FAN53601 / FAN53611 6 MHz, 600 mA / 1 A Synchronous Buck Regulator Features 600 mA or 1 A Output Current Capability 24 A Typical Quiescent Current 6 MHz Fixed-Frequency Operation Best-in-Class Load Transient Response Best-in-Class Efficiency 2.3 V to 5.5 V Input Voltage Range Low Ripple Light-Load PFM Mode Forced PWM and External Clock Synchronization Internal Soft-Start Input Under-Voltage Lockout (UVLO) Thermal Shutdown and Overload Protection Optional Output Discharge 6-Bump WLCSP, 0.4 mm Pitch Applications 3G, 4G, WiFi(R), WiMAXTM, and WiBro(R) Data Cards Tablets DSC, DVC Netbooks(R), Ultra-Mobile PCs Description The FAN53601/11 is a 6 MHz, step-down switching voltage regulator, available in 600 mA or 1 A options, that delivers a fixed output from an input voltage supply of 2.3 V to 5.5 V. Using a proprietary architecture with synchronous rectification, the FAN53601/11 is capable of delivering a peak efficiency of 92%, while maintaining efficiency over 80% at load currents as low as 1 mA. The regulator operates at a nominal fixed frequency of 6 MHz, which reduces the value of the external components to as low as 470 nH for the output inductor and 4.7 F for the output capacitor. In addition, the Pulse Width Modulation (PWM) modulator can be synchronized to an external frequency source. At moderate and light loads, Pulse Frequency Modulation (PFM) is used to operate the device in Power-Save Mode with a typical quiescent current of 24 A. Even with such a low quiescent current, the part exhibits excellent transient response during large load swings. At higher loads, the system automatically switches to fixed-frequency control, operating at 6 MHz. In Shutdown Mode, the supply current drops below 1 A, reducing power consumption. For applications that require minimum ripple or fixed frequency, PFM Mode can be disabled using the MODE pin. The FAN53601/11 is available in 6-bump, 0.4 mm pitch, Wafer-Level Chip-Scale Package (WLCSP). MODE All trademarks are the property of their respective owners. L1 SW A1 A2 B1 B2 C1 C2 VIN CIN 2.2F EN 470nH FB 4.7F GND COUT Figure 1. Typical Application (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator October 2015 Part Number Output (1) Voltage Max. Output Current Active (2) Discharge Max. VIN Package 1.000 V 1.050 V 1.100 V 1.150 V 1.300 V 1.350 V 1.233 V 1.820 V 2.050 V 1.233 V 1.200 V 1.800 V 600 mA 600 mA 1A 1A 1A 1A 1A 600 mA 1A 1A 1A 1A Yes Yes Yes Yes Yes Yes No No Yes Yes Yes Yes 5.5 V WLCSP-6, 0.4 mm Pitch FAN53601AUC10X FAN53601AUC105X FAN53611AUC11X FAN53611AUC115X FAN53611AUC13X FAN53611AUC135X FAN53611UC123X FAN53601UC182X FAN53611AUC205X FAN53611AUC123X FAN53611AUC12X FAN53611AUC18X Temperature Packing Range -40 to +85C Tape and Reel Notes: 1. Other voltage options available on request. Contact a Fairchild representative. 2. All voltage and output current options are available with or without active discharge. Contact a Fairchild representative. Pin Configurations MODE A1 A2 VIN VIN A2 A1 MODE SW B1 B2 EN EN B2 B1 SW FB C1 C2 GND GND C2 C1 FB Figure 2. Bumps Facing Down Figure 3. Bumps Facing Up Pin Definitions Pin # Name A1 MODE Description MODE. Logic 1 on this pin forces the IC to stay in PWM Mode. A logic 0 allows the IC to automatically switch to PFM during light loads. The regulator also synchronizes its switching frequency to four times the frequency provided on this pin. Do not leave this pin floating. B1 SW Switching Node. Connect to output inductor. C1 FB Feedback / VOUT. Connect to output voltage. C2 GND B2 EN Enable. The device is in Shutdown Mode when voltage to this pin is < 0.4 V and enabled when > 1.2 V. Do not leave this pin floating. A2 VIN Input Voltage. Connect to input power source. Ground. Power and IC ground. All signals are referenced to this pin. (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com 2 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Ordering Information Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. Symbol VIN VSW VCTRL Parameter Input Voltage Min. Max. -0.3 7.0 Units V (3) V (3) V (3) V Voltage on SW Pin -0.3 VIN + 0.3 EN and MODE Pin Voltage -0.3 VIN + 0.3 Other Pins -0.3 VIN + 0.3 Human Body Model per JESD22-A114 2.0 Charged Device Model per JESD22-C101 1.5 ESD Electrostatic Discharge Protection Level TJ Junction Temperature -40 +150 C TSTG Storage Temperature -65 +150 C +260 C TL Lead Soldering Temperature, 10 Seconds kV Note: 3. Lesser of 7 V or VIN+0.3 V. Recommended Operating Conditions The Recommended Operating Conditions table defines the conditions for actual device operation. Recommended operating conditions are specified to ensure optimal performance to the datasheet specifications. Fairchild does not recommend exceeding them or designing to Absolute Maximum Ratings. Symbol VCC IOUT L CIN COUT Parameter Min. Max. Units 2.3 5.5 V Output Current for FAN53601 0 600 mA Output Current for FAN53611 0 1 A Supply Voltage Range Inductor Typ. 470 Input Capacitor nH 2.2 Output Capacitor 1.6 TA Operating Ambient Temperature TJ Operating Junction Temperature 4.7 F 12.0 F -40 +85 C -40 +125 C Thermal Properties Junction-to-ambient thermal resistance is a function of application and board layout. This data is measured with four-layer 2s2p boards in accordance to JEDEC standard JESD51. Special attention must be paid to not exceed junction temperature TJ(max) at a given ambient temperature TA. Symbol JA Parameter Junction-to-Ambient Thermal Resistance (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 Typical Unit 125 C/W www.fairchildsemi.com 3 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Absolute Maximum Ratings Minimum and maximum values are at VIN = VEN = 2.3 V to 5.5 V, VMODE = 0 V (AUTO Mode), TA = -40C to +85C; circuit of Figure 1 , unless otherwise noted. Typical values are at TA = 25C, VIN = VEN = 3.6 V. Symbol Parameter Conditions Min. Typ. Max. No Load, Not Switching 24 50 PWM Mode 8 Units Power Supplies IQ I(SD) VUVLO Quiescent Current Shutdown Supply Current EN = GND, VIN = 3.6 V Under-Voltage Lockout Threshold Rising VIN VUVHYST Under-Voltage Lockout Hysteresis A mA 0.25 1.00 A 2.15 2.27 V 200 mV Logic Inputs: EN and MODE Pins VIH Enable HIGH-Level Input Voltage VIL Enable LOW-Level Input Voltage VLHYST Logic Input Hysteresis Voltage IIN Enable Input Leakage Current 1.2 V 0.4 100 Pin to VIN or GND V mV 0.01 1.00 A Switching and Synchronization fSW fSYNC (4) Switching Frequency (4) MODE Synchronization Range VIN = 3.6 V, TA = 25C, PWM Mode, ILOAD = 10 mA 5.4 6.0 6.6 MHz Square Wave at MODE Input 1.3 1.5 1.7 MHz ILOAD = 0 to 600 mA 0.953 1.000 1.048 PWM Mode 0.967 1.000 1.034 ILOAD = 0 to 1 A 1.298 1.350 1.402 PWM mode 1.309 1.350 1.391 ILOAD = 0 to 1 A 1.185 1.233 1.281 PWM Mode 1.192 1.233 1.274 ILOAD = 0 to 600 mA 1.755 1.820 1.885 PWM Mode 1.781 1.820 1.859 ILOAD = 0 to 1 A 1.054 1.100 1.147 PWM Mode 1.061 1.100 1.140 ILOAD = 0 to 1 A 1.250 1.300 1.350 PWM Mode 1.259 1.300 1.341 ILOAD = 0 to 1 A 1.104 1.150 1.196 PWM Mode 1.110 1.150 1.190 ILOAD = 0 to 600 mA 1.003 1.050 1.097 PWM Mode 1.016 1.050 1.084 ILOAD = 0 to 1 A, VIN = 2.7 V to 5.5 V 1.973 2.050 2.127 PWM Mode, VIN = 2.7 V to 5.5 V 2.004 2.050 2.096 ILOAD = 0 to 1 A 1.152 1.200 1.248 PWM Mode 1.160 1.200 1.240 ILOAD = 0 to 1 A 1.732 1.800 1.868 PWM Mode 1.756 1.800 1.844 180 300 Regulation 1.000 V 1.35 V 1.233 V 1.820 V 1.100 V VO Output Voltage Accuracy 1.300 V 1.150 V 1.050 V 2.050 V 1.200 V 1.800 V tSS Soft-Start VIN = 4.5 V, From EN Rising Edge (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 4 V s www.fairchildsemi.com FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Electrical Characteristics Minimum and maximum values are at VIN = VEN = 2.3 V to 5.5 V, VMODE = 0 V (AUTO Mode), TA = -40C to +85C; circuit of Figure 1 , unless otherwise noted. Typical values are at TA = 25C, VIN = VEN = 3.6 V. Symbol Parameter Conditions Min. Typ. Max. Units Output Driver RDS(on) ILIM(OL) VIN = VGS = 3.6 V 175 m NMOS On Resistance VIN = VGS = 3.6 V 165 m PMOS Peak Current Limit Open-Loop for FAN53601, VIN = 3.6 V, TA = 25C 900 1100 1250 mA Open-Loop for FAN53611, VIN = 3.6 V, TA = 25C 1500 1750 2000 mA 230 Thermal Shutdown 150 C Thermal Shutdown Hysteresis 15 C RDIS Output Discharge Resistance TTSD THYS Notes: 4. 5. PMOS On Resistance EN = GND Limited by the effect of tOFF minimum (see Operation Description section). The Electrical Characteristics table reflects open-loop data. Refer to the Operation Description and Typical Characteristics Sections for closed-loop data. (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com 5 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Electrical Characteristics (Continued) Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25C. 95% Efficiency Efficiency 90% 85% 80% 75% 2.7 3.6 4.2 5.0 70% 0 200 400 600 800 VIN VIN VIN VIN 92% 90% 88% 86% 84% 82% 80% 78% 76% 74% 72% 70% 68% 66% 64% 62% 60% 1000 - 40C, AUTO +25C, AUTO +85C, AUTO - 40C, PWM +25C, PWM +85C, PWM 0 200 400 Load Current (mA) 1000 Figure 5. Efficiency vs. Load Current and Temperature, Auto Mode, Dotted for FPWM 90% 90% 88% 88% 86% 86% 84% 84% 82% 82% 80% 80% Efficiency Efficiency 800 Load Current (mA) Figure 4. Efficiency vs. Load Current and Input Voltage, Auto Mode, Dotted for Decreasing Load 78% 76% 74% 78% 76% 74% 72% 70% 72% - 40C, AUTO +25C, AUTO +85C, AUTO - 40C, PWM +25C, PWM +85C, PWM 68% 70% 2.7 3.6 4.2 5.0 68% 66% 64% 0 200 400 600 800 66% VIN VIN VIN VIN 64% 62% 60% 1000 0 200 400 Load Current (mA) 600 800 1000 Load Current (mA) Figure 6. Efficiency vs. Load Current and Input Voltage, VOUT = 1.23 V, Auto Mode, Dotted for Decreasing Load 3 Figure 7. Efficiency vs. Load Current and Temperature, VOUT = 1.23 V, Auto Mode, Dotted for FPWM 90% 2.7VIN, AUTO 3.6VIN, AUTO 4.2VIN, AUTO 2 88% 86% 84% 5.0VIN, AUTO 2.7VIN, PWM 3.6VIN, PWM 4.2VIN, PWM 5.0VIN, PWM 1 82% Efficiency Output Regulation (%) 600 0 80% 78% 76% 74% 72% 70% -1 2.7 VIN 3.6 VIN 4.2 VIN 5.0 VIN 68% 66% -2 64% 0 100 200 300 400 500 600 0 Load Current (mA) 200 300 400 500 600 Load Current (mA) Figure 8. Output Regulation vs. Load Current, VOUT = 1.00 V, Dotted for Auto Mode (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 100 Figure 9. Efficiency vs. Load Current, VOUT = 1.00 V, Dotted for Decreasing Load www.fairchildsemi.com 6 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Typical Performance Characteristics Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25C. 3 3 2.7VIN, AUTO 3.6VIN, AUTO 4.2VIN, AUTO 5.0VIN, AUTO 2.7VIN, PWM 3.6VIN, PWM 4.2VIN, PWM 5.0VIN, PWM 1 2 Output Regulation (%) Output Regulation (%) 2 2.7VIN, AUTO 3.6VIN, AUTO 4.2VIN, AUTO 5.0VIN, AUTO 2.7VIN, PWM 3.6VIN, PWM 4.2VIN, PWM 5.0VIN, PWM 0 -1 1 0 -1 -2 -2 0 200 400 600 800 1000 0 200 Load Current (mA) Figure 10. VOUT (%) vs. Load Current and Input Voltage, Normalized to 3.6 VIN, 500 mA Load, FPWM, Dotted for Auto Mode 600 800 350 350 300 300 250 200 150 100 250 200 150 100 PWM PWM PFM PFM 50 50 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.5 3.0 Input Voltage (V) 35 4.0 4.5 5.0 5.5 Figure 13. PFM / PWM Boundary vs. Input Voltage, VOUT = 1.23 V 15 - 40C, EN=VIN +25C, EN=VIN +85C, EN=VIN - 40C, EN=1.8V +25C, EN=1.8V +85C, EN=1.8V - 40C +25C +85C 12 Input Current (mA) 30 3.5 Input Voltage (V) Figure 12. PFM / PWM Boundary vs. Input Voltage Input Current (A) 1000 Figure 11. VOUT (%) vs. Load Current and Input Voltage, VOUT = 1.23 V, Normalized to 3.6 VIN, 500 mA Load, FPWM, Dotted for Auto Mode Load Current (mA) Load Current (mA) 400 Load Current (mA) 25 9 6 20 3 15 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 2.5 Input Voltage (V) 3.5 4.0 4.5 5.0 5.5 Input Voltage (V) Figure 14. Quiescent Current vs. Input Voltage and Temperature, Auto Mode; EN = VIN Solid, Dotted for o o o EN=1.8 V (-40 C, +25 C, +85 C) (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 3.0 Figure 15. Quiescent Current vs. Input Voltage and Temperature, Mode = EN = VIN (FPWM) www.fairchildsemi.com 7 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Typical Performance Characteristics (Continued) Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25C. 25 Switching Frequency (KHz) 20 Output Ripple (mVpp) 7,500 2.7VIN, AUTO 3.6VIN, AUTO 5.0VIN, AUTO 2.7VIN, PWM 3.6VIN, PWM 5.0VIN, PWM 15 10 5 6,000 4,500 3,000 2.7VIN, AUTO 3.6VIN, AUTO 5.0VIN, AUTO 1,500 2.7VIN, PWM 3.6VIN, PWM 0 5.0VIN, PWM 0 0 200 400 600 800 1000 0 Load Current (mA) 200 400 600 800 1000 Load Current (mA) Figure 16. Output Ripple vs. Load Current and Input Voltage, FPWM, Dotted for Auto Mode Figure 17. Frequency vs. Load Current and Input Voltage, Auto Mode, Dotted for FPWM Figure 18. Load Transient, 10-200-10 mA, 100 ns Edge Figure 19. Load Transient, 200-800-200 mA, 100 ns Edge Figure 20. Line Transient, 3.3-3.9-3.3 VIN, 10 s Edge, 36 mA Load Figure 21. Line Transient, 3.3-3.9-3.3 VIN, 10 s Edge, 600 mA Load (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com 8 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Typical Performance Characteristics (Continued) Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25C. Figure 22. Combined Line / Load Transient, 3.9-3.3 VIN, Figure 23. Combined Line / Load Transient, 3.3-3.9 VIN, 10 s Edge, 36-400 mA Load, 100 ns Edge 10 s Edge, 400-36 mA Load, 100 ns Edge Figure 24. Startup, 50 Load Figure 25. Startup, 3 Load Figure 26. Shutdown, 10k Load, No Output Discharge Figure 27. Shutdown, No Load, Output Discharge Enabled (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com 9 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Typical Performance Characteristics (Continued) Unless otherwise noted, VIN = VEN = 3.6 V, VMODE = 0 V (AUTO Mode), VOUT = 1.82 V, and TA = 25C. Figure 28. Over-Current, Load Increasing Past Current Limit, FAN53601 Figure 29. 250 m Fault, Rapid Fault, Hiccup, FAN53601 Figure 30. Over-Current, Load Increasing Past Current Limit, FAN53611 Figure 31. 250 m Fault, Rapid Fault, Hiccup, FAN53611 70 70 36mA Load 24mA Load 600mA Load 500mA Load 60 50 PSRR (dB) PSRR (dB) 60 40 30 50 40 30 20 20 0.1 1 10 100 1000 0.1 Frequency (KHz) 10 100 1000 Frequency (KHz) Figure 32. PSRR, 50 and 3 Load (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 1 Figure 33. PSRR, 50 and 3 Load, VOUT = 1.23 V www.fairchildsemi.com 10 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Typical Performance Characteristics (Continued) The FAN53601/11 is a 6 MHz, step-down switching voltage regulator available in 600 mA or 1 A options that delivers a fixed output from an input voltage supply of 2.3 V to 5.5 V. Using a proprietary architecture with synchronous rectification, the FAN53601/11 is capable of delivering a peak efficiency of 92%, while maintaining efficiency over 80% at load currents as low as 1 mA. IDISP COUT where dV dt (1) dV refers to the soft-start slew rate. dt To prevent shut down during soft-start, the following condition must be met: The regulator operates at a nominal fixed frequency of 6 MHz, which reduces the value of the external components to as low as 470 nH for the output inductor and 4.7 F for the output capacitor. In addition, the PWM modulator can be synchronized to an external frequency source. IDISP ILOAD IMAX(DC) (2) where IMAX(DC) is the maximum load current the IC is guaranteed to support. Control Scheme Startup into Large COUT The FAN53601/11 uses a proprietary, non-linear, fixedfrequency PWM modulator to deliver a fast load transient response, while maintaining a constant switching frequency over a wide range of operating conditions. The regulator performance is independent of the output capacitor ESR, allowing for the use of ceramic output capacitors. Although this type of operation normally results in a switching frequency that varies with input voltage and load current, an internal frequency loop holds the switching frequency constant over a large range of input voltages and load currents. Multiple soft-start cycles are required for no-load startup if COUT is greater than 15 F. Large COUT requires light initial load to ensure the FAN53601/11 starts appropriately. The IC shuts down for 1.3 ms when IDISP exceeds ILIMIT for more than 200 s of current limit. The IC then begins a new softstart cycle. Since COUT retains its charge when the IC is off, the IC reaches regulation after multiple soft-start attempts. MODE Pin Logic 1 on this pin forces the IC to stay in PWM Mode. A logic 0 allows the IC to automatically switch to PFM during light loads. If the MODE pin is toggled with a frequency between 1.3 MHz and 1.7 MHz, the converter synchronizes its switching frequency to four times the frequency on the MODE pin. For very light loads, the FAN53601/11 operates in Discontinuous Current Mode (DCM) single-pulse PFM Mode, which produces low output ripple compared with other PFM architectures. Transition between PWM and PFM is seamless, allowing for a smooth transition between DCM and CCM. The MODE pin is internally buffered with a Schmitt trigger, which allows the MODE pin to be driven with slow rise and fall times. An asymmetric duty cycle for frequency synchronization is also permitted as long as the minimum time below VIL(MAX) or above VIH(MAX) is 100 ns. Combined with exceptional transient response characteristics, the very low quiescent current of the controller maintains high efficiency; even at very light loads; while preserving fast transient response for applications requiring tight output regulation. Current Limit, Fault Shutdown, and Restart Enable and Soft-Start A heavy load or short circuit on the output causes the current in the inductor to increase until a maximum current threshold is reached in the high-side switch. Upon reaching this point, the high-side switch turns off, preventing high currents from causing damage. The regulator continues to limit the current cycle-by-cycle. After 16 cycles of current limit, the regulator triggers an over-current fault, causing the regulator to shut down for about 1.3 ms before attempting a restart. When EN is LOW, all circuits are off and the IC draws ~250 nA of current. When EN is HIGH and VIN is above its UVLO threshold, the regulator begins a soft-start cycle. The output ramp during soft-start is a fixed slew rate of 50 mV/s from Vout = 0 to 1 V, then 12.5 mV/s until the output reaches its setpoint. Regardless of the state of the MODE pin, PFM Mode is enabled to prevent current from being discharged from COUT if soft-start begins when COUT is charged. If the fault is caused by short circuit, the soft-start circuit attempts to restart and produces an over-current fault after about 200 s, which results in a duty cycle of less than 15%, limiting power dissipation. In addition, all voltage options can be ordered with a feature that actively discharges FB to ground through a 230 path when EN is LOW. Raising EN above its threshold voltage activates the part and starts the soft-start cycle. During softstart, the internal reference is ramped using an exponential RC shape to prevent overshoot of the output voltage. Current limiting minimizes inrush during soft-start. The closed-loop peak-current limit is not the same as the open-loop tested current limit, ILIM(OL), in the Electrical Characteristics table. This is primarily due to the effect of propagation delays of the IC current limit comparator. The current-limit fault response protects the IC in the event of an over-current condition present during soft-start. As a result, the IC may fail to start if heavy load is applied during startup and/or if excessive COUT is used. Under-Voltage Lockout (UVLO) When EN is HIGH, the under-voltage lockout keeps the part from operating until the input supply voltage rises high enough to properly operate. This ensures no misbehavior of the regulator during startup or shutdown. The current required to charge COUT during soft-start commonly referred to as "displacement current" is given as: (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com 11 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Operation Description 1 fSW min , 6MHz tSW ( MAX ) When the die temperature increases, due to a high load condition and/or a high ambient temperature; the output switching is disabled until the die temperature falls sufficiently. The junction temperature at which the thermal shutdown activates is nominally 150C with a 15C hysteresis. (3) where: VOUT IOUT ROFF tSW ( MAX ) 40ns 1 V IN IOUT RON VOUT Minimum Off-Time Effect on Switching Frequency (4) where: tOFF(MIN) is 40 ns. This imposes constraints on the maximum VOUT that the FAN53601/11 can provide or the maximum VIN output voltage it can provide at low VIN while maintaining a fixed switching frequency in PWM Mode. ROFF = RDSON _ N DCR L RON = RDSON _ P DCR L When VIN is LOW, fixed switching is maintained as long as: VOUT 1 tOFF ( MIN ) fSW 0.7 . VIN The switching frequency drops when the regulator cannot provide sufficient duty cycle at 6 MHz to maintain regulation. This occurs when VOUT is 1.82 V and VIN is below 2.7 V at high load currents (see Figure 34). Switching Frequency (KHz) 7,500 6,000 4,500 2.7VIN, AUTO 2.3VIN, AUTO 2.7VIN, PWM 2.3VIN, PWM 3,000 1,500 0 0 200 400 600 800 1000 Load Current (mA) Figure 34. Frequency vs. Load Current to Demonstrate tOFFMIN Effect, VIN = 2.3 V and 2.7 V, VOUT = 1.82 V, Auto Mode, FPWM Dotted (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com 12 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator The calculation for switching frequency is given by: Thermal Shutdown (TSD) The increased RMS current produces higher losses through the RDS(ON) of the IC MOSFETs, as well as the inductor DCR. Selecting the Inductor The output inductor must meet both the required inductance and the energy-handling capability of the application. The inductor value affects average current limit, the PWM-toPFM transition point, output voltage ripple, and efficiency. Increasing the inductor value produces lower RMS currents, but degrades transient response. For a given physical inductor size, increased inductance usually results in an inductor with lower saturation current and higher DCR. The ripple current (I) of the regulator is: Table 1 shows the effects of inductance higher or lower than the recommended 1 H on regulator performance. V VOUT V I OUT IN (5) VIN L fSW The maximum average load current, IMAX(LOAD), is related to the peak current limit, ILIM(PK), by the ripple current, given by: IMAX (LOAD) ILIM(PK) I 2 Output Capacitor Table 2 suggests 0402 capacitors. 0603 capacitors may further improve performance in that the effective capacitance is higher. This improves transient response and output ripple. (6) Increasing COUT has no effect on loop stability and can therefore be increased to reduce output voltage ripple or to improve transient response. Output voltage ripple, VOUT, is: The transition between PFM and PWM operation is determined by the point at which the inductor valley current crosses zero. The regulator DC current when the inductor current crosses zero, IDCM, is: IDCM I 2 f C ESR2 1 VOUT IL SW OUT 2 D 1 D 8 fSW COUT (7) Input Capacitor The FAN53601/11 is optimized for operation with L = 470 nH, but is stable with inductances up to 1 H (nominal). The inductor should be rated to maintain at least 80% of its value at ILIM(PK). The 2.2 F ceramic input capacitor should be placed as close as possible between the VIN pin and GND to minimize the parasitic inductance. If a long wire is used to bring power to the IC, additional "bulk" capacitance (electrolytic or tantalum) should be placed between CIN and the power source lead to reduce the ringing that can occur between the inductance of the power source leads and CIN. Efficiency is affected by the inductor DCR and inductance value. Decreasing the inductor value for a given physical size typically decreases the DCR; but because I increases, the RMS current increases, as do the core and skin effect losses. IRMS (9) IOUT (DC) 2 I2 12 The effective capacitance value decreases as V IN increases due to DC bias effects. (8) Table 1. Effects of Changes in Inductor Value (from 470 nH Recommended Value) on Regulator Performance IMAX(LOAD) VOUT Transient Response Increase Increase Decrease Degraded Decrease Decrease Increase Improved Inductor Value Table 2. Recommended Passive Components and their Variation Due to DC Bias Component Description Vendor Min. Typ. Max. L1 470 nH, 2012,90 m, 1.1 A Murata LQM21PNR47MC0 Murata LQM21PNR54MG0 Hitachi Metals HLSI 201210R47 300 nH 470 nH 520 nH CIN 2.2 F, 6.3 V, X5R, 0402 Murata or Equivalent GRM155R60J225ME15 GRM188R60J225KE19D 1.0 F 2.2 F COUT 4.7 F, X5R, 0402 Murata or Equivalent GRM155R60G475M GRM155R60E475ME760 1.6 F 4.7 F (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com 13 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator Applications Information There are only three external components: the inductor and the input and output capacitors. For any buck switcher IC, including the FAN53601/11, it is important to place a low-ESR input capacitor very close to the IC, as shown in Figure 35. The input capacitor ensures good input decoupling, which helps reduce noise appearing at the output terminals and ensures that the control sections of the IC do not behave erratically due to excessive noise. This reduces switching cycle jitter and ensures good overall performance. It is important to place the common GND of CIN and COUT as close as possible to the C2 terminal. There is some flexibility in moving the inductor further away from the IC; in that case, VOUT should be considered at the COUT terminal. Figure 35. PCB Layout Guidance The following information applies to the WLCSP package dimensions on the next page: Product-Specific Dimensions D E X Y 1.160 0.030 0.860 0.030 0.230 0.180 (c) 2010 Fairchild Semiconductor Corporation FAN53601 / FAN53611 * Rev. 1.8 www.fairchildsemi.com 14 FAN53601 / FAN53611 -- 6 MHz 600 mA / 1 A Synchronous Buck Regulator PCB Layout Guidelines F 0.03 C E 2X A 0.40 B A1 BALL A1 INDEX AREA D (O0.20) Bottom of Cu Pad 0.40 F (O0.30) Solder Mask Opening 0.03 C 2X TOP VIEW RECOMMENDED LAND PATTERN (NSMD PAD TYPE) 0.06 C 0.05 C 0.3780.018 0.2080.021 0.5860.039 E SEATING PLANE C D SIDE VIEWS NOTES: A. NO JEDEC REGISTRATION APPLIES. B. DIMENSIONS ARE IN MILLIMETERS. O0.2600.010 6X 0.40 0.005 C B 0.40 (Y) +/-0.015 A F 1 2 (X) +/-0.015 BOTTOM VIEW C A B C. DIMENSIONS AND TOLERANCES PER ASMEY14.5M, 2009. D. DATUM C, THE SEATING PLANE IS DEFINED BY THE SPHERICAL CROWNS OF THE BALLS. E. PACKAGE TYPICAL HEIGHT IS 586 MICRONS 39 MICRONS (547-625 MICRONS). F. FOR DIMENSIONS D, E, X, AND Y, SEE PRODUCT DATASHEET. G. DRAWING FILENAME: MKT-UC006ACrev6. TRADEMARKS The following includes registered and unregistered trademarks and service marks, owned by Fairchild Semiconductor and/or its global subsidiaries, and is not intended to be an exhaustive list of all such trademarks. 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