ST1S03A 1.5A, 1.5 MHz Adjustable, with inhibit function Step-down switching regulator in DFN6 3x3 Features ■ Step-down current mode PWM (1.5MHz) DCDC converter ■ 2% DC output voltage tolerance ■ Internal soft start for start-up current limitation and power on delay of 50-100µs ■ Typical efficiency: > 85% ■ Inhibit function ■ 1.5A Output current capability ■ Not switching quiescent current: max 1.5mA over temperature range ■ Switch VDS: max 200mV @ ISW=750mA ■ Uses tiny capacitors and inductors ■ Available in DFN6 3x3 exposed pad Description The ST1S03A is a step down DC-DC converter optimized for powering low-voltage digital core in HDD applications and, generally, to replace the high current linear solution when the power DFN6 (3x3) dissipation may cause an high heating of the application environment. It provides up to 1.5A over an input voltage range of 3V to 5.5V. An high switching frequency (1.5MHz) allows the use of tiny surface-mount components: as well as the resistor divider to set the output voltage value, only an inductor, a schottky diode and two capacitors are required. Besides, a low output ripple is guaranteed by the current mode PWM topology and by the use of low E.S.R. SMD ceramic capacitors. The device is thermal protected and current limited to prevent damages due to accidental short circuit. The ST1S03A is available in DFN6 (3x3). Order codes May 2007 Part number Packaging Package ST1S03APMR Tape & reel DFN6 (3x3 mm) ST1S03AIPMR Tape & reel DFN6 (3x3 mm) ST1S03APUR Tape & reel DFN6D (3x3 mm) ST1S03AIPUR Tape & reel DFN6D (3x3 mm) Rev. 3 1/14 www.st.com 14 ST1S03A Contents Contents 1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 2/14 ST1S03A 1 Figure 1. Diagram Diagram Schematic diagram 3/14 ST1S03A Pin configuration 2 Pin configuration Figure 2. Pin configuration (top view) ST1S03AI ST1S03A Table 1. Pin description Pin N° Symbol 1 2 3 4 GND SW VIN_SW 5 6 N.C./INH 4/14 VFB VIN_A Note Voltage of feedback System ground Output of the internal power switch Power supply for the mosfet switch Power supply for the analog circuit Not connected / or inhibit ST1S03A 3 Maximum ratings Maximum ratings Table 2. Absolute maximum ratings Symbol VIN_SW VIN_A VINH SWITCH Voltage VFB IVFB Parameter Value Unit Positive power supply voltage -0.3 to 7 V Positive power supply voltage -0.3 to 7 V Max voltage of inhibit pin -0.3 to 6 V Max. voltage of output pin -0.3 to 7 V Feedback voltage Common mode input voltage TJ Max junction temperature TSTG Storage temperature range TLEAD Lead temperature (soldering) 10 sec Note: Table 3. Symbol RthJA RthJC 2.5 V 1 mA 150 °C -25 to 150 °C 300 °C Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional Operation under these conditions is not implied. Thermal data Parameter Value Unit Thermal resistance junction-ambient 10 °C/W Thermal resistance junction-case 55 °C/W 5/14 ST1S03A Electrical characteristics 4 Electrical characteristics Table 4. Electrical characteristics (VIN_SW = VIN_A = VINH = 5V, CI = 4.7µF, CO = 22µF, L1 = 3.3µH, TJ = 0 to 125°C (unless otherwise specified. Typical values are referred to 25°C) Symbol Parameter FB Feedback voltage IFB VFB Pin bias current IQ Quiescent current VINH Test conditions Min. Typ. Max. Unit 784 800 816 mV 600 nA VINH > 1.2V 1.5 mA VINH < 0.4V 1 µA Device ON 1.2 Inhibit threshold V Device OFF 0.4 IO Output current VI = 2.7 to 5.5V 1.5 A IO Output current VI = 2.7 to 5.5V 0.8 A 1 mA IMIN Minimum output current %VO/ΔVI Reference line regulation VI = 2.7V to 5.5V 0.2 %VO/ ΔVI %VO/ΔIO Reference load regulation IO = 10mA to 1.5A 0.2 %VO/ ΔIO PWMfS PWM Switching frequency VFB = 0.8V, TA = 25°C Note: 1 DMAX 1.2 Maximum duty cycle ISW Switching current limitation VDS Switch VDS 1.5 1.8 87 MHz % 2.5 A ISW = 800mA 200 mV IO = 10mA to 100mA, VO = 3.3V 70 IO = 100mA to 1.5A, VO = 3.3V 85 Thermal shutdown Note: 1 130 Thermal shutdown hysteresis Note: 1 %VO/ΔIO Load transient response IO = 100mA to 1.5A, TA = 25°C tR = tF ≥ 100ns, Note: 1 -3 +3 %VO %VO/ΔIO @ IO=Short Short circuit removal response IO = 10mA to short, TA = 25°C Note: 1 -10 +10 %VO ν TSHDN THYS Efficiency Note: 1 Guaranteed by design, but not tested in production 6/14 % 150 °C 15 °C ST1S03A 5 Figure 3. Typical application Typical application Application circuit Application notes The ST1S03A is an adjustable current mode PWM step-down DC/DC converter with internal 1.5A power switch, packaged in a 6-lead DFN 3x3. It’s a complete 1.5A switching regulator with its internal compensation eliminating additional component. The constant frequency, current mode, PWM architecture and stable operation with ceramic capacitors results in low, predictable output ripple. However, in order to maximize the power conversion efficiency with light load, the regulator reduces automatically the switching frequency when the output load becomes less than 250mA typically. To clamp the error amplifier reference voltage a Soft Start control block generating a voltage ramp, has been implemented. Besides an On-Chip Power on Reset of 50=100µs ensure the proper operation when switching on the power supply. Other circuits fitted to the device protection are the Thermal Shut down block which turn off the regulator when the junction temperature exceeds 150°C typically and the Cycleby-cycle Current Limiting that provides protection against shorted outputs. Being the ST1S03A an adjustable regulator, the output voltage is determined by an external resistor divider. The desired value is given by the following equation: VO = VFB[1+R1/R2] To make the device working, only other four external components are required: an inductor a schottky and two capacitors. The chosen inductor must be able to not saturate at the peak current level. Besides, its value can be selected keeping in account that a large inductor value increases the efficiency at low output current and reduces output voltage ripple, while a smaller inductor can be chosen when it is important to reduce the package size and the total cost of the application. Finally, the ST1S03A has been designed to work properly with X5R or X7R SMD ceramic capacitors both at the input and at the output this kind of capacitors, thanks to their very low series resistance (ESR), minimize the output voltage ripple. Other low ESR capacitors can be used according to the need of the application without invalidate the right functioning of the device. 7/14 Typical application ST1S03A Due to the high switching frequency and peak current, it is important to optimize the application environment reducing the length of the PCB traces and placing all the external component near the device. 8/14 ST1S03A 6 Package mechanical data Package mechanical data In order to meet environmental requirements, ST offers these devices in ECOPACK® packages. These packages have a Lead-free second level interconnect. The category of second Level Interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com. 9/14 ST1S03A Package mechanical data DFN6 (3x3) MECHANICAL DATA mm. inch DIM. MIN. TYP MAX. MIN. TYP. MAX. A 0.80 1.00 31.5 39.4 A1 0 0.05 0.0 2.0 A2 0.65 0.75 25.6 29.5 A3 0.20 b 0.33 D 2.90 D2 1.92 E 2.90 E2 1.11 e L 3.00 0.43 13.0 3.10 114.2 2.12 75.6 3.10 114.2 1.31 43.7 0.95 0.20 L1 0.45 118.1 122.0 83.5 118.1 122.0 51.6 7.9 17.7 9.4 0.13 0.20 16.9 37.4 0.24 L2 K 3.00 7.9 5.1 7.9 7387339A 10/14 ST1S03A Package mechanical data DFN6D (3x3) Mechanical Data mm. inch. Dim. Min. A 0.80 A1 0 A3 0.02 Max. Min. 1.00 0.031 0.05 0 0.20 b 0.23 D 2.90 D2 2.23 E 2.90 E2 1.50 e L Typ. 3.00 3.00 0.40 Max. 0.039 0.001 0.002 0.008 0.45 0.009 3.10 0.114 2.50 0.088 3.10 0.114 1.75 0.059 0.95 0.30 Typ. 0.018 0.118 0.122 0.098 0.118 0.122 0.069 0.037 0.50 0.012 0.016 0.020 7946637B 11/14 ST1S03A Package mechanical data Tape & Reel QFNxx/DFNxx (3x3) Mechanical Data mm. inch. Dim. Min. Typ. A Min. Typ. 330 13.2 Max. 12.992 C 12.8 D 20.2 0.795 N 60 2.362 T 12/14 Max. 0.504 0.519 18.4 0.724 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.315 ST1S03A 7 Revision history Revision history Table 5. Revision history Date Revision Changes 04-May-2006 1 First release. 06-Jun-2006 2 Table 2. has been updated. 29-May-2007 3 Add new mechanical data DFN6D and order codes has been updated. 13/14 ST1S03A Please Read Carefully: Information in this document is provided solely in connection with ST products. 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