LM2576T-3.3 - HTC Korea - Datasheet.Support

3.0A, 15V, Step-Down Switching Regulator

FEATURES

3.3V, 5.0V, 12V, 15V, and Adjustable Output Versions

Adjustable Version Output Voltage Range, 1.23 to 37V

+/- 4% AG10Maximum Over Line and Load Conditions

Guaranteed 3.0A Output Current

Wide Input Voltage Range

Requires Only 4 External Components

52kHz Fixed Frequency Internal Oscillator

TTL Shutdown Capability, Low Power Standby Mode

High Efficiency

Uses Readily Available Standard Inductors

Thermal Shutdown and Current Limit Protection

Moisture Sensitivity Level(MSL) Equals1

Applications

Simple High-Efficiency Step-Down(Buck) Regulator

Efficient Pre-Regulator for Linear Regulators

On-Card Switching Regulators

Positive to Negative Converter(Buck-Boost)

Negative Step-Up Converters

Power Supply for Battery Chargers

DESCRIPTION ORDERING INFORMATION

The LM2576 series of regulators are monolithic integrated

circuits ideally suited for easy and convenient design of a

step-down switching regualtor(buck converter).

All circuits of this series are capable of driving a 3.0A load

with excellent line and load regulation. These devices are

available in fixed output voltages of 3.3V, 5.0V,12V, 15V,

and an adjustable output version.

These regulatiors were designed to minimize the number of externalcomponents to simplify the

power supply design. Standard series of inductors optimized for use with the LM2576 are offered

by several different inductor manufacturers.

Since the LM2576 converter is a switch-mode power supply, its efficiency is significantly higher in

comparison with popular three-terminal limear reguators, especially with higher input voltages.

available from several different manufacturers. This feature greatly simplifies the design of

switch-mode power supplies. The LM2576 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 0oC to 125 oC).

External shutdown is included, featuring 80 Ua(typical) standby current. The output switch includes

cycle-bycycle current limiting, as well as thermal shutdown for full protection under fault conditions.

TO-220

LM2576R LM2576R-X.X TO-263

LM2576

In many cases, the power dissipated is so low that no heatsink is required or its size could

be reduced dramatically. A standard series of inductors optimized for use with the LM2576 are

LM2576TV-X.X LM2576T-X.X

Device Marking Package

LM2576T-X.X LM2576T-X.X

TO-220V

HTC

TO-220V

TO-220

1. Vin

2. Output

3. Ground

4. Feedback

5. On/Off

TO-263(D2)

3.0A, 15V, Step-Down Switching Regulator

HTC

LM2576

Typical Application (Fixed Output Voltage Versions)

ure 1. Block Dia

ram and T

ical A

lication

ABSOLUTE MAXIMUM RATINGS

(Absolute Maximum Ratings indicate limits beyond which damage to the device may

occur )

TO-220, 5-Lead

TO-263

Thermal Resistance, Junction-to-Ambient

Thermal Resistance, Junction-to-case

Thermal Resistance, Junction-to-Ambient

Thermal Resistance, Junction-to-case

Power Dissipation

3.0A, 15V, Step-Down Switching Regulator

HTC

LM2576

OPERATING RATINGS (Operating Ratings indicate conditions for which the device is intended to be

functional, but do not guarantee specific performance limits. For guaranteed specifications and test

conditions, see the Electrical Characteristics.)

ELECTRICAL CHARACTERISTICS / SYSTEM PARAMETERS ([Note 1] Test Circuit Figure 15)

(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version, Vin = 25 V for

the 12 V version, and Vin = 30 V for the 15 V version. ILoad = 500 mA. For typical values TJ = 25°C,

for min/max values TJ is the operating junction temperature range that applies [Note 2], unless

otherwise noted.)

1. External components such as the catch diode, inductor, input and output capacitors can affect

switching regulator system performance.

When the LM2576 is used as shown in the Figure 15 test circuit, system performance will be as

shown in system parameters section .

2. Tested junction temperature range for the LM2576: Tlow = –40°C Thigh = +125°C

3.0A, 15V, Step-Down Switching Regulator LM2576

HTC

ELECTRICAL CHARACTERISTICS / Device Parameters

(Unless otherwise specified, Vin = 12 V for the 3.3 V, 5.0 V, and Adjustable version, Vin = 25 V for the 12

V version, and Vin = 30 V for the 15 V version. ILoad = 500 mA. For typical values TJ = 25°C, for min/ma

values TJ is the operating junction temperature range that applies [Note 2], unless otherwise noted.)

3. The oscillator frequency reduces to approximately 18 kHz in the event of an output short or an overload

which causes the regulated output voltage to drop approximately 40% from the nominal output voltage. This

self protection feature lowers the average dissipation of the IC by lowering the minimum duty cycle from 5%

down to approximately 2%.

4. Output (Pin 2) sourcing current. No diode, inductor or capacitor connected to output pin.

5. Feedback (Pin 4) removed from output and connected to 0 V.

6. Feedback (Pin 4) removed from output and connected to +12 V for the Adjustable, 3.3 V, and

5.0V ersions, and +25 V for the 12 V and15 V versions, to force the output transistor “off”.

7. Vin = 40 V.

3.0A, 15V, Step-Down Switching Regulator

HTC

LM2576

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)

3.0A, 15V, Step-Down Switching Regulator

LM2576

HTC

TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)

3.0A, 15V, Step-Down Switching Regulator LM2576

HTC

[ TYPICAL PERFORMANCE CHARACTERISTICS ]

3.0A, 15V, Step-Down Switching Regulator LM2576

HTC

3.0A, 15V, Step-Down Switching Regulator

This pin is the positive input supply for the LM2576 step–down switching

regulator.In order to minimize voltage transients and to supply the switching

currents needed by the regulator, a suitable input bypass capacitor must be

present .(Cin in Figure 1).

This is the emitter of the internal switch. The saturation voltage Vsat of this

output switch is typically 1.5 V. It should be kept in mind that the PCB area

connected to this pin should be kept to a minimum in order to minimize

coupling to sensitive circuitry.

Circuit ground pin. See the information about the printed circuit board layout.

This pin senses regulated output voltage to complete the feedback loop.

The signal is divided by the internal resistor divider network R2, R1 and

applied to the non–inverting input of the internal error amplifier. In the

Adjustable version of the LM2576 switching regulator this pin is the direct

input of the error amplifier and the resistor network R2, R1 is connected

externally to allow programming of the output voltage.

It allows the switching regulator circuit to be shut down using logic level

signals, thus dropping the total input supply current to approximately 80 mA.

The threshold voltage is typically 1.4 V. Applying a voltage above this value

(up to +Vin) shuts the regulator off. If the voltage applied to this pin is lower

than 1.4V or if this pin is left open, the regulator will be in the "on" condition

LM2576

HTC

Symbol

1Vin

Output2

Gnd3

Description

Feedback4

5 ON/OFF

PIN FUNCTION DESCRIPTION