1-1-2 Switching Mode Regulator ICs STA820M Series Separate Excitation Switching Mode Regulator ICs with Flywheel Diode ■Features ■Lineup • Output current: 3A • High efficiency: TYP 83% (STA821M) Part Number Output Voltage (V) STA821M 5 Output voltage: 3.3V, 9V, 12V; adjustable types currently being planned • Built-in flywheel diode (Schottky-barrier diode) • Requires only 3 discrete components: output coil, input and output capacitors ■Absolute Maximum Ratings*1 • Phase correction and output voltage adjustment performed internally Parameter • Built-in reference oscillator (110kHz) Symbol Ratings Unit DC Input Voltage VIN 31 V Output Current IO 3 A PD1 18.2 (With infinite heatsink) W • Built-in foldback-overcurrent and thermal protection circuits Power PD2 2.7 (Without heatsink, stand-alone operation) W • Built-in ON/OFF circuit (soft start available) Junction Temperature Tj +125 °C Storage Temperature Tstg –40 to +125 °C Thermal Resistance (Junction to Case) θ j-c 5.5 °C/W Thermal Resistance (Junction to Ambient Air) θ j-a 37 °C/W ■Applications • Power supplies for telecommunication equipment Dissipation*2 *1: The absolute maximum ratings show the destructive limit. No parameter should exceed the ratings in transient or normal operations. *2: Limited by thermal protection. • On-board local power supplies • OA equipment • For stabilization of the secondary-side output voltage of switching power supplies ■Recommended Operating Conditions*1 Ratings Parameter Symbol STA821M Unit min. max. DC Input Voltage Range VIN 7 30 Output Current Range*2 IO 0 3 V A Operating Junction Temperature Range Tjop –30 +125 °C Ambient Temperature Range*2 Top –30 +80 °C *1: The recommended operating conditions show the operating conditions required for the normal circuit function described in the electrical characteristics. These conditions must be followed in actual use. *2: Limited by Ta-PD characteristics. ■Electrical Characteristics (Ta=25°C) Ratings Parameter Symbol STA821M min. VO Output Voltage 4.8 Conditions Terminal*2 Conditions 40 VSSL Outflow Current at Low Voltage ISSL Quiescent Circuit Current 100 mV 10 40 mV VIN=20V, IO=0.5 to 1.5A ±0.5 mV/ °C 3.1 Conditions Low Level Voltage kHz VIN=10 to 30V, IO=1A ∆VO/∆T IS % VIN=20V, IO=1A VLoad Overcurrent Protection Starting Current V 110 Conditions Temperature Coefficient of Output Voltage ON/OFF fO Conditions Load Regulation 5.2 VIN=20V, IO=1A VLine Line Regulation 5.0 83 Conditions Oscillation Frequency max. VIN=20V, IO=1A η Efficiency*1 Unit typ. A VIN=20V 0.2 15 Conditions Iq Conditions V 25 35 µA VSSL=0.2V 4 mA VIN=20V, IO=0A *1: Efficiency is calculated from the following formula. η(%) = VO·IO VIN·IIN × 100 *2: Pin 7 is the ON/OFF pin. Soft start at power on can be performed by connecting a capacitor 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. ON/OFF-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. STA821M STA821M STA821M 7 ON/OFF 7 ON/OFF 7 ON/OFF C3 VO. ON/OFF 88 ICs Soft start C3 Soft start +VO. ON/OFF STA820M Series ■External Dimensions (SIP8 [STA 8Pin]) (Unit : mm) 4±0.2 STA821M a 1.2±0.1 (Measured at the root) (1) 3.15±0.5 9±0.2 1.7MAX 2.3±0.2 b SK Pin Assignment q SWOUT w GND e VIN r N.C t GND y VOS u ON/OFF i GND 2–(R1) 2–(R 0.65 ) R-END (3.1) 1.15+0.2 –0.1 7×P2.54±0.1=(17.78) (Measured at the root) C1.5±0.5 0.55+0.2 –0.1 4.3±0.7 (Measured at the tip) 20.15±0.3 0.7 1 2 3 4 5 6 7 Plastic Mold Package Type Flammability: UL 94V-0 Product Mass: Approx. 2.0 g 0.7 Plan View 8 ■Block Diagram STA821M VIN C1 3 SW OUT VIN + 1 L VOUT + Internal Power Supply Overcurrent Protection Di Latch & Driver Reset C2 GND 2 Oscillator 7 + – ON/OFF Comparator Error Amplifier VOS Thermal Protection 6 + – Reference Voltage GND 5,8 ■Ta-PD Characteristics ■Typical Connection Diagram 20 3.VIN STA821M + 7.ON/OFF C1 6.VOS 2.GND 5,8.GND + C2 C3 GND GND C1 C2 C3 L1 1000µF/50V : 1000µF/25V : 0.47µF/10V(only when the soft start function is used) : 100µH : 18 VOUT Power Dissipation PD (W) VIN Without Insulating Sheet With Silicone Grease Heatsink: Aluminum With Infinite Heatsink L1 1.SW 16 14 12 10 PD = VO·IO 100×100×2mm (11.5°C/W) 100 –1 ηχ 8 6 50×50×2mm (17.9°C/W) VO : Output voltage 4 25×50×2mm (25°C/W) 2 IO Without Heatsink (37°C/W) 0 –25 0 25 50 VIN : Input voltage 75 100 125 : Output current ηχ : Efficiency (%) Ambient Temperature Ta (°C) ICs 89