ACE725E 24V , 1.2A High Efficiency Step-Down Converter Description The ACE725E is a wide input range, high-efficiency, high frequency DC-to-DC step-down switching regulator, capable of delivering up to 1.2A of output current. With a fixed switching frequency of 1.4MHz, this current mode PWM controlled converter allows the use of small external components, such as ceramic input and output caps, as well as small inductors, while still providing low output ripples. Together with the tiny package ACE725E is in, without external compensation components, it is an ideal solution for system designer with stringent board space requirements. ACE725E also employs a proprietary control scheme that switches the device into a power save mode during light load, thereby extending the range of high efficiency operation. ACE725E is available SOT23-6 Packages. Features Wide Input Operating Range from 4.5V to 24V High Efficiency:Up to 94% Capable of Delivering 1.2A 1.4MHz Switching frequency No External Compensation Needed Current Mode control Logic Control Shutdown Thermal shutdown and UVLO Available in SOT23-6 Package Application Set top boxes Security Surveillance systems LED lighting Absolute Maximum Rating Parameter Value IN Voltage –0.3V to 26V SW ,EN Voltage –0.3V to VIN+0.3 BST Voltage –0.3V to SW+6V FB Voltage –0.3V to 6V SW to ground current Internally limited Operating Temperature Range –40°C to 85°C Storage Temperature Range .–55°C to 150°C Thermal Resistance SOT23-6 θJA 220 θJC 110 °C/W (Note: Exceeding these limits may damage the device. Exposure to absolute maximum rating conditions for long periods may affect device reliability.) VER 1.1 1 ACE725E 24V , 1.2A High Efficiency Step-Down Converter Typical Application VIN 12V 5 IN 25V 4 10μF 1 BST 10nF SW 6 VOUT 3.3V/1.2A EN B230A 49.9K FB GND 6.3V 3 22μF 16.2K 2 Packaging Type SOT-23-6 SOT-23-6 Description 2 BST GND 3 FB 4 EN 5 IN 6 SW 1 Function Bootstrap pin. Connect a 10nF capacitor from this pin to SW. Ground Feedback Input. Connect an external resistor divider from the output to FB and GND to set VOUT Enable pin for the IC. Drive this pin high to enable the part, low to disable. Supply Voltage. Bypass with a 10μF ceramic capacitor to GND. Inductor Connection. Connect an inductor Between SW and the regulator output. VER 1.1 2 ACE725E 24V , 1.2A High Efficiency Step-Down Converter Ordering information ACE725E XX + H Halogen - free Pb - free GM : SOT-23-6 Block Diagram VER 1.1 3 ACE725E 24V , 1.2A High Efficiency Step-Down Converter Electrical Characteristics VIN = 12V, unless otherwise specified. Typical values are at Parameter Input Voltage Range Input UVLO Input OVP Input Supply Current Input Shutdown Current FB Feedback Voltage FB Input Current Switching Frequency Fold-Back Frequency High side Switch ON Resistance High side Switch Current Limit SW Leakage Current EN Input Current EN Input Low Voltage Thermal Shutdown TA=25°C Conditions Min Typ 4.2 Rising, Hysteresis=140mV Rising, Hysteresis=1.3V VFB=0.9V 0.79 Max Unit 24 V 3.55 V 26 V 0.6 mA 6 uA 0.81 0.83 V uA 1.8 MHz 0.01 1.0 VFB=0V ISW=200mA VIN = 12V, VIN=12V, VSW=0, EN=GND 100 250 1.5 1 Hysteresis=40℃ 1.4 KHz 500 2 1.5 mΩ A 10 uA 1 uA 3 V °C 150 VER 1.1 4 ACE725E 24V , 1.2A High Efficiency Step-Down Converter Typical Characteristics (Typical values are at TA=25°C unless otherwise specified) Efficiency Vs IOUT Efficiency Vs IOUT IOUT (A) IOUT (A) VOUT Normalized % Vs IIOUT IOUT(mA) Maximum IPEAK Vs DUTY CYCLE (%) VOUT Vs VIN VIN (V) VIN IQ Vs VIN VIN (V) VER 1.1 5 ACE725E 24V , 1.2A High Efficiency Step-Down Converter Typical Characteristics (Typical values are at TA=25°C unless otherwise specified) VFB Vs Temperature Temperature(℃) Frequency Vs Temperature Temperature(℃) Load Transient Response Vin=12 V, VOUT=5V, IOUT= 0.2A to 1.0A 2ms/div Max IOUT Vs Temperature Temperature(℃) Load Transient Response Vin=12 V, VOUT=3.3V, IOUT= 0.2A to 1.0A Ims/div Switching Waveform Vin=12 V, VOUT=5V, IOUT= 0.5A 500ms/div VER 1.1 6 ACE725E 24V , 1.2A High Efficiency Step-Down Converter Typical Characteristics (Typical values are at TA=25°C unless otherwise specified) Start-up Waveform through EN Vin=12 V, VOUT=5V, IOUT= 0A 5ms/div Shutdown Waveform through EN Vin=12 V, VOUT=5V, IOUT= 0A Start-up Waveform through EN Vin=12 V, VOUT=5V, IOUT= 0.5A 2ms/div Shutdown Waveform through EN Vin=12 V, VOUT=5V, IOUT=0.5A 5ms/div Short-Circuit Response Vin=12 V, VOUT=5V, IOUT=0A to Short 2ms/div Short-Circuit Recovery Vin=12 V, VOUT=5V, IOUT=Short to 0A 0.5ms/div 0.5ms/div VER 1.1 7 ACE725E 24V , 1.2A High Efficiency Step-Down Converter FUNCTIONAL DECRIPTIONS Loop Operation The ACE725E is a wide input range, high-efficiency, DC-to-DC step-down switching regulator, capable of delivering up to 1.2A of output current, integrated with a 250m high-side MOSFET. It uses a PWM current-mode control scheme. An error amplifier integrates error between the FB signal and the internal reference voltage. The output of the integrator is then compared to t he sum of a current-sense signal and the slope compensation ramp. This operation generates a PWM signal that modulates the duty cycle of the power MOSFETs to achieve regulation for output voltage. Light Load Operation Traditionally, a fixed constant frequency PWM DC-DC regulator always switches even when the output load is small. When energy is shuffling back and forth through the power MOSFETs, power is lost due to the finite RDSONs of the MOSFETs and parasitic capacitances. At light load, this loss is prominent and efficiency is therefore very low. ACE725E employs a proprietary control scheme that improves efficiency in this situation by enabling the device into a power save mode during light load, thereby extending the range of high efficiency operation. APPLICATION INFORMATION 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 1.2A maximum output current, the maximum inductor ripple current is 400 mA. The inductor size is estimated as following equation LIDEAL=(VIN(MAX)-VOUT)/IRIPPLE*DMIN*(1/FOSC) Therefore, for VOUT=5V, The inductor values is calculated to be L = 7μH. Chose 6.8μH or 10μH For VOUT =3.3V, The inductor values is calculated to be L = 4.9μH. Chose 4.7μH VER 1.1 8 ACE725E 24V , 1.2A High Efficiency Step-Down Converter Output Capacitor Selection For most applications a nominal 22μF or larger capacitor is suitable. The ACE725E internal compensation is designed for a fixed corner frequency that is equal to 1 FC=2∗ π√COUT∗ L=20Khz For example, for VOUT=5V, L=6.8μH, COUT=22μF. 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 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. Components Selection VOUT (V) 8 5 3.3 2.5 COUT (μF) 22x2 22x2 22x2 22x2 L (μH) 10 to 15 6.8 to 10 4.7 to 10 3.3 to 10 VER 1.1 9 ACE725E 24V , 1.2A High Efficiency Step-Down Converter Packing Information SOT-23-6 SYMBL A B C D E F G H I J K MIN 2.7 1.7 -1.5 2.5 0.2 1 0.7 0 0.2 0.1 MILLIMETER NOM 2.9 1.9 0.95 1.6 2.8 0.4 1.1 0.8 --0.15 MAX 3.1 2.1 -1.8 3.1 0.5 1.3 0.9 0.1 -0.25 VER 1.1 10 ACE725E 24V , 1.2A High Efficiency 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 11