High Power Step-Down Synchronous DC/DC Controller

APW7057 High Power Step-Down Synchronous DC/DC Controller Features • Operates from +5V Input • 0.8V Internal Reference Voltage - ±1.5% Accuracy Over Line, Load and Temp. General Description The APW7057 is a 300kHz constant frequency voltage mode synchronous switching controller that drives external N-channel MOSFETs. When the input supply drops close to output, the upper MOSFET remains on, achieving 100% duty cycle. Internal loop compensation is optimized for fast transient response, eliminating external compensation network. The precision 0.8V reference makes this part suitable for a wide variety of low voltage applications. Soft start is internally set to 2ms, limiting the input in-rush current and preventing the output from overshoot during powering up. The APW7057 has over current and short circuit protections. Over current protection is achieved by monitoring the voltage drop across the high side MOSFET, eliminating the need for a current sensing resistor and short circuit condition is detected through the FB pin. If either fault conditions occur, the APW7057 would initiate the soft start cycle. After three cycles and if the fault condition persists, the controller will be shut down. To restart the controller, either recycle the VCC supply or momentarily pull the OSCSET pin below 1.25V. The APW7057 can be shutdown by pulling the OCSET pin below 1.25V. In shutdown, both gate drive signals will be low. The controller is available in a small SOP8 package. • 0.8V to VCC Output Range • Full Duty Cycle Range - 0% to 100% • Internal Loop Compensation • Internal Soft Start - Typical 2ms • Programmable Over-Current Protection - Lossless Sensing Using MOSFET RDS (ON) • • • • Under-Voltage Protection Drives External N-Channel MOSFETs Shutdown Control Small SOP-8 Package Applications • • • • • • • Motherboard Graphics Cards Cable or DSL Modems, Set Top Boxes DSP Supplies Memory Supplies 5V Input DC-DC Regulators Distributed Power Supplies Pinouts BOOT UGATE GND LGATE 1 2 3 4 8 7 6 5 PHASE OCSET FB VCC SOP-8 (Top View ) ANPEC reserves the right to make changes to improve reliability or manufacturability without notice, and advise customers to obtain the latest version of relevant information to verify before placing orders. Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003 1 www.anpec.com.tw APW7057 Ordering and Marking Information Package Code APW 7057 K : SOP-8 Operating Junction Tem p. Range Handling Code Tem p. Range Package Code C : 0 to 70 °C Handling Code TU : Tube TR : Tape & Reel APW 7057 K : APW 7057 XXXXX XXXXX - Date Code Block Diagram VCC BOOT UnderVoltage Lockout Shutdown OCSET IOCSET 40uA OC Com parator Soft-Start and Fault Logic OCP UVLO PHASE UGATE 0.5V UVP Soft-Start Inhibit Gate PW M Control VCC FB VR E F 0.8V - COMP + Error Am plifier + - LGATE FO S C 300kHz Oscillator GND . E C K H / Figure 1. Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003 2 www.anpec.com.tw APW7057 Typical Application R3 C3 1uF 5 2.2 VIN D1 1N4148 C1 1uF + +5V C2 1000uF x2 R4 8.2k C7 470pF 7 OCSET VCC BOOT 1 Q3 U G ATE 2 C4 0.1uF Q1 L1 3.3uH VO UT +2.5V/10A C5 1000uF x2 Shutdown 8 P H AS E 6 U1 APW 7057 LG ATE FB GND 3 + 4 Q2 R1 5.1k R2 2.4k C6 0.1uF Q1: APM2014N UC Q2: APM2014N UC Q3: APM2300A AC C2: 1000uF/10V, ESR = 25m Ω C5: 1000uF/6.3V, ESR = 25m Ω .ECKH/Figure 2. Absolute Maximum Ratings Symbol V CC V BOOT Parameter VCC Supply Voltage (VCC to GND) BOOT Supply Voltage (BOOT to GND) PHASE, OCSET to GND Input Voltage FB to GND Input Voltage Maxim um Junction Tem perature T STG T SDR V ESD Storage Tem perature Maxim um Soldering Tem perature, 10 Seconds Minim um ESD Rating Rating -0.3 ~ 7 -0.3 ~ 15 -0.3 ~ 12 -0.3 ~ V CC +0.3 125 -65 ~ 150 300 ±2 Unit V V V V o o o C C C kV Thermal Characteristics Symbol θJA Parameter Junction-to-Ambient Resistance in free air (SOP-8) 3 Value 160 Unit o C/W Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003 www.anpec.com.tw APW7057 Recommended Operating Conditions Symbol V CC V OUT V IN TA TJ VCC Supply Voltage Output Voltage of the Switching Regulator (Note) Input Voltage of the Switching Regulator (Note) Ambient Temperature Junction Temperature Parameter Range 5 ± 5% 0.8 ~ V CC 3.3 ~ V CC 0 ~ 70 0 ~ 125 Unit V V V o o C C Note : Refer to the typical application circuit  Electrical Characteristics Unless otherwise specified, these specifications apply over VCC=5V, VBOOT=12V and TA= 0~70 oC. Typical values are at TA=25oC. Symbol Parameter Test Conditions APW7057 Min Typ Max Unit SUPPLY CURRENT IVCC IBOOT VCC Nominal Supply Current BOOT Nominal Supply Current Rising VCC Threshold Falling VCC Threshold OSCILLATOR FOSC Free Running Frequency Ramp Upper Threshold Ramp Lower Threshold ∆V OSC VREF Ramp Amplitude Reference Voltage Reference Voltage Accuracy ERROR AMPLIFIER DC Gain FP FZ First Pole Frequency First Zero Frequency UGATE Duty Range FB Input Current Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003 4 UGATE and LGATE Open UGATE Open 2.1 2.1 mA mA Under Voltage Lockout(UVLO) 4.0 3.8 250 4.2 4.0 300 2.85 0.95 1.9 0.8 -1.5 +1.5 4.4 4.2 340 V V kHz V V VP-P V % REFERENCE VOLTAGE 75 10 1 0 100 0.1 dB Hz kHz % µA www.anpec.com.tw APW7057 Electrical Characteristics (Cont.) Unless otherwise specified, these specifications apply over VCC=5V, VBOOT=12V and TA= 0~70 oC. Typical values are at TA=25oC. Symbol Parameter Test Conditions APW7057 Min Typ 0.6 7.3 0.6 1.8 50 VOCSET=4.5V FB falling 34 40 0.5 15 46 Max Unit PWM CONTROLLER GATE DRIVERS UGATE Source UGATE Sink LGATE Source LGATE Sink TD IOCSET UVFB Dead Time OCSET Sink Current FB Under-Voltage Level FB Under-Voltage Hysteresis SOFT-START AND SHUTDOWN TSS Soft-Start Interval Shutdown Threshold OCSET Shutdown Hysteresis VOCSET Falling 2 1.25 20 mS V mV PROTECTION µA V mV VUAGTE=1V VUGATE=1V VLGATE=1V VLGATE=1V A Ω A Ω nS Functional Pin Description BOOT (Pin 1) This pin provides the supply voltage to the high side MOSFET driver. A voltage no greater than 13V can be connected to this pin as a supply to the driver. For driving logic level N-channel MOSEFT, a bootstrap circuit can be use to create a suitable driver’s supply. UGATE (Pin 2) This pin provides gate drive for the high-side MOSFET. GND (Pin 3) Signal and power ground for the IC. All voltage levels are measured with respect to this pin. Tie this pin to the ground plane through the lowest impedance connection available. Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003 5 LGATE (Pin 4) This pin provides the gate drive signal for the low side MOSFET. VCC (Pin 5) This is the main bias supply for the controller and its low side MOSFET driver. Must be closely decoupled to GND (Pin 3). DO NOT apply a voltage greater than 5.5V to this pin. FB (Pin 6) This pin is the inverting input of the error amplifier and it receives the feedback voltage from an exter- www.anpec.com.tw APW7057 Functional Pin Description nal resistive divider across the output (VOUT). The output voltage is determined by: VOUT = 0.8V(1+ ROUT ) RGND the over current limit. An internally generated 40uA current source will flow through this resistor, creating a voltage drop. This voltage will be compared with the voltage across the high side MOSFET. The threshold of the over current limit is therefore given where ROUT is the resistor connected between VOUT and FB while RGND is the resistor connected from FB to GND. OCSET (Pin 7) This pin serves two functions: as a shutdown control and for setting the over current limit threshold. Pulling this pin below 1.25V shuts the controller down, forcing the UGATE and LGATE signals to be at 0V. A soft start cycle will be initiated upon the release of this pin. A resistor (Rocset) connected between this pin and the drain of the high side MOSFET will determine PHASE (Pin 8) This pin is connected to the source of the high-side MOSFET and is used to monitor the voltage drop across the high-side MOSFET for over-current protection. by: IOI = 40uA x ROCSET RDS(ON) An over current condition will cycle the soft start function. After three consecutive cycles and if the fault condition persists, the controller will be shut down. To restart the controller, either recycle the VCC supply or momentarily pull the OSCSET pin below 1.25V. Typical Characteristics Reference Voltage vs. Junction Temperature 0.812 Switching Frequency vs. Junction Temperature 350 Switching Frequency, FOSC (kHz) 340 330 320 310 300 290 280 270 260 250 -50 -25 0 25 50 75 100 125 150 Reference Voltage, VREF (V) 0.808 0.804 0.800 0.796 0.792 0.788 -50 -25 0 25 50 75 100 125 150 Junction Temperature (oC) Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003 6 Junction Temperature (°C) www.anpec.com.tw APW7057 Typical Characteristics (Cont.) OCSET Current vs. Junction Temperature 46 45 44 43 42 41 40 39 38 37 36 35 34 -50 -25 0 25 50 75 100 125 150 OCSET Current , IOCSET (µA) Junction Temperature (oC) Operating Waveforms (Refer to the typical application circuit) 1. Load Transient Response : IOUT = 0A -> 10A -> 0A - IOUT slew rate = Ó 10A/µS IOUT = 0A -> 10A IOUT = 0A -> 10A -> 0A VOUT IOUT = 10A -> 0A VOUT VOUT VUGATE 10A VUGATE IOUT 0A IOUT IOUT Ch1 : VOUT, 100mV/Div, DC, Offset = 2.50V Ch2 : VUGATE, 10V/Div, DC Ax1 : IOUT, 5A/Div Time : 10µS/Div BW = 20MHz Ch1 : VOUT, 100mV/Div, DC, Offset = 2.50V Ax1 : IOUT, 5A/Div Time : 100µS/Div BW = 20MHz Ch1 : VOUT, 100mV/Div, DC, Offset = 2.50V Ch2 : VUGATE, 10V/Div, DC Ax1 : IOUT, 5A/Div Time : 10µS/Div BW = 20MHz Copyright  ANPEC Electronics Corp. Rev. A.3 - Oct., 2003 7 www.anpec.com.tw APW7057 Operating Waveforms 2. UGATE and LGATE UGATE Rising IOUT=10A VUGATE IOUT=10A VUGATE (Refer to the typical application circuit) UGATE Falling VLGATE VLGATE Ch1 : VUGATE, 2V/Div, DC Time : 125nS/Div Ch2 : VLGATE, 2V/Div, DC BW = 500MHz Ch1 : VUGATE, 2V/Div, DC