LinearVoltageRegulators Motorola Semiconductor Products, LinearVoltageRegulators Datasheet - Page 19

• Manufacturer Part Number: LinearVoltageRegulators
• Description: Analog And Interface Integratedcircuits Selector Guide & Cross Reference
• Manufacturer: Motorola Semiconductor Products

Switching Regulator Control Circuits
Easy Switcher
Step–Down Voltage Regulators
LM2574N–XX
T J = –40 to +125 C, Case 626
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.
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 manufactur-
ers.
ply, its efficiency is significantly higher in comparison with
popular three–terminal linear regulators, especially with high-
er 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.
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, featur-
ing 60 A (typical) standby current. The output switch in-
cludes cycle–by–cycle current limiting, as well as thermal
shutdown for full protection under fault conditions.
Unregulated
MOTOROLA
48
The LM2574 series of regulators are monolithic integrated
These regulators were designed to minimize the number
Since the LM2574 converter is a switch–mode power sup-
The LM2574 features include a guaranteed 4% tolerance
DC Input
C in
Feedback
Sig Gnd
+V in
5
1
2
Single–Ended Controllers with On–Chip Power Switch
R2
R1
1.0 k
Band–Gap
Reference
Representative Block Diagram and Typical Application
1.235 V
Fixed Gain
Error Amplifier
18 kHz
Freq
Shift
Oscillator
52 kHz
Comparator
3.1 V Internal
Regulator
(continued)
Reset
Latch
Current
Features
Applications
Adjustable Output
Limit
ON/OFF
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
3.3 V, 5.0 V, 12 V, 15 V, and Adjustable Output Versions
Adjustable Version Output Voltage Range, 1.23 to 37 V
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
Simple and High–Efficiency Step–Down (Buck)
Regulators
XX = Voltage Option, i.e., 3.3, 5, 12, 15 V; and ADJ for
ANALOG AND INTERFACE INTEGRATED CIRCUITS
4% max over Line and Load Conditions
Shutdown
Driver
Thermal
SELECTOR GUIDE & CROSS REFERENCE
1.0 Amp
Switch
ON/OFF
Output
Pwr Gnd
3
7
4
Voltage Versions
For adjustable version
R1 = open, R2 = 0
D1
Output
3.3 V
5.0 V
12 V
15 V
L1
C out
8.84 k
11.3 k
1.7 k
3.1 k
( )
R2
V out
Load