Philips Semiconductors
Product data
500 mA LDO with ON/OFF control and V
ref
bypass
SA57022-XX
GENERAL DESCRIPTION
The SA57022-XX has an extremely precise fixed output with a
typical accuracy of
±2%.
It is designed to provide very low dropout
and ultra low noise with an optional Bypass pin, and fast transient
response. Supply current is reduced to zero (typical).
The SA57022-XX incorporates both over-temperature and
over-current protection. The SA57022-XX is stable with an output
capacitor of only 1.0
µF
and has a maximum output current of
500 mA. It is available in the 7-pin small outline package (SOP002).
FEATURES
•
Very low dropout voltage: 300 mV typ. (I
out
= 500 mA)
•
High precision output voltage:
±2%
•
Output current capacity: 500 mA
•
Low noise: 75
µV
rms
typ. @ 20 Hz to 80 KHz, for C
n
= 470 pF.
•
Extremely good line regulation: 10 mV typical
•
Extremely good load regulation: 20 mV typical
•
Low temperature drift co-efficient to V
out
:
±100
ppm/°C
•
Internal current limit and thermal shut-down circuits
•
Input voltage range: –0.3 V to 12 V
•
Wide preset output voltage range: 1.8 V to 5 V
•
Wide operating temperature range: –40
°C
to +85
°C
SIMPLIFIED SYSTEM DIAGRAM
V
IN
APPLICATIONS
•
Battery-operated systems
•
Portable computers
•
Cameras, VCRs and camcorders
•
PCMCIA cards, modems, pagers
•
Cellular/GSM/PHS phones
•
Linear post-regulator for SMPS
•
Instrumentation
7
1
V
OUT
CURRENT
LIMIT
DRIVER
R
REFERENCE
5
ON/OFF
BIAS
THERMAL
SHUTDOWN
R
GND 3
4
BYPASS
SL01527
Figure 1. Simplified system diagram.
2003 Oct 13
2
Philips Semiconductors
Product data
500 mA LDO with ON/OFF control and V
ref
bypass
SA57022-XX
ORDERING INFORMATION
PACKAGE
TYPE NUMBER
SA57022-XXD
DESCRIPTION
small outline 7-pin surface mount (see dimensional drawing)
VERSION
SOP002
TEMPERATURE
RANGE
–40 to +85
°C
NOTE:
The device has six voltage output options, indicated by the
XX
on
the order code.
XX
18
25
28
30
33
50
VOLTAGE (Typical)
1.8 V
2.5 V
2.8 V
3.0 V
3.3 V
5.0 V
Part number marking
Each package is marked with a four letter code. The first three
letters designate the product. The fourth letter, represented by ‘x’, is
a date tracking code.
Part number
SA57022-18
SA57022-25
SA57022-28
SA57022-30
SA57022-33
SA57022-50
Marking
ALMx
ALNx
ALPx
ALRx
ALSx
ALTx
PIN CONFIGURATION
PIN DESCRIPTION
PIN
SYMBOL
V
OUT
NC
GND
BYPASS
DESCRIPTION
Regulated output voltage.
No connection.
Ground.
Reference bypass input. Connecting a
470 pF capacitor further reduces output
noise.
Output voltage On/Off control pin.
Substrate ground pin. This pin must be
connected to ground.
Power supply input.
1
2
V
OUT
NC
GND
BYPASS
1
2
7
V
IN
SA57022-XX
3
4
6
GND
3
4
5
ON/OFF
5
SL01525
ON/OFF
GND
V
IN
6
Figure 2. Pin configuration.
7
MAXIMUM RATINGS
SYMBOL
V
IN
V
IN(OPR)
I
OUT
T
oper
T
stg
P
D
P
D
Supply voltage
Operating voltage
Output current
Operating temperature
Storage temperature
Power dissipation (Note 1)
Power dissipation (Note 2)
PARAMETER
MIN.
–0.3
V
OUT(typ)
+ 0.5
0
–40
–40
–
–
MAX.
+12
V
OUT(typ)
+ 10
500
+85
+150
400
950
UNIT
V
V
mA
°C
°C
mW
mW
NOTES:
1. Unattached.
2. Mounted on double-sided glass epoxy PCB, with copper ground plane 192
×
142
×
1.2 mm.
2003 Oct 13
3
Philips Semiconductors
Product data
500 mA LDO with ON/OFF control and V
ref
bypass
SA57022-XX
APPLICATION INFORMATION
VOLTAGE
INPUT
C
IN
= 1
µF
CERAMIC
7
V
IN
6
SUB
5
ON/OFF
V
OUT
1
TO LOAD
NC
2
GND
3
BYPASS
4
C
OUT
= 2.2
µF
CERAMIC
C
n
= 470 pF
CERAMIC
SL01526
Figure 3. Typical application circuit.
Input capacitor
An input capacitor of 1.0
µF
(min) should be connected from V
IN
to
GND if there is more than 10 inches of wire between the regulator
and the AC filter capacitor, or if a battery is operated as the power
source. The capacitor should be less than 1 cm from the input pin.
Aluminum electrolytic or tantalum capacitor types can be used.
(Because many aluminum electrolytic capacitors freeze at
approximately –30
°C,
solid tantalums are recommended for
applications operating below –25
°C.)
When operating from sources
other than batteries, supply-noise rejection and transient response
can be improved by increasing the value of the input and output
capacitors and employing passive filtering techniques.
Thermal shutdown
Integrated thermal protection circuitry shuts the regulator off when
die temperature exceeds 150
°C.
The regulator remains off until the
die temperature drops to approximately 140
°C.
Power dissipation
The amount of power the regulator dissipates is primarily a function
of input and output voltage, and output current. The following
equation is used to calculate worst case actual power dissipation:
P
D
[
V
IN(max)
*
V
OUT(min)
I
LOAD(max)
Eqn. (1)
Output capacitor
Phase compensation is used to ensure stable operation even if load
current varies. For this reason, an output capacitor with good
frequency characteristics is needed. Set it as close to the circuit as
possible, with wires as short as possible. A 1.0
µF
capacitor from
V
OUT
to ground is recommended. The output capacitor should have
an ESR (effective series resistance) of 5.0
Ω
or less, and a resonant
frequency above 1.0 MHz.
Where:
P
D
= worst case actual power dissipation
V
IN(max)
= maximum voltage on V
IN
V
OUT(min)
= minimum regulator output voltage
I
LOAD(max)
= maximum output (load) current
The maximum allowable power dissipation, as shown in Equation (2),
is a function of the maximum ambient temperature (T
amb(max)
), the
maximum allowable die temperature (125
°C),
and the thermal
resistance from junction-to-air (R
th(j–a)
).
P
D(max)
+
T
j(max)
*
T
amb(max)
R
th(j*a)
Eqn. (2)
Optional BYPASS capacitor
A 470 pF capacitor connected from the BYPASS input to ground
reduces noise present on the internal reference, which in turn
significantly reduces output noise. This capacitor must have low
leakage, because the pin is high impedance. If output noise is not a
concern, this pin may be left unconnected. Larger capacitor values
may be used, but results in a longer time period to rated output
voltage when power is initially applied.
The SUB (heat sink) pin must be connected to ground with a wide
trace.
PCB layout hints
The component placement around the LDO should be done carefully
to achieve good dynamic line and load response. The input and
noise capacitor should be kept close to the LDO. The rise in junction
temperature depends on how efficiently the heat is carried away
from the junction to ambient. The junction to lead thermal
impedance is a characteristic of the package and fixed. The thermal
impedance between lead to ambient can be reduced by increasing
the copper area on PCB. Increase the input, output and ground
trace area to reduce the junction-to-ambient impedance.
ON/OFF
The regulator is fully enabled when a logic HIGH is applied to this
input. The regulator enters shutdown when a logic LOW is appplied
to this input. During shutdown, regulator output voltage falls to
zero,and supply current is reduced to 1.0
µA
max, and V
OUT
falls to
zero. For use as an always-on regulator, connect ON/OFF pin to the
supply voltage, as shown in Figure 3.
Optional BYPASS diode
If the voltage on the output pin rises above the input voltage, as
might happen in some applications, the overcurrrent will flow via
internal parasitic diodes from output to input. To prevent this,
connect a bypass diode between the output and input pins.
2003 Oct 13
5
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