ST1S03 1.5A, 1.5 MHz adjustable, step-down switching regulator in DFN6 Features ■ Step-down current mode PWM (1.5MHz) DC-DC converter ■ 2% DC output voltage tolerance ■ Internal soft start for START-UP current limitation and power on delay of 50-100µs ■ Typical efficiency: > 70% over all operating conditions DFN6 (3x3mm) ■ 1.5A Output current capability ■ Not switching quiescent current: max 2.5mA over temperature range ■ Switch VDS: max 350mV @ ISW=750mA ■ Uses tiny capacitors and inductors ■ Available in DFN 3x3 exposed pad Description The ST1S03 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 dissipation may cause an high heating of the application environment. It provides up to 1.5A over an input voltage range of 3V to 16V. 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 ST1S03 is available in DFN6. Order codes March 2007 Part number Packaging Package ST1S03PM ST1S03PMR DFN6 (3x3 mm) ST1S03PU ST1S03PUR DFN6D (3x3 mm) Rev. 5 1/17 www.st.com 17 ST1S03 Contents 1 Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5 Application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 6 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 7 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2/17 ST1S03 Diagram 1 Diagram Figure 1. Schematic diagram 3/17 Pin configuration ST1S03 2 Pin configuration Figure 2. Pin connections (top view) Table 1. Pin description Pin N° Symbol 1 VFB Voltage of Feedback 2 GND System Ground 3 SW Output of the internal Power Switch 4 VIN_SW 5 VIN_A Power Supply for the Analog Circuit 6 N.C. Not Connected 4/17 Name and function Power Supply for the MOSFET Switch ST1S03 Maximum ratings 3 Maximum ratings Table 2. Absolute maximum ratings Symbol Parameter Value Unit VI_SW Positive Power Supply Voltage -0.3 to 16 V VI_SW Positive Power Supply Voltage -0.3 to 16 V Max Voltage of output pin -0.3 to 16 V SWITCH Voltage VFB Feedback Voltage 2.5 V IVFB Common mode input voltage ±1 mA Max Junction Temperature 150 °C -25 to 150 °C 300 °C TJ TSTG Storage Temperature Range TLEAD Lead Temperature (Soldering) 10 Sec. Note: Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional Operation under these conditions is not implied. Table 3. Thermal data Symbol Parameter Value Unit RthJC Thermal resistance junction-case 10 °C/W RthJA Thermal resistance junction-ambient 55 °C/W 5/17 Electrical characteristics ST1S03 4 Electrical characteristics Table 4. Electrical characteristics (VIN_SW = VIN_A = 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 PSRR Feedback PSRR Test Conditions Typ. Max. Unit 784 800 816 mV 1Hz < Frequency VIN IFB VFB Pin bias current BW Bandwidth of error amplifier Closed Loop IQ Quiescent current No Switching IO Output current VIN =3V to 16V IMIN Min. -60 dB 600 Minimum output current 300 nA KHz 2.5 mA 1.5 A 1 mA %VO/∆VIN Reference line regulation VIN = 3V to 16V 0.032 0.06 %VO/ ∆VIN %VO/∆IO Reference load regulation IO = 10mA to 1.2A 0.0014 0.003 %VO/ mA PWM fS PWM Switching frequency (1) VFB = 0.8V, TA =25°C 1.5 1.8 MHz DMAX Maximum duty cycle ISWL Switching current limitation VDS Switch VDS E TSHDN THYS ∆VO/∆IO 87 IO =10mA to 1.2A (1) ∆VO/∆IO@ Short circuit removal response(1) IO = 10mA to short, TA = 25°C IO=short 1. Guaranteed by design, but not tested in production. 6/17 350 70 130 IO = 100mA to 700mA tR = tF ≥ 100ns, TA = 25°C A 200 Thermal shut down hysteresis (1) Load transient response (1) % 1.65 ISW = 750 mA Efficiency Thermal shut down 1.2 -5 mV % 150 °C 15 °C +5 %VO +5 %VO ST1S03 5 Application notes Application notes The ST1S03 is an adjustable current mode PWM step-down DC/DC converter with internal 1.5A power switch, packaged in 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 keep the output regulated, the devices goes in pulse skipping mode when a very light load is required. 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 Cycle-by-cycle Current Limiting that provides protection against shorted outputs. Being the ST1S03 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: a Schottky diode, an inductor 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 ST1S03 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 invalidating the right functioning of the device. 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. 7/17 Typical application 6 Typical application Figure 3. Application circuits 8/17 ST1S03 ST1S03 Typical performance characteristics 7 Typical performance characteristics Figure 4. (L1=3.3µH, CI = 4.7µF, CO = 22µF, unless otherwise specified) Load voltage feedback vs temp. Figure 5. Voltage feedback vs temperature Figure 6. Line output voltage regulation vs temperature Figure 7. Figure 8. Voltage feedback vs output current Figure 9. Line voltage feedback vs temperature PWM Switching frequency vs temperature 9/17 Typical performance characteristics ST1S03 Figure 10. Quiescent current vs temperature Figure 11. Quiescent current vs input voltage Figure 12. Minimum operating voltage vs output voltage Figure 13. Efficiency vs temperature Figure 14. Efficiency vs output current Figure 15. Switch VDS vs temperature 10/17 ST1S03 Typical performance characteristics Figure 16. Switch RDS-ON vs temperature Figure 17. Switch current limitation vs temperature Figure 18. Load transient response Figure 19. Load transient response VCC=5V, IO=100mA to 780mA, CI=4.7µF, CO=22µF, L=3.3µH, TON=38µs, TJ=25°C VCC=5V, IO=200mA to 1.2A, CI=4.7µF, CO=22µF, L=3.3µH, TON=38µs, TJ=25°C Figure 20. Start-Up transient Figure 21. Start-Up transient VCC = 5V, TJ = 25°C VCC = 5V, TJ = 25°C 11/17 Package mechanical data 8 ST1S03 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. 12/17 ST1S03 Package mechanical data DFN6 (3x3) MECHANICAL DATA mm. inch. DIM. MIN. TYP MAX. MIN. TYP. MAX. A 0.80 1.00 0.031 0.039 A1 0 0.05 0.0 0.02 A2 0.65 0.75 0.026 0.030 A3 0.20 b 0.33 D 2.90 D2 1.92 E 2.90 E2 1.11 e L 3.00 0.43 0.013 3.10 0.114 2.12 0.076 3.10 0.114 1.31 0.044 0.95 0.20 L1 0.45 0.118 0.122 0.083 0.118 0.122 0.052 0.008 0.018 0.009 0.13 0.20 0.017 0.037 0.24 L2 K 3.00 0.08 0.005 0.008 7387339A 13/17 Package mechanical data ST1S03 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 14/17 ST1S03 Package mechanical data Tape & Reel QFNxx/DFNxx (3x3) MECHANICAL DATA mm. inch DIM. MIN. TYP A MAX. MIN. TYP. 330 13.2 12.992 C 12.8 D 20.2 0.795 N 60 2.362 T 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 15/17 Revision history ST1S03 9 Revision history Table 5. Revision history Date Revision 11-Nov-2004 1 First Release. 08-Feb-2005 2 Maturity Change. 03-Mar-2005 3 Mistake on Figure 1, TJ is changed 125 ==> 150°C on Table 3. 13-Jul-2005 4 Add new package SO-8 exposed pad. 29-Mar-2007 5 Package SO-8 has been removed and the document has been reformatted. 16/17 Changes ST1S03 Please Read Carefully: Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at any time, without notice. All ST products are sold pursuant to ST’s terms and conditions of sale. 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