ANALOG DEVICES LT 1076 CT-5 Datasheet

LT1076-5

5V Step-Down

Switching Regulator

FEATURES

n

Fixed 5V Output

n

2A On-Board Switch

n

100kHz Switching Frequency

n

2% Output Voltage Tolerance Over Temperature

n

Greatly Improved Dynamic Behavior

n

Available in Low Cost 5- and 7-Lead Packages

n

Only 9.5mA Quiescent Current

n

Operates Up to 60V Input

APPLICATIONS

n

5V Output Buck Converter

n

Tapped Inductor Buck Converter with 4A Output at

5V

n

Positive-to-Negative Converter

DESCRIPTION

The LT®1076-5 is a 2A fi xed 5V output monolithic bipolar
switching regulator which requires only a few external parts
for normal operation. The power switch, all oscillator and
control circuitry, all current limit components, and an output
monitor are included on the chip. The topology is a classic
positive “buck” confi guration but several design innova­tions allow this device to be used as a positive-to-negative
converter, a negative boost converter, and as a fl yback con­verter. The switch output is specifi ed to swing 40V below
ground, allowing the LT1076-5 to drive a tapped inductor
in the buck mode with output currents up to 4A.

The LT1076-5 uses a true analog multiplier in the feedback
loop. This makes the device respond nearly instantaneously
to input voltage fl uctuations and makes loop gain indepen­dent of input voltage. As a result, dynamic behavior of the
regulator is signifi cantly improved over previous designs.

On-chip pulse by pulse current limiting makes the LT1076­5 nearly bust-proof for output overloads or shorts. The
input voltage range as a buck converter is 8V to 60V, but
a self-boot feature allows input voltages as low as 5V in
the inverting and boost confi gurations.

TYPICAL APPLICATION

8V TO 40V

+ +

C3
200μF

V

GND

IN

LT1076-5

The LT1076-5 is available in a low cost 5- and 7-lead TO­220 packages with frequency pre-set at 100kHz and current
limit at 2.6A. See Application Note 44 for design details.

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

Basic Positive Buck Converter

†

V

SENSE

V

C

SW

R3

1.5k
C2

0.033μF

100μH**

MBR340*

C1
500μF

25V

LT1076-5 TA01

5V
≤1.8A

MBR330P MAY BE USED

*

≤ 25V

FOR V

IN

COILTRONICS #100-1-52

**

HURRICANE #HL-AG210LL

†

VALUE MAY BE REDUCED TO 50μH
FOR OUTPUT LOADS BELOW 1.5A

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LT1076-5

ABSOLUTE MAXIMUM RATINGS

Input Voltage

LT1076-5 .............................................................45V

LT1076HV-5 .........................................................64V

Switch Voltage with Respect to Input Voltage

LT1076-5 ..............................................................64V

LT1076HV-5 .........................................................75V

Switch Voltage with Respect to Ground Pin

Negative)

(V

SW

LT1076-5 (Note 6) ................................................35V

(Note 1)

Sense Pin Voltage ............................................ –2V, 10V

Maximum Operating Ambient Temperature Range

LT1076C-5, LT1076HVC-5 ....................... 0°C to 70°C

LT1076I-5, LT1076HVI-5 ..................... –40°C to 85°C

Maximum Operating Junction Temperature Range

LT1076C-5, LT1076HVC-5 ..................... 0°C to 125°C

LT1076I-5, LT1076HVI-5 ................... –40°C to 125°C

Maximum Storage Temperature ............ –65°C to 150°C

Lead Temperature (Soldering, 10 sec) ..................300°C

LT1076HV-5 (Note 6) ...........................................45V

PACKAGE/ORDER INFORMATION

FRONT VIEW

5

V

IN

V

4

3

2

1

Q PACKAGE

5-LEAD PLASTIC DD

= 4°C/W, θJA = 30°C/W

θ

JC

FRONT VIEW

TAB

IS

GND

T PACKAGE

5-LEAD PLASTIC TO-220

LEADS ARE FORMED STANDARD

FOR STRAIGHT LEADS, ORDER FLOW 06

= 4°C/W, θJA = 50°C/W

θ

JC

SW

GND

V

C

FB/SENSE

5
4
3
2
1

V

IN

GND

SENSE

TAB IS

V

SW

TAB

V

C

GND

IS

FRONT VIEW

7
6
5

GND

θJC = 4°C/W, θJA = 30°C/W

7-LEAD PLASTIC TO-220

θJC = 4°C/W, θJA = 50°C/W

4
3
2
1

R PACKAGE

7-LEAD PLASTIC DD

FRONT VIEW

7
6
5
4
3
2
1

T7 PACKAGE

SHDN
V

C

SENSE
GND
I

LIM

V

SW

V

IN

SHDN

SENSE

I

LIM

V

IN

V

GND

V

C

SW

Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/

Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.

ORDER PART

NUMBER

ORDER PART

NUMBER

LT1076CQ-5 LT1076CR-5

ORDER PART

NUMBER

LT1076CT-5

ORDER PART

NUMBER

LT1076CT7-5
LT1076HVCT-5
LT1076IT-5
LT1076HVIT-5

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at TJ = 25°C. VIN = 25V, unless otherwise noted.

SYMBOL CONDITIONS MIN TYP MAX UNITS

Switch “On” Voltage (Note 2) I

Switch “Off” Leakage V

= 0.5A

SW

I

= 2A

SW

= 25V, VSW = 0

IN

V

= 25V, VSW = 0

IN

l
l

1.2

1.7

150
250

μA
μA

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V
V

LT1076-5

ELECTRICAL CHARACTERISTICS

The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T

SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Current (Note 3) V

Minimum Supply Voltage Normal Mode

Switch Current Limit (Note 5) I

Maximum Duty Cycle

Switching Frequency

Switching Frequency Line Regulation 8V ≤ V

Error Amplifi er Voltage Gain (Note 8) 1V ≤ V

Error Amplifi er Transconductance
(Note 8)

Error Amplifi er Source and Sink
Current

Sense Pin Divider Resistance 358 kΩ

Sense Voltage V

Output Voltage Tolerance V

Output Voltage Line Regulation 8V ≤ VIN ≤ V

VC Voltage at 0% Duty Cycle

Multiplier Reference Voltage 24 V

Shutdown Pin Current V

Shutdown Thresholds Switch Duty Cycle = 0

Thermal Resistance Junction to Case 4°C/W

= 5.5V, VIN ≤ 40V

OUT

40V < V
V

< 60V

IN

= 0.1V (Device Shutdown) (Note 9)

SHDN

Start-Up Mode (Note 4)

= Open

LIM

R

= 10k (Note 10)

LIM

R

= 7k (Note 10)

LIM

TJ ≤ 125°C
V

= V

OUT

SENSE

≤ V

IN

MAX

≤ 4V 2000 V/V

C

Source (V
Sink (V

SENSE

SENSE

= 2V

C

(Nominal) = 5V

OUT

= 5.5V)

All Conditions of Input Voltage, Output Voltage,
Temperature and Load Current

MAX

Over Temperature

= 5V

SHDN

V

≤ V

SHDN

THRESHOLD

Fully Shut Down

= 25°C. VIN = 25V, unless otherwise noted.

J

= 0V (Note 5)

(Note 8)

= 4.5V)

(Note 7)

(≅ 2.5V)

l
l

l
l

l

2 2.6

8.5

9.0

140

7.3

3.5

11
12

300

8.0

4.8

3.2 A

1.8

1.2

l

85 90 %

90

l

85

100

110
120

20

l

0.03 0.1 %/V

3700 5000 8000 μmho

100

0.7

l

4.85 5 5.15 V

l

l

140

1.0

±0.5
±1.0

225

1.6

±2
±3

0.005 0.02 %/V

1.5

l

–4.0

5102050μA

2.2

0.1

2.45

0.30

2.7

0.5

mA
mA

μA

V
V

A
A

kHz
kHz
kHz

μA

mA

%
%

V

mV/°C

μA

V
V

Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.

Note 2: To calculate maximum switch “on” voltage at currents between
low and high conditions, a linear interpolation may be used.

Note 3: A sense pin voltage (V

) of 5.5V forces the VC pin to its low

SENSE

clamp level and the switch duty cycle to zero. This approximates the zero
load condition where duty cycle approaches zero.

Note 4: Total voltage from V
up for proper regulation. For T

pin to ground pin must be ≥ 8V after start-

IN

< 25°C, limit = 5V.

A

Note 5: Switch frequency is internally scaled down when the sense pin
voltage is less than 2.6V to avoid extremely short switch on times. During

current limit testing, V

is adjusted to give a minimum switch on time

SENSE

of 1ms.

Note 6: Switch to input voltage limitation must also be observed.
Note 7: V

= 40V for the LT1076-5 and 60V for the LT1076HV-5.

MAX

Note 8: Error amplifi er voltage gain and transconductance are
specifi ed relative to the internal feedback node. To calculate gain and
transconductance from the Sense pin (Output) to the V

pin, multiply by

C

0.44.
Note 9: Does not include switch leakage.

Rk

− 1

LIM

I

≈

Note 10:

LIM

k

5

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