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ST1S03
1.5A, 1.5 MHZ ADJUSTABLE, STEP-DOWN SWITCHING REGULATOR IN DFN6
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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 50-100s 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
DFN6 (3x3)
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 Figure 1: Schematic Diagram
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.
March 2005
Rev. 3
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ST1S03
Table 1: Order Codes
SYMBOL ST1S03 DFN6 ST1S03PM (Tape & Reel) ST1S03RPM
Figure 2: Pin Connection (top through view)
Table 2: Pin Description
PIN N 1 2 3 4 5 6 Symbol VFB GND SW VIN_SW VIN_A N.C. Voltage of Feedback Sistem Ground Output of the internal Power Swithch Power Supply for the MOSFET Switch Power Supply for the Analog Circuit Not Connected Name and Function
Table 3: Absolute Maximum Ratings
Symbol VI_SW VI_SW SWITCH Voltage VFB IVFB TJ TSTG TLEAD Parameter Positive Power Supply Voltage Positive Power Supply Voltage Max Voltage of output pin Feedback Voltage Common mode input voltage Max Junction Temperature Storage Temperature Range Lead Temperature (Soldering) 10 Sec. Value -0.3 to 16 -0.3 to 16 -0.3 to 16 2.5 1 150 -25 to 150 300 Unit V V V V mA C C 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 RTHJ-C RTHJ-A Parameter Thermal Resistance Junction-case Thermal Resistance Junction-ambient DFN6 10 55 Unit C/W C/W
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ST1S03
Table 5: Electrical Characteristics (VIN_SW = VIN_A = 5V, CI = 4.7F, CO = 22F, L1 = 3.3H, TJ = 0 to 125C, unless otherwise specified. Typical values are referred to 25C)
Symbol FB PSRR IFB BW IQ IOUT IMIN %VOUT/ VIN %VOUT/ IOUT PWM fS DMAX ISWL VDS E TSHDN THYS VOUT/ IOUT Parameter Feedback Voltage Feedback PSRR VFB Pin Bias Current Bandwidth of Error Amplifier Closed Loop Quiescent Current No Switching Output Current Minimum Output Current Reference Line Regulation Reference Load Regulation PWM Switching Frequency (1) Maximum Duty Cycle Switching Current Limitation Switch VDS Efficiency Thermal Shut Down (1) Thermal Shut Down Hysteresis (1) Load Transient Response (1) ISW = 750 mA IOUT =10mA to 1.2A 70 130 150 15 IOUT = 100mA to 700mA tR = tF 100ns, TA = 25C IOUT = 10mA to short, TA = 25C -5 +5 +5 VIN = 3V to 16V IOUT = 10mA to 1.2A VFB = 0.8V, TA =25C 1.2 VIN =3V to 16V 1.5 1 0.032 0.0014 1.5 87 1.65 200 350 0.06 0.003 1.8 300 2.5 Test Conditions 1Hz < Frequency VIN Min. 784 Typ. 800 -60 Max. 816 600 Unit mV dB nA KHz mA A mA %VOUT /VIN %VOUT /mA MHz % A mV % C C %VO %VO
Short Circuit Removal VOUT/ Response (1) IOUT @IO = short
NOTE 1: Guaranteed by design, not tested in production.
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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 = 100s 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 150C 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 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.
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ST1S03
TYPICAL CHARACTERISTICS (CIN = 4.7F, CO = 22F, L1 = 3.3H, 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
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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
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ST1S03
Figure 16: Switch RDS-ON vs Temperature Figure 19: Load Transient Response
VCC=5V, I O=200mA to 1.2A, CI=4.7F, CO=22F, L=3.3H, TON=38s, TJ=25C
Figure 17: Switch Current Limitation vs Temperature
Figure 20: Start-Up Transient
VCC = 5V, T J = 25C
Figure 18: Load Transient Response
Figure 21: Start-Up Transient
VCC=5V, I O=100mA to 780mA, C I=4.7F, CO=22F, L=3.3H, TON=38s, TJ=25C
VCC = 5V, T J = 25C
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ST1S03
DFN6 (3x3) MECHANICAL DATA
mm. DIM. MIN. A A1 A2 A3 b D D2 E E2 e L L1 L2 K 0.20 0.20 0.24 0.13 7.9 0.33 2.90 1.92 2.90 1.11 0.95 0.45 7.9 9.4 5.1 3.00 3.00 0.80 0 0.65 0.20 0.43 3.10 2.12 3.10 1.31 13.0 114.2 75.6 114.2 43.7 37.4 17.7 118.1 118.1 TYP MAX. 1.00 0.05 0.75 MIN. 31.5 0.0 25.6 7.9 16.9 122.0 83.5 122.0 51.6 TYP. MAX. 39.4 2.0 29.5 inch
7387339A
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ST1S03
Tape & Reel QFNxx/DFNxx (3x3) MECHANICAL DATA
mm. DIM. MIN. A C D N T Ao Bo Ko Po P 3.3 3.3 1.1 4 8 12.8 20.2 99 101 14.4 0.130 0.130 0.043 0.157 0.315 TYP MAX. 330 13.2 0.504 0.795 3.898 3.976 0.567 MIN. TYP. MAX. 12.992 0.519 inch
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ST1S03
Table 6: Revision History
Date 11-Nov-2004 08-Feb-2005 03-Mar-2005 Revision 1 2 3 Description of Changes First Release. Maturity Change. Mistake on Figure 1, TJ is changed 125 ==> 150C on Table 3.
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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. The ST logo is a registered trademark of STMicroelectronics All other names are the property of their respective owners (c) 2005 STMicroelectronics - All Rights Reserved STMicroelectronics group of companies Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America www.st.com
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