|
|
PDF LM2574 Data sheet ( Hoja de datos )
| Número de pieza | LM2574 | |
| Descripción | STEP-DOWN VOLTAGE REGULATOR | |
| Fabricantes | Motorola Semiconductors | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LM2574 (archivo pdf) en la parte inferior de esta página. Total 24 Páginas | ||
|
No Preview Available !
Order this document by LM2574/D
Advance Information
Easy Switcher™ 0.5 A
Step-Down Voltage Regulator
The LM2574 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 0.5 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 optimized for use with the LM2574 are offered by several different
inductor manufacturers.
Since the LM2574 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 most cases, the power
dissipated by the LM2574 regulator is so low, that the copper traces on the
printed circuit board are normally the only heatsink needed and no additional
heatsinking is required.
The LM2574 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 60 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, 1.23 to 37 V ±4% max over
Line and Load Conditions
• Guaranteed 0.5 A Output Current
• Wide Input Voltage Range: 4.75 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
LM2574
EASY SWITCHER™
0.5 A STEP–DOWN
VOLTAGE REGULATOR
SEMICONDUCTOR
TECHNICAL DATA
8
1
N SUFFIX
PLASTIC PACKAGE
CASE 626
PIN CONNECTIONS
FB 1
Sig Gnd 2
ON/OFF 3
Pwr Gnd 4
8*
7 Output
6*
5 Vin
(Top View)
* No internal connection, but should be soldered to
* PC board for best heat transfer.
DEVICE TYPE/NOMINAL OUTPUT VOLTAGE
LM2574–3.3
LM2574–5
LM2574–12
LM2574–15
LM2574–ADJ
3.3 V
5.0 V
12 V
15 V
1.23 V to 37 V
ORDERING INFORMATION
Device
Operating
Temperature Range Package
LM2574N–XX TA = –40° to +125°C DIP–8
XX = Voltage Option, i.e, 3.3, 5, 12, 15 V; and ADJ for
Adjustable Output.
This document contains information on a new product. Specifications and information herein
are subject to change without notice.
© Motorola, Inc. 1997
Rev 0
1 page  
LM2574
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 16)
Figure 2. Normalized Output Voltage
1.0
0.8 Vin = 20 V
0.6
ILoad = 100 mA
Normalized at TJ = 25°C
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
–50 –25
0
25 60
75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 3. Line Regulation
1.4
1.2 ILoad = 100 mA
1.0 TJ = 25°C
0.8
0.6 3.3 V, 5.0 V and ADJ
0.4
0.2
0 12 V and 15 V
–0.2
–0.4
–0.6
0 5.0 10 15 20 25 30 35
Vin, INPUT VOLTAGE (V)
40
Figure 4. Dropout Voltage
2.0
L = 300 µH
1.5 ILoad = 500 mA
1.0
ILoad = 100 mA
0.5
0
–50 –25
0
25 60
75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 5. Current Limit
1.4
1.3 Vin = 25 V
1.2
1.1
1.0
0.9
0.8
0.7
–50 –25 0 25 60 75 100
TJ, JUNCTION TEMPERATURE (°C)
125
Figure 6. Quiescent Current
20
18 Vout = 5.0 V
Measured at
16 Ground Pin
TJ = 25°C
14
12 ILoad = 500 A
10
8.0 ILoad = 100 mA
6.0
4.0
0 5.0 10 15 20 25 30 35 40
Vin, INPUT VOLTAGE (V)
200
180
160
140
120
100
80
60
40
20
0
–50
Figure 7. Standby Quiescent Current
VON/OFF = 5.0 V
Vin = 40 V
Vin = 12 V
–25 0 25 60 75 100
TJ, JUNCTION TEMPERATURE (°C)
125
MOTOROLA ANALOG IC DEVICE DATA
5
5 Page 
LM2574
Procedure (Fixed Output Voltage Version) (continued) In order to simplify the switching regulator design, a step–by–step
design procedure and example is provided.
Procedure
Example
5. Output Capacitor Selection (Cout)
A. Since the LM2574 is a forward–mode switching regulator
with voltage mode control, its open loop 2–pole–1–zero
frequency characteristic has the dominant pole–pair
determined by the output capacitor and inductor values. For
stable operation and an acceptable ripple voltage,
(approximately 1% of the output voltage) a value between
100 µF and 470 µF is recommended.
B. 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 at least 8.0 V is appropriate, and a 10 V
or 16 V rating is recommended.
5. Output Capacitor Selection (Cout)
A. Cout = 100 µF to 470 µF standard aluminium electrolytic.
B. Capacitor voltage rating = 20 V.
Procedure (Adjustable Output Version: LM2574–ADJ)
Procedure
Given Parameters:
Vout = Regulated Output Voltage
Vin(max) = Maximum DC Input Voltage
ILoad(max) = Maximum Load Current
1. Programming Output Voltage
To select the right programming resistor R1 and R2 value (see
+ ǒ ) ǓFigure 2) use the following formula:
Vout
Vref 1.0
R2
R1
where Vref = 1.23 V
Resistor R1 can be between 1.0 kΩ and 5.0 kΩ. (For best
+ ǒ * Ǔtemperature coefficient and stability with time, use 1% metal
film resistors).
R2
R1
Vout
Vref
1.0
Example
Given Parameters:
Vout = 24 V
Vin(max) = 40 V
ILoad(max) = 0.4 A
1. Programming Output Voltage (selecting R1 and R2)
Select R1 and R2 :
ǒ ) ǓVout = 1.23 1.0
R2
R1
Select R1 = 1.0 kΩ
+ ǒ * Ǔ + ǒ * ǓR2
R1
Vout
Vref
1.0
1.0
k
10 V
1.23 V
1.0
R2 = 18.51 kΩ, choose a 18.7 kΩ metal film resistor.
2. Input Capacitor Selection (Cin)
To prevent large voltage transients from appearing at the input
and for stable operation of the converter, an aluminium or
tantalum electrolytic bypass capacitor is needed between the
input pin +Vin and ground pin Gnd. This capacitor should be
located close to the IC using short leads. This capacitor should
have a low ESR (Equivalent Series Resistance) value.
For additional information see input capacitor section in the
“EXTERNAL COMPONENTS” section of this data sheet.
3. Catch Diode Selection (D1)
A. Since the diode maximum peak current exceeds the
regulator maximum load current the catch diode current
rating must be at least 1.2 times greater than the maximum
load current. For a robust design, the diode should have a
current rating equal to the maximum current limit of the
LM2574 to be able to withstand a continuous output short.
B. The reverse voltage rating of the diode should be at least
1.25 times the maximum input voltage.
2. Input Capacitor Selection (Cin)
A 22 µF aluminium electrolytic capacitor located near the input
and ground pin provides sufficient bypassing.
3. Catch Diode Selection (D1)
A. For this example, a 1.0 A current rating is adequate.
B. Use a 50 V MBR150 Schottky diode or any suggested fast
recovery diodes in Table 1.
MOTOROLA ANALOG IC DEVICE DATA
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LM2574.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LM2574 | SIMPLE SWITCHER 0.5A Step-Down Voltage Regulator |  National Semiconductor |
| LM2574 | Step-Down Switching Regulator |  ON Semiconductor |
| LM2574 | 52kHz Simple 0.5A Buck Regulator |  Micrel Semiconductor |
| LM2574 | LM2574/LM2574HV SIMPLE SWITCHER 0.5A Step-Down Voltage Regulator (Rev. C) |  Texas Instruments |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |