GS-R1012 120w step-down switching regulator june 1994 1/7 type v i v o i o GS-R1012 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-r 1012 is a step-down switching voltage regulator suitable to provide 12v/10a output volt- age from a wide input voltage range (18 to 36v). absolute maximum ratings symbol parameter value unit v i dc input voltage 40 v v iinh high inhibit voltage 28 v t stg storage temperature range C 20 to +105 c t cop operating case temperature range 0 to +75 c
electrical characteristics (t amb = 25 c unless otherwise specified) symbol parameter test conditions min typ max unit v i input voltage v o = 12v i o = 1.5 to 10a 18 24 36 v l i input current v i = 24v i o = 10a 5,6 a l ir reflected input current v i = 24v i o = 10a with external filter (c = 1000 m f) 400 500 mapp v ien enable input voltage v i = 18 to 36v i o = 1.5 to 10a 01.2v v iinh inhibit input voltage v i = 18 to 36v i o = 1.5 to 10a 224v l iinh inhibit input current v i = 18 to 36v i o =1.5 to 10a v iinh = 5v 0.3 0.5 ma v o output voltage v i = 18 to 36v i o = 1.5 to 10a 11.4 12 12.6 v v or output ripple voltage v i = 24v i o = 10a 150 mvpp d v ol line regulation v i = 18 to 36v i o = 10a 0.5 % d v oo load regulation v i = 24v i o = 1.5 to 10a 1% d v o remote sense compensation v i = 24v i o = 10a 0.5 v i o output current * v i = 18 to 36v v o = 12v 010a i ol output current limiting v i = 18 to 36v 10.5 11.5 a i osc short-circuit output current v i = 24v 16 a d i o current sharing deviation v i = 24v i o = 2 to 10a two modules in parallel 10 % t ss soft-start time v i = 24v i o = 10a 15 ms tr1 line transient recovery time v i = 15 to 36v i o = 5a 60 m s tr2 load transient recovery time v i = 24v i o = 1.5 to 10a 100 m s f s switching frequency v i = 24v i o = 1.5 to 10a 100 khz h efficiency v i = 18 to 36v i o = 10a 90 92 % r thc thermal resistance case-to-ambient 7.5 c/w * note: when output current is less than 1.5a, output ripple voltage increases due to discontinuous operation. 2/7 GS-R1012
3/7 dimensions in mm (inches). connection diagram and mechanical data pin description pin function description 1 gnd input return for input voltage source. internally connected to pin 10,11. 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 1000 m f/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 output current path. internally connected to pin 1. GS-R1012
4/7 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 1000 m f/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. parallel operation to increase available output regulated power, the module features the parallel connection possibility with equal cur rent sharing and maximum deviation of 10% (two modules in parallel). see the connec- tion 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, avoid- ing latch-up problems with certain types of loads. figure 1. figure 2. GS-R1012
5/7 thermal characteristics: 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 ba- sic concepts will be explained to better understand the problem. the thermal resistance between two points is rep- resented 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 am- bient 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 mod- ule provides 10a is 75 c (see fig. 6). lets 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: t case = t amb + p d r th = 40 + 10.4 7.5 = 118 c this value exceeds the maximum allowed tempera- ture 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, lets first determine what the total thermal resistance should be. r th = t casemax - t amb p d = 75 - 40 10.4 = 3.37 c / w this value is the resulting value of the additional heatsink thermal resistance. figure 3. figure 4. GS-R1012
6/7 figure 6. - output current vs. t case. 88 89 90 91 92 93 94 95 96 97 98 0 1 2 3 4 5 6 7 8 9 10 typ. eff. (%) vi= 18v vi= 24v vi= 36v figure 5. - efficiency vs. output current. 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 manufacturers type height (mm) rth ( c/w) alutronic pr139 20 3 pr140 19 2 pr159 20 2.5 assman v5440 19 3 v5805 15 2 v5280 19 2 aavid 60885 14 4.5 60660 25.5 1.5 62355 33.5 3 austerlitz ks50 12 3 ks100.3 15 2.5 fischer sk16 25.5 1.5 sk52 19 2 sge bosari l30 21 3 lz50 24 3 thermalloy 6155 14 4.5 6601 14 5 6176 24 4.5 6320 30 1.5 7/7 custom made heat-sink that can be experimently designed and tested. 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 not ice. this publication s upersedes and replaces all informat ion previously supplied. sgs-thomson microelectronics products are not authorized for use as critical components in life s upport devices or systems without express written approval of sgs-thomson microelectronics. ? 1994 sgs-thomson microelectronics C all rights reserved sgs-thomson microelectronics group of companies australia - brazil - china - france - germany - hong kong - italy - japan - korea - mal aysia - malta - morocco - the netherlands - singapore - spain - sweden - switzerland - t aiwan - thailand - united kingdom - u.s.a. GS-R1012
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