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LT1176CN8-5#PBF

P1-P3P4-P6P7-P8
LT1176/LT1176-5
1
11765fb
TYPICAL APPLICATION
FEATURES
DESCRIPTION
Step-Down
Switching Regulator
The LT
®
1176 is a 1A monolithic bipolar switching regulator
which requires only a few external parts for normal opera-
tion. The power switch, all oscillator and control circuitry
Basic 5V Positive Buck Converter
APPLICATIONS
n
1.2A Onboard Switch
n
100kHz Switching Frequency
n
Excellent Dynamic Behavior
n
DIP and Surface Mount Packages
n
Only 8mA Quiescent Current
n
Preset 5V Output Available
n
Operates Up to 35V Input
n
Micropower Shutdown Mode
n
Buck Converter with Output Voltage Range of
2.5V to 30V
n
Positive-to-Negative Converter
n
Negative Boost Converter
n
Multiple Output Buck Converter
L, LT, LTC, LTM, Linear Technology, SwitcherCAD and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
and all current limit components are included on the chip.
The topology is a classic positive buck configuration but
several design innovations allows 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 below ground.
The LT1176 uses a true analog multiplier in the feedback
loop. This makes the device respond nearly instantaneously
to input voltage fluctuations and makes loop gain indepen-
dent of input voltage. As a result, dynamic behavior of the
regulator is significantly improved over previous designs.
On-chip pulse by pulse current limiting makes the LT1176
nearly bust proof for output overloads or shorts. The input
voltage range as a buck converter is 8V to 35V, but a self
boot feature allows input voltages as low as 5V in the
inverting and boost configurations.
The LT1176 is available in a low cost 8-lead DIP package
with frequency preset at 100kHz and current limit at 1.7A.
An adjustable output is offered as well as a preset 5V ver-
sion. For further design details and application help, see
the LT1074/LT1076 data sheet and Application Note 44.
5V Buck Converter Efficiency
V
C
GND
LT1176-5
R3
2.7k
C2
0.01µF
1N5819
+
C3
100µF
+
C1
470µF
25V
11765 TA01
5V, 0.8A
10V T0 35V
L1*
100µH
*COILTRONICS #100-1-52
PULSE ENGINEERING, INC. #PE-92102
HURRICANE #HL-AG210LL
THESE ARE LOW COST POWDERED IRON CORES. OPTIMUM EFFICIENCY
AND SMALLEST SIZE IS OBTAINED BY USING A LOW LOSS CORE SUCH
AS MAGNETICS INC. KOOL Mµ. SEE EFFICIENCY GRAPH.
V
IN
V
SW
SENSE
LOAD CURRENT (A)
60
EFFICIENCY (%)
70
80
90
0.2 0.4 0.6 0.8
11765 TA02
1.00.1 0.3 0.5 0.7 0.9
L = 100µH ON MAGNETICS INC.
SIZE T-50 KOOL Mµ CORE
V
IN
= 20V
V
IN
= 10V
LT1176/LT1176-5
2
11765fb
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
Input Voltage ............................................................. 38V
Switch Voltage with Respect to Input Voltage...........50V
Switch Voltage with Respect to Ground Pin
(V
SW
Negative) (Note 7) ............................................20V
Feedback Pin Voltage
........................................ –2V, 10V
Shutdown Pin Voltage (Not to Exceed V
IN
) ...............35V
Status Pin Voltage
(Current Must Be Limited to 5mA When Status Pin
Switches ON) ........................................................30V
1
2
3
4
8
7
6
5
TOP VIEW
V
IN
I
LIM
GND
FB/SENSE
V
SW
V
C
STATUS
SHUTDOWN
N8 PACKAGE
8-LEAD PLASTIC DIP
T
JMAX
= 125°C, θ
JA
= 90°C/W
1
2
3
4
5
6
7
8
9
10
TOP VIEW
SW PACKAGE
20-LEAD PLASTIC SOL
20
19
18
17
16
15
14
13
12
11
V
IN
NC
I
LIM
GND
GND
GND
GND
NC
FB/SENSE
NC
V
SW
NC
V
C
GND
GND
GND
GND
STATUS
SHUTDOWN
NC
T
JMAX
= 125°C, θ
JA
= 50°C/W
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LT1176CN8#PBF LT1176CN8 8-Lead Plastic DIP 0°C to 125°C
LT1176CN8-5#PBF LT1176CN8-5 8-Lead Plastic DIP 0°C to 125°C
LT1176CSW#PBF LT1176CSW#TRPBF LT1176CSW 20-Lead Plastic SOL 0°C to 125°C
LT1176CSW-5#PBF LT1176CSW-5#TRPBF LT1176CSW-5 20-Lead Plastic SOL 0°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
I
LIM
Pin Voltage (Forced) .........................................5.5V
Maximum Operating Ambient Temperature Range
LT1176C/LT1176C-5 ................................. 0°C to 70°C
Maximum Operating Junction Temperature Range
LT1176C/LT1176C-5 ............................... 0°C to 125°C
Storage Temperature Range
.................. –65°C to 150°C
Lead Temperature (Soldering, 10 sec)
...................300°C
*These thermal resistance numbers are for typical mounting technique. Lower thermal
resistance can be obtained with large copper lands, thermal glues or heat sinks.
(Note 1)
LT1176/LT1176-5
3
11765fb
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
Switch ON Voltage (Note 2) I
SW
= 0.2A
I
SW
= 1A
l
l
1.1
1.4
V
V
Switch OFF Leakage V
IN
= 25V, V
SW
= 0
V
IN
= V
MAX
, V
SW
= 0 (Note 8)
150
250
µA
µA
Supply Current (Note 3) V
FB
= 2.5V, V
IN
≤ 35V
V
SHDN
= 0.1V (Device Shutdown) (Note 9)
l
l
7.5
140.0
10
300
mA
µA
Minimum Supply Voltage Normal Mode
Startup Mode (Note 4)
l
l
7.3
3.5
8.0
4.8
V
V
Switch Current Limit (Note 5) I
LIM
Open
R
LIM
= 10k (Note 6)
R
LIM
= 7k (Note 6)
l
1.2 1.7
1.2
0.8
2.2 A
A
A
Maximum Duty Cycle
l
85 90 %
Switching Frequency
V
FB
= 0V Through 2k (Note 5) (LT1176)
V
SENSE
= 0V (Note 5) (LT1176-5)
l
90
85
100
20
20
110
120
kHz
kHz
kHz
kHz
Switching Frequency Line Regulation 8V ≤ V
IN
≤ V
MAX
(Note 8)
l
0.03 0.1 %/V
Error Amplifier Voltage Gain (Note 10) 1V ≤ V
C
≤ 4V 2000 V/V
Error Amplifier Transconductance (Note 10) 3700 5000 8000 µmho
Error Amplifier Source and Sink Current Source (V
FB
= 2V or V
SENSE
= 4V)
Sink (V
FB
= 2.5V or V
SENSE
= 5.5V)
100.0
0.7
140
1.0
225.0
1.6
µA
mA
Feedback Pin Bias Current (LT1176) V
FB
= V
REF
l
0.5 2 µA
Reference Voltage (LT1176) V
C
= 2V
l
2.155 2.21 2.265 V
Reference Voltage Tolerance (LT1176) V
REF
(Nominal) = 2.21V
All Conditions of Input Voltage, Output Voltage,
Temperature and Load Current
l
±0.5
±1.0
±2
±3
%
%
Sense Voltage (LT1176-5) V
C
= 2V
l
4.85 5 5.15 V
Sense Voltage Tolerance (LT1176-5) V
OUT
(Nominal) = 5V
All Conditions of Input Voltage,
Temperature and Load Current
l
±0.5
±0.1
±2
±3
%
%
Sense Pin Divider Resistance (LT1176-5) 3 5 8 kΩ
Output Voltage Line Regulation 8V ≤ V
IN
≤ V
MAX
(Note 8)
l
0.005 0.02 %/V
V
C
Voltage at 0% Duty Cycle
Overtemperature
l
1.5
–4.0
V
mV/°C
Multiplier Reference Voltage 24 V
Shutdown Pin Current V
SHDN
= 5V
V
SHDN
≤ V
THRESHOLD
(@ 2.5V)
l
l
5 10 20
50
µA
µA
Shutdown Thresholds Switch Duty Cycle = 0
Fully Shutdown
l
l
2.2
0.1
2.45
0.30
2.7
0.5
V
V
Status Window As a Percent of Output Voltage ±4 ±5 ±6 %
Status High Level I
STATUS
= 10µA Sourcing
l
3.5 4.5 5.0 V
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. T
J
= 25°C, V
IN
25V, unless otherwise noted.
P1-P3P4-P6P7-P8

LT1176CN8-5#PBF

Mfr. #:
Buy LT1176CN8-5#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators 5V 1A Step-down Sw Reg
Lifecycle:
New from this manufacturer.
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