HELP and Supplemental Information File @LT@E @HTable of Contents@E (Use the Tab key and the arrow keys to highlight the desired table item, then press the Enter key to go to the highlighted table item.) 0.0 @GVersion 3.3 vs Version 4.3@E 1.0 @GHow to use this file@E 2.0 @GIntroduction@E 3.0 @GAbout the Main Menu@E 4.0 @GProgram Outline@E 4.1 @GSpecifying a new power supply (New)@E 4.2 @GCalculating the operating values@E 4.3 @GSelecting Components@E 4.4 @GEditing the input requirements (Edit Requirements)@E 4.5 @GEditing the component values (Edit Components)@E 4.6 @GCalculating stability information (Stability Analysis)@E 4.7 @GSelecting a package (Package Selection)@E 4.8 @GCalculating thermal information (Thermal Analysis)@E 4.9 @GViewing and printing the schematic (Schematic)@E 4.10 @GViewing, saving and printing the parts list (Parts List)@E 4.11 @GSaving the power supply (Save, Save as...)@E 4.12 @GOpening an existing power supply (Open)@E 5.0 @GNotes and Warnings@E 5.1 @G"Input Voltage is too Low"@E 5.2 @G"Output Current is too High"@E 5.3 @G"Output #1 Filter Required"@E 5.4 @G"Output #1 Ripple Voltage is too Low"@E 5.5 @G"Insufficient Phase Margin"@E 5.6 @G"Possible Current Limit Runaway"@E 5.7 @G"Maximum Duty Cycle is Exceeded"@E 6.0 @GGeneral Information@E 6.1 @GStandard Units@E 6.2 @GIntegrated Circuit Options@E 6.3 @GGuaranteed system performance@E 6.4 @GUnity gain crossover frequency and phase margin@E 6.5 @GOuput capacitor ESR@E 6.6 @GComponents not found in the database@E 7.0 @GMilitary Switching Regulator Design Considerations@E 7.1 @GOutput Capacitor Selection@E 7.2 @GInductor Selection@E 7.3 @GInput Capacitor Selection@E 7.4 @GCatch Diode Selection@E 7.5 @GTopology Selection@E @H0.0 Version 3.3 vs Version 4.3@E @L0.0@E @LVersion 3.3 vs Version 4.3@E Version 4.3 designs DC-DC converters using the newest SIMPLE SWITCHER (R) converter products. Based on the specifications you enter, the software automatically selects the appropriate type of converter. The types of converters that can be designed using Version 4.3 include: Converters based on LM2594, LM2595, LM2596, LM2597, LM2598 and LM2599: Step-down (buck): single output, output voltage is lower than the minimum input voltage, e.g. Vout = 3.3V, Vin = 12 to 18V. Using LM2594 and LM2597, the output current must be 0.5A or less. LM2595 and LM2598, the output current must be 1.0A or less. LM2596 and LM2599, the output current must be 3.0A or less. Converters based on LM2585, LM2586, LM2587 and LM2588: Flyback: single output, output voltage falls inside the input voltage range, e.g. Vout = 12V, Vin = 8 to 16V Flyback: two or three outputs, output voltages positive or negative with at least one positive output, e.g. Vout1 = 12V, Vout2 = -12V, Vin = 4 to 6V Boost (step-up): single output, output voltage greater than the maximum input voltage, e.g. Vout = 12V, Vin = 4.5 to 5.5V Version 3.3 supports our original family of SIMPLE SWITCHER converters which includes the LM2574, LM2575 and LM2576 step-down ICs and the LM2577 flyback IC. @H1.0 How to use this file@E @L1.0@E @LHow to use this file@E Use the arrow, page up, page down, home and end keys to move through this HELP text. Key topics like those listed as headings in the table of contents appear in yellow text. To jump to a key topic, move the cursor to highlight the topic and press the enter key. To return, press the backspace key. Press the tab key to move the cursor to the next key topic and shift + tab to move the cursor to the previous key topic. @H2.0 Introduction@E @L2.0@E @LIntroduction@E This program automates the design of DC-DC converters. It bases all designs on SIMPLE SWITCHER (R) switching regulator ICs. This version automates the design of buck, boost and flyback DC-DC converters based on the LM2585, LM2586, LM2587, LM2588, LM2594, LM2595, LM2596, LM2597, LM2598 and LM2599. Buck converters step the input voltage down, boost converters step the input voltage up, and flyback converters typically convert the input voltage into multiple voltages. @H3.0 About the Main Menu@E @L3.0@E @LAbout the Main Menu@E In this version of the program, the Main Menu is the only menu. Use the Main Menu to execute commands like Save and to view information about your DC-DC converter like the schematic and the parts list. To select a menu item, first use the arrow keys to move the pointer to the menu item, then press the Enter key. Unavailable menu items appear in gray. A description of the menu item at which the pointer currently points appears near the bottom of the screen. You can also use hot keys to select a menu item. For example, pressing the E hot key immediately executes the Edit Components command. Hot keys appear in in red. Hot keys remain active while the Main Menu is hidden. Menu Item Hot Key Open O New N Save S Save as A Edit Requirements R Edit Components E Stability Analysis B IC Selection I Thermal Analysis T Schematic M Parts List P View Main Screen V Help F1 Exit X @H4.0 Program Outline@E @L4.0@E @LProgram Outline@E @H4.1 Specifying a new power supply (New)@E @L4.1@E @LSpecifying a new power supply (New)@E Use this dialog box to specify your DC-DC converter. The pointer indicates the next specification to be entered. Type the specification, then press the Enter key. The pointer automatically moves down to the next specification field. You can change your entries at any time in the process. Use the arrow keys to move the pointer to the entry in question and simply type the new entry followed by Enter. After you have entered the specifications to your satisfaction, press O (the ok hot key) and Switchers Made Simple will design your DC-DC converter. A brief description of the specification at which the pointer currently points appears in the information bar near the bottom of the screen. Do not type units. By default, the program uses V (Volts), A (Amperes) and degreesC (degrees Celsius). You can use the suffixes m, u, p, k and M to designate milli, micro, pico, kilo and mega respectively. For example, to specify 50 millivolts for Vripple1, you can enter either .05 or 50m. To specify 50 megavolts, you can enter either 50M or 50000000. The program will bring to your attention any specifications that violate those of the SIMPLE SWITCHER family of ICs. The program will also warn you about mistakes like entering a negative value for Vin or specifying a Ta min greater than your Ta max. How to change topologies: If you have been doing designs in one topology (e.g. buck) and you want to do a design in another topology (e.g. boost), you must start a New Design. You can’t just change the requirements, because the software expects that the topology has remained the same, and interprets those new requirements as being incorrect. This is a protection feature built into the software, to help prevent the user from accidentally entering wrong input requirements. @H4.2 Calculating the operating values@E @L4.2@E @LCalculating the operating values@E Upon completing the design of your DC-DC converter, the program displays three columns of information. The column labeled Operating Values contains two types of information: Specifications of the SIMPLE SWITCHER IC selected for your converter, and the results of calculations made during the design process. The operating values describe the expected operation of a converter built with the components selected by Switchers Made Simple. You can effectively select other components using the Edit Components command. The resulting operating values are valid as long as you did not violate a component limit value. @H4.3 Selecting Components@E @L4.3@E @LSelecting Components@E The program selects standard components from an internal database and displays all component values in the Component Values column. The database available to this version of the program contains standard components as follows: inductors and transformers from Coilcraft, Pulse, Renco and Schott; diodes from General Instruments and Motorola; and input and output capacitors from Nichicon and Panasonic. The program does not select a heatsink, but the program does calculate and display (under Component Values) the maximum allowable thermal resistance of the heatsink required by your converter. @H4.4 Editing the input requirements (Edit Requirements)@E @L4.4@E @LEditing the input requirements (Edit Requirements)@E Even after the program designs your DC-DC converter, you can change any or all of the specifications. Simply select the Edit Requirements command and use the resulting dialog box to edit your previous specifications. Press the O hot key when you finish editing and the program will design a new DC-DC converter that meets your new specifications. Your previous converter will be lost unless you save it prior to editing the requirements. Pressing the C hot key cancels your changes and keeps the previous converter design. @H4.5 Editing the component values (Edit Components)@E @L4.5@E @LEditing the component values (Edit Components)@E You may wish to design in components other than those selected by the program. To effectively accomplish this, use the Edit Components command to edit any or all component values. Upon selecting the Edit Components command from the Main Menu (or pressing the E hot key) the Edit Parts Properties dialog box appears. Use the arrow keys to move the pointer. Type the new value and press enter. To be sure the resulting DC-DC converter works properly, do not violate the limit values listed to the right of the component values. Press O and Switchers Made Simple recalculates all pertinent operating values taking into account current component values. The program may automatically change some component values because they depend on the values you edited. Do not type units. By default, the program uses V (Volts), Ohms, H (Henries), F (Farads) and degreesC/W (thermal resistance). You can use the same suffixes available in the Input Requirements dialog box. The program flags excessively large values of inductance and capacitance, as well as component values below the limit values of the design. @H4.6 Calculating stability information (Stability Analysis)@E @L4.6@E @LCalculating stability information (Stability Analysis)@E The program selects components that ensure stable operation. To view the unity gain crossover frequency and the phase margin, press the B hot key or look for them near the bottom of the Operating Values column. Editing component values can affect the stability of your converter. To ensure stable operation, be sure the component values you enter meet the limit values listed in the Edit Parts Properties dialog box. The program will warn you about insufficient phase margin. @H4.7 Selecting a package (Package Selection)@E @L4.7@E @LSelecting a package (Package Selection)@E The program selects a SIMPLE SWITCHER IC and a package, but you can use the IC Selection command to override either. Selecting the command from the Main Menu or pressing the I hot key brings up the Package Selection dialog box. This box contains a list of SIMPLE SWITCHER IC and package combinations. Switchers Made Simple lists only those combinations that can be use to build the converter as specified by you, so the length of the list depends on the specifications. Use the arrow keys to move the pointer through the list. Information on the IC and package combination currently pointed at appears to the right of the list. To select an IC and package combination, point at it and press the escape key or the enter key. The program will redesign your DC-DC converter based on the selected combination. @H4.8 Calculating thermal information (Thermal Analysis)@E @L4.8@E @LCalculating thermal information (Thermal Analysis)@E The program calculates the worst-case junction temperature of the IC and lists the temperature as IC Tj in the Operating Values column. The program bases the calculation on the converter specifications as provided by you. If needed, the program specifies a heatsink to limit IC Tj to 110 degrees Celsius. @H4.9 Viewing and printing the schematic (Schematic)@E @L4.9@E @LViewing and printing the schematic (Schematic)@E The complete schematic of your converter is displayed, including values for all components, as well as the input and output voltages. When a key is pressed, a dialog box will ask if you wish to print the schematic. If the answer is Y (yes), another dialog box will ask for the printer type. The available types are HP or compatible laser printer, and Epson or compatible dot-matrix printer. The selected printer must be directly connected to your computer; this program cannot print to a network printer. @H4.10 Viewing, saving and printing the parts list (Parts List)@E @L4.10@E @LViewing, saving and printing the parts list (Parts List)@E The complete parts list of your converter is displayed. The list includes: > Converter Filename (if saved) > Part Summary (components, with value, manufacturer, and part number) > Supply Parameters (the Input Requirements of your design) > Operating Values (calculations made for your design) > Parts List (all details for each component) > Manufacturers of components (with address, phone, and fax) After viewing the parts list, you may exit back to the main screen (ESC), save the parts list (F2), or print the parts list (F3). To save the parts list, press F2. A dialog box will open, into which the new file name can be entered. The dialog box also shows a list of any other existing saved parts lists. The file name can be up to 8 characters long (letters or numbers). An extension of .LST will be added automatically to the filename. If an existing filename is entered, the old file will be replaced with the new parts list. The filename of the parts list does not need to match the name of the converter design, although this is often convenient. To print the parts list, press F3. A dialog box will ask for the printer type. The available types are HP or compatible laser printer, and Epson or compatible dot-matrix printer. The selected printer must be directly connected to your computer; this program cannot print to a network printer. @H4.11 Saving the power supply (Save, Save as...)@E @L4.11@E @LSaving the power supply (Save, Save as...)@E To save your new design for future reference, use either the Save command ("S" hot key) or Save As command ("A" hot key). A Save File dialog box will open, into which the new file name can be entered. The dialog box also shows a list of any other existing saved designs. The file name can be up to 8 characters long (letters or numbers). An extension of .SMS will be added automatically to the filename. If an existing filename is entered, the old design will be replaced with the new design. When the filename has been typed into the appropriate space, press the Enter key, then either O (for OK) or C (for Cancel). The dialog box will close, returning you to the main screen. The new filename will appear at the bottom right-hand corner of the screen. It will also appear on the schematic and parts list, both on-screen and in the print-outs. If a saved design is modified, it can be saved under the existing filename by pressing the S hot key. To save it with a different filename, use the Save As command ("A" hot key). @H4.12 Opening an existing power supply (Open)@E @L4.12@E @LOpening an existing power supply (Open)@E A previously-saved design can be retrieved by the command Open File ("O" hot key) on the Main Menu. A dialog box will open, showing the available design files. Select the desired file, press the Enter key, and the main screen will display the selected design. @H5.0 Notes and Warnings@E @L5.0@E @LNotes and Warnings@E After you have entered the power supply Input Requirements, the software begins calculations for the design. These calculations include the converter type, the SIMPLE SWITCHER IC to be used, and the operating conditions of the design. If, at any point in the calculations, the software determines that the design cannot be made using the new SIMPLE SWITCHER products, a Warning will be shown. The cause of the Warning is given, and you are instructed how to change the Requirements so your design can be generated. If there is special information that you should know about your design, a Note will be shown. When you are finished reading the Note, you can press any key to continue to the Main Screen, which shows the completed design. The following subsections describe selected Notes and Warnings in greater detail than can be done in the on-screen dialog box. @H5.1 "Input Voltage is too Low"@E @L5.1@E @L"Input Voltage is too Low"@E This warning will appear if the Input Requirements have specified a minimum input voltage that is lower than the minimum operating voltage of the type of SIMPLE SWITCHER converter to be used for the design. The dialog box gives the minimum input voltage that can be used by this converter. @H5.2 "Output Current is too High"@E @L5.2@E @L"Output Current is too High"@E This warning will appear if the Input Requirements have specified a load current that is beyond the capability of the available SIMPLE SWITCHER converters. If you are working on a boost or flyback design, the maximum output current can be increased by increasing the minimum input voltage and/or decreasing the output voltage. The dialog box gives the maximum output current that can be delivered by this converter, under input and output voltage requirements you have requested. @H5.3 "Output #1 Filter Required"@E @L5.3@E @L"Output #1 Filter Required"@E In a Flyback design, this note will appear if the requested Vripple limit cannot be met with standard components from the program databases. This generally occurs with Vripple specified between 0.5% and 1% of Vout. The dialog box gives the actual (calculated) Vout p-p of the design, to compare with the requested Vripple. After pressing a key to continue, you can view the design as calculated, or modify the Input Requirements to allow higher Vripple. If you wish to reduce Vout p-p to be under the Vripple limit, a filter can be added to the output voltage in question. A typical filter consisting of a series inductor (about 20uH) and parallel capacitor (about 100uF) can reduce the ripple by a factor of 10 or more. Note that the series inductor must be rated for the full output load current. __________ | SIMPLE | | SWITCHER |Vout Vin--| DC/DC |-----[ L ]--X--- Vout (low ripple) | CONVERTER| | |__________| [C] | | Ground Ground @H5.4 "Output #1 Ripple Voltage is too Low"@E @L5.4@E @L"Output #1 Ripple Voltage is too Low"@L This warning will appear if the Input Requirement for Vripple1 less than 0.5% of Vout1. The software is not able to generate a design that is assured to meet this Vripple limit. The dialog box gives the minimum recommended value for Vripple1. If the output ripple voltage must be lower than 0.5% of Vout, a filter added to the output voltage (as described in Section 5.6) can often give the desired results. @H5.5 "Insufficient Phase Margin"@E @L5.5@E @L"Insufficient Phase Margin"@E For buck regulators in which values at or near the calculated minimum output capacitance and ESR are used, this warning indicates the expected stability of the regulator will be less than the target range. The measure of stability, the phase margin, can be improved by two techniques, changing the output capacitor & ESR values, or changing to an adjustable-output IC. Changing output capacitor & ESR values: Increasing the values of the output capacitor and its ESR tend to increase the phase margin, showing an improvement in stability. The software gives a recommended range for these values. If ESR is increased too much, output ripple voltage will increase beyond the target value. If output capacitance is increased too much, the regulator bandwidth will be low (degrading transient response) and the physical size of the capacitors could be too large for a reasonable design. Using adjustable version for flexible compensation: The phase margin of buck converters using the adjustable-voltage LM259X ICs is usually better compared to the fixed-output versions, because feedforward compensation is added by the software. To obtain a solution with an adjustable part, you can set the output voltage at (for example) 5.01V instead of 5.0V. The software will give you a solution with an adjustable part, with the same output requirements. However, a feedforward capacitor will be added across the upper feedback resistor. This will improve the regulator phase margin, and will reduce the dependency of the frequency response on the output capacitor ESR. The primary benefit of this feedforward compensation is to allow the use of a wider range of output capacitors, including those with extremely low ESR. @H5.6 "Possible Current Limit Runaway"@E @L5.6@E @L"Possible Current Limit Runaway"@E In a Flyback design, this note will appear when the software detects a combination of high Vin Max and high transformer turns ratio that may prevent proper current limit of the IC. This note indicates that, because the switch has a minimum on-time greater than zero, the switch current limit may not be maintained in an output short circuit condition. This condition is common to flyback regulators, and it not unique to SIMPLE SWITCHER converters. The reason for the condition is that, during the minimum on-time of the switch, energy can build up in a high-turns-ratio transformer that cannot be completely dissipated by losses in the output diode/capacitor network (with output shorted to ground). This will eventually cause the transformer core to saturate. When the switch then turns on at the next cycle, the current limit is not engaged fast enough to protect the switch from the high current it must conduct from the saturated transformer. In general, to avoid this possible problem, the minimum input voltage (Vin Min) needs to be increased, to allow the transformer to have a lower turns ratio. Alternatively, the maximum input voltage (Vin Max) can be reduced, so that the maximum power that can be transferred during short circuit is reduced. @H5.7 "Maximum Duty Cycle is Exceeded"@E @L5.7@E @L"Maximum Duty Cycle is Exceeded"@L In a Boost design, this warning can appear when the Input Requirements for an existing design are modified for either lower Vin Min or higher Vout1 than can be supported by a Boost converter. The warning includes the minimum input voltage that can be used to develop the required Vout1. If this change is not possible in your application, an alternative would be to design a new supply with these requirements. The software will select the best topology to meet the requirements. @H6.0 General Information@E @L6.0@E @LGeneral Information@E @H6.1 Standard Units@E @L6.1@E @LStandard Units@E @HInput Requirements dialog box@E Do not type units. By default, the program uses V (Volts), A (Amperes) and degreesC (degrees Celsius). You can use the suffixes m, u, p, k and M to designate milli, micro, pico, kilo and mega respectively. For example, to specify 50 millivolts for Vripple1, you can enter either .05 or 50m. To specify 50 megavolts, you can enter either 50M or 50000000. Note: If more than one character is typed into the space allowed for the suffix, only the first character will be used. Thus, if you have specified a value of 50 mX for Vripple, it will be interpreted as 50 mV. If the same value was specified for Iload, it will be interpreted as 50 mA. @HEdit Part Properties (Edit Components) dialog box@E Do not type units. By default, the program uses V (Volts), Ohms, H (Henries), F (Farads) and degreesC/W (thermal resistance). You can use the same suffixes available in the Input Requirements dialog box. Only the first character of the suffix typed in will be used. The program flags excessively large values of inductance and capacitance, as well as component values below the limit values of the design. @H6.2 Integrated Circuit Options@E @L6.2@E @LIntegrated Circuit Options@E @HFor Buck Converters@E This version of the program designs buck DC-DC converters around the LM259x family. This family includes LM2594, LM2595 and LM2596 and thier feature versions LM2597, LM2598 and LM2599 respectively. All these devices are offered in four output voltage versions: 3.3V, 5V, 12V and adjustable; and in two package options: 8-pin dual-in-line (DIP) and 8-pin surface-mount (SMT) for LM2594 and LM2597, 5-pin TO-220 and 5-pin TO-263 (SMT) for LM2595 and LM2596, and 7-pin TO-220 and 7-pin TO-263 (SMT) for LM2598 and LM2599. Switching frequency is typically 150 kHz. Important operating ratings of these devices include: 4.5V <= Vin <= 40V, ILOAD <= 0.5A (LM2594 and LM2597), ILOAD <= 1.0A (LM2595 and LM2598), ILOAD <= 3.0A (LM2596 and LM2599), and -40 degreesC <= TJ <= +125 degreesC. For proper regulation, Vin must be greater than Vout; see the device datasheets for details. The software takes these ratings and limits into account in the design of your converter. Both the LM2594 and LM2597 have on/off control. In the on state, the converter operates normally; when commanded off, the converter is put into a low-power state, and the output is turned off. The logic for the two converters is opposite: For the LM2594, low is "on"; for the LM2597, high or open is "on". This relationship is the same for the LM2595 and its feature version the LM2598 and the LM2596 and its feature version the LM2599. This reversal occurs because the on/off control input of the feature devices also serves as the soft-start node. In addition, the feature versions feature programmable soft-start, an error flag with programmable delay, and a bias supply input for higher effficiency at high input voltages. Please refer to the device datasheets for instructions on the use of these features. @HFor Boost and Flyback Converters@E This version of the program designs flyback and boost DC-DC converters around the LM258x family. This family includes LM2585 and LM2587 and their feature versions LM2586 and LM2588 respectively. All these devices are offered in four output voltage versions: 3.3V, 5V, 12V and adjustable. The 5- and 7-pin TO-220 and 5- and 7-pin TO-263 (SMT) packages make up the package options. Important operating ratings of these devices include: 4V <= Vin <= 40V, ISWITCH <= 5A (LM2587 and LM2588), ISWITCH <= 3A (LM2585 and LM2586) and -40 degreesC <= TJ <= +125 degreesC. Of course, the program automatically takes these ratings into account when it designs your converters. The nominal switching frequency of all these devices is typically 100 kHz. The switching frequency of the feature devices can be adjusted up to 200 kHz, or synchronized with an external signal in the range of 100 kHz to 200 kHz. In addition, the LM2586 and the LM2588 feature on/off control. Please refer to the LM2585 and the LM2588 datasheets for instructions on the use of these features. @H6.3 Guaranteed system performance@E @L6.3@E @LGuaranteed system performance@E The output voltage tolerance of a DC-DC converter designed with Switchers Made Simple is guaranteed to be +- 5% or better over the specified line, load and ambient temperature ranges. Please note the following exceptions to this guarantee. If the converter uses an adjustable output voltage SIMPLE SWITCHER IC, the output tolerance may be somewhat worse depending on the tolerance of the divider resistors used to set the output voltage. This program selects divider resistors having a 1% tolerance. Flyback converters directly regulate only one main output, while regulation of any auxiliary outputs occurs only through transformer coupling. The voltage tolerance of the main output meets the guarantee, but the voltage tolerance of any auxiliary output will be somewhat worse. @H6.4 Unity gain crossover frequency and phase margin@E @L6.4@E @LUnity gain crossover frequency and phase margin@E @H6.5 Ouput capacitor ESR@E @L6.5@E @LOuput capacitor ESR@E The equivalent series resistance (ESR) of the output filter capacitor plays an important role in maintaining the stability of a DC-DC converter. To guarantee the stability of your converter, this program selects output filter capacitors that meet calculated ESR limit values. The program displays these limit values in the edit components dialog box. To meet the limits, the program selects low ESR, high frequency capacitors from an internal database. If you decide to use capacitors from a vendor not included in the database, use only a product line that specifies ESR at a frequency higher than 120 Hz (like 10 kHz or 100 kHz). Capacitors lacking high frequency specifications are not intended for use in a DC-DC converter. The ESR of aluminum electrolytic capacitors changes with temperature and may increase substantially at low temperatures. If your specifications call for an ambient temperature below -10 degrees Celsius, this program will not select an actual filter capacitor from the internal database. In this case, you can use the capacitor specifications provided by the software and a detailed capacitor datasheet to select the output filter capacitor. @H6.6 Components not found in the database@E @L6.6@E @LComponents not found in the database@E @H7.0 Military Switching Regulator Design Considerations@E @L7.0@E @LMilitary Switching Regulator Design Considerations@E @H7.1 Output Capacitor Selection@E @L7.1@E @LOutput Capacitor Selection@E Military systems designers who are bound to design solely with mil spec components may want to consider using tantalum capacitor instead of standard aluminum electrolytic. The benefits of tantalum capacitors are that they are readily available in many levels of military qualification, and work well with the LM2595J over the -55C to +125C range, and they work well singularly or paralleled. Choosing tantalum capacitors provides definite benefits for military applications but there are some design considerations to keep in mind. The ESR of tantalum capacitors becomes very low at high temperature. The LM2595J has been designed to depend on a minimum of 0.05 Ohm of ESR to dampen load pulses. Output capacitor selection criteria: * Min ESR @ 52KHz, 125C>0.05 Ohm. * Max Ripple current @ 40KHz=1/2 ILOAD. * MIN Voltage rating @ 125C=1.25 Voutput. All the tantalums we have tested have worked well and have been much more steady over temperature than the aluminum electrolytic. Military qualified tantalum capacitors may be procured from Sprague Electric. For more information on Sprague military capacitors call (413)664-4431 @H7.2 Inductor Selection@E @L7.2@E @LInductor Selection@E Military qualified inductors may be procured from several different manufacturers. Renco can provide direct military qualified inductors from National's Simple Switcher inductor code. For more information on mil spec Renco Inductors call 1-800-645-5828. If you prefer to use a custom inductor, Switchers Made Simple will accept your inductor specifications and design a custom circuit to accommodate your inductor. Mil-STD-1286 may provide inductor selection guidance for your specific military application. @H7.3 Input Capacitor Selection@E @L7.3@E @LInput Capacitor Selection@E Tantalum capacitors are a very good choice for input capacitors in military applications due to their very low ESR. Input Capacitor selection criteria: * Max Ripple current @ 40KHz=1/2(Voutput/Vinput)Iload * Min capacitance = 47 uF. Mil-STD-198 may provide capacitor selection guidance for your specific military application. @H7.4 Catch Diode Selection@E @L7.4@E @LCatch Diode Selection@E Military qualified Schottky Diodes may be procured from Unitrode and Micro Semi. Unitrode part number 1N6492JANTX and generic as USD245. For more information on Unitrode military schottky diodes call 1-617-926-0404. Also, Micro Semi offers the 1N5819JTX. Components selection criteria: * Max current rating = 1.2 A ILOAD * Min reverse voltage = 1.25 Vinput. For a current list of military qualified Schottky diode contact the Defense Electronics supply center's qualifications desk in Dayton, Ohio at 513-296-6010. @H7.5 Topology Selection@E @L7.5@E @LTopology Selection@E The Switchers Made Simple software makes switching regulator design and component selection simple. It covers the standard regulator topologies but, it does not model performance and does not account for drift over temperature in the passive components. Worst case specs can be entered into the software to account for drifts. Innovative applications notes describing circuits using the Simple Switcher can be obtained by contacting National's Customer Response Center at 1-800-272-9959 or your local National sales office. SIMPLE SWITCHER and Switchers Made Simple are registered trademarks of National Semiconductor Corporation. Copyright National Semiconductor Corporation 1998. All rights reserved.