NR885K

1-1-3 DC/DC Converter ICs NR885K Surface-Mount, Current Mode Control, SynchronousSwitchingStep-down Switching Mode Full-Mold, Separate Excitation Step-down Rectifier Mode Regulator ICs ■Features • • • • • • • • • • • • • Compact surface-mount package (HSOP8) Input voltage range (VIN): VO + 3 to 18 V Synchronous rectifier mode High efficiency: 90% Introduction of current mode control method A ceramic capacitor can be used for output Built-in phase correction component Output current: 3 A Reference voltage and accuracy of 0.8 V ± 2% Oscillation frequency: 350 kHz Output ON/OFF available Undervoltage lockout Soft start function Parameter ■Absolute Maximum Ratings Parameter Symbol Ratings Unit Conditions Input Voltage Power Dissipation Junction Temperature Storage Temperature Thermal Resistance (Junction to Lead (4 pins)) Thermal Resistance (Junction to Ambient Air) VIN PD Tj Tstg θj-c θj-a 20 1.69 –40 to +150 –40 to +150 40 74 V W °C °C °C/W °C/W When mounted on 30 × 30 mm glass-epoxy board (with a 25 × 25 mm copper area) When mounted on a 30 × 30 mm glass-epoxy board (with a 25 × 25 mm copper area) ■Recommended Operating Conditions Input Voltage Range Output Current Range Output Voltage Range Operating Temperature Range Symbol VIN Io Vo Top Ratings 4.5 or VO + 3* to 18 0 to 3.0 0.8 to 14 –40 to +85 Unit V A V °C *: The minimum value of the input voltage range is 4.5 V or VO + 3 V, whichever is higher. ■Applications • • • • Power supply for LCDTV and PDP Power supply for DVD, BD, and STB On-board local power supply Power supply for LBP and PPC ■Electrical Characteristics Parameter Reference Voltage Temperature Coefficient of Reference Voltage Efficiency Oscillation Frequency Line Regulation Load Regulation Overcurrent Protection Starting Current Quiescent Circuit Current 1 Quiescent Circuit Current 2 Outflow Current at Low Voltage SS Pin Open Voltage Inflow Current EN Pin On Threshold Voltage Maximum ON Duty Minimum ON Time Thermal Protection Start Temperature Thermal Protection Return Hysteresis Symbol VREF ⊿VREF/⊿T η (Ta=25°C, VIN=12V, VO=3.3V, and Io=1A, unless otherwise specified) min. 0.784 fo VLINE VLoad Is IIN IIN(off) IEN/SS VSSH IEN VC/EH DMAX DMIN TSD TSD_hys 280 Ratings typ. 0.800 ±0.05 90 350 50 50 6 max. 0.816 Unit V mV/℃ % kHz mV mV A mA µA µA V µA V % nsec ℃ ℃ Ta=–40℃ to +85℃ Conditions 420 VIN=6.3V to 18V Io=0.1A to 3A VEN=3V Io=0A, VEN=0V VSS=0V VEN=10V 3.1 6.0 10 14 100 2.1 6 0.7 151 10 3.0 50 1.4 90 150 165 20 *: Pin 8 is the SS pin. Soft start at power on can be performed with a capacitor connected to this pin. The SS pin is pulled up to the power supply in the IC, so applying the external voltage is prohibited. NR885K 8 SS C9  Soft start 20 ICs NR885K ■External Dimensions (HSOP8) (Unit : mm) 0.05±0.05 4.40 6.20 Pin 1 Mark 0.08±0.08 0.695 TYP 5.20 A 1.50 Enlarged View of A 1.27 0.40 0.4 Pin Assignment q BS w VIN e SW r GND t FB y NC u EN i SS *: The heat slug on the rear side is at the ground potential. Plastic Mold Package Type Flammability: UL 94V-0 Product Mass: Approx. 0.1g 2.90 ■Block Diagram 2 IN OSC Σ 2.70 Current Sense BS Drive REG 5V 1 3.5V 7 EN ON/ OFF P.REG VREF OCP 0.8V + PWM LOGIC 5V 0.15 SW 3 TSD Compensation UVLO 6 NC 3.5V 10uA SS GND 4 SS 8 + + Error Amp 0.8V FB 5 ■Typical Connection Diagram VIN R3 C10 SW 3 L1 2 VIN 7 EN C2 C1 8 SS GND 4 1 BS Vout NR885K FB NC 6 5 R4 C4 C5 R5 C9 R6 D1 C1, C2: 10µF/25V C4, C5: 22µF/16V C9: 0.1µF C10: 0.1µF L1: 10µH R3: 20Ω to 47Ω R4+R5: 5kΩ  (VO=3.3V) R6: 1.6kΩ Option ICs 21