Low-Voltage Current-Mode Synchronous PWM Buck Regulator

FAN2013 2A Low-Voltage Current-Mode Synchronous PWM Buck Regulator November 2006 FAN2013 2A Low-Voltage Current-Mode Synchronous PWM Buck Regulator Features ■ 95% Efficiency, Synchronous Operation ■ Adjustable Output Voltage from 0.8V to VIN ■ 4.5V to 5.5V Input Voltage Range ■ Up to 2A Output Current ■ Fixed-Frequency 1.3MHz PWM Operation ■ 100% Duty Cycle, Low-Dropout Operation ■ Soft-Start Function ■ Excellent Load Transient Response ■ Power-Good Flag ■ Over-Voltage, Under-Voltage Lockout, Short-Circuit, Description The FAN2013 is a high-efficiency, low-noise synchronous PWM current mode DC-DC converter designed for low-voltage applications. It provides up to 2A continuous load current from the 4.5V to 5.5V input. The output voltage is adjustable over a wide range of 0.8V to VIN by means of an external voltage divider. The FAN2013 is enabled when the input voltage on the VIN pin exceeds the UVLO threshold. A current-mode control loop with a fast transient response ensures excellent line and load regulation. The fixed 1.3MHz switching frequency enables designers to choose a small, inexpensive external inductor and capacitor. Filtering can be accomplished with small components, reducing space and cost. and Thermal Shutdown Protections ■ 3x3mm 6-lead MLP Package Applications ■ Hard Disk Drive ■ Set-Top Box ■ Point-of-Load Power ■ Notebook Computer ■ Communications Equipment Protection features include input under-voltage lockout, short-circuit protection, and thermal shutdown. Soft-start www.DataSheet4U.com limits in-rush current during start-up conditions. The device is available in a 3x3mm 6-lead MLP. Typical Application PG +5V VIN PVIN 10µF 6 5 4 1 FB PGND SW P1 (AGND) 10K L1 2 3 R2 R1 VOUT 40µF 2.2µH Figure 1. Typical Application Ordering Information Part Number FAN2013MPX Output Voltage 0.8V - VIN Pb-Free Yes Package Type MLP-6 3x3mm Packing Method Tape and Reel © 2006 Fairchild Semiconductor Corporation FAN2013 Rev. 1.0.0 www.fairchildsemi.com FAN2013 2A Low-Voltage Current-Mode Synchronous PWM Buck Regulator Pin Assignment Top View FB PGND SW 1 2 6 PG VIN PVIN P1 (AGND) 5 3 4 3x3mm 6-Lead MLP Figure 2. FAN2013 Pin Assignment Pin Description Pin # P1 1 2 3 4 5 6 Name AGND FB PGND SW PVIN VIN PG Description Analog Ground. P1 must be soldered to the PCB ground. Feedback Input. Adjustable voltage option; connect this pin to the resistor divider. Power Ground. This pin is connected to the internal MOSFET switches. This pin must be externally connected to AGND. Switching Node. This pin is connected to the internal MOSFET switches. Supply Voltage Input. This pin is connected to the internal MOSFET switches. Supply Voltage Input. Open Drain Power Good. © 2006 Fairchild Semiconductor Corporation FAN2013 Rev. 1.0.0 2 www.fairchildsemi.com FAN2013 2A Low-Voltage Current-Mode Synchronous PWM Buck Regulator Absolute Maximum Ratings Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Absolute maximum ratings apply individually only, not in combination. Unless otherwise specified, all other voltages are referenced to AGND. Symbol VIN θJC TL TSTG TJ Supply Voltage PVIN and any other pin Parameter Min. -0.3 -0.3 (1) Max. 6.2 VIN 8 260 Unit. V V °C/W °C °C °C kV Thermal Resistance-Junction to Tab, 3x3mm 6-lead MLP Lead Soldering Temperature (10 seconds) Storage Temperature Junction Temperature Electrostatic Discharge (ESD) Protection Level (2) -65 -40 HBM CDM 3.5 2 150 150 Notes: 1. Junction-to-ambient thermal resistance, θJA, is a strong function of PCB material, board thickness, thickness and number of copper planes, number of via used, diameter of via used, available copper surface, and attached heat sink characteristics. 2. Using Mil Std. 883E, method 3015.7 (Human Body Model) and EIA/JESD22C101-A (Charge Device Model). Recommended Operating Conditions Symbol VIN VOUT IOUT L CIN COUT TA Supply Voltage Range Output Voltage Range, Adjustable Version Output Current Inductor(3) Input Capacitor(3) Output Capacitor(3) Operating Ambient Temperature Range 10 20 -40 2.2 20 40 +85 Parameter Min. 4.5 0.8 Typ. Max. 5.5 VIN 2.0 Unit V V A μH μF μF °C Notes: 3. Refer to the Applications Information section for further details. © 2006 Fairchild Semiconductor Corporation FAN2013 Rev. 1.0.0 3 www.fairchildsemi.com FAN2013 2A Low-Voltage Current-Mode Synchronous PWM Buck Regulator Electrical Characteristics VIN = 4.5V to 5.5V, VOUT = 1.2V, IOUT = 200mA, CIN = 10µF, COUT = 40µF, L = 2.2µH, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C. Parameter Input Voltage Quiescent Current UVLO Threshold PMOS On Resistance NMOS On Resistance P-Channel Current Limit Over-Temperature Protection Switching Frequency Line Regulation Load Regulation Output Voltage During Load Transition(4) Output Voltage During Load Transition(4) Reverse Leakage Current into Pin SW Reference Voltage, VREF Conditions IOUT = 0mA VIN rising Hysteresis VIN = VGS = 5V VIN = VGS = 5V 4.5V < VIN < 5.5V Rising temperature Hysteresis Min. 4.5 Typ. 5 Max. 5.5 10 4.0 Units V mA V mV mΩ mΩ 3.5 3.7 150 90 90 2.8 3.5 150 20 4.2 A °C °C 1000 VIN = 4.5 to 5.5V IOUT = 100mA 0mA ≤ IOUT ≤ 2000mA IOUT from 1500mA to 100mA COUT = 60µF IOUT from 100mA to 1500mA COUT = 60µF VIN = Open, EN = GND, Vsw = 5.5V VIN = 4.5 to 5.5V 0mA ≤ IOUT ≤ 2000mA TA = 0C to +85C VIN = 4.5 to 5.5V 0mA ≤ IOUT ≤ 2000mA TA = -40C to +85C FB voltage rising Hysteresis Isink=6mA, open drain output -5 1300 0.16 0.2 1600 kHz %/V 0.6 5 % % % 0.1 0.8 -2 1 µA V 2 % Output Voltage Accuracy -3 0.95 x VOUT 2 100 3 % V % µs Power Good Output Threshold and Hysteresis Power Good Output Delay Power Good Output Voltage Low 0.4 1.07 x VOUT 2 V V % Over-Voltage Protection (OVP) Threshold and FB voltage rising Hysteresis Hysteresis Notes: 4. Refer to the load transient response test waveform in Figure 3. ILOAD (mA) 1500 tr = 100nsec ss tf = 100nsec 100 0 ss 0.6 ssss 4.6 Time (msec) Figure 3. Load Transient Response Test Waveform © 2006 Fairchild Semiconductor Corporation FAN2013 Rev. 1.0.0 4 www.fairchildsemi.com FAN2013 2A Low-Voltage Current-Mode Synchronous PWM Buck Regulator Typical Performance Characteristics TA = 25°C, CIN = 10µF, COUT = 40µF, L = 2.2µH, VIN = 5V, VOUT = 1.2V unless otherwise noted. Figure 4. Start-up with 100mA Resistive Load Figure 5. Start-up with 2A Resistive Load Figure 6. Load Transient Response 1.5A to 100mA Figure 7. Load Transient Response 100mA to 1.5A Figure 8. Output Voltage Regulation Figure 9. Power Efficiency © 2006 Fairchild Semiconductor Corporation FAN2013 Rev. 1.0.0 5 www.fairchildsemi.com FAN2013 2A Low-Voltage Current-Mode Synchronous PWM Buck Regulator Block Diagram PG VIN PVIN REF FB PG COMP UNDER VOLTAGE LOCKOUT IS CURRENT SENSE GND DIGITAL SOFT START FB ERROR AMP 0.8V COMP LOGIC CONTROL MOSFET DRIVER SW GND IS OVER VOLTAGE COMP OSC SLOPE COMPENSATION REF FB GND Figure 10. Block Diagram Operation Description The FAN2013 is a step-down pulse-width modulated (PWM) current mode converter with a fixed switching frequency of 1.3MHz. At the rising edge of each clock cycle, the P-channel transistor is turned on until the PWM comparator trips or the current limit is reached. During the ON time, the inductor current ramps up and is monitored by the internal current-mode control loop. After a minimum dead time, the N-channel transistor is turned ON and the inductor current ramps down. As the clock cycle is completed, the N-channel switch is turned OFF and the next clock cycle starts. The duty cycle is given by the ratio of output voltage and input voltage. The converter runs at minimum duty cycle when output voltage is at minimum and input voltage is at maximum, and at 100% duty cycle when the input voltage approaches the output voltage, as described below. ble voltage drops of the input voltage and eliminates the output voltage overshoot. The soft-start is implemented as a digital circuit, increasing the switch current in four steps to the P-channel current limit (3.5A). Typical startup time for a 40µF output capacitor with a load current of 2.0A is 800µs. Output Over-Voltage Protection When output voltage, VOUT, reaches approximately 7% above the nominal value, the device turns OFF the Pchannel switch and turns ON part of the N-channel transistor with a built-in current limit of about 400mA. When VOUT reaches the hysteresis of about 2%, the device starts switching normally in closed loop. If output voltage is pulled up by an external voltage source with a current limit higher than typical 400mA, the output voltage stays up at the external voltage source level. The over-voltage protection is designed to limit the output voltage excursion in case of a transient response from full load to a minimum load. 100% Duty Cycle Operation As the input voltage approaches the output voltage and the duty cycle exceeds the typical 95%, the converter turns the P-channel transistor continuously on. In this mode, the output voltage is equal to the input voltage, minus the voltage drop across the P-channel transistor: VOUT = VIN – ILOAD × (RDS_ON + RL) EQ 1 where RDS_ON = P-channel switch ON resistance ILOAD = Output current RL = Inductor DC resistance Output Short-Circuit Protection The switch peak current is limited cycle by cycle to a typical value of 3.5A. In the event of an output voltage short circuit, the device operates with a frequency of 400kHz and minimum duty cycle, making the average typical input current .45A. UVLO and Soft Star