1
LT1076-5
S
FEATURE
U
A
O
PPLICATI
TYPICAL
Basic Positive Buck Converter
5V Step-Down
Switching Regulator
D
U
ESCRIPTIO
s
Fixed 5V Output
s
2A On-Board Switch
s
100kHz Switching Frequency
s
2% Output Voltage Tolerance Over Temperature
s
Greatly Improved Dynamic Behavior
s
Available in Low Cost 5-Lead Package
s
Only 9.5mA Quiescent Current
s
Operates Up to 60V Input
s
5V Output Buck Converter
s
Tapped Inductor Buck Converter with 4A Output
at 5V
s
Positive-to-Negative Converter
U
S
A
O
PPLICATI
The LT1076-5 is a 2A fixed 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" configuration but several design
innovations allow this device to be used as a positive-to-
negative converter, a negative boost converter, and as a
flyback converter. The switch output is specified 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 instanta-
neously to input voltage fluctuations and makes loop gain
independent of input voltage. As a result, dynamic behav-
ior of the regulator is significantly improved over previous
designs.
On-chip pulse by pulse current limiting makes the LT1076-
5 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 configurations.
The LT1076-5 is available in a low cost 5-lead TO-220
package with frequency pre-set at 100kHz and current
limit at 2.6A. See Application Note 44 for design details.
LT1076-5
V
SW
SENSE
V
C
GND
R3
1.5k
C2
0.033
F
C3
200
F
+
100
H**
MBR340*
MBR330P MAY BE USED
FOR V
IN
25V
COILTRONICS #100-1-52
HURRICANE #HL-AG210LL
VALUE MAY BE REDUCED TO 50
H
FOR OUTPUT LOADS BELOW 1.5A
8V TO 40V
+
C1
500
F
25V
LT1076-5 TA01
V
IN
5V
1.8A
*
**
2
LT1076-5
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
(V
SW
Negative)
LT1076-5 (Note 5) .............................................. 35V
LT1076HV-5 (Note 5) ......................................... 45V
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
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
W
U
U
PACKAGE/ORDER I FOR ATIO
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Switch "On" Voltage (Note 1)
I
SW
= 0.5A
q
1.2
V
I
SW
= 2A
q
1.7
V
Switch "Off" Leakage
V
IN
= 25V, V
SW
= 0
150
A
V
IN
= V
MAX
, V
SW
= 0 (Note 6)
250
A
Supply Current (Note 2)
V
OUT
= 5.5V, V
IN
40V
q
8.5
11
mA
40V < V
IN
< 60V
q
9.0
12
mA
V
SHDN
= 0.1V (Device Shutdown) (Note 8)
140
300
A
Minimum Supply Voltage
Normal Mode
q
7.3
8.0
V
Start-Up Mode (Note 3)
q
3.5
4.8
V
Switch Current Limit (Note 4)
I
LIM
= Open
q
2
2.6
3.2
A
R
LIM
= 10k (Note 9)
1.8
A
R
LIM
= 7k (Note 9)
1.2
A
Maximum Duty Cycle
q
85
90
%
ELECTRICAL C
C
HARA TERISTICS
T
J
= 25
C, V
IN
= 25V, unless otherwise noted.
T
JMAX
= 110
C
ORDER PART
NUMBER
LT1076CR-5
LT1076CY-5
R PACKAGE
7-LEAD PLASTIC DD
FRONT VIEW
SHDN
V
C
SENSE
GND
I
LIM
V
SW
V
IN
7
6
5
4
3
2
1
LT1076CT-5
LT1076HVCT-5
LT1076IT-5
LT1076HVIT-5
FOR STRAIGHT LEADS, ORDER FLOW 06
T
JMAX
= 110
C,
JA
= 130
C/W
T PACKAGE
5-LEAD TO-220
FRONT VIEW
5
4
3
2
1
V
IN
GND
SENSE
V
SW
V
C
Y PACKAGE
7-LEAD TO-220
SHDN
SENSE
I
LIM
V
IN
V
C
GND
V
SW
FRONT VIEW
7
6
5
4
3
2
1
Consult factory for Military grade parts.
WILL VARY FROM APPROXIMATELY 30
C/W WITH
2.8IN
2
OF 1 OZ COPPER TO 70
C/W WITH 0.20IN
2
OF
1 OZ COPPER.
T
JMAX
= 110
C,
JA
= 130
C/W
3
LT1076-5
ELECTRICAL C
C
HARA TERISTICS
T
J
= 25
C, V
IN
= 25V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Switching Frequency
90
100
110
kHz
T
J
125
C
q
85
120
kHz
V
OUT
= V
SENSE
= 0V (Note 4)
20
kHz
Switching Frequency Line Regulation
8V
V
IN
V
MAX
(Note 7)
q
0.03
0.1
%/ V
Error Amplifier Voltage Gain (Note 7)
1V
V
C
4V
2000
V/ V
Error Amplifier Transconductance (Note 7)
3700
5000
8000
mho
Error Amplifier Source and Sink Current
Source (V
SENSE
= 4.5V)
100
140
225
A
Sink (V
SENSE
= 5.5V)
0.7
1.0
1.6
mA
Sense Pin Divider Resistance
3
5
8
k
Sense Voltage
V
C
= 2V
q
4.85
5
5.15
V
Output Voltage Tolerance
V
OUT
(Nominal) = 5V
0.5
2
%
All Conditions of Input Voltage, Output Voltage,
q
1.0
3
%
Temperature and Load Current
Output Voltage Line Regulation
8V
V
IN
V
MAX
(Note 6)
q
0.005
0.02
%/ V
V
C
Voltage at 0% Duty Cycle
1.5
V
Over Temperature
q
4.0
mV/
C
Multiplier Reference Voltage
24
V
Shutdown Pin Current
V
SHDN
= 5V
5
10
20
A
V
SHDN
V
THRESHOLD
(
2.5V)
50
A
Shutdown Thresholds
Switch Duty Cycle = 0
2.2
2.45
2.7
V
Fully Shut Down
0.1
0.30
0.5
V
Thermal Resistance Junction to Case
4
C/ W
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1: To calculate maximum switch "on" voltage at currents between
low and high conditions, a linear interpolation may be used.
Note 2: A sense pin voltage (V
SENSE
) of 5.5V forces the V
C
pin to its low
clamp level and the switch duty cycle to zero. This approximates the zero
load condition where duty cycle approaches zero.
Note 3: Total voltage from V
IN
pin to ground pin must be
8V after start-
up for proper regulation. For T
A
< 25
C, limit = 5V.
Note 4: 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
SENSE
is adjusted to give a minimum switch on time
of 1
s.
Note 5: Switch to input voltage limitation must also be observed.
Note 6: V
MAX
= 40V for the LT1076-5 and 60V for the LT1076HV-5.
Note 7: Error amplifier voltage gain and transconductance are specified
relative to the internal feedback node. To calculate gain and
transconductance from the Sense pin (Output) to the V
C
pin, multiply by
0.44.
Note 8: Does not include switch leakage.
Note 9: I
LIM
R
LIM
1k
5k
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
4
LT1076-5
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900
q
FAX
: (408) 434-0507
q
TELEX
: 499-3977
LINEAR TECHNOLOGY CORPORATION 1994
PACKAGE DESCRIPTIO
U
Dimensions in inches (millimeters) unless otherwise noted.
0.147 0.155
(3.73 3.94)
DIA
0.390 0.410
(9.91 10.41)
0.045 0.055
(1.14 1.40)
0.235 0.258
(5.97 6.55)
0.026 0.036
(0.66 0.91)
0.103 0.113
(2.62 2.87)
Y7 0893
0.260 0.320
(6.60 8.13)
0.045 0.055
(1.14 1.40)
0.169 0.185
(4.29 4.70)
0.095 0.115
(2.41 2.92)
0.155 0.195
(3.94 4.95)
0.620
(15.75)
TYP
0.560 0.590
(14.22 14.99)
0.016 0.022
(0.41 0.56)
0.700 0.728
(17.78 18.49)
0.135 0.165
(3.43 4.19)
0.152 0.202
(3.86 5.13)
R Package, 7-Lead Plastic DD
Y Package, 7-Lead TO-220
LT/GP 0794 5K REV A PRINTE IN USA
T Package, 5-Lead TO-220
T5 (FORMED) 0694
0.028 0.038
(0.711 0.965)
0.057 0.077
(1.448 1.956)
0.135 0.165
(3.429 4.191)
0.700 0.728
(17.780 18.491)
0.045 0.055
(1.143 1.397)
0.095 0.115
(2.413 2.921)
0.013 0.023
(0.330 0.584)
0.620
(15.75)
TYP
0.155 0.195
(3.937 4.953)
0.152 0.202
(3.860 5.130)
0.260 0.320
(6.604 8.128)
0.165 0.180
(4.293 4.572)
0.147 0.155
(3.734 3.937)
DIA
0.390 0.415
(9.906 10.541)
0.330 0.370
(8.382 9.398)
0.460 0.500
(11.684 12.700)
0.570 0.620
(14.478 15.748)
0.230 0.270
(5.842 6.858)
DD7 0693
0.060
(1.524)
0.401 0.015
(10.185 0.381)
15 TYP
0.030 0.008
(0.762 0.203)
0.331
+0.012
0.020
(
)
8.407
+0.305
0.508
0.143
+0.012
0.020
(
)
3.632
+0.305
0.508
0.050 0.010
(1.270 0.254)
0.022 0.005
(0.559 0.127)
0.105 0.008
(2.667 0.203)
0.004
+0.008
0.004
(
)
0.102
+0.203
0.102
0.050 0.012
(1.270 0.305)
0.059
(1.499)
TYP
0.050 0.008
(1.270 0.203)
0.175 0.008
(4.445 0.203)
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