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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 soft start for start-up current limitation and power on delay of 50-100s 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 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).
DFN6 (3x3)
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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
Order codes
Part number ST1S03APMR ST1S03AIPMR ST1S03APUR ST1S03AIPUR May 2007 Packaging Tape & reel Tape & reel Tape & reel Tape & reel Rev. 3 Package DFN6 (3x3 mm) DFN6 (3x3 mm) DFN6D (3x3 mm) DFN6D (3x3 mm) 1/14
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Contents
ST1S03A
Contents
1 2 3 4
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Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5 6 7
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ST1S03A
Diagram
1
Figure 1.
Diagram
Schematic diagram
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Pin configuration
ST1S03A
2
Figure 2.
Pin configuration
Pin configuration (top view)
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ST1S03A
ST1S03AI
Table 1.
Pin N 1 2 3 4 5 6
Pin description
Symbol VFB GND SW VIN_SW VIN_A N.C./INH 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 Note
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ST1S03A
Maximum ratings
3
Table 2.
Maximum ratings
Absolute maximum ratings
Parameter Positive power supply voltage Positive power supply voltage Max voltage of inhibit pin 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 7 -0.3 to 7 -0.3 to 6 -0.3 to 7 2.5 1 150 -25 to 150 300 Unit V V V V V mA C C C
Symbol VIN_SW VIN_A VINH SWITCH Voltage VFB
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TSTG TLEAD
Note:
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 Thermal resistance junction-ambient Thermal resistance junction-case Value 10 55 Unit C/W C/W
Table 3.
Symbol RthJA RthJC
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Electrical characteristics
ST1S03A
4
Table 4.
Electrical characteristics
Electrical characteristics (VIN_SW = VIN_A = VINH = 5V, CI = 4.7F, CO = 22F, L1 = 3.3H, TJ = 0 to 125C (unless otherwise specified. Typical values are referred to 25C)
Symbol FB IFB
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Parameter Feedback voltage VFB Pin bias current Quiescent current
Test conditions
Min. 784
Typ. 800
Max. 816 600
Unit mV nA mA A V
VINH > 1.2V VINH < 0.4V Device ON 1.2
1.5 1
VINH IO IO IMIN %VO/VI %VO/IO PWMfS DMAX ISW VDS TSHDN THYS %VO/IO %VO/IO @ IO=Short
Inhibit threshold Device OFF Output current Output current Minimum output current Reference line regulation VI = 2.7V to 5.5V IO = 10mA to 1.5A VFB = 0.8V, TA = 25C Note: 1 1.2 VI = 2.7 to 5.5V VI = 2.7 to 5.5V 1.5 0.8 1 0.2 0.4
A A mA %VO/ VI %VO/ IO 1.8 MHz % A 200 mV %
Reference load regulation PWM Switching frequency Maximum duty cycle Switching current limitation Switch VDS Efficiency Thermal shutdown Thermal shutdown hysteresis Load transient response
0.2 1.5 87 2.5
ISW = 800mA IO = 10mA to 100mA, VO = 3.3V IO = 100mA to 1.5A, VO = 3.3V Note: 1 Note: 1 IO = 100mA to 1.5A, TA = 25C tR = tF 100ns, Note: 1 IO = 10mA to short, TA = 25C Note: 1 -3 70 85 130 150 15
C C +3 %VO
Short circuit removal response
-10
+10
%VO
Note: 1 Guaranteed by design, but not tested in production
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ST1S03A
Typical application
5
Figure 3.
Typical application
Application circuit
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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=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 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.
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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.
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ST1S03A
Package mechanical data
6
Package mechanical data
In order to meet environmental requirements, ST offers these devices in ECOPACK(R) 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.
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Package mechanical data
ST1S03A
DFN6 (3x3) MECHANICAL DATA
mm. DIM. MIN. A A1 A2 A3
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inch MAX. 1.00 0.05 0.75 MIN. 31.5 0.0 25.6 7.9 0.43 13.0 114.2 75.6 114.2 43.7 37.4 0.45 7.9 9.4 0.13 5.1 7.9 17.7 118.1 118.1 16.9 122.0 83.5 122.0 51.6 TYP. MAX. 39.4 2.0 29.5
TYP
0.80 0 0.65 0.20 0.33 2.90 1.92 2.90 1.11 0.95 0.20 0.24 3.00 3.00
b D D2 E E2 e L L1 L2 K
3.10 2.12 3.10 1.31
0.20
7387339A
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ST1S03A
Package mechanical data
DFN6D (3x3) Mechanical Data
mm. Dim. Min. A A1 A3
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inch. Max. 1.00 Min. 0.031 0 0.001 0.008 0.45 0.009 0.114 0.088 0.114 0.059 0.037 0.50 0.012 0.016 0.020 0.118 0.118 0.018 0.122 0.098 0.122 0.069 Typ. Max. 0.039 0.002
Typ.
0.80 0 0.02 0.20 0.23 2.90 2.23 2.90 1.50 0.95 0.30 0.40 3.00 3.00
0.05
b D D2 E E2 e L
3.10 2.50 3.10 1.75
7946637B
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Package mechanical data
ST1S03A
Tape & Reel QFNxx/DFNxx (3x3) Mechanical Data
mm. Dim. Min. A C D
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inch. Max. 330 Min. Typ. Max. 12.992 0.504 0.795 2.362 18.4 0.724 0.130 0.130 0.043 0.157 0.315 0.519
Typ.
12.8 20.2 60
13.2
N T Ao Bo Ko Po P
3.3 3.3 1.1 4 8
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ST1S03A
Revision history
7
Table 5.
Revision history
Revision history
Revision 1 2 3 First release. Table 2. has been updated. Add new mechanical data DFN6D and order codes has been updated. Changes
Date 04-May-2006 06-Jun-2006 29-May-2007
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ST1S03A
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