BL9384B 3A, 20V High Efficiency Synchronous Step-Down Converter • • • • • • • • • • DESCRIPTION The BL9384B is a wide input range, high efficiency, DC-to-DC step-down switching regulator, capable of delivering up to 3A of output current. Current mode PWM control allows the use of small external components, such as ceramic input and output caps, as well as small inductors, while still providing low output ripples. On top of the integrated internal synchronous rectifier that eliminates external Schottky diode, Overall BL9384B is a highly efficient and robust solution for DC-DC step-down applications that requires wide input ranges. APPLICATIONS • • • • • • BL9384B is available ESOP8 Packages. FEATURES • • Up to 94% efficiency High efficiency (>85%) at light load No External Schottky Diode Needed Current Mode control 0.923V Reference for Low Output voltages Logic Control Shutdown Thermal shutdown and UVLO Start-up current run-away protection Short circuit protection Available in ESOP8 Package Wide Input Operating Range from 4.5V to 20V Capable of Delivering 3A LCD TVs Green Electronics/ Appliances Distributed Power Systems Notebook computers FPGA power supplies LED drivers TYPICAL APPLICATION PIN OUT www.belling.com.cn 1 V1.0 BL9384B MARK and ORDERING INFORMATION Mark Explanation XX: Year YY: Week ZZ: Internal code PINOUT DESCRIPTION PIN # 1 2 3 4 5 6 7 8 NAME BST DESCRIPTION Bootstrap pin. Connect a 100nF capacitor from this pin to SW IN Supply Voltage. Bypass with a 10μF ceramic capacitor to GND SW Inductor Connection. Connect an inductor Between SW and the regulator output. GND Ground FB Feedback Input. Connect an external resistor divider from the output to FB and GND to set VOUT COMP EN Compensation pin. COMP is used to compensate the regulation control loop. Connect a series RC network from COMP to GND to compensate the regulation control loop. Enable pin for the IC. Drive this pin to high to enable the part, low to disable. SS Soft start pin. Connect a 0.1 uF capacitor from this pin to GND BLOCK DIAGRAM VIN + Current Ramp Current Sensor + Oscillator - CLK 3.3V BST COMP + Current Comparator + 0.923V Error + Amplifier SW Logic Control - - FB 3.3V LDO Current Sensor + 1.2V + GND EN www.belling.com.cn - 2 V1.0 BL9384B ABSOLUTE MAXIMUM RATING Parameter Value Input Voltage Range, SW, EN Voltage Junction Temperature(Tj) BST Voltage FB Voltage SW to ground curren Operating Temperature(To) ESOP-8L Package Thermal Resistance (θjc) Storage Temperature(Ts) -0.3V-22V 125°C –0.3V to SW+5V –0.3V to 6V Internally limited -40°C –85°C 10°C / W -55°C - 150°C Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability. ELECTRICAL CHARACTERISTICS (VIN=12V, unless otherwise specified. Typical values are at TA=25°C) Symbol Parameter VDD Input Voltage Range UVLO_UP UVLO,IN UVLO Rising Vref Feedback Voltage Ifb Feedback Leakage current Iq Quiescent Current Conditions Min Typ 5 Rising, Hysteresis=140mV Max Unit 20 V 4.2 V 0.923 V 0.1 Active, Vfb=1V, No Switching 60 Shutdown 0.1 Ven=2V, Vin=12V 0.4 uA uA 3 uA Fsoc Switching Frequency 360 KHz RdsonP PMOS Rdson 185 mohm RdsonN NMOS Rdson 100 mohm Ilimit Peak Current Limit Ven EN Input Low Voltag Isw TSD SW Leakage Current 4.4 V VIN=12V,VSW=0 or 12V, EN= GND Over Temperature Proection www.belling.com.cn A 1.3 10 μA °C 150 3 V1.0 BL9384B TYPICAL PERFORMANCE CHARACTERISTICS (Vin=12V, Vout=3.3V, L=10uH, Cout=47uF, TA=25°C, unless otherwise stated) Steady State Test Startup through Enable VIN=12V, Vout=3.3V Iout=3A,Iin=0.65A VIN=12V, Vout=3.3V Iout=2.5A(Resistance load) Heavy Load Operation Medium Load Operation Light Load Operation 3A LOAD 1.5A LOAD 0.4A LOAD Short Circuit Protection Short Circuit Recovery Load Transient www.belling.com.cn 4 Shutdown through Enable VIN=12V, Vout=3.3V Iout=2.5A(Resistance load) 1.5A LOAD→3A LOAD→1.5A LOAD V1.0 BL9384B FUNCTIONAL DESCRIPTION The BL9384B is a synchronous, currentmode, step-down regulator. It regulates input voltages from 5V to 20V down to an output voltage as low as 0.923V, and is capable of supplying up to 3A of load current. N-Channel MOSFET switches are integrated on the BL9384B to down convert the input voltage to the regulated output voltage. Since the top MOSFET needs a gate voltage great than the input voltage, a boost capacitor connected between BST and SW pins is required to drive the gate of the top switch. The boost capacitor is charged by the internal 3.3V rail when SW is low. Current-Mode Control The BL9384B utilizes current-mode control to regulate the output voltage. The output voltage is measured at the FB pin through a resistive voltage divider and the error is amplified by the internal transconductance error amplifier. COMP pin is output of the internal error amplifier and is compared to the switch current measured internally to control the output current limit. Vin Under-Voltage Protection A resistive divider can be connected between Vin and ground, with the central tap connected to EN, so that when Vin drops to the pre-set value, EN drops below 1.2V to trigger input under voltage lockout protection. PFM Mode Output Current Run-Away Protection The BL9384B operates in PFM mode at light load. In PFM mode, switch frequency is continuously controlled in proportion to the load current, i.e. switch frequency is decreased when load current drops to boost power efficiency at light load by reducing switch-loss, while switch frequency is increased when load current rises, minimizing both load current and output voltage ripples. At start-up, due to the high voltage at input and low voltage at output, current inertia of the output inductance can be easily built up, resulting in a large start-up output current. A valley current limit is designed in the BL9384B so that only when output current drops below the valley current limit can the bottom power switch be turned off. By such control mechanism, the output current at start-up is well controlled. Shut-Down Mode Output Short Protection The BL9384B operates in shut-down mode when voltage at EN pin is driven below 0.3V. In shut-down mode, the entire regulator is off and the supply current consumed by the BL9384B drops below 1uA. When output is shorted to ground, output current rapidly reaches its peak current limit and the top power switch is turned off. Right after the top power switch is turned off, the bottom power switch is turned on and stay on until the output current falls below the valley current limit. When output Power Switch www.belling.com.cn 5 V1.0 BL9384B current is below the valley current limit, the top power switch will be turned on again and if the output short is still present, the top power switch is turned off when the peak current limit is reached and the bottom power switch is turned on. This cycle goes on until the output short is removed and the regulator comes into normal operation again. PCB Layout Note Thermal Protection 3. The ground plane on the PCB should be as large as possible for better heat dissipation. 1. Place the input decoupling capacitor as close to BL9384B (VIN pin and PGND) as possible to eliminate noise at the input pin. 2. Put the feedback trace as far away from the inductor and noisy power traces as possible. When the temperature of the BL9384B rises above 150°C, it is forced into thermal shut-down. Only when core temperature drops below 125°C can the regulator becomes active again. PACKAGE OUTLINE Package ESOP8 Devices per reel 2500 Unit mm Package specification： www.belling.com.cn 6 V1.0