Datasheet

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10701fe

LT1070/LT1071

FEATURES

APPLICATIO S

DESCRIPTIO

TYPICAL APPLICATIO

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.

10.7k

1.24k

1070/71 TA01

12V

1µF

1000µF

C3*

100µF

L1**

150µH

LT1070

GND

100µF

10µH

OUTPUT

FILTER

REQUIRED IF INPUT LEADS ≥ 2"

PULSE ENGINEERING 92113

INPUT VOLTAGE (V)

POWER (W)**

100

1070/71 TA02

BOOST

BUCK/BOOST

= 30V

FLYBACK

ISOLATED

BUCK/BOOST

= 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.

Summary of content (12 pages)

PAGE 1
LT1070/LT1071 5A and 2.5A High Efficiency Switching Regulators DESCRIPTIO U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Wide Input Voltage Range: 3V to 60V Low Quiescent Current: 6mA Internal 5A Switch (2.
PAGE 2
LT1070/LT1071 W W U 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) .......................
PAGE 3
LT1070/LT1071 ELECTRICAL CHARACTERISTICS 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. SYMBOL PARAMETER CONDITIONS VFB Flyback Reference Voltage IFB = 50µA ● Change in Flyback Reference Voltage BV VSAT ILIM 0.
PAGE 4
LT1070/LT1071 U W 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.
PAGE 5
LT1070/LT1071 U W 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 1 0 2 3 4 SWITCH CURRENT (A) 60 40 20 0 10 0 1070/71 G10 30 40 20 INPUT VOLTAGE (V) 60 50 Shutdown Mode Supply Current –22 180 4500 480 –20 470 –18 440 –12 430 –10 FEEDBACK PIN CURRENT (AT THRESHOLD) 420 0 140 120 TJ = 150°C 100 80 60 – 55°C ≤ TJ ≤ 125°C 40 –6 20 –4 25 50 75 100 125 150 TEMPERATURE (°C) 0 410 400 –5
PAGE 6
LT1070/LT1071 U W TYPICAL PERFORMANCE CHARACTERISTICS Switch “Off” Characteristics 300 1000 900 7000 TJ = 25°C 500 VSUPPLY = 400 3V 300 15V 40V 55V TRANSCONDUCTANCE (µmho) 600 VFB = 1.5V (CURRENT INTO VC PIN) 100 0 –100 VFB = 0.8V (CURRENT OUT OF VC PIN) – 200 200 – 300 100 0 0 10 20 30 40 50 60 70 80 90 100 SWITCH VOLTAGE (V) 5000 30 gm 4000 0 0.5 2.0 1.5 1.0 VC PIN VOLTAGE (V) 1070/71 G19 2.
PAGE 7
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.
PAGE 8
LT1070/LT1071 U 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 GND LOAD VSW + OPTIONAL INPUT FILTER R1 4.64k VC FB 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 + LT1070 D2 1N914 R1 3.
PAGE 9
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 R3 680Ω 6 C5* 100µF – V+ 2 R5 5k V – LM308 COMP 3 4 + + • C1 0.33µF 8 R4 1.
PAGE 10
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 GND FB VC C1 200µF R2 1.
PAGE 11
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 VOUT 5V 6A 1 N + D2 VIN + • VOUT + VF (N)(VIN) SECONDARY VOLTAGE AREA “c” = AREA “d” TO MAINTAIN ZERO DC VOLTS ACROSS SECONDARY c 0V d ∆I • IPRI VSW R1 3.
PAGE 12
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 0.47µF R4 1.5k + • +V + IN 5V C5* 100µF + LT1070/LT1071 COM C4 500µF • VSW + C1 500µF N N VIN L1 10µF 15V C6 200µF N = 0.875 = 7:8 FOR VOUT = 15V ≈16V SWITCH VOLTAGE FB GND + L2 10µF –15V C5 200µF VC VIN 500Ω tOFF 0V tON R2 C2 5k 0.