1-1-2 Switching Mode Regulator ICs SI-8511NVS Surface-Mount, Synchronous Rectifier Step-down Switching Mode Regulator Control ICs ■Features ■Absolute Maximum Ratings • Surface-mount package (TSSOP24) • High efficiency due to synchronous rectification: 92% (at VIN = 5V, IO = 1A, VO = 2.5V) • Capable of downsize a choke-coil due to IC's high switching frequency (400kHz typ, On Time Control). (Compared with conventional Sanken devices) Parameter (Ta=25°C) Symbol Ratings Unit Control-System DC Input Voltage VCC 7 V DC Input Voltage VIN 25 V Boost Block Input Voltage VH 30 V EN Terminal Input Voltage VEN VCC V VPWRGD 7 V Junction Temperature Tj +150 °C Storage Temperature Tstg –40 to +150 °C PWRGD Terminal Applied Voltage • Low reference voltage (Vref) of 1.1V. The output voltage is variable from 1.1V to 6V. • High-speed response to a load • Compatible with low ESR capacitors • Soft start and output ON/OFF available • Built-in overcurrent and output-overvoltage protection circuits • PWRGD function to indicate the output voltage status • High precision reference voltage: 1.1V ± 1.2% ■Applications • Power supplies for notebook PCs and mobile devices • Onboard local power supplies • OA equipment • For stabilization of the secondary-side output voltage of switching power supplies ■Recommended Operating Conditions Symbol Ratings Unit Control System Input Voltage Range Parameter VCC 4.5 to 5.5 V Input Voltage Range VIN 3 to 18 V Output Voltage Range VO 1.1 to 6 V Operating Temperature Range Top –20 to +85 °C ■Electrical Characteristics (Ta=25°C unless otherwise specified) Parameter Symbol Dynamic Output Voltage Characteristics Temperature Coefficient of Output Voltage ∆VO/∆T Circuit Current min. –1.2% typ. max. 1.1 +1.2% ±0.03 Unit V mV/°C Conditions VIN=5V, VCC=5V, VSNS connected to VO, IO=0A VIN=5V, VCC=5V, VSNS connected to VO, IO=0A, Ta=0 to 85°C Circuit Current (VCC Terminal) Iop 6 mA VCC=5V, EN=H, FADJ:open Circuit Current (VIN Terminal) Iop 1 mA VIN=5V, EN=H Standby Current 1 (VCC Terminal) Istd1 100 µA VCC=5V, EN=L Standby Current 2 (VIN Terminal) Istd2 50 µA VIN=5V, EN=L Undervoltage UVLO Operating Voltage 1 (VCC Terminal) Lockout UVLO Operating Voltage 2 (VIN Terminal) On Time Control VO Ratings Vuvlo1 3.7 4.45 V VIN=5V Vuvlo2 2.5 2.9 V VCC=5V On Time Ton 1.27 µS VCC=5V, VIN=5V, VO=2.5V Minimum Off Time Toff 0.7 µS VCC=5V REF Terminal Voltage Vref 1.3 V VCC=5V REF Terminal Source Current Iref 100 µA VCC=5V 1.1 1.2 High Side Drive On Resistance (high side) RonHH 5.5 Ω VH-VLIN=5V On Resistance (low side) RonHL 5.5 Ω VH-VLIN=5V Low Side Drive On Resistance (high side) RonLH 5.5 Ω VCC=5V On Resistance (low side) RonLL 5.5 Ω VCC=5V Bootstrap Bootstrap Voltage Protection System 82 VH-VLIN 4.5 Current for Current Limit Detection Ilim 90 Soft Start Terminal Current Iss 5 5.5 V 100 110 µA VCC=5V, VIN=5V µA VCC=5V ±20 EN Low Level Voltage Vcelo 0 0.8 V VCC=5V EN High Level Voltage Vcehi 2.4 VCC V VCC=5V EN Bias Level Current ICE 5 µA VCC=5V, EN=5V PWRGD Good Voltage (high side) Vsens 1.32 V VCC=5V PWRGD Good Voltage (low side) Vsens 0.88 V VCC=5V PWRGD Low Output Voltage Vpwrgd 0.4 V VCC=5V, Ipwrgd=120µA PWRGD Terminal Current Ipwrgd 120 µA VCC=5V, Vpwrgd=0.4V PWRGD Leakage Current Ipwrgd 5 µA Vpwrgd=5V ICs SI-8511NVS ■External Dimensions (TSSOP24) (Unit : mm) 2.0 φ Mirror surface Depth 0.02 to 0.08 11 ° A 11 ° 13 24 1.0 φ Mirror surface (6.4) 12 11 ° 1 11 ° 1.90 3.00 7.6±0.2 5.60±0.1 Depth 0.02 to 0.08 +0.1 0.15 –0.05 0.65 0.375 TYP 0.22+0.1 –0.05 0.12 M A 7.80±0.1 0.4 7.9±0.2 11° 1.15±0.05 11° Plastic Mold Package Type Flammability: UL94V-0 Product Mass: Approx. 1.36g ° 11 0.08 S 0~10 11° 0.10±0.05 S 0.50±0.2 ° ■Block Diagram (Pin Assignment) VIN + +5V VCC1 ILIM VIN ISEN VCC2 OCP PRE_REG EN H : ON L : OFF EN UVLO Vpreg VH Level Shift Gate Driver OFF Clamp Latch Buff DRVH VO Synchronous Cont. (Logic) POWER_GOOD H : GOOD L : NG PWRGD LIN + Buff Logic Power Good DRVL PGND – Switching + Constant On Time Cont. + COMP – VO VSNS – OSC + SS GND OVP_SL FADJ Open : Change Frequency Short : 400KHz Operation FSET 14 SS 12 SKIP Open : Skip Mode L : No Skip Mode ■Typical Connection Diagram VIN R2 C1 : 10 µ F VCC : 5V D2 : SFPL52 C7 : 0.1 µ F R1 5mΩ R5 10Ω 1 2 3 4 C6 0.1 ~ 1 µ F C9 1000 pF 5 6 7 8 VCC R7 47kΩ R10 2.2kΩ R9 9 10 NC NC DRVH LIN VH DRVL VIN PGND ISEN VCC2 ILIN OVP_SL SI-8511NVS GND VSNS VO VCC1 SS EN PWRGD SKIP REF FADJ Q1 24 L1 : 10 µ H 23 22 21 20 VO + Q2 D1 SJPJ-L3 R6 10Ω C5 : 4.7 µ F 19 R12 18 C4 : 3.3 µ F VCC 17 C8 : 220pF 16 15 EN SKIP PWRGD 11 12 NC NC 14 13 R11 : 100kΩ R8 : 200kΩ R13 R4 47kΩ C3 0.1 µ F C2 : 330 µ F MOS FET Q1, Q2 • Be sure to use logic type MOS FET as Q1 and Q2. If you use a normal power MOS FET type, the ON resistance may not drop to a satisfactory level due to a shortage of VGS. This may deteriorate the efficiency and cause overheating. Diode D1 • Be sure to use a Schottky-barrier diode for D1. If other diodes like fast recovery diodes are used, IC 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. • Take care concerning heat radiation from the choke coil caused by magnetic saturation due to overload or short-circuit load. Capacitor C1, C2 • As large ripple currents flow through C1 and C2, use high-frequency and lowimpedance capacitors suitable for switching mode power supplies. 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 a ceramic capacitor, which may cause an abnormal oscillation. * To create the optimum operating conditions, place the components as close as possible to each other. ICs 83