1-1-3 DC/DC Converter ICs NR885K Surface-Mount, Full-Mold,Current Separate Mode Excitation Control, Synchronous Step-down Switching Rectifier Step-down Mode Regulator Switching ICs Mode ■Features • • • • • • • • • • • • • ■Absolute Maximum Ratings 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 Parameter Symbol Ratings Unit 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 Conditions 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) Built-in phase correction component Output current: 3 A ■Recommended Operating Conditions Reference voltage and accuracy of 0.8 V ± 2% Symbol VIN Io Vo Top Parameter Oscillation frequency: 350 kHz Input Voltage Range Output Current Range Output Voltage Range Operating Temperature Range Output ON/OFF available Undervoltage lockout Soft start function 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 Symbol 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 VREF ⊿VREF/⊿T (Ta=25°C, VIN=12V, VO=3.3V, and Io=1A, unless otherwise specified) min. 0.784 η 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 3.1 max. 0.816 420 6.0 6 6 0.7 151 10 3.0 50 1.4 90 150 165 20 10 14 100 2.1 Conditions Unit V mV/℃ % kHz mV mV A mA µA µA V µA V % nsec ℃ ℃ Ta=–40℃ to +85℃ VIN=6.3V to 18V Io=0.1A to 3A VEN=3V Io=0A, VEN=0V VSS=0V VEN=10V *: 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) 0.05±0.05 6.20 4.40 Pin 1 Mark 0.08±0.08 (Unit : mm) 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. Enlarged View of A 1.50 0.695 TYP 5.20 0.15 A 0.4 1.27 2.70 0.40 2.90 Plastic Mold Package Type Flammability: UL 94V-0 Product Mass: Approx. 0.1g ■Block Diagram 2 IN Σ OSC Current Sense BS 3.5V ON/ OFF 7 EN P.REG 1 Drive REG OCP 5V VREF 0.8V SW + - PWM LOGIC 3 5V TSD Compensation UVLO 6 FB + + Error Amp NC 3.5V 0.8V 5 10uA SS SS GND 4 8 ■Typical Connection Diagram VIN R3 2 VIN 7 EN C2 1 BS C10 SW NR885K C1 8 SS GND 4 R4 FB Vout L1 3 5 NC 6 R5 C9 Option R6 D1 C4 C5 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 ICs 21