LT1176CSW-5#TRPBF [Linear]
LT1176/LT1176-5 - Step-Down Switching Regulator; Package: SO; Pins: 20; Temperature Range: 0°C to 70°C;型号: | LT1176CSW-5#TRPBF |
厂家: | Linear |
描述: | LT1176/LT1176-5 - Step-Down Switching Regulator; Package: SO; Pins: 20; Temperature Range: 0°C to 70°C 开关 光电二极管 |
文件: | 总8页 (文件大小:137K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LT1176/LT1176-5
Step-Down
Switching Regulator
and all current limit components are included on the chip.
The topology is a classic positive buck configuration but
severaldesigninnovationsallowsthisdevicetobeusedas
apositive-to-negativeconverter,anegativeboostconverter,
and as a flyback converter. The switch output is specified
to swing below ground.
FEATURES
n
1.2A Onboard Switch
n
100kHz Switching Frequency
n
Excellent Dynamic Behavior
n
DIP and Surface Mount Packages
n
Only 8mA Quiescent Current
The LT1176 uses a true analog multiplier in the feedback
loop.Thismakesthedevicerespondnearlyinstantaneously
toinputvoltagefluctuationsandmakesloopgainindepen-
dent of input voltage. As a result, dynamic behavior of the
regulator is significantly improved over previous designs.
n
Preset 5V Output Available
n
Operates Up to 35V Input
n
Micropower Shutdown Mode
APPLICATIONS
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.
n
Buck Converter with Output Voltage Range of
2.5V to 30V
n
Positive-to-Negative Converter
n
Negative Boost Converter
Multiple Output Buck Converter
n
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.
DESCRIPTION
TheLT®1176isa1Amonolithicbipolarswitchingregulator
which requires only a few external parts for normal opera-
tion. The power switch, all oscillator and control circuitry
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.
TYPICAL APPLICATION
Basic 5V Positive Buck Converter
5V Buck Converter Efficiency
90
L1*
100µH
L = 100µH ON MAGNETICS INC.
SIZE T-50 KOOL Mµ CORE
5V, 0.8A
10V T0 35V
V
IN
V
SW
LT1176-5
SENSE
V
= 10V
IN
1N5819
80
70
60
V
= 20V
IN
GND
V
C
+
C1
470µF
25V
R3
2.7k
+
C3
100µF
C2
0.01µF
*COILTRONICS #100-1-52
PULSE ENGINEERING, INC. #PE-92102
HURRICANE #HL-AG210LL
11765 TA01
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
LOAD CURRENT (A)
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.
11765 TA02
11765fb
1
LT1176/LT1176-5
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Voltage.............................................................38V
Switch Voltage with Respect to Input Voltage...........50V
Switch Voltage with Respect to Ground Pin
I
Pin Voltage (Forced) .........................................5.5V
LIM
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
(V Negative) (Note 7)............................................20V
SW
Feedback Pin Voltage........................................–2V, 10V
Shutdown Pin Voltage (Not to Exceed V )...............35V
IN
Status Pin Voltage
(Current Must Be Limited to 5mA When Status Pin
Switches ON)........................................................30V
*These thermal resistance numbers are for typical mounting technique. Lower thermal
resistance can be obtained with large copper lands, thermal glues or heat sinks.
PIN CONFIGURATION
TOP VIEW
V
1
2
3
4
5
6
7
8
9
20
19 NC
18
V
IN
SW
NC
TOP VIEW
I
V
LIM
C
V
1
2
3
4
8
7
6
5
V
V
GND
GND
17 GND
IN
SW
I
16 GND
LIM
C
GND
15 GND
GND
STATUS
GND
14 GND
FB/SENSE
SHUTDOWN
NC
13 STATUS
12 SHUTDOWN
11 NC
N8 PACKAGE
8-LEAD PLASTIC DIP
FB/SENSE
T
= 125°C, θ = 90°C/W
NC 10
JMAX
JA
SW PACKAGE
20-LEAD PLASTIC SOL
T
JMAX
= 125°C, θ = 50°C/W
JA
ORDER INFORMATION
LEAD FREE FINISH
LT1176CN8#PBF
LT1176CN8-5#PBF
LT1176CSW#PBF
LT1176CSW-5#PBF
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
8-Lead Plastic DIP
TEMPERATURE RANGE
0°C to 125°C
LT1176CN8
LT1176CN8-5
LT1176CSW
LT1176CSW-5
8-Lead Plastic DIP
0°C to 125°C
LT1176CSW#TRPBF
LT1176CSW-5#TRPBF
20-Lead Plastic SOL
20-Lead Plastic SOL
0°C to 125°C
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/
11765fb
2
LT1176/LT1176-5
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. TJ = 25°C, VIN 25V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
Switch ON Voltage (Note 2)
I
SW
I
SW
= 0.2A
= 1A
1.1
1.4
V
V
Switch OFF Leakage
V
IN
V
IN
= 25V, V = 0
150
250
µA
µA
SW
= V
, V = 0 (Note 8)
MAX SW
l
l
Supply Current (Note 3)
Minimum Supply Voltage
Switch Current Limit (Note 5)
V
V
= 2.5V, V ≤ 35V
SHDN
7.5
10
mA
µA
FB
IN
= 0.1V (Device Shutdown) (Note 9)
140.0
300
l
l
Normal Mode
Startup Mode (Note 4)
7.3
3.5
8.0
4.8
V
V
l
I
Open
1.2
85
1.7
1.2
0.8
2.2
A
A
A
LIM
R
R
= 10k (Note 6)
= 7k (Note 6)
LIM
LIM
l
l
Maximum Duty Cycle
Switching Frequency
90
%
90
85
100
110
120
kHz
kHz
kHz
kHz
V
V
= 0V Through 2k (Note 5) (LT1176)
20
20
FB
SENSE
= 0V (Note 5) (LT1176-5)
l
Switching Frequency Line Regulation
Error Amplifier Voltage Gain (Note 10)
Error Amplifier Transconductance (Note 10)
Error Amplifier Source and Sink Current
8V ≤ V ≤ V
(Note 8)
MAX
0.03
2000
5000
0.1
%/V
V/V
IN
1V ≤ V ≤ 4V
C
3700
8000
µmho
Source (V = 2V or V
= 4V)
= 5.5V)
100.0
0.7
140
1.0
225.0
1.6
µA
mA
FB
SENSE
SENSE
Sink (V = 2.5V or V
FB
l
l
Feedback Pin Bias Current (LT1176)
Reference Voltage (LT1176)
V
= V
0.5
2
µA
V
FB
REF
V = 2V
C
2.155
4.85
3
2.21
2.265
Reference Voltage Tolerance (LT1176)
V
REF
(Nominal) = 2.21V
0.5
1.0
2
3
%
%
l
l
l
All Conditions of Input Voltage, Output Voltage,
Temperature and Load Current
Sense Voltage (LT1176-5)
V = 2V
C
5
5.15
V
Sense Voltage Tolerance (LT1176-5)
V
OUT
(Nominal) = 5V
0.5
0.1
2
3
%
%
All Conditions of Input Voltage,
Temperature and Load Current
Sense Pin Divider Resistance (LT1176-5)
Output Voltage Line Regulation
5
8
kΩ
l
l
8V ≤ V ≤ V
(Note 8)
MAX
0.005
0.02
%/V
IN
V Voltage at 0% Duty Cycle
C
1.5
–4.0
V
Overtemperature
mV/°C
Multiplier Reference Voltage
Shutdown Pin Current
24
10
V
l
l
V
SHDN
V
SHDN
= 5V
5
20
50
µA
µA
≤ V
(@ 2.5V)
THRESHOLD
l
l
Shutdown Thresholds
Switch Duty Cycle = 0
Fully Shutdown
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
%
V
l
Status High Level
I
= 10µA Sourcing
3.5
4.5
5.0
STATUS
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3
LT1176/LT1176-5
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. TJ = 25°C, VIN 25V, unless otherwise noted.
PARAMETER
CONDITIONS
= 1.6mA Sinking
MIN
TYP
0.25
9
MAX
UNITS
V
l
Status Low Level
Status Delay Time
Status Minimum Width
I
0.4
STATUS
µs
30
µs
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 5: Switch frequency is internally scaled down when the feedback pin
voltage is less than 1.3V to avoid extremely short switch-on times. During
testing, V or V
is adjusted to give a minimum switch-on time of
FB
SENSE
1µs.
Note 2: To calculate maximum switch ON voltage at current between low
Note 6: I = (R – 1k)/7.65k
LM LIM
and high conditions, a linear interpolation may be used.
Note 7: Switch to input voltage limitation must also be observed.
Note 8: V = 35V
Note 9: Does not include switch leakage.
Note 10: Error amplifier voltage gain and transconductance are
specified relative to the internal feedback node. To calculate gain and
Note 3: A feedback pin voltage (V ) of 2.5V forces the V pin to its low
FB
C
MAX
clamp level and the switch duty cycle to zero. This approximates the
zero load condition where duty cycle approaches zero. The LT1176-5 has
V
= 5.5V.
SENSE
Note 4: Total voltage from V pin to ground pin must be ≥ 8V after
IN
transconductance from the sense pin (Output) to the V pin on the
C
start-up for proper regulation.
LT1176-5, multiply by 0.44.
Application Hints
Although the LT1176 has a peak switch rating of 1.2A and a maximum duty
cycle of 85%, it must be used cautiously in applications which require high
switch current and high duty cycle simultaneously, to avoid excessive chip
temperature. Thermal resistance is 90°C/W for the 8-pin DIP package and
50°C/W for the 20-pin SO. This limits continuous chip power dissipation to
the 0.5W to 1W range. These numbers assume typical mounting techniques.
Extra or thick copper connected to the leads can reduce thermal resistance.
Bonding the package to the board or using a clip style heat sink can also help.
Thefollowingformulaswillgivechippowerdissipationandpeakswitchcurrent
for the standard buck converter. Note that surges less than 30 seconds do not
need to be considered from a thermal standpoint, but for proper regulation,
they must not result in peak switch currents exceeding the 1.2A limit.
Power = I
(V /V ) + V [7mA + 3mA (V /V ) + 0.012 (I
)]
LOAD OUT IN
IN
OUT IN
LOAD
5
I
= I + [V (V – V )]/2E (V )(L)
LOAD(PEAK) OUT IN OUT IN
PEAK
Example: V = 15V, V
= 5V, I
= 0.5A Continuous, 0.8A Peak,
LOAD
IN
OUT
L = 100µH
Power (I
= 0.5A) = 0.38W
= 0.8A) = 0.97A
LOAD
I
(I
PEAK LOAD
Where component size or height is critical, we suggest using solid tantalum
capacitors (singly or in parallel), but be sure to use units rated for switching
applications. Coiltronics is a good source for low profile surface mount
inductorsandAVXmakeshighqualitysurfacemounttantalumcapacitors.For
further help, use Application Notes 19 and 44,LTC’s SwitcherCAD® computer
design program, and our knowledgeable application department.
11765fb
4
LT1176/LT1176-5
BLOCK DIAGRAM
INPUT SUPPLY
0.3V
10µA
320µA
+
6V
µPOWER
6V TO ALL
CIRCUITRY
REGULATOR
AND BIAS
SHUTDOWN
500Ω
–
2.35V
CURRENT LIMIT
SHUTDOWN
CURRENT LIMIT
COMP
0.16Ω
+
–
+
–
C2
I
LIM
4.5V
10k
SHUTDOWN
FREQ SHIFT
R
R/S
LATCH
R
G1
100kHz
OSCILLATOR
S
Q
SYNC
OUTPUT
VOLTAGE
MONITOR
3V
P-P
V
IN
400Ω
+
–
Z
+
C1
ANALOG
X MULTIPLIER
XYZ
A1
STATUS
ERROR
AMP
PULSE WIDTH
COMPARATOR
SWITCH
OUTPUT
SW
2.21V
–
Y
(V
)
11765 BD
2.8k
2.2k*
V
24V (EQUIVALENT)
FB/SENSE
C
*CONNECTED ON 5V VERSION ONLY
11765fb
5
LT1176/LT1176-5
PACKAGE DESCRIPTION
N8 Package
8-Lead PDIP (Narrow .300 Inch)
(Reference LTC DWG # 05-08-1510)
.400ꢁ
(10.160)
MAX
8
ꢀ
6
5
4
.255 .015ꢁ
(6.4ꢀꢀ 0.381)
1
2
3
.130 .005
.300 – .325
.045 – .065
(3.302 0.12ꢀ)
(1.143 – 1.651)
(ꢀ.620 – 8.255)
.065
(1.651)
TYP
.008 – .015
(0.203 – 0.381)
.120
.020
(0.508)
MIN
(3.048)
MIN
+.035
.325
–.015
.018 .003
(0.45ꢀ 0.0ꢀ6)
.100
(2.54)
BSC
+0.889
8.255
(
)
N8 1002
–0.381
NOTE:
INCHES
1. DIMENSIONS ARE
MILLIMETERS
ꢁTHESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .010 INCH (0.254mm)
11765fb
6
LT1176/LT1176-5
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
01/11 Corrected Typical Application
Updated part markings in Order Information
Revised Electrical Characteristics
Updated Package Description
1
2
3
8
3
B
2/11
Revised Shutdown Pin Current in Electrical Characteristics
11765fb
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 representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
7
LT1176/LT1176-5
PACKAGE DESCRIPTION
SW Package
20-Lead Plastic Small Outline (Wide .300 Inch)
(Reference LTC DWG # 05-08-1620)
.050 BSC .045 .005
.030 .005
TYP
.496 – .512
(12.598 – 13.005)
NOTE 4
N
19 18
16
14 13 12 11
20
N
17
15
.325 .005
.420
MIN
.394 – .419
(10.007 – 10.643)
NOTE 3
1
2
3
N/2
N/2
RECOMMENDED SOLDER PAD LAYOUT
.291 – .299
(7.391 – 7.595)
NOTE 4
2
3
5
7
8
9
10
1
4
6
.037 – .045
.093 – .104
.010 – .029
(0.940 – 1.143)
¥ 45∞
(2.362 – 2.642)
(0.254 – 0.737)
.005
(0.127)
RAD MIN
0 – 8 TYP
.050
(1.270)
BSC
.004 – .012
.009 – .013
(0.102 – 0.305)
NOTE 3
(0.229 – 0.330)
.014 – .019
.016 – .050
(0.406 – 1.270)
INCHES
(MILLIMETERS)
S20 (WIDE) 0502
(0.356 – 0.482)
TYP
NOTE:
1. DIMENSIONS IN
2. DRAWING NOT TO SCALE
3. PIN 1 IDENT, NOTCH ON TOP AND CAVITIES ON THE BOTTOM OF PACKAGES ARE THE MANUFACTURING OPTIONS.
THE PART MAY BE SUPPLIED WITH OR WITHOUT ANY OF THE OPTIONS
4. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.
MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
11765fb
LT 0211 REV B • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
8
●
●
LINEAR TECHNOLOGY CORPORATION 1993
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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