LM2596S ADJ PDF

It is capable of driving a 3. This device is available in adjustable output version and it is internally compensated to minimize the number of external components to simplify the power supply design. Since LM converter is a switch? The LM operates at a switching frequency of kHz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Available in a standard 5? External shutdown is included, featuring 80 mA typical standby current.

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These devices are available in fixed output voltages of 3. Requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation, and a fixed-frequency oscillator. The LM series operates at a switching frequency of kHz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators.

Available in a standard 5-lead TO package with several different lead bend options, and a 5-lead TO surface mount package. A standard series of inductors are available from several different manufacturers optimized for use with the LM series. This feature greatly simplifies the design of switch-mode power supplies. External shutdown is included, featuring typically 80 A standby current. Self protection features include a two stage frequency reducing current limit for the output switch and an over temperature shutdown for complete protection under fault conditions.

Features n 3. Infrared 10 sec. T Package Soldering, 10 sec. 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. Note 2: The human body model is a pF capacitor discharged through a 1.

Note 3: Typical numbers are at 25C and represent the most likely norm. Note 4: All limits guaranteed at room temperature standard type face and at temperature extremes bold type face.

All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control SQC methods. Note 5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator system performance. When the LM is used as shown in the Figure 1 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics.

Note 6: The switching frequency is reduced when the second stage current limit is activated. Note 7: No diode, inductor or capacitor connected to output pin. Note 8: Feedback pin removed from output and connected to 0V to force the output transistor switch ON. Note 9: Feedback pin removed from output and connected to 12V for the 3.

Note Junction to ambient thermal resistance no external heat sink for the TO package mounted vertically, with the leads soldered to a printed circuit board with 1 oz.

Note Junction to ambient thermal resistance with the TO package tab soldered to a single printed circuit board with 0. Note Junction to ambient thermal resistance with the TO package tab soldered to a single sided printed circuit board with 2. Note Junction to ambient thermal resistance with the TO package tab soldered to a double sided printed circuit board with 3 in2 of 1 oz.

See Application Information in this data sheet and the thermal model in Switchers Made Simple version 4. B: Inductor Current 0. Rapidly switching currents associated with wiring inductance can generate voltage transients which can cause problems. For minimal inductance and ground loops, the wires indicated by heavy lines should be wide printed circuit traces and should be kept as short as possible. For best results, external components should be located as close to the switcher lC as possible using ground plane construction or single point grounding.

If open core inductors are used, special care must be taken as to the location and positioning of this type of inductor. Allowing the inductor flux to intersect sensitive feedback, lC groundpath and COUT wiring can cause problems.

When using the adjustable version, special care must be taken as to the location of the feedback resistors and the associated wiring. Physically locate both resistors near the IC, and route the wiring away from the inductor, especially an open core type of inductor. See application section for more information. Inductor Selection L1 A. Select the correct inductor value selection guide from Figures Figure 4, Figure 5, or Figure 6. Output voltages of 3. For all other voltages, see the design procedure for the adjustable version.

From the inductor value selection guide, identify the inductance region intersected by the Maximum Input Voltage line and the Maximum Load Current line. Each region is identified by an inductance value and an inductor code LXX. This capacitor should be located close to the IC using short capacitor leads and short copper traces. Do not use capacitors larger than F. For additional information, see section on output capacitors in application information section. To simplify the capacitor selection procedure, refer to the quick design component selection table shown in Figure 2.

This table contains different input voltages, output voltages, and load currents, and lists various inductors and output capacitors that will provide the best design solutions. The capacitor voltage rating for electrolytic capacitors should be at least 1. For computer aided design software, see Switchers Made Simple version 4.

Use the inductor selection guide for the 5V version shown in Figure 5. From the inductor value selection guide shown in Figure 5, the inductance region intersected by the 12V horizontal line and the 3A vertical line is 33 H, and the inductor code is L The inductance value required is 33 H. From the table in Figure 8, go to the L40 line and choose an inductor part number from any of the four manufacturers shown. In most instance, both through hole and surface mount inductors are available.

See section on output capacitors in application information section. From the quick design component selection table shown in Figure 2, locate the 5V output voltage section.

In the load current column, choose the load current line that is closest to the current needed in your application, for this example, use the 3A line. In the maximum input voltage column, select the line that covers the input voltage needed in your application, in this example, use the 15V line.

Continuing on this line are recommended inductors and capacitors that will provide the best overall performance. The capacitor list contains both through hole electrolytic and surface mount tantalum capacitors from four different capacitor manufacturers. In this example aluminum electrolytic capacitors from several different manufacturers are available with the range of ESR numbers needed.

For a 5V output, a capacitor voltage rating at least 7. This amount of ESR would result in relatively high output ripple voltage. A 16V or 25V capacitor will reduce the ripple voltage by approximately half. Catch Diode Selection D1 A. The catch diode current rating must be at least 1.

Also, if the power supply design must withstand a continuous output short, the diode should have a current rating equal to the maximum current limit of the LM The most stressful condition for this diode is an overload or shorted output condition. The reverse voltage rating of the diode should be at least 1. This diode must be fast short reverse recovery time and must be located close to the LM using short leads and short printed circuit traces.

Because of their fast switching speed and low forward voltage drop, Schottky diodes provide the best performance and efficiency, and should be the first choice, especially in low output voltage applications.

Ultra-fast recovery, or High-Efficiency rectifiers also provide good results. Ultra-fast recovery diodes typically have reverse recovery times of 50 ns or less. Rectifiers such as the 1N series are much too slow and should not be used. Input Capacitor CIN A low ESR aluminum or tantalum bypass capacitor is needed between the input pin and ground pin to prevent large voltage transients from appearing at the input. This capacitor should be located close to the IC using short leads.

In addition, the RMS current rating of the input capacitor should be selected to be at least 12 the DC load current. The capacitor manufacturers data sheet must be checked to assure that this current rating is not exceeded. The curve shown in Figure 13 shows typical RMS current ratings for several different aluminum electrolytic capacitor values.

For an aluminum electrolytic, the capacitor voltage rating should be approximately 1. Caution must be exercised if solid tantalum capacitors are used see Application Information on input capacitor. The tantalum capacitor voltage rating should be 2 times the maximum input voltage and it is recommended that they be surge current tested by the manufacturer. Use caution when using ceramic capacitors for input bypassing, because it may cause severe ringing at the VIN pin.

For additional information, see section on input capacitors in Application Information section. Refer to the table shown in Figure In this example, a 5A, 20V, 1N Schottky diode will provide the best performance, and will not be overstressed even for a shorted output. With a nominal input voltage of 12V, an aluminum electrolytic capacitor with a voltage rating greater than 18V 1. The next higher capacitor voltage rating is 25V.

The RMS current rating requirement for the input capacitor in a buck regulator is approximately 12 the DC load current.

In this example, with a 3A load, a capacitor with a RMS current rating of at least 1. The curves shown in Figure 13 can be used to select an appropriate input capacitor. From the curves, locate the 35V line and note which capacitor values have RMS current ratings greater than 1. For surface mount designs, solid tantalum capacitors can be used, but caution must be exercised with regard to the capacitor surge current rating see Application Information on input capacitors in this data sheet.

Programming Output Voltage Selecting R1 and R2, as shown in Figure 1 Use the following formula to select the appropriate resistor values. Solve for R2. Select a value for R1 between and 1. The lower resistor values minimize noise pickup in the sensitive feedback pin. Calculate the inductor Volt microsecond constant E T V s , from the following formula: 2.

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You have chosen to save the following item to a parts list:. Sign up using Email and Password. Verbal Kint 2, 1 3 The product detailed below complies with the specifications published by RS Components. The product does not contain any of the restricted substances in concentrations and applications banned by the Directive, and for components, the product is capable of being worked on at the higher temperatures required by lead—free soldering. The Manufacturers and RS disclaim kms warranties including implied warranties of merchantability or fitness for a particular purpose and are not liable for any damages arising from your use of or your inability to use the Information downloaded from this website.

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