ST1S03 1.5A, 1.5 MHZ ADJUSTABLE, STEP-DOWN SWITCHING REGULATOR IN DFN6 ■ ■ ■ ■ ■ ■ ■ ■ ■ STEP-DOWN CURRENT MODE PWM (1.5MHz) DC-DC CONVERTER 2% DC OUTPUT VOLTAGE TOLERANCE INTERNAL SOFT START FOR START-UP CURRENT LIMITIATION AND POWER ON DELAY OF 50-100µs TYPICAL EFFICIENCY: > 70% OVER ALL OPERATING CONDITIONS 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 DFN6 (3x3) 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 package. Figure 1: Schematic Diagram March 2005 Rev. 3 1/11 ST1S03 Table 1: Order Codes SYMBOL DFN6 (Tape & Reel) ST1S03 ST1S03PM ST1S03RPM Figure 2: Pin Connection (top through view) Table 2: Pin Description PIN N° Symbol Name and Function 1 VFB 2 3 4 GND SW VIN_SW 5 VIN_A Power Supply for the Analog Circuit 6 N.C. Not Connected Voltage of Feedback Sistem Ground Output of the internal Power Swithch Power Supply for the MOSFET Switch Table 3: 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 -0.3 to 16 V 2.5 V SWITCH Voltage Max Voltage of output pin VFB Feedback Voltage IVFB Common mode input voltage TJ Max Junction Temperature TSTG Storage Temperature Range TLEAD Lead Temperature (Soldering) 10 Sec. ±1 mA 150 °C -25 to 150 °C 300 °C Absolute Maximum Ratings are those beyond which damage to the device may occur. Functional operation under these condition is not implied. Table 4: Thermal Data Symbol 2/11 DFN6 Unit RTHJ-C Thermal Resistance Junction-case Parameter 10 °C/W RTHJ-A Thermal Resistance Junction-ambient 55 °C/W ST1S03 Table 5: 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 FB PSRR Parameter Feedback Voltage Feedback PSRR Test Conditions Min. Typ. Max. Unit 784 800 -60 816 mV dB 1Hz < Frequency VIN IFB VFB Pin Bias Current BW IQ Bandwidth of Error Amplifier Closed Loop Quiescent Current No Switching IOUT Output Current IMIN Minimum Output Current VIN =3V to 16V 600 nA 2.5 KHz mA 300 1.5 A 1 mA %VOUT/ ∆VIN Reference Line Regulation VIN = 3V to 16V 0.032 0.06 %VOUT /∆VIN %VOUT/ ∆IOUT Reference Load Regulation IOUT = 10mA to 1.2A 0.0014 0.003 %VOUT /mA PWM fS VFB = 0.8V, TA =25°C 1.5 1.8 MHz DMAX PWM Switching Frequency (1) Maximum Duty Cycle ISWL Switching Current Limitation VDS E TSHDN THYS ∆VOUT/ ∆IOUT 87 Switch VDS ISW = 750 mA IOUT =10mA to 1.2A Thermal Shut Down (1) Short Circuit Removal ∆VOUT/ Response (1) ∆IOUT @IO = short % 1.65 Efficiency Thermal Shut Down Hysteresis (1) Load Transient Response (1) 1.2 200 IOUT = 10mA to short, TA = 25°C 350 70 130 IOUT = 100mA to 700mA tR = tF ≥ 100ns, TA = 25°C A -5 mV % 150 °C 15 °C +5 %VO +5 %VO NOTE 1: Guaranteed by design, not tested in production. 3/11 ST1S03 APPLICATION NOTES The ST1S03 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 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 Figure 3: Application Circuit 4/11 resistor divider. The desired value is given by the following equation: VOUT = 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. ST1S03 TYPICAL CHARACTERISTICS (CIN = 4.7µF, CO = 22µF, L1 = 3.3µH, unless otherwise specified) Figure 4: Load Voltage Feedback vs Temperature Figure 7: Line Voltage Feedback vs Temperature Figure 5: Voltage Feedback vs Temperature Figure 8: Voltage Feedback vs Output Current Figure 6: Line Output Voltage Regulation vs Temperature Figure 9: PWM Switching Frequency vs Temperature 5/11 ST1S03 Figure 10: Quiescent Current vs Temperature Figure 13: Efficiency vs Temperature Figure 11: Quiescent Current vs Input Voltage Figure 14: Efficiency vs Output Current Figure 12: Minimum Operating Voltage vs Output Voltage Figure 15: Switch VDS vs Temperature 6/11 ST1S03 Figure 16: Switch RDS-ON vs Temperature Figure 19: Load Transient Response VCC=5V, I O=200mA to 1.2A, CI=4.7µF, CO=22µF, L=3.3µH, TON=38µs, TJ=25°C Figure 17: Switch Current Limitation vs Temperature Figure 20: Start-Up Transient VCC = 5V, T J = 25°C Figure 18: Load Transient Response Figure 21: Start-Up Transient VCC=5V, I O=100mA to 780mA, C I=4.7µF, CO=22µF, L=3.3µH, TON=38µs, TJ=25°C VCC = 5V, T J = 25°C 7/11 ST1S03 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 8/11 ST1S03 Tape & Reel QFNxx/DFNxx (3x3) MECHANICAL DATA mm. inch DIM. MIN. TYP A MAX. MIN. TYP. 330 C 12.8 D 20.2 N 99 13.2 MAX. 12.992 0.504 0.519 0.795 101 T 3.898 3.976 14.4 0.567 Ao 3.3 0.130 Bo 3.3 0.130 Ko 1.1 0.043 Po 4 0.157 P 8 0.315 9/11 ST1S03 Table 6: Revision History Date Revision 11-Nov-2004 08-Feb-2005 1 2 03-Mar-2005 3 10/11 Description of Changes First Release. Maturity Change. Mistake on Figure 1, TJ is changed 125 ==> 150°C on Table 3. ST1S03 Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. 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