1-1-3 DC/DC Converter ICs SI-8000SD Series Surface Mount, Separate Excitation Step-down Switching Mode ■Features ■Lineup • Surface-mount package (TO263-5) Part Number SI-8033SD VO (V) 3.3 • Output current: 3.0A SI-8050SD 5.0 IO (A) • High efficiency: 79% typ. (SI-8033SD), 84% typ. (SI-8050SD) 3 ■Absolute Maximum Ratings • Requires only 4 discrete external components Parameter • Internally-adjusted phase correction and output voltage • Built-in reference oscillator (60kHz) Symbol Ratings Unit DC Input Voltage VIN 43*1 V Power Dissipation*2 PD 3 W °C Conditions When mounted on glass-epoxy board 40 × 40 mm (copper area: 100%) • Built-in overcurrent and thermal protection circuits Junction Temperature Tj +125 Storage Temperature Tstg –40 to +125 °C Thermal Resistance (Junction to Case) θ j-c 3 °C/W • Output ON/OFF available Thermal Resistance (Junction to Ambient Air) θ j-a 33.3 °C/W • Soft start available by S.S pin When mounted on glass-epoxy board 40 × 40 mm (copper area: 100%) *1: 35V for SI-8033SD *2: Limited by thermal protection circuit. ■Applications • Power supplies for telecommunication equipment • Onboard local power supplies ■Recommended Operating Conditions Ratings Parameter Symbol SI-8033SD SI-8050SD 5.5 to 28 7 to 40 Unit DC Input Voltage Range VIN1 Output Current Range* IO 0 to 3.0 V A Operating Junction Temperature Range Tjop –30 to +125 °C Operating Temperature Range* Top –30 to +125 °C *: Limited by Ta-PD characteristics. ■Electrical Characteristics (Ta=25°C) Ratings Parameter Symbol SI-8033SD min. Output Voltage Line Regulation Load Regulation Temperature Coefficient of Output Voltage Overcurrent Protection Starting Current Start f Conditions ∆VO/∆Ta 20 5.0 5.2 79 84 VIN=20V, IO=1A 60 60 V % kHZ VIN=20V, IO=1A 80 40 100 mV VIN=10 to 30V, IO=1A 30 10 40 VIN=15V, IO=0.5 to 1.5A VIN=20V, IO=0.5 to 1.5A ±0.5 ±0.5 mV mV/°C 3.1 VIN=15V VIN=20V 0.2 0.2 30 Conditions 40 20 A V 30 40 µA VSSL=0.2V SI-8000SD SI-8000SD 5 ON/OFF 5 ON/OFF C3 VOUT. ON/OFF ICs max. VIN=15V, IO=1A * 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 VSSL 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 C3 flows into the ON/OFF control transistor. Therefore, limit the current securely to protect the transistor if C3 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. 20 Unit typ. VIN=20V, IO=1A 3.1 Conditions ISSL 4.8 10 Conditions Outflow Current at Low Voltage 3.43 VIN=8 to 28V, IO=1A ∆VOLOAD VSSL 3.3 25 Conditions Low-Level Voltage min. VIN=15V, IO=1A ∆VOLINE IS1 max. VIN=15V, IO=1A Conditions Oscillation Frequency Pin* 3.17 η Efficiency Soft VO Conditions SI-8050SD typ. Soft start SI-8000SD 5 ON/OFF C3 Soft start +VOUT. ON/OFF SI-8000SD Series ■External Dimensions (TO263-5) (Unit : mm) ±0.2 10.0 (4.4) 1.2 ±0.2 4.5 15.30 ±0.3 ±0.3 ±0.1 ±0.2 ±0.3 2.0 2.54 ±0.2 (0.75) (R0.3) 0 to 6° (0.5) ±0.1 ±0.1 0.8 ±0.25 ) (1.7 ±0.25 (1.7 ) 1 2 3 4 Plastic Mold Package Type Flammability: 94V-0 Product Mass: Approx. 1.48g ±0.2 2.4 (R0.3) 4.9 15.3 9.2± ±0.2 ±0.15 0.10 (3°) (3°) 4.9 ±0.10 0.88 ±0.2 (2×R0.45) (3°) (6.8) ±0.2 φ1.5 Dp: 1.3 +0.10 –0.05 9.2 (4.6) 3-R0.3 (1.75) (15°) Pin Assignment q VIN w SWOUT e GND r VOS t S.S (8.0) ±0.2 (0.40) Case temperature measurement point (1.7 ±0.25 ) 0.8 ±0.25 (1.7 ) 5 ±0.2 9.9 (3°) (3°) 2-R0.3 ±0.02 10.0 ■Block Diagram ■Reference Data Copper Laminate Area on Glass Epoxy Board vs. thermal resistance (junction to ambient air) (Typical Value) VIN SWOUT 2 Thermal resistance (junction to ambient air) θ j-a (°C/W) 1 Overcurrent protection Internal power supply Oscillator Reset Latch & driver Thermal protection Comparator VOS 4 Error amplifier Reference voltage S.S 55 50 With glass epoxy board of 40 × 40 mm 45 40 35 30 0 200 400 600 800 1000 1200 1400 1600 1800 Copper Laminate Area (mm2) GND 5 3 ■Typical Connection Diagram L1 1 VIN SWOUT VIN SI-8000SD C1 + S.S 5 GND 3 VOS 2 VOUT 4 + D1 C2 C1 : 50V/1000µF C2 : 50V/1000µF C3 : 0.01µF (only when soft start function is used) L1 : 150µH D1 : SPB-G56 (Sanken) C3 GND GND Diode D1 • Be sure to use Schottky-barrier diode as D1. If other diodes like fast recovery diodes are used, ICs may be destroyed because of the reverse voltage generated by the recovery voltage or ON voltage. Choke coil L1 • 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 C1, C2, and C3 • As large ripple currents flow through C1 and C2, use high-frequency and low-impedance capacitors aiming for switching-mode-power-supply use. Especially when the impedance of C2 is high, the switching waveform may become abnormal at low temperatures. For C2, do not use a capacitor with an extremely low equivalent series resistance (ESR) such as an OS capacitor or a tantalum capacitor, which may cause an abnormal oscillation. • C3 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. ICs 21