ACE725 24V/1.2A Asynchronous Buck Converter Description The ACE725 is a high efficiency current-mode asynchronous, 24V/1.2A buck converter. Its input voltage ranges from 4V to 24V and it provides an adjustable regulated output voltage from 0.810V to 5.5V while delivering up to 1.2A of output current. The switching frequency is set to 1.4MHz, which works with a inductor as small as 4.7uH. And the ACE725 will automatically switch between PFM and PWM mode based on the load current, thus to enhance the converter efficiency at light load. ACE725 consists of many protection blocks such as UVLO, input voltage over voltage protection to stand much higher input voltage spike, thermal protection and output short circuit protection. Features Adjustable Output Voltage, Vfb=0.810V Output current is up to 1.2A Range of operation input voltage: 4-24V Input voltage UVLO: 3.7V (voltage decreasing) Input Overvoltage Protection @26V Withstand input voltage spike >30V Operating current at zero load: 0.8mA (typ.) Line regulation: 0.1%/V (typ.) Load regulation: 10mV (typ.) High efficiency, up to 90% Environment Temperature: -20℃~85℃ Application Security Camera Consumer Electronic Device for automobile Portable DVD ADSL Modem, WLAN router Other 12V or double cell Li-ion battery powered device Typical Application and PIN OUT ACE725 VER 1.2 1 ACE725 24V/1.2A Asynchronous Buck Converter Absolute Maximum Ratings Parameter Max Input voltage 30V Package Thermal Resistance SOT-23-6 (ΘJC) 110℃/W SOT-23-6 (ΘJA) 220℃/W Operating Junction Temperature (TJ) 125℃ Ambient Temperature (TA) -20℃ to 85℃ ESD (HBM) >2000V Storage Temperature (Ts) -40℃ to 150℃ Note: Exceed these limits to damage to the device. Exposure to absolute maximum rating conditions may affect device reliability. Packaging Type SOT-23-6 6 5 4 1 2 3 SOT-23-6 Description Function 1 BST High side power transistor gate drive boost input 2 GND Ground 3 FB 4 EN 5 VIN 6 SW Feedback input with reference voltage set to 0.810V Enable input. Setting it to high level or connecting to Vin via a resistor may turn on the chip, while setting it to ground level will turn off the chip. Power input, the input capacitor should be placed as close to VIN and GND pin as possible Power switching node to connect inductor Ordering Information ACE725 XX + H Halogen - free Pb - free GM : SOT-23-6 VER 1.2 2 ACE725 24V/1.2A Asynchronous Buck Converter Low Current Consumption Input Current at Zero Load Block Diagram VER 1.2 3 ACE725 24V/1.2A Asynchronous Buck Converter Recommended work conditions Parameter Value Input Voltage Range 4~24V Output Voltage Range 0.81~5.5V Operating Junction Temperature (TJ) -20℃~125℃ Electrical Characteristics (TA=25℃, VIN=3V, VCE=3V, unless otherwise noted) Parameter Symbol Conditions Input Voltage Range VDD Output Voltage Range VOUT Feedback Voltage Vref Vin=12V, Ven=5V UVLO Voltage VUVLO Vin H -->L,Iout=0.5A Feedback Leakage current Ifb Quiescent Current Iq Line Regulation Min Max Units 4 24 V 0.81 5.5 V 0.83 V 0.79 Typ 0.81 3.7 V 0.1 0.4 uA Active, Vfb=1V, No Switching 0.6 1.0 mA Shutdown, Vin=8V 6 10 uA LnReg Vin=5V to 12V 0.1 %/V Load Regulation LdReg Iout=0.1 to 1.2A 0.02 %/A Switching Frequency Fsoc Ven=3V, Vin=12V High side Switch Rdson RdsonH Isw=200mA Peak Inductor Current Limit llimit Vin=12V, Vout=5V EN High Threshold Venh EN Low Threshold Venl Input Over-Voltage Protection Vovp Ven=3V 26 V Over Temperature Protection TSD Hystersis=40℃ 150 ℃ 1 1.4 1.8 MHz 250 350 mohm 1.5 2 1 1.5 A 3 V 0.5 V Typical Performance Characteristics (Vin=12V, Vout=5.0V, L=4.7uH, Cin=10uF, Cout=22uF, TA=25℃, unless otherwise stated) VER 1.2 4 ACE725 24V/1.2A Asynchronous Buck Converter Typical Performance Characteristics (Vin=12V, Vout=5.0V, L=4.7uH, Cin=10uF, Cout=22uF, TA=25℃, unless otherwise stated) VER 1.2 5 ACE725 24V/1.2A Asynchronous Buck Converter Typical Performance Characteristics (Vin=12V, Vout=5.0V, L=4.7uH, Cin=10uF, Cout=22uF, TA=25℃, unless otherwise stated) Functional Descriptions Loop Operation The ACE725 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 250mΩ MOSFET, with external schottky diode. 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 the 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. Current Limit There is a cycle-by-cycle current limit on the high-side MOSFET of 1.5A(typ). When the current flowing out of SW exceeds this limit, the high-side MOSFET turns off and the external schottky diode rectifier turns on. Unlike the traditional method of current limiting by limiting the voltage at the internal compensation node, which usually has large variation due to duty cycle variance, this type of peak current limiting scheme provides a relatively more accurate limit for output current, thereby lowering the requirements for system design. Light Load Operation Traditionally, a fixed current mode 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. ACE725 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. VER 1.2 6 ACE725 24V/1.2A Asynchronous Buck Converter Component Selection When setting up the ACE725 for different output voltage, please use following recommended component value for the best performance. VOUT(V) COUT(uF) L(uH) 5 22 6.8-10 3.3 22 4.7-10 2.5 22 3.3-10 Thermal Consideration ACE725 is high efficiency Buck converter, which means it consumes very few power when converting the high voltage to low voltage. However, when output power is very large, like 5V/1.2A, the output power is as high as 6W, a heat dissipation path is strongly recommended to be routed on PCB. ACE725 is in SOT23-6 package. The heat is conducted out via Pin 2 (GND), so the heat dissipation route on PCB should be connected to the Pin 2 of the chip. Packing Information SOT-23-6 VER 1.2 7 ACE725 24V/1.2A Asynchronous Buck 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 1.2 8