ST1S03A
1.5 A, 1.5 MHz adjustable, with inhibit function
step-down switching regulator
Features
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Step-down current mode PWM (1.5 MHz) DC-
DC converter
2 % DC output voltage tolerance
Internal soft start for start-up current limitation
and power on delay of 50-100 µs
Typical efficiency: > 85 %
Inhibit function
1.5 A output current capability
Not switching quiescent current: max 1.5 mA
over temperature range
Switch V
DS
: max 200 mV @ I
SW
= 750 mA
Uses tiny capacitors and inductors
Available in DFN6D 3x3 exposed pad
DFN6D (3x3 mm)
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
dissipation may cause an high heating of the
application environment. It provides up to 1.5 A
over an input voltage range of 3 V to 5.5 V. An high
switching frequency (1.5 MHz) 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 ESR SMD ceramic
capacitors. The device is thermal protected and
current limited to prevent damages due to
accidental short circuit. The ST1S03A is available
in DFN6D (3x3 mm).
Table 1.
Device summary
Order codes
ST1S03APUR
ST1S03AIPUR
June 2008
Packaging
Tape and reel
Tape and reel
Rev 6
Package
DFN6D (3x3 mm)
DFN6D (3x3 mm)
1/14
www.st.com
14
ST1S03A
Contents
1
2
3
4
5
6
7
8
Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Application notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2/14
Pin configuration
ST1S03A
2
Figure 2.
Pin configuration
Pin configuration (top view)
ST1S03A
ST1S03AI
Table 2.
Pin n°
1
2
3
4
5
6
Pin description
Symbol
V
FB
GND
SW
V
IN_SW
V
IN_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
Name and function
4/14
ST1S03A
Maximum ratings
3
Table 3.
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
V
IN_SW
V
IN_A
V
INH
SWITCH
Voltage
V
FB
I
VFB
T
J
T
STG
T
LEAD
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
55
10
Unit
°C/W
°C/W
Table 4.
Symbol
R
thJA
R
thJC
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