SC46208

SC46208 1.25MHz, 600mA, HIGH EFFICIENCY SYNCHRONOUS STEP-DOWN DC-DC CONVERTER DESCRIPTION SC46208 is a synchronous step-down DC-DC converter with high efficiency. It adopts small flat package. The device features 2.5~5.5V input voltage, 600mA output current, peak current mode PWM and integrated compensation net, which is ideal for powering portable equipment that runs from a single cell Li+ battery without external components. The device integrates an internal switch which eliminates the Schottky diode, 1.25MHz high frequency allows the periphery to adopt SMT inductor and capacitor, thus reduce the size of total solution. It can also run at 100% duty cycle for low dropout operation, that is lower than 1μA shutdown current and 20μA quiescent current in power saving mode. It extends battery life in portable system through increasing the efficiency under light loads. SC46208 is available in an adjustable version and fixed version. APPLICATION * Cellular Telephones * PDAs * Wireless Equipment * MP3 player * Digital Camera * Portable Instruments FEATURES * High efficiency up to 95% * Automatic Power Saving Mode at light loads, only 20μA quiescent current. * Wide input voltage range: +2. 5V~+5.5V * Output voltage range: 0.6V~VIN * High output current 600mA * Low dropout operation: 100% * Shutdown current ILOAD(max) + Iripple = (1+ 20%)ILOAD(max) 2 The max. load current is 600mA, for most applications, the inductor of 720mA rating value is enough; for higher efficiency, please choose an inductor with low DC series resistance (DCR). To reduce the noise, use a shielded bobbin inductor. Capacitor Selection The low ESR capacitor is required to keep the output voltage ripple small. There, the multilayer ceramic capacitor is recommended due to their low ESR and small size. In the most applications, 10-22μF output capacitors are enough, higher capacitor can be used to reduce the output ripple and improve transient response. The low ESR input capacitor reduces the surge current drawn from the input and switching noise from the device. Ceramic capacitor is the best selection for input capacitor, and the capacitor should be as near as possible to chip. A 4.7μF ceramic capacitor is sufficient for most applications. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http://www.silan.com.cn REV:1.1 2008.09.10 Page 5 of 11 SC46208 Setting The Output Voltage For voltage adjustable version, SC46208 adjusts the output voltage through two serial resistors, refer to fig. below. We can calculate the output voltage through the following equation: VOUT = (1+ R1)X0.6V R2 The selection of resistor R1, R2 should give attention to the quiescent power and external interfere. Higher impedance reduces the quiescent current (I=0.6V/R2), and lower resistance gives better noise immunity, and is less sensitive to interference, layout parasitics and FB node leakage current. A proper value of feed-forward capacitor C1 can improve the noise immunity of the feedback loops, especially in an improper layout. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http://www.silan.com.cn REV:1.1 2008.09.10 Page 6 of 11 SC46208 TYPICAL APPLICATION CIRCUIT Fig. 1：Output voltage adjustable regulator, single battery to 2.5V converter Fig.2：Output voltage fixed regulator Note: The circuit and parameters are reference only, please set the parameters of the real application circuit based on the real test. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http://www.silan.com.cn REV:1.1 2008.09.10 Page 7 of 11 SC46208 TYPICAL ELECTRICAL CHARACTERISTICS CURVES (Tamb=25°C, unless otherwise specified) Efficiency VS Input Voltage of SC46208 100 95 90 85 80 75 70 65 60 55 50 2 3 4 Input Voltage(V) 5 6 VOUT=1.8V IOUT=0.1mA IOUT=1mA IOUT=600mA IOUT=100mA IOUT=10mA HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http://www.silan.com.cn Frequency(MHz) Efficiency (%) REV:1.1 2008.09.10 Page 8 of 11 SC46208 TYPICAL ELECTRICAL CHARACTERISTICS CURVES (Tamb=25°C, unless otherwise specified) Output Voltage VS Load Current 1.844 1.834 1.824 1.814 1.804 1.794 1.784 1.774 0 VIN＝3.6V TA=25 C 100 200 300 400 500 600 700 800 900 Load Current(mA) SC46208 Load Step VOUT 100mV/DIV AC COUPLED Output Ripple Voltage VOUT (5mV/DIV) SW (5V/DIV) IL (500mA/DIV) IL 500mA/DIV ILOAD 500mA/DIV 20mS/DIV VIN=3.6V VOUT=1.8V ILOAD=50mA to 600mA Time(500ns/DIV) VIN=3.6V VOUT=1.2V ILOAD=600mA HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http://www.silan.com.cn REV:1.1 2008.09.10 Page 9 of 11 SC46208 PACKAGE OUTLINE SOT-23-5 2.92±0.10 0～8° 0.35 0.2 0.45±0.15 Unit: mm 2.80±0.15 1.60±0.10 0.950 1.90±0.10 0.70 0.15±0.05 MOS DEVICES OPERATE NOTES: Electrostatic charges may exist in many things. Please take following preventive measures to prevent effectively the MOS electric circuit as a result of the damage which is caused by discharge: The operator must put on wrist strap which should be earthed to against electrostatic. Equipment cases should be earthed. All tools used during assembly, including soldering tools and solder baths, must be earthed. MOS devices should be packed in antistatic/conductive containers for transportation. Note：Silan reserves the right to make changes without notice in this specification for the improvement of the design and performance. Silan will supply the best possible product for customers. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http://www.silan.com.cn 0～0.100 1.10±0.05 1.15±0.10 REV:1.1 2008.09.10 Page 10 of 11