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1989