BL9382C

BL9382C 2A, 24V Synchronous Step-Down Converter DESCRIPTION FEATURES The BL9382C is a current mode monolithic buck voltage converter. Operating with an input range of 4.5-24V, the BL9382C delivers 2A of continuous output current with two integrated N-Channel MOSFETs. At light loads, regulators operate in low frequency to maintain high efficiency and low output ripple. The BL9382C guarantees robustness with over current protection, thermal protection, start-up current run-away protection, and input under voltage lockout. The BL9382C is available in a 8-pin SOP8 package, which provides a compact solution with minimal external components.          4.5V to 24V operating input range 2A output current Up to 94% efficiency High efficiency (85>%) at light load Fixed 500kHz Switching frequency Input under voltage lockout Available in SOP8 package Start-up current run-away protection Over current protection Thermal protection APPLICATIONS      Distributed Power Systems Networking Systems FPGA, DSP, ASIC Power Supplies Green Electronics/ Appliances Notebook Computers TYPICAL APPLICATION www.belling.com.cn 1 V1.0 BL9382C PIN CONFIGURATION TOP VIEW ABSOLUTE MAXIMUM RATING1） VIN, EN, SW Pin ................................................................................................................. -0.3V to 24V BST Pin ................................................................................................................... SW-0.3V to SW+5V All other Pins ......................................................................................................................... -0.3V to 6V Junction Temperature2) 3) ..................................................................................................................150ºC Lead Temperature ......................................................................................................................260ºC Storage Temperature .................................................................................................. -65ºC to +150ºC RECOMMENDED OPERATING CONDITIONS Input Voltage VIN ................................................................................................................4.5V to 24V Output Voltage Vout................................................................................................................. 0.6V to 22V Operating Junction Temperature(TJ)....................................................................................-40ºC to 125ºC THERMAL PERFORMANCE4） θJA θJc SOP8 ..................................................................................................................................... 90...45ºC/W Note： 1) 2) 3) 4) Exceeding these ratings may damage the device. The BL9382C guarantees robust performance from -40°C to 150°C junction temperature. The junction temperature range specification is assured by design, characterization and correlation with statistical process controls. The BL9382C includes thermal protection that is intended to protect the device in overload conditions. Thermal protection is active when junction temperature exceeds the maximum operating junction temperature. Continuous operation over the specified absolute maximum operating junction temperature may damage the device. Measured on JESD51-7, 4-layer PCB. www.belling.com.cn 2 V1.0 BL9382C ELECTRICAL CHARACTERISTICS VIN=12V, TA=25℃, unless otherwise stated. Item Symbol Condition Min. Typ. Max. Units VIN Undervoltage Lockout Thershold VIN_MIN VIN falling 3.8 V VIN Undervoltage Lockout Hysteresis VIN_MIN_HYST VIN rising 300 mV Shutdown Supply Current ISD VEN=0V Supply Current IQ VEN=5V, VFB=2V Feedback Voltage VFB Top Switch Resistance RDS(ON)T 170 mΩ Bottom Switch Resistance RDS(ON)B 110 mΩ Top Switch Leakage Current ILEAK_TOP Bottom Switch Leakage Current ILEAK_BOT Top Switch Current Limit ILIM_TOP Switch Frequency 1 50 0.895 0.923 VIN=24V, VEN=0V, VSW=0V VIN=24V, VEN=0V, VSW=0V μA 0.951 V 0.5 uA 0.5 uA 3.8 A FSW 500 kHz Minimum On Time TON_MIN 100 ns Minimum Off Time TOFF_MIN VFB=0.7V 100 ns EN shut down threshold voltage VEN_TH VEN falling, FB=0V 1.2 V EN shut down hysteresis VEN_HYST VEN rising, FB=0V 100 mV Thermal Shutdown TTSD 145 ℃ Temperature Hysteresis THYS 19 ℃ www.belling.com.cn Minimum Duty Cycle μA 3 V1.0 BL9382C PIN DESCRIPTION PIN NAME Description 1 BST 2 IN 3 SW 4 GND 5 FB 6 NC Not Connected. 7 EN Drive EN pin high to turn on the regulator and low to turn off the regulator. 8 NC Not Connected. Boostrap pin for top switch. A 0.01uF or larger capacitor should be connected between this pin and the SW pin to supply current to the top switch and top switch driver. Input voltage pin. VIN supplies power to the IC. Connect a 4.6V to 24V supply to VIN and bypass VIN to GND with a suitably large capacitor to eliminate noise on the input to the IC. SW is the switching node that supplies power to the output. Connect the output LC filter from SW to the output load. Power ground pin. Output feedback pin. FB senses the output voltage and is regulated by the control loop to 0.8V. Connect a resistive divider at FB. BLOCK DIAGRAM VIN + Current Ramp Current Sensor + Oscillator - CLK 3.3V BST + SS Current Comparator + 0.6V Error + Amplifier SW Logic Control - - FB 3.3V LDO Current Sensor + 1.3V + GND EN www.belling.com.cn - 4 V1.0 BL9382C TYPICAL PERFORMANCE CHARACTERISTICS Vin =12V, Vout = 3.3V, L = 4.7μH, Cout = 22μF, TA = +25°C, unless otherwise noted Steady State Test Startup through Enable Shutdown through Enable VIN=12V, Vout=3.3V Iout=2A VIN=12V, Vout=3.3V Iout=2A(Resistive load) VIN=12V, Vout=3.3V Iout=2A(Resistive load) Heavy Load Operation Medium Load Operation Light Load Operation 2A LOAD 1A LOAD 0 A LOAD Short Circuit Protection VIN=12V, Vout=3.3V Iout=2A- Short www.belling.com.cn Short Circuit Recovery Load Transient VIN=12V, Vout=3.3V Iout= Short-2A 1A LOAD → 2A LOAD → 1A LOAD 5 V1.0 BL9382C FUNCTIONAL DESCRIPTION Vin Under-Voltage Protection The BL9382C is a synchronous, buck voltage converter. 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. Current-Mode Control The BL9382C utilizes current-mode control to regulate the FB voltage. Voltage at the FB pin is regulated at 0.923V so that by connecting an appropriate resistor divider between VOUT and GND, designed output voltage can be achieved. Output Current Run-Away Protection 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 BL9382C 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. PFM Mode The BL9382C 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. Over Current Protection and Hiccup Internal Soft-Start. BL9382C has a cycle-by-cycle current limit. When the inductor current triggers current limit, BL9382C enters hiccup mode and periodically restart the chip. BL9382C will exit hiccup mode while not triggering current limit. Soft-start makes output voltage rising smoothly by following an internal SS voltage until SS voltage is higher than the internal reference voltage. It can prevent the overshoot of output voltage during startup. Short Circuit Protection Power Switch If a current higher than 5A is detected through TOP FET when it’s on, we consider SW is shorted to GND. The chip stops switching for few cycles and switch once to check whether SW is still shorted to GND. This cycle will be repeated until SW is not shorted to GND. N-Channel MOSFET switches are integrated on the BL9382C to down convert the input voltage to the regulated output voltage. Since the top MOSFET needs a gate voltage greater 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. www.belling.com.cn If FB voltage is detected lower than 100mV for few cycles and chip triggers current limit meanwhile, FB pin is considered shorted to GND. The chip won’t switching unless restart. 6 V1.0 BL9382C Thermal Protection When the temperature of the BL9382C rises above 140°C, it is forced into thermal shut-down. www.belling.com.cn Only when core temperature drops below 130°C can the regulator becomes active again. 7 V1.0 BL9382C APPLICATION INFORMATION Output Voltage Set The output voltage is determined by the resistor divider connected at the FB pin, and the voltage ratio is: VFB VOUT  Thus the input capacitor can be calculated by the following equation when the input ripple voltage is determined. R3 C1 R 2  R3 where VFB is the feedback voltage and VOUT is the output voltage.  V OUT  1  0.923 V  R2(kΩ) 2.5 10 17 3.3 10 26.1 5 11 48.4 VOUT  VIN   The input capacitor can be electrolytic, tantalum or ceramic. To minimizing the potential noise, a small X5R or X7R ceramic capacitor, i.e. 0.1uF, should be placed as close to the IC as possible when using electrolytic capacitors. The following table lists the recommended values. R3(kΩ)  1  switching frequency, △VIN is the input ripple current. R3   VOUT(V) V OUT  fs  V IN VIN   where C1 is the input capacitance value, fs is the Choose R3 around 10kΩ, and then R2 can be calculated by: R2 ILOAD A 10uF ceramic capacitor is recommended in typical application. Output Capacitor The output capacitor is required to maintain the DC output voltage, and the capacitance value determines the output ripple voltage. The output voltage ripple can be calculated by: V OUT Input Capacitor ILOAD  VOUT  VIN   1  VIN 1    RESR  8  f  C  s 2   The output capacitors also affect the system stability and transient response, and a 22uF ceramic capacitor is recommended in typical application.   where ILOAD is the load current, VOUT is the output voltage, VIN is the input voltage. www.belling.com.cn VOUT  The output capacitor can be low ESR electrolytic, tantalum or ceramic, which lower ESR capacitors get lower output ripple voltage. VOUT  VIN  fs  L   1  where C2 is the output capacitance value and RESR is the equivalent series resistance value of the output capacitor. The input capacitor is used to supply the AC input current to the step-down converter and maintaining the DC input voltage. The ripple current through the input capacitor can be calculated by: IC1 VOUT 8 V1.0 BL9382C Inductor External Soft-start Capacitor The inductor is used to supply constant current A soft-start capacitor is required to set the soft-start period，which controls the rate of the output voltage rise. Take the startup current and voltage rise rate into consideration, a 0.1uF ceramic capacitor is recommended. to the output load, and the value determines the ripple current which affect the efficiency and the output voltage ripple. The ripple current is typically allowed to be 30% of the maximum PCB Layout Note switch current limit, thus the inductance value For minimum noise problem and best operating performance, the PCB is preferred to following the guidelines as reference. can be calculated by: L VOUT  fs  I L   1  VOUT  VIN   1. Place the input decoupling capacitor as close to BL9382C (VIN pin and PGND) as possible to eliminate noise at the input pin. where VIN is the input voltage, VOUT is the output voltage, fs is the switching frequency, and △IL is the peak-to-peak inductor ripple The loop area formed by input capacitor and GND must be minimized. current. External Boostrap Capacitor 2. Put the feedback trace as far away from the inductor and noisy power traces as possible. A boostrap capacitor is required to supply voltage to the top switch driver. A 0.1uF low ESR ceramic capacitor is recommended to connected to the BST pin and SW pin. www.belling.com.cn 3. The ground plane on the PCB should be as large as possible for better heat dissipation. 9 V1.0 BL9382C REFERENCE DESIGN Reference 1： VIN: 4.5V ~ 24V VOUT: 3.3V IOUT: 0~2A Reference 2： VIN: 8V ~ 24V VOUT: 5V IOUT: 0~2A www.belling.com.cn 10 V1.0 BL9382C PACKAGE OUTLINE UNIT: mm SOP8 0.42±0.10 2.03 7.62 6.0±0.5 3.81 0.51 1.27 1.27TYP RECOMMENDED LAND PATTERN TOP VIEW 3.9±0.4 0.20±0.10 SEE DETAIL“A” 1.75MAX 5.0±0.5 0.15±0.10 SIDE VIEW 0.25 0.25～0.50 FRONT VIEW 0～8° 0.4～1.27 DETAIL“A” BOTTOM VIEW www.belling.com.cn 11 V1.0