ST763A
SERIES
3.3V STEP DOWN
CURRENT MODE PWM DC-DC CONVERTERS
s
s
s
s
s
s
s
s
s
OUTPUT VOLTAGE 3.3V
SUPPLY VOLTAGE RANGE FROM 3.3V TO
11V
GUARANTEED OUTPUT CURRENT: 500mA
TYPICAL OPERATION FREQUENCY:
200KHz
VERY LOW QUIESCENT CURRENT: 0.6mA
ON MODE 0.2µA OFF MODE
SWITCH ON/OFF CONTROL
TYPICAL EFFICENCY: 90%
OPERATING TEMPERATURE RANGE:
-40°C TO 85°C
AVAILABLE IN SO-8 AND DIP-8 PACKAGES
DIP-8
SO-8
DESCRIPTION
The ST763A is a step-down switching regulator . It
operates from 3.3V to 11V giving a fixed 3.3V
output voltage, delivering up to 500mA. The
mainly features are typical efficiency of 90%,
quiescent current of 0.6mA, and only 0.2µA in
shut-down.
The PWM current mode control provides precise
output regulation and very good transient
response. Output voltage accuracy is guaranteed
to be
±5%
over line, load and temperature
variations. A minimum number of external
components is used and the fixed frequency
switching allows easy filtering of output ripple and
noise.
Other features of this ddevice are cycle-by-clicle
current limiting, overcurrent limiting, under voltage
lockout and programmable soft-start protection.
A 22µH inductor works in most applications, so no
sophisticated design is necessary.
Package available are SO-8 and DIP-8.
Typical application are in 5V to 3.3V converters,
cellular phones, portable instruments, hand-held
computers, and peripherals.
SCHEMATIC DIAGRAM
November 2000
1/10
ST763A SERIES
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 (AC series)
(AB 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
ST763AB
ST763AC
DIP8
ST763ABN
ST763ACN
SO-8
ST763ABD
ST763ACD
SO-8 (T&R)
ST763ABDTR
ST763ACDTR
2/10
ST763A SERIES
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 47nF capacitor
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
3.3V 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
3/10
ST763A SERIES
ELECTRICAL CHARACTERISTICS
(V
CC
=5V, I
O
= 0mA, T
A
= T
MIN
to T
MAX
, unless otherwise specified.)
Symbol
V
CC
V
O
∆V
O
∆V
O
η
Parameter
Input Voltage
Output Voltage
Line Regulation
Load Regulatio
Power Efficency
I
O
= 1 to 500mA
I
O
=300mA
I
O
=100mA
ON Mode (Including Switch Current)
OFF Mode
V
IH
V
IL
I
SHDN
V
LOCK
I
LEAK
V
REF
∆V
REF
f
OSC
R
C
SHDN Input High Threshold
SHDN Input Low Threshold
Shutdown Input Leakage
Current
Under Voltage Lockout
LX Leakage Current
Reference Voltage
Temeperature Reference
Drift
Switching Frequency
Compensation Pin
Impedance
2
0.25
1
V
CC
Falling
I
LX
=500mA
V
CC
= 12V
T
A
= 25°C
T
A
= T
MIN
to T
MAX
159
V
LX
= 0V
1.18
2.7
1
10
1.25
50
200
7500
212.5
1.32
3
V
CC
= 4 to 11V
I
O
=0 to 300mA
V
CC
= 4.75 to 11V I
O
=0 to 500mA
Test Conditions
Min.
3.3
3.135
3.135
3.3
3.3
0.13
0.005
88
90
0.6
0.2
2.5
100
Typ.
Max.
11
3.465
3.465
Unit
V
V
V
%/V
%/mA
%
%
mA
µA
V
V
µA
V
Ω
nA
V
ppm/°C
KHz
Ω
I
SUPPLY
Supply Current
R
DS(on)
LX On Resistance
TYPICAL APPLICATION CIRCUIT
SHDN
REF
0.047 µF
Vin
Vcc
+
22 µH
100 µF
1 µF
Lx
STPS330U
SS
1500 pF
GND
OUT
Vout
CC
+
470 pF
220 µF
4/10
ST763A SERIES
TYPICAL PERFORMANCE CHARACTERISTICS
(unless otherwise specified T
j
= 25°C
Figure 1 :
Output Voltage vs Temperature
Figure 4 :
Efficency vs Temperature
Figure 2 :
Output Voltage vs Input Voltage
Figure 5 :
Efficency vs Output Current
Figure 3 :
Reference Voltage vs Temperature
Figure 6 :
LX Leakage Current vs Temperature
5/10
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