HTC LM2596 Service Manual

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3.0A, 150Khz, 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%. Maximum Over Line and Load Conditions

Guaranteed 3.0A Output Current

Wide Input Voltage Range

Requires Only 4 External Components

150Khz 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

LM2596

TO-220

TO-220V

TO-263(D2)

1. Vin

2. Output

3. Ground

4. Feedback

5. On/Off

DESCRIPTION

The LM2596 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 LM2596 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.

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 LM2596 are

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

switch-mode power supplies. The LM2596 features include a guaranteed +/- 4% tolerance

on output voltage within specified input voltages and output load conditions, and +/-15% 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.

ORDERING INFORMATION

Device Marking Package LM2596T-X.X LM2596T-X.X TO-220 LM2596TV-X.X LM2596T-X.X LM2596R LM2596R-X.X TO-263

TO-220V

HTC

Oct 2004 - Rev 0

3.0A, 15V, Step-Down Switching Regulator

Typical Application (Fixed Output Voltage Versions)

LM2596

680 uF

LM2596-5.0

33 uH

1N5824

220 uF

Figure 1. Block Diagram and Typical Application

ABSOLUTE MAXIMUM RATINGS

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

TO-220, 5-Lead

Thermal Resistance, Junction-to-Ambient Thermal Resistance, Junction-to-case

TO-263

Thermal Resistance, Junction-to-Ambient Thermal Resistance, Junction-to-case

HTC

Oct 2004 - Rev 0

3.0A, 15V, Step-Down Switching Regulator

LM2596

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 2)

(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.)

LM2596-3.3 ([ Note 1]. Test Circuit Figure 2 )

LM2596-5.0 ([ Note 1]. Test Circuit Figure 2 )

LM2596-5.0 ([ Note 1]. Test Circuit Figure 1 )

LM2596-12 ([ Note 1]. Test Circuit Figure 2 )

LM2596-15 ([ Note 1]. Test Circuit Figure 2 )

LM2596-ADJ ([ Note 1]. Test Circuit Figure 2 )

HTC

Oct 2004 - Rev 0

3.0A, 15V, Step-Down Switching Regulator

LM2596

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.)

127

110

3.4

150 173

1.16

100

4.53.6

100

173

1.4

1.5

6.9

7.5

50 30

250

2.0

2 V LOGIC = 2.5V (Regulator OFF) V LOGIC = 0.5V (Regulator ON)

1. External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the LM2596 is used as shown in the Figure 1 test circuit, system performance will be as shown in system parameters section .

2. Tested junction temperature range for the LM2596 : T

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.

LOW = –0°C THIGH = +125°C

2.0

1.3

5 15

0.02 5.0

0.6

HTC

Oct 2004 - Rev 0

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