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PDF LM2575 Data sheet ( Hoja de datos )
| Número de pieza | LM2575 | |
| Descripción | EASY SWITCHERE 1.0 A STEP-DOWN VOLTAGE REGULATOR | |
| Fabricantes | Motorola Semiconductors | |
| Logotipo |  |
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 1. - 1A, Step-Down Switching Regulator  Hay una vista previa y un enlace de descarga de LM2575 (archivo pdf) en la parte inferior de esta página. Total 26 Páginas | ||
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LM2575
Advance Information
Easy Switcher™ 1.0 A
Step-Down Voltage Regulator
EASY SWITCHER™
1.0 A STEP–DOWN
VOLTAGE REGULATOR
The LM2575 series of regulators are monolithic integrated circuits ideally
suited for easy and convenient design of a step–down switching regulator
(buck converter). All circuits of this series are capable of driving a 1.0 A load
with excellent line and load regulation. These devices are available in fixed
output voltages of 3.3 V, 5.0 V, 12 V, 15 V, and an adjustable output version.
These regulators were designed to minimize the number of external
components to simplify the power supply design. Standard series of
inductors optimised for use with the LM2575 are offered by several different
inductor manufacturers.
Since the LM2575 converter is a switch–mode power supply, its efficiency
is significantly higher in comparison with popular three–terminal linear
regulators, especially with higher input voltages. In many cases, the power
dissipated by the LM2575 regulator is so low, that no heatsink is required or
its size could be reduced dramatically.
The LM2575 features include a guaranteed ±4% tolerance on output
voltage within specified input voltages and output load conditions, and ±10%
on the oscillator frequency (±2% over 0°C to 125°C). External shutdown is
included, featuring 80 µA typical standby current. The output switch includes
cycle–by–cycle current limiting, as well as thermal shutdown for full
protection under fault conditions.
Features
• 3.3 V, 5.0 V, 12 V, 15 V, and Adjustable Output Versions
• Adjustable Version Output Voltage Range of 1.23 V to 37 V ±4%
Maximum Over Line and Load Conditions
• Guaranteed 1.0 A Output Current
• Wide Input Voltage Range: 4.75 V to 40 V
• Requires Only 4 External Components
• 52 kHz Fixed Frequency Internal Oscillator
• TTL Shutdown Capability, Low Power Standby Mode
• High Efficiency
• Uses Readily Available Standard Inductors
• Thermal Shutdown and Current Limit Protection
Applications
• Simple and High–Efficiency Step–Down (Buck) Regulators
• Efficient Pre–Regulator for Linear Regulators
• On–Card Switching Regulators
• Positive to Negative Converters (Buck–Boost)
• Negative Step–Up Converters
• Power Supply for Battery Chargers
SEMICONDUCTOR
TECHNICAL DATA
T SUFFIX
PLASTIC PACKAGE
CASE 314D
1
5
Pin 1. Vin
2. Output
3. Ground
4. Feedback
5. ON/OFF
TV SUFFIX
PLASTIC PACKAGE
CASE 314B
Heatsink surface
connected to Pin 3.
1
5
D2T SUFFIX
PLASTIC PACKAGE
CASE 936A
(D2PAK)
1
5
Heatsink surface (shown as terminal 6 in case outline
drawing) is connected to Pin 3.
DEVICE TYPE/NOMINAL OUTPUT VOLTAGE
LM2575–3.3
LM2575–5
LM2575–12
LM2575–15
LM2575–Adj
3.3 V
5.0 V
12 V
15 V
1.23 V to 37 V
ORDERING INFORMATION
Device
Operating
Temperature Range Package
LM2575T–**
Straight Lead
LM2575TV–** TJ = –40° to +125°C Vertical Mount
LM2575D2T–**
Surface Mount
This document contains information on a new product. Specifications and information herein
arMe OsuTbjOecRt tOo cLhAangAeNwAithLoOut GnotIiCce.DEVICE DATA
** = Voltage Option, ie. 3.3, 5.0, 12, 15 V and
** =\Adjustable Output.
© Motorola, Inc. 1997
Rev 1
1
1 page  
LM2575
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 14)
Figure 2. Normalized Output Voltage
0.6
Vin = 20 V
0.4
ILoad = 200 mA
Normalized at
TJ = 25°C
0.2
0
–0.2
–0.4
–0.6
–50
–25 0
25 50
75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 3. Line Regulation
1.0
ILoad = 200 mA
0.8 TJ = 25°C
0.6 3.3 V, 5.0 V and Adj
0.4
0.2
0 12 V and 15 V
–0.2
0
5.0 10 15 20 25 30 35
Vin, INPUT VOLTAGE (V)
40
Figure 4. Switch Saturation Voltage
1.2
1.1
1.0
0.9
–40°C
0.8
0.7 25°C
0.6
125°C
0.5
0.4
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
SWITCH CURRENT (A)
Figure 5. Current Limit
3.0
2.5
2.0
1.5
1.0
0.5
0
–50
Vin = 25 V
–25 0
25 50 75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 6. Dropout Voltage
2.0
1.8
ILoad = 1.0 A
1.6
∆Vout = 5%
Rind = 0.2 Ω
1.4
1.2
1.0 ILoad = 200 mA
0.8
0.6
0.4
–50
–25 0 25 50 75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 7. Quiescent Current
20
Vout = 5.0 V
18 Measured at
Ground Pin
16 TJ = 25°C
14
ILoad = 1.0 A
12
10
8.0 ILoad = 200 mA
6.0
4.0
0 5.0 10 15 20 25 30 35 40
Vin, INPUT VOLTAGE (V)
MOTOROLA ANALOG IC DEVICE DATA
5
5 Page 
LM2575
Procedure (Adjustable Output Version: LM2575–Adj) (continued)
Procedure
Example
4. Inductor Selection (L1)
A. Use the following formula to calculate the inductor Volt x
+ ǒ Ǔmicrosecond [V x µs] constant:
ExT
Vin – Vout
Vout
Von
x
106
F[Hz]
[V
x
ms]
B. Match the calculated E x T value with the corresponding
number on the vertical axis of the Inductor Value Selection
Guide shown in Figure 21. This E x T constant is a measure
of the energy handling capability of an inductor and is
dependent upon the type of core, the core area, the number
of turns, and the duty cycle.
C. Next step is to identify the inductance region intersected by
the E x T value and the maximum load current value on the
horizontal axis shown in Figure 21.
D. From the inductor code, identify the inductor value. Then
select an appropriate inductor from the Table 1 or Table 2.
The inductor chosen must be rated for a switching
frequency of 52 kHz and for a current rating of 1.15 x IIoad.
The inductor current rating can also be determined by
) ǒ Ǔcalculating the inductor peak current:
Ip(max) + ILoad(max)
Vin – Vout ton
2L
where ton is the “on” time of the power switch and
+ton
Vout x 1
Vin fosc
For additional information about the inductor, see the
inductor section in the “External Components” section of
this data sheet.
4. Inductor Selection (L1)
A. Calculate E x T [V x µs] constant:
+ +E x T
(12 – 8.0)
x
8.0
12
x
1000
52
51 [V x ms]
B. E x T = 51 [V x µs]
C. ILoad(max) = 1.0 A
Inductance Region = L220
D. Proper inductor value = 220 µH
Choose the inductor from the Table 1 or Table 2.
5. Output Capacitor Selection (Cout)
A. Since the LM2575 is a forward–mode switching regulator
with voltage mode control, its open loop 2–pole–2–zero
frequency characteristic has the dominant pole–pair
determined by the output capacitor and inductor values.
For stable operation, the capacitor must satisfy the
following requirement:
wCout
7.785
Vin(max)
Vout x L [µH]
[µF]
B. Capacitor values between 10 µF and 2000 µF will satisfy
the loop requirements for stable operation. To achieve an
acceptable output ripple voltage and transient response, the
output capacitor may need to be several times larger than
the above formula yields.
C. Due to the fact that the higher voltage electrolytic capacitors
generally have lower ESR (Equivalent Series Resistance)
numbers, the output capacitor’s voltage rating should be at
least 1.5 times greater than the output voltage. For a 5.0 V
regulator, a rating of at least 8V is appropriate, and a 10 V
or 16 V rating is recommended.
5. Output Capacitor Selection (Cout)
w +A.
Cout
7.785
12
8.220
53 µF
To achieve an acceptable ripple voltage, select
Cout = 100 µF electrolytic capacitor.
MOTOROLA ANALOG IC DEVICE DATA
11
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet LM2575.PDF ] | |
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