42 ics features surface-mount package (to263-5) output current: 3.0a ? igh efficiency: 79% typ. (si-8033sd), 84% typ. (si-8050sd) requires only 4 discrete external components internally-adjusted phase correction and output voltage built-in reference oscillator (60khz) built-in overcurrent and thermal protection circuits output on/off available soft start available by s.s pin lineup absolute maximum ratings unit v w c c c/w c/w ratings 43* 1 3 +125 ?0 to +125 3 33.3 symbol v in p d t j t stg j-c j-a pa r ameter dc input voltage po w er dissipation* 2 j unction temperature storage temperature thermal resistance (junction to case) thermal resistance (junction to ambient air) pa rt number si-8033sd si-8050sd v o (v) 3.3 5.0 i o (a) 3 conditions when mounted on glass-epoxy board 40 40 mm (copper area: 100%) when mounted on glass-epoxy board 40 40 mm (copper area: 100%) *1: 35v for si-8033sd *2: limited by thermal protection circuit. electrical characteristics unit v % kh z mv mv mv/ c a v a pa r ameter output voltage efficiency oscillation frequency line regulation load regulation te mperature coefficient of output voltage overcurrent protection starting current soft low-level voltage start pin * outflow current at low voltage symbol v o conditions conditions f conditions ? v oline conditions ? v oload conditions ? v o / ? t a i s1 conditions v ssl i ssl conditions (t a =25 c) pa r ameter dc input voltage range output current range* operating junction temperature range operating temperature range* symbol v in1 i o t jop t op ratings si-8033sd si-8050sd 5.5 to 28 7 to 40 0 to 3.0 ?0 to +125 ?0 to +125 unit v a c c *: limited by ta-p d characteristics. recommended operating conditions * pin 5 is a soft start pin. soft start at power on can be performed with a capacitor connected to this pin. the output can also be turned on/off with this pin. the output is stopped by setting the voltage of this pin to v ssl or lower. soft-start pin voltage can be changed with an open-collector drive circuit of a transistor. when using both the soft-start and on/off functions together, the discharge current from c 3 flows into the on/off control transistor. therefore, limit the current securely to protect the transistor if c 3 capacitance is large. the on/off pin is pulled up to the power supply in the ic, so applying the external voltage is prohibited. if this pin is not used, leave it open. ratings si-8033sd si-8050sd min. typ. max. min. typ. max. 3.17 3.3 3.43 4.8 5.0 5.2 v in =15v, i o =1a v in =20v, i o =1a 79 84 v in =15v, i o =1a v in =20v, i o =1a 60 60 v in =15v, i o =1a v in =20v, i o =1a 25 80 40 100 v in =8 to 28v, i o =1a v in =10 to 30v, i o =1a 10 30 10 40 v in =15v, i o =0.5 to 1.5a v in =20v, i o =0.5 to 1.5a 0.5 0.5 3.1 3.1 v in =15v v in =20v 0.2 0.2 20 30 40 20 30 40 v ssl =0.2v surface mount, separate excitation step-down switching mode regulator ics si-8000sd series applications ? ow er supplies for telecommunication equipment onboard local power supplies si-8000sd si-8000sd on/off 5 on/off 5 on/off c3 c3 5 v out. on/off soft start soft start +v out. on/off si-8000sd 1-1-2 switching mode regulator ics
43 ics si-8000sd series external dimensions (to263-5) (unit : mm) pin assignment q v in w sw out e gnd r v os t s.s plastic mold package type flammability: 94v-0 product mass: approx. 1.48g (0.40) 2.54 0.3 (4.6) 9.2 0.2 1.2 0.2 4.9 0.2 (0.75) 2.0 0.1 15.3 0.3 9.9 0.2 case temperature measurement point (15 ) (0.5) 2-r0.3 10.0 0.02 3-r0.3 (r0.3) (r0.3) 0.88 0.10 1.5 dp: 0.2 (1.7 0.25 ) 12345 (1.7 0.25 ) 0.8 0.1 4.5 0.2 1.3 0.10 0.15 2.4 0.2 +0.10 ?.05 (3 ) (3 ) (3 ) (3 ) (3 ) 0 to 6 15.30 0.3 (6.8) 9.2 0.2 4.9 0.2 (1.75) (2 r0.45) (1.7 0.25 ) (1.7 0.25 ) 0.8 0.1 10.0 0.2 (4.4) (8.0) block diagram 4 3 5 gnd s.s 2 v in sw out v os 1 reset latch & driver thermal protection oscillator comparator error amplifier internal power supply overcurrent protection reference voltage reference data copper laminate area on glass epoxy board vs. thermal resistance (junction to ambient air) (typical value) 55 50 45 40 35 30 02 00 400 600 800 1000 copper laminate area (mm 2 ) thermal resistance (junction to ambient air) j-a ( c/w) 1200 1400 1600 1800 with glass epoxy board of 40 40 mm t ypical connection diagram v in c 1 c 3 d1 l1 c 2 v in gnd s.s gnd si-8000sd sw out v os 12 4 3 5 + + v out gnd diode d 1 ? e sure to use schottky-barrier diode as d 1 . if other diodes like fast recovery diodes are used, ics may be destroyed because of the reverse voltage generated by the recove ry voltage or on v oltage. choke coil l 1 if the winding resistance of the choke coil is too high, the efficiency may drop below the rated value. as the overcurrent protection starting current is about 3.5 a, take care concerning heat radiation from the choke coil caused by magnetic saturation due to overload or short-circuited load. capacitors c 1 , c 2 , and c 3 as large ripple currents flow through c 1 and c 2 , use high-frequency and low-impedance capacitors aiming for switching-mode-power-supply use. especially when the impedance of c 2 is high, the switching waveform may become abnormal at low temperatures. f or c 2 , do not use a capacitor with an extremely low equivalent series resistance (esr) such as an os capacitor or a tantalum capacit or, which may cause an abnormal oscillation. ? 3 is a capacitor for soft start. leave pin 5 open if the soft start function is not used. this pin is pulled up with a pull-up resistor inside the ics. to create the optimum operating conditions, place the components as close as possible to each other. c 1 : 50v/1000 f c 2 : 50v/1000 f c 3 : 0.01 f (only when soft start function is used) l 1 : 150 h d 1 : spb-g56 (sanken)
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