ST730A
5V STEP-DOWN,
CURRENT-MODE PWM DC-DC CONVERTERS
s
s
s
s
s
s
s
s
s
s
UP TO 450mA LOAD CURRENTS
200kHz HIGH-FREQUENCY
CURRENT-MODE PWM
85% TO 96% EFFICIENCIES
33µH OR 100µH PRE-SELECTED
INDUCTOR VALUE, NO COMPONENT
DESIGN REQUIRED
0.8mA QUIESCENT CURRENT
0.3µA SHUTDOWN SUPPLY CURRENT
ADJUSTABLE OUTPUT VOLTAGE
OVERCURRENT, SOFT-START AND
UNDERVOLTAGE LOCKOUT PROTECTION
CYCLE-BY-CYCLE CURRENT LIMITING
PACKAGE AVAILABLE: DIP-8 AND SO-8
DIP-8
SO-8
DESCRIPTION
The ST730A is a 5V output CMOS, step-down
switching regulator. The ST730A accepts inputs
between 5.2V and 11V and delivers 450mA.
Typical efficiencies are 85% to 96%.
Quiescent supply current is 0.8mA and only 0.3µA
in shutdown mode. The output does not exhibit
frequency over this specified range. Pulse-width
modulation (PWM) current-mode control provides
SCHEMATIC DIAGRAM
precise output regulation and excellent transient
responses.
Output
voltage
accuracy
is
guaranteed to be ±5% over line, load, and
temperature varations.
Fixed-frequency switching and absence of
subharmonic ruipple allows easy filtering of output
ripple and noise, as well as the use of small
external components. This regulators require only
a single inductor value to work in most
applications, so no inductor design is necessary.
Typical applications are: Cellular phones & radios,
portable Instruments, Portable Communications
Equipments and Computer Peripherals.
January 2003
1/9
ST730A
ABSOLUTE MAXIMUM RATINGS
Symbol
V
CC
V
LX
V
SHDN
V
S
,V
C
I
LX
I
REF
P
TOT
T
stg
T
op
DC Input Voltage
Switch Pin Voltage
Shutdown Voltage (SHDN)
Soft Start (SS) and Compensation Capacitor (CC) Pins Voltage
Switching Peak Current
Reference Current
Continuous Power Dissipation at T
A
=70°C (DIP-8)
(SO-8)
Storage Temperature Range
Operating Junction Temperature Range (C series)
(B series)
Parameter²
Value
-0.3 to 12
-0.3 to (V
CC
+ 0.3)
-0.3 to (V
CC
+ 0.3)
-0.3 to (V
CC
+ 0.3)
2
2.5
550
344
-40 to +150
0 to +70
-40 to +85
Unit
V
V
V
V
A
mA
mW
mW
°C
°C
°C
Absolute Maximum Ratings are those values beyond which damage to the device may occur. Functional operation under these condition is
not implied.
THERMAL DATA
Symbol
R
thj-amb
Parameter
Thermal Resistance Junction-ambient (*)
SO-8
160
DIP-8
100
Unit
°C/W
(*) This value depends from thermal design of PCB on which the device is mounted.
ORDERING CODES
TYPE
ST730AB
ST730AC
DIP8
ST730ABN
ST730ACN
SO-8
ST730ABD
ST730ACD
SO-8 (T&R)
ST730ABD-TR
ST730ACD-TR
2/9
ST730A
CONNECTION DIAGRAM
(top view)
PIN DESCRIPTION
Pin N°
1
2
3
4
5
6
7
8
Symbol
SHDN
REF
SS
CC
OUT
GND
LX
V
CC
Name and Function
Shutdown control (active low): If connected to GND the IC is in shutdown.
Connect to V
CC
for normal operation (ON MODE)
Reference Output Voltage: (1.25V): Bypass to GND with a capacitor that does not
exceed 47nF
Soft Start: a capacitor between SS and GND provides soft-start and short-circuit
protections.
Compensation Capacitor Input: externally compensates the outer (voltage)
feedback loop. Connect to OUT with 330pF capacitor
Output Voltage Sense Input: provides regulation of feedback sensing. Connect to
5V output.
Ground
Switch Output. Drain of internal P-Channel Power MOSFET
Supply Voltage Input. Bypass to GND with 1µF ceramic capacitance and large
value electrolytic capacitor in parallel. The 1µF capacitor must be as close as
possible to the GND and V
CC
pins
3/9
ST730A
TYPICAL PERFORMANCE CHARACTERISTICS
(unless otherwise specified T
j
= 25°C
Figure 1 :
Efficency vs Output Current
Figure 4 :
Oscillator Frequency vs Input Voltage
Figure 2 :
Supply Current vs Temperature
Figure 5 :
Peak Inductor Current vs Output
Current
Figure 3 :
Oscillator Frequency vs Temperature
Figure 6 :
Output Voltage vs Output Current
5/9
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