GS-R1012 120W STEP-DOWN SWITCHING REGULATOR Type GS-R1012 Vi Vo Io 18 to 36 V 12 V 10 A FEATURES Wide input voltage range (18 to 36V) High efficiency (90% min.) Parallel operation with current sharing Synchronization Remote inhibit/enable Remote load voltage sense Output short-circuit protection Soft-start PCB or chassis mountable DESCRIPTION The GS-R1012 is a step-down switching voltage regulator suitable to provide 12V/10A output voltage from a wide input voltage range (18 to 36V). ABSOLUTE MAXIMUM RATINGS Symbol Vi Parameter DC Input Voltage Viinh High Inhibit voltage Tstg Storage Temperature Range Tcop Operating Case Temperature Range June 1994 Value Unit 40 V 28 V – 20 to +105 °C 0 to +75 °C 1/7 GS-R1012 ELECTRICAL CHARACTERISTICS (Tamb = 25°C unless otherwise specified) Parameter Symbol Test Conditions Vi Input Voltage Vo = 12V li Input Current Vi = 24V Io = 1.5 to 10A lir Reflected Input Current Vi = 24V Io = 10A with external filter (C = 1000µF) Min 18 Io = 10A Typ Max 24 36 5,6 400 Unit V A 500 mApp Vien Enable Input Voltage Vi = 18 to 36V Io = 1.5 to 10A 0 1.2 V Viinh Inhibit Input Voltage Vi = 18 to 36V Io = 1.5 to 10A 2 24 V liinh Inhibit Input Current Vi = 18 to 36V Io =1.5 to 10A Viinh = 5V 0.3 0.5 mA 12 12.6 Vo Output Voltage Vi = 18 to 36V Io = 1.5 to 10A Vor Output Ripple Voltage Vi = 24V Io = 10A Line Regulation Vi = 18 to 36V Io = 10A δVOL 11.4 150 δVOO Load Regulation Vi = 24V ∆Vo Remote Sense Compensation Vi = 24V Io = 10A Io Output Current* Vi = 18 to 36V Iol Output Current Limiting Vi = 18 to 36V Iosc Short-circuit Output Current δIo Io = 1.5 to 10A 0.5 % 1 % 0.5 V 0 10 A 10.5 11.5 A Vi = 24V 16 A Current Sharing Deviation Vi = 24V Io = 2 to 10A two modules in parallel 10 % tss Soft-start Time Vi = 24V tr1 Line Transient Recovery Time tr2 fs η R thc Vo = 12V Io = 10A 15 ms Vi = 15 to 36V Io = 5A 60 µs Load Transient Recovery Time Vi = 24V Io = 1.5 to 10A 100 µs Switching Frequency Vi = 24V Io = 1.5 to 10A 100 kHz Efficiency Vi = 18 to 36V Io = 10A 90 Thermal Resistance Case-to-ambient * Note: when output current is less than 1.5A, output ripple voltage increases due to discontinuous operation. 2/7 V mVpp 92 % 7.5 °C/W GS-R1012 CONNECTION DIAGRAM AND MECHANICAL DATA Dimensions in mm (inches). PIN DESCRIPTION Pin Function Description 1 GND Input 2 Inhibit The converter is ON (Enable) when this pin is unconnected or the voltage applied is lower than 1.2V. The converter is OFF (Inhibit) for a control voltage in the range of 2 to 24V. 3 + Vin DC Input voltage; recommended maximum voltage is 36V. External capacitor between pin 3 and pin 1 is mandatory; recommended value is 1000µF/50V for switching application. 4,5 + Vout +12V output voltage. 6 + Sense Senses the remote load high side. To be connected to pin 4,5 when remote sense is not used. 7 Sync Synchronization output. See figures 1,2,3,4. Take care to leave the pin open when is not used. 8 Parallel Parallel output. See figures 1,2,3,4. Take care to leave the pin open when is not used. 9 - Sense Senses the remote load return. To be connected to pin 10,11 when remote sense is not used. In parallel configuration, take care to connect all -S pins together (see figures 1,2,3,4). 10,11 GND Output Return for input voltage source. Internally connected to pin 10,11. Return for output current path. Internally connected to pin 1. 3/7 GS-R1012 USER NOTES Input Voltage The recommended operating maximum DC input voltage is 36V inclusive of the ripple voltage. The use of an external low ESR, high ripple current capacitor located as close the module as possible is mandatory; recommended value is 1000µF/50V. Softstart To avoid heavy inrush current the output voltage rise time is typically 15ms in any condition of load. Remote Sensing The remote voltage sense compensation range is for a total drop of 500mV equally shared between the load connecting wires. It is a good practice to shield the sensing wires to avoid oscillations. See the connection diagram on figures 1, 2, 3, 4. Figure 1. 4/7 Parallel Operation To increase available output regulated power, the module features the parallel connection possibility with equal current sharing and maximum deviation of 10% (two modules in parallel). See the connection diagram on figures 1, 2, 3, 4. Module Protection The module is protected against occasional and permanent shortcircuits of the output pins to ground, as well as against output current overload. It uses a current limiting protection circuitry, avoiding latch-up problems with certain types of loads. Figure 2. GS-R1012 Figure 3. Figure 4. Thermal characterist ics: how to choose the heat-sink Sometimes the GS-R1012 requires an external heat-sink depending both operating temperature conditions and power. Before entering into calculations details, some basic concepts will be explained to better understand the problem. The thermal resistance between two points is represented by their temperature difference in front of a specified dissipated power, and it is expressed in Degree Centigrade per Watt (°C/W). For GS-R1012 the thermal resistance case to ambient is 7.5°C/W. This means that an internal power dissipation of 1W will bring the case temperature at 7.5°C above the ambient temperature. The maximum case temperature to which the module provides 10A is 75°C (see fig. 6). Let’s suppose to have a GS-R1012 that delivers a load current of 10A at an ambient temperature of 40°C. The dissipated power in this operating condition is about 10.4W (at typical efficiency of 92%), and the case temperature of the module will be: TCase = TAmb + Pd × Rth = 40 + 10.4 × 7.5 = 118°C This value exceeds the maximum allowed temperature and an external heat-sink must be added. To this purpose four holes (see mechanical drawing) are provided on the metal surface of the module. To calculate this heat-sink, let’s first determine what the total thermal resistance should be. Rth = TCaseMAX − Tamb = 75 − 40 = 3.37°C / W Pd 10.4 This value is the resulting value of the additional heatsink thermal resistance. 5/7 GS-R1012 Figure 5. - Efficiency vs. Output Current. Typ. eff. (%) 98 97 96 95 94 Vi= 18V 93 92 Vi= 24V 91 Vi= 36V 90 89 88 0 1 2 3 Figure 6. - Output Current vs. T case. 6/7 4 5 6 7 8 9 10 GS-R1012 The following list may help the designer to select the proper commercially available heat-sink. Sometimes it can be more convenient to use a custom made heat-sink that can be experimently designed and tested. Manufacturers Type ALUTRONIC PR139 20 3 PR140 19 2 PR159 20 2.5 V5440 19 3 V5805 15 2 V5280 19 2 60885 14 4.5 60660 25.5 1.5 62355 33.5 3 KS50 12 3 KS100.3 15 2.5 SK16 25.5 1.5 SK52 19 2 L30 21 3 LZ50 24 3 6155 14 4.5 6601 14 5 6176 24 4.5 6320 30 1.5 ASSMAN AAVID AUSTERLITZ FISCHER SGE BOSARI THERMALLOY Height (mm) Rth (°C/W) Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specification mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. 1994 SGS-THOMSON Microelectronics – All Rights Reserved SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - China - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands Singapore - Spain - Sweden - Switzerland - Taiwan - Thailand - United Kingdom - U.S.A. 7/7