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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 TO-263(D2) TO-220V TO-220
LM2576
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
1. 2. 3. 4. 5. Vin Output Ground Feedback On/Off
DESCRIPTION
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.
ORDERING INFORMATION
Device LM2576T-X.X LM2576TV-X.X LM2576R Marking LM2576T-X.X LM2576T-X.X LM2576R-X.X Package TO-220 TO-220V TO-263
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. 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 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.
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3.0A, 15V, Step-Down Switching Regulator
Typical Application (Fixed Output Voltage Versions)
LM2576
Figure 1. Block Diagram and Typical Application
ABSOLUTE MAXIMUM RATINGS (Absolute Maximum Ratings indicate limits beyond which damage to the device may occur )
Power Dissipation
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
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3.0A, 15V, Step-Down Switching Regulator
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 = 25C, 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 = -40C Thigh = +125C
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3.0A, 15V, Step-Down Switching Regulator
ELECTRICAL CHARACTERISTICS / Device Parameters
LM2576
(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 = 25C, for min/max 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.
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3.0A, 15V, Step-Down Switching Regulator
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)
LM2576
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3.0A, 15V, Step-Down Switching Regulator
LM2576
TYPICAL PERFORMANCE CHARACTERISTICS (Circuit of Figure 15)
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3.0A, 15V, Step-Down Switching Regulator
LM2576
[ TYPICAL PERFORMANCE CHARACTERISTICS ]
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3.0A, 15V, Step-Down Switching Regulator
LM2576
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3.0A, 15V, Step-Down Switching Regulator
LM2576
PIN FUNCTION DESCRIPTION Symbol 1
Vin
Description This pin is the positive input supply for the LM2576 step-down switching
2
3 4
5
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). Output 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. Gnd Feedback 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. ON/OFF 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
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