ACE722E 3MHz 2A Step-Down Converter Description The ACE722E is a high-efficiency, DC-to-DC step-down switching regulator, capable of delivering up to 2A of output current. The devices operate from an input voltage range of 2.6V to 5.5V and provide output voltages from 0.6V to VIN, making the ACE722E ideal for low voltage power conversions. Running at a fixed frequency of 3MHz allows the use of small inductance value and low DCR inductors, thereby achieving higher efficiencies. Other external components, such as ceramic input and output caps, can also be small due to higher switching frequency, while maintaining exceptional low noise output voltages. Built-in EMI reduction circuitry makes this converter ideal power supply for RF applications. Internal soft-start control circuitry reduces inrush current. Short-circuit and thermal-overload protection improves design reliability. ACE722E is housed in a tiny SOT23-5/ DFN2x2-8L package Features ŋ up to 96% Up to 2A Max output current 3MHz Frequency Internal Compensation Clock Dithering Tiny SOT23-5/ DFN2x2-8L Package Application USB ports/HubS Portable Devices Cellphones Tablet PC Set Top Boxes Absolute Maximum Rating Parameter Value Max Input Voltage 6V Max Operating Junction Temperature(Tj) 125 Ambient Temperature(Ta) -20℃~85℃ Pacage Thermal Resistance (Θ jc) DFN2x2-8L 25℃/W Power Dissipation SOT-23-5 250mW Storage Temperature(Ts) -40℃-150℃ Lead Temperature & Time 260℃,105 ESD (HBM) >2000V Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability VER 1.1 1 ACE722E 3MHz 2A Step-Down Converter Packaging Typ SOT23-5 DFN2x2-8 Ordering information ACE722E XX + H Halogen - free Pb - free BN：SOT-23-5 DN：DFN2x2-8 Pin Description SOT23-5 PIN # NAME DESCRIPTION 1 EN 2 GND 3 SW Inductor Connection. Connect an inductor Between SW and the regulator output. 4 IN 5 FB Supply Voltage. Short to PIN. Bypass with a 10μF ceramic capacitor to GND Feedback Input. Connect an external resistor divider from the output to FB and GND to set the output to a voltage between 0.6V and VIN Enable pin for the IC. Drive this pin to high to enable the part, low to disable. Ground DFN2x2-8L PIN # NAME DESCRIPTION 1 PGND Power Ground. Bypass with a 10μF ceramic capacitor to PVIN 2 SW 3 AGND 4 FB 5 EN Inductor Connection. Connect an inductor Between SW and the regulator output. Analog Ground, Connect to PGND Feedback Input. Connect an external resistor divider from the output to FB and GND to set the output to a voltage between 0.6V and VIN Enable pin for the IC. Drive this pin to high to enable the part, low to disable. 6 MODE When forced high, the device operates in fixed frequency PWM mode. When forced low, it enables the Power Save Mode with automatic transition from PFM mode to fixed frequency PWM mode. This pin must be terminated. 7 AVIN Analog Power. Short externally to PVIN 8 PVIN Supply Voltage. Bypass with a 10μF ceramic capacitor to PGND VER 1.1 2 ACE722E 3MHz 2A Step-Down Converter BLOCK DIAGRAM VER 1.1 3 ACE722E 3MHz 2A Step-Down Converter Electrical Characteristics (VIN = 3.6V, unless otherwise specified. Typical values are at TA = 25℃.) Parameter Conditions Input Voltage Range Input UVLO Input Supply Current Min 2.6 FB Input Voltage Units 5.5 V 2.1 V VFB =0.65V,MODE=GND 30 μA VIN =2.5 to 5.5V 0.588 Current 0.1 1 0.6 0.612 0.6 Load Regulation VIN =2.7 to 5.5V Switching Frequency 2.4 μA V μA 0.01 Output Voltage Range Line Regulation Max Rising, Hysteresis=200mV Input Shutdown Current FB Feedback Typ VIN V 0.15 %/A 0.04 %/V 3 3.6 MHz NMOS Switch On Resistance ISW =200mA 100 150 mΩ PMOS Switch On Resistance ISW =200mA 80 120 mΩ 2.5 3 A VOUT=5.5V,VSW=0 or 5.5V,EN= GND 10 μA EN=MODE=GND 1 μA PMOS Switch Current Limit SW Leakage Current EN, MODE Input Current EN,MODE Input Low Voltage 0.4 V EN,MODE Input High Voltage Thermal Shutdown 1.5 Rising, Hysteresis =15°C 160 V °C VER 1.1 4 ACE722E 3MHz 2A Step-Down Converter Typical Application Circuit SOT23-5 DFN2x2-8L Efficiency Vs IOUT IOUT (mA) TYPICAL CHARACTERISTICS (Typical values are at TA = 25℃ unless otherwise specified.) VER 1.1 5 ACE722E 3MHz 2A Step-Down Converter SOT23-5 Efficiency Vs IOUT IOUT (mA) Efficiency Vs IOUT Efficiency Vs IOUT IOUT (mA) IQ VS VIN IOUT (mA) VOUT Accuracy Vs IOUT (mA) VOUT Accuracy VS VIN VIN (V) VER 1.1 6 ACE722E 3MHz 2A Step-Down Converter TYPICAL CHARACTERISTICS (Typical values are at TA = 25℃ unless otherwise specified.) SWITCHING WAVEFORMS Light Load 20mA SWITCHING WAVEFORMS Medium Load 0.5A Load Transient VOUT=1.8V 0.2 A to 1.5 A SWITCHING WAVEFORMS Light Load 20mA Load Transient VOUT=1.2V 0.2 A to 1.0 A Short-Circuit Recovery VER 1.1 7 ACE722E 3MHz 2A Step-Down Converter Short-UP Waveform No Load Short-UP Waveform IOUT=1A Short down Waveform IOUT=1A VER 1.1 8 ACE722E 3MHz 2A Step-Down Converter TYPICAL CHARACTERISTICS (Typical values are at TA = 25℃ unless otherwise specified.) DFN2x2-8L Efficiency Vs IOUT IOUT (mA) Efficiency Vs IOUT IOUT (mA) VOUT Accuracy Vs IOUT IOUT (mA) Efficiency Vs IOUT IOUT (mA) Efficiency Vs IOUT IOUT (mA) VOUT Accuracy Vs vin VIN (V) VER 1.1 9 ACE722E 3MHz 2A Step-Down Converter TYPICAL CHARACTERISTICS (Typical values are at TA = 25℃ unless otherwise specified.) SWITCHING WAVEFORMS Light Load 20mA Mode=VIN SWITCHING WAVEFORMS Medium Load 0.5A Load Transient VOUT=1.8V 0.2 A to 1.5 A SWITCHING WAVEFORMS Light Load 20mA Mode=GND Load Transient V OUT=1.2V 0.2 A to 1.0 A Short-Circuit Recovery VER 1.1 10 ACE722E 3MHz 2A Step-Down Converter Short-UP Waveform No Load Short-UP Waveform IOUT=1A Short down Waveform IOUT=1A VER 1.1 11 ACE722E 3MHz 2A Step-Down Converter FUNCTIONAL DECRIPTIONS The ACE722E high efficiency switching regulator is a small, simple, DC-to-DC step-down converter capable of delivering up to 2A of output current. The device operates in pulse- width modulation (PWM) at 3MHz from a 2.6V to 5.5V input voltage and provides an output voltage from 0.6V to VIN, making the ACE722E ideal for on-board post-regulation applications. An internal synchronous rectifier improves efficiency and eliminates the typical Schottky free-wheeling diode. Using the on resistance of the internal high-side MOSFET to sense switching currents eliminates current- sense resistors, further improving efficiency and cost. Load Operation ACE722E uses a PWM current-mode control scheme. An open-loop comparator compares the integrated voltage- feedback signal against the sum of the amplified current- sense signal and the slope compensation ramp. At each rising edge of the internal clock, the internal high-side MOSFET turns on until the PWM comparator terminates the on cycle. During this on-time, current ramps up through the inductor, sourcing current to the output and storing energy in the inductor. The current mode feedback system regulates the peak inductor current as a function of the output voltage error signal. During the off cycle, the internal high-side P- channel MOSFET turns off, and the internal low-side N- channel MOSFET turns on. The inductor releases the stored energy as its current ramps down while still providing current to the output. Current Sense An internal current-sense amplifier senses the current through the high-side MOSFET during on time and produces a proportional current signal, which is used to sum with the slope compensation signal. The summed signal then is compared with the error amplifier output by the PWM comparator to terminate the on cycle. Current Limit There is a cycle-by-cycle current limit on the high-side MOSFET. When the current flowing out of SW exceeds this limit, the high-side MOSFET turns off and the synchronous rectifier turns on. ACE722E utilizes a frequency fold-back mode to prevent overheating during short-circuit output conditions. The device enters frequency fold-back mode when the FB voltage drops below 200mV, limiting the current to IPEAK and reducing power dissipation. Normal operation resumes upon removal of the short-circuit condition. Soft-start ACE722E has a internal soft-start circuitry to reduce supply inrush current during startup conditions. When the device exits under-voltage lockout (UVLO), shutdown mode, or restarts following a thermal-overload event, the l soft-start circuitry slowly ramps up current available at SW. VER 1.1 12 ACE722E 3MHz 2A Step-Down Converter UVLO and Thermal Shutdown If IN drops below 1.9V, the UVLO circuit inhibits switching. Once IN rises above 2.1V, the UVLO clears, and the soft-start sequence activates. Thermal-overload protection limits total power dissipation in the device. When the junction temperature exceeds TJ= +160°C, a thermal sensor forces the device into shutdown, allowing the die to cool. The thermal sensor turns the device on again after the junction temperature cools by 15°C, resulting in a pulsed output during continuous overload conditions. Following a thermal- shutdown condition, the soft-start sequence begins. DESIGN PROCEDURE Setting Output Voltages Output voltages are set by external resistors. The FB threshold is 0.6V. RTOP = RBOTTOM x [(VOUT / 0.6) - 1] Inductor Selection The peak-to-peak ripple is limited to 30% of the maximum output current. This places the peak current far enough from the minimum overcurrent trip level to ensure reliable operation while providing enough current ripples for the current mode converter to operate stably. In this case, for 2A maximum output current, the maximum inductor ripple current is 667 mA. The inductor size is estimated as following equation: LIDEAL=(VIN(MAX)-VOUT)/IRIPPLE*DMIN*(1/FOSC) Therefore, for VOUT=1.8V, The inductor values is calculated to be L = 0.60μH. Chose 1Μh. For VOUT =1.2V, The inductor values is calculated to be L = 0.469μH. Chose 0.47μH The resulting ripple is IRIPPLE =(VIN(MAX)-VOUT)/LACTUAL*DMIN*(1/FOSC) When, VOUT=1.8V, IRIPPLE = 403mA VOUT=1.2V, IRIPPLE = 665mA Output Capacitor Selection For most applications a nominal 10μ F or 22μ F capacitor is suitable. The ACE722E internal compensation is designed for a fixed corner frequency that is equal to 1 FC= 1 2∗ π√COUT∗ L = 50Khz For example, for VOUT=1.8V, L=1μ H, COUT=10μ F, for VOUT =1.2V, L=0.47μ H, COUT=22μ F The output capacitor keeps output ripple small and ensures control-loop stability. The output capacitor must also have low impedance at the switching frequency. Ceramic, polymer, and tantalum capacitors are suitable, with ceramic exhibiting the lowest ESR and high-frequency impedance. Output ripple with a ceramic output capacitor is approximately as follows: VRIPPLE = IL(PEAK)[1 / (2π x fOSC x COUT)] If the capacitor has significant ESR, the output ripple component due to capacitor ESR is as follows: VRIPPLE(ESR) = IL(PEAK) x ESR VER 1.1 13 ACE722E 3MHz 2A Step-Down Converter Input Capacitor Selection The input capacitor in a DC-to-DC converter reduces current peaks drawn from the battery or other input power source and reduces switching noise in the controller. The impedance of the input capacitor at the switching frequency should be less than that of the input source so high-frequency switching currents do not pass through the input source. The output capacitor keeps output ripple small and ensures control-loop stability. VER 1.1 14 ACE722E 3MHz 2A Step-Down Converter Packing Information SOT-23-5 DFN2X2-8L VER 1.1 15 ACE722E 3MHz 2A Step-Down Converter Notes ACE does not assume any responsibility for use as critical components in life support devices or systems without the express written approval of the president and general counsel of ACE Electronics Co., LTD. As sued herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and shoes failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. ACE Technology Co., LTD. http://www.ace-ele.com/ VER 1.1 16