Rev. 11/21/00
ALPHA
AS2930
1
8-Pin Surface Mount
Top View
2
3
4
5
6
7
8
SPX2955
OUTPUT
SENSE
SHUTDOWN
GROUND
INPUT
FEEDBACK
5V/ 3.3V TAP
ERROR
SPX2955/56/57
350mA Low Drop Out Voltage Regulator
with Shutdown
(PRELIMINARY INFORMATION)
FEATURES
APPLICATIONS
Output Accuracy 5V, 3.3V@ 350mA Output Battery Powered Systems
Very Low Quiescent Current
Cordless Telephones
Low Dropout Voltage
Radio Control Systems
Extremely Tight Load And Line Regulation
Portable/Palm Top/Notebook Computers
Very Low Temperature Coefficient
Portable Consumer Equipment
Current & Thermal Limiting
Portable Instrumentation
Error Flag Warns Of Output Dropout
Automotive Electronics
Logic-Controlled Electronic Shutdown
SMPS Post-Regulator
Output Programmable From 1.24V to 29V
Voltage Reference
PRODUCT DESCRIPTION
The SPX2955/56/57 is a low power voltage regulator. This device is an excellent choice for use in battery-powered applications such
as cordless telephones, radio control systems, and portable computers. The SPX2955/56/57 features very low quiescent current
(100
A Typ.) and very low dropout voltage. This includes a tight initial tolerance of 1% max and 2% max., and very low output
temperature coefficient, making the SPX2955/56/57 useful as a low-power voltage reference.
The error flag output feature is used as power-on reset for warning of a low output voltage, due to a falling voltage input of batteries.
Another feature is the logic-compatible shutdown input which enables the regulator to be switched on and off. The SPX2955/56/57 is
offered in 3-pin and 5-pin TO-220 package compatible with other 5 volt and adjustable regulators, in 8-Pin Plastic Dip SO-8 (same pin
out as SPX2951) and surface mount TO-263 packages.
The regulator output voltage (of the 8-pin package and 5-pin TO-220 & TO-263) may be pin-strapped for a 5V and 3.3V or
programmed from 1.24V to 29V with an external pair of resistors. Look for SPX2951 for 150mA and SPX2954 for 250mA
applications.
PIN CONNECTIONS
TO-263-5 Package
Top View
1 2 3 4 5
SPX2956/57
INPUT
GND
INPUT
ERROR
OUTPUT
GND
Five Lead Package Pin Functions:
1)
SPX2956
SPX2957
3)
4)
5)
ADJUST
SHUTDOWN
OUTPUT
SHUTDOWN
2)
Front View
3
2
1
TO-263-3 Package
V
OUT
GND
V
IN
SPX2955
Top View
SPX2956/57
TO-220-5 Package
5
4
3
2
1
Front View
TO-220-3 Package
SPX2955
1
2
3
V
OUT
GND
V
IN
Rev. 11/21/00
SPX2955/56/57
ABSOLUTE MAXIMUM RATINGS
Power Dissipation..........................................Internally Limited
Operating Input Supply Voltage....................... 3.0V to +60V
Lead Temp. (Soldering, 5 Seconds) ................................ 260C
Feedback Input Voltage ..................................-1.5V to +30V
Storage Temperature Range .............................. -65 to +150C
Shutdown Input Voltage..................................-0.3V to +30V
Operating Junction Temperature Range (Note 9)
Error Comparator Output ................................-0.3V to +30V
SPX2955/56/57...................................... -40C to +125C
ESD Rating ............................................................ 2KV Min
ELECTRICAL CHARACTERISTICS
at V
S
=15V,T
A
=25C, unless otherwise specified. Boldface applies over the full
operating temperature range.
PARAMETER
CONDITIONS
(Note 2)
Typ.
SPX2955/56/57A
Min Max
SPX2955/56
Min Max
UNITS
3.3V Version
Output Voltage
-
40
C
T
J
+125C
1mA
I
L
350mA
3.3
3.3
3.267
3.217
3.333
3.382
3.234
3.185
3.366
3.415
V
5V Version
Output Voltage
-
40
C
T
J
+125C
1mA
I
L
350mA
5.0
5.0
4.950
4.880
5.050
5.120
4.900
4.870
5.100
5.130
V
All Voltage Options
SPX2955/56/57A SPX2955/56/57
Output Voltage
Temperature Coefficient
(Note 1)
20
100 150
ppm/C
Line Regulation ( Note 3)
6V
V
IN
30V (Note 4)
0.03 0.1
0.40
0.20
0.80
%max
Load Regulation ( Note 3 )
I
L
= 1 to 350mA
I
L
= 0.1 to 1mA
0.04
0.20
0.30
0.30
0.50
%max
Dropout Voltage
( Note 5 )
I
L
= 1mA
I
L
= 100mA
I
L
= 250mA
I
L
= 350mA
60
220
250
375
100
150
250
300
300
420
400
500
100
150
250
300
350
420
500
600
mV
Ground Current
I
L
= 1mA
I
L
= 100mA
I
L
= 250mA
I
L
= 350mA
50
0.5
4
5
100
150
1
2
8
10
10
15
100
150
1
2
8
10
10
15
A
mA
Current Limit
V
OUT
= 0
700
800
700
800
mA
Thermal Regulation
0.05
0.2
0.2
%/w
Output Noise,
10Hz to 100kHz
I
L
= 100mA
C
L
= 2.2F
C
L
= 33F
400
260
V
Vrms
Rev. 11/21/00
SPX2955/56/57
(Continued)
PARAMETER
CONDITIONS
(Note 2)
Typ. SPX2955/57A
Min Max
SPX2955/57
Min Max
UNITS
Adjustable Versions only
Typ. SPX2955/57A
SPX2955/57B
Reference Voltage
1.235 1.210
1.200
1.260
1.270
1.200
1.990
1.270
1.280
V
Reference Voltage
Over Temperature (Note 6)
1.185 1.285 1.185 1.285 V
Feedback Pin Bias Current
20 40
60
60
80
NA
Reference Voltage Temperature
Coefficient
(Note 7)
50
ppm/C
Feedback Pin Bias Current
Temperature Coefficient
0.1
nA/C
Error Comparator
Output Leakage Current
V
0H
= 30V
0.01
1.00
2.00
1.00
2.00
A
Output Low Voltage
V
IN
= 4.5V
I
0L
= 400
A
150 250
400
250
400
mV
Upper Threshold Voltage
(Note 8)
60
40
25
40
25
mV
Lower Threshold Voltage
(Note 8)
75
95
140
95
140
mV
Hysteresis (Note
8)
15
mV
Shutdown Input
Input logic Voltage
Low (Regulator ON)
High (Regulator OFF)
1.3
2.0
0.7
2.0
0.7
V
Shut down Pin Input Current
V
S
= 2.4V
V
S
= 30V
30
450
50
100
600
750
90
150
800
1000
A
Regulator Output Current in Shutdown
3
10
20
15
25
A
Note 1: Output or reference voltage temperature coefficients defined as the worst case voltage change divided by the total temperature range.
Note 2: Unless otherwise specified all limits are guaranteed for T
j
= 25
C, V
IN
= 6V, I
L
= 100
A and C
L
= 1
F. Additional conditions for the 8-pin versions are
feedback tied to 5V tap and output tied to output sense (V
OUT
= 5V) and V
SHUTDOWN
0.8V.
Note 3: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output voltage due to heating effects are
covered under the specification for thermal regulation.
Note 4: Line regulation for the SPX2955/56/57 is tested at 150
C for I
L
= 1 mA. For I
L
= 100
A and T
J
= 125
C, line regulation is guaranteed by design to 0.2%. See
typical performance characteristics for line regulation versus temperature and load current.
Note 5: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below its nominal value measured at 1V differential at
very low values of programmed output voltage, the minimum input supply voltage of 2V ( 2.3V over temperature) must be taken into account.
Note 6: V
REF
V
OUT
(Vin - 1V), 2.3 Vin30V, 100AI
L
250 mA, T
J
T
JMAX
.
Note 7: Comparator thresholds are expressed in terms of a voltage differential at the feedback terminal below the nominal reference voltage measured at 6V input. To
express these thresholds in terms of output voltage change, multiply by the error amplifier gain = V
OUT
/V
REF
= (R1 + R2)/R2. For example, at a programmed output
voltage of 5V, the Error output is guaranteed to go low when the output drops by 95 mV x 5V/1.235 = 384 mV. Thresholds remain constant as a percent of V
OUT
as
V
OUT
is varied, with the dropout warning occurring at typically 5% below nominal, 7.5% guaranteed.
Note 8: V
SHUTDOWN
2V, V
IN
30V, V
OUT
=0, Feedback pin tied to 5V Tap.
Note 9: The junction -to-ambient thermal resistance of the TO-92 package is 180
C/ W with 0.4" leads and 160C/ W with 0.25" leads to a PC board.
The thermal resistance of the 8-Pin DIP package is 105
C/W junction-to-ambient when soldered directly to a PC board. Junction-to-ambient thermal resistance for the
SOIC (S) package is 160
C/W.
Rev. 11/21/00
FEEDBACK
INPUT
OUTPUT
UNREGULATED DC
SHUTDOWN
GROUND
ERROR
______
5V TAP
SENSE
5V @ 350mA
MAX
TO CMOS OR
TTL
REFERENCE
ERROR DETECTION
COMPARATOR
ERROR
AMPLIFIER
1.23V
FROM
CMOS OR
TTL
+
+
+
+
+
+
60 mV
3
7
8
1
2
6
5
4
..
60k
330k
180k
..
..
..
1
F
_
_
SPX2955/56/57 Block Diagram
SPX2955/56/57
Rev. 11/21/00
SPX2955/56/57
APPLICATION HINTS
EXTERNAL CAPACITORS
The stability of the SPX2955/56/57 requires a 2.2
F or greater
capacitor between output and ground. Oscillation could occur
without this capacitor. Most types of tantalum or aluminum
electrolytic works fine here. For operations of below -25
C solid
tantalum is recommended since the many aluminum types have
electrolytes the freeze at about 30
C. The ESR of about 5 or
less and resonant frequency above 500kHz are the most
important parameters in the value of the capacitor. The capacitor
value can be increased without limit.
At lower values of output current, less output capacitance is
required for stability. For the currents below 10mA the value of
the capacitor can be reduced to 0.5
F and 0.15F for 1mA. More
output capacitance needed for the 8-pin version at voltages below
5V since it runs the error amplifier at lower gain. At worst case
5
F or greater must be used for the condition of 250mA load at
1.23V output.
The SPX2955/56/57, unlike other low dropout regulators will
remain stable and in regulation with no load in addition to the
internal voltage divider. This feature is especially important in
application like CMOS RAM keep-alive. When setting the output
voltage of the SPX2955/56/57, a minimum load of 10mA is
recommended.
If there is more than 10 inches of wire between the input and the
AC filter capacitor or if a battery is used as the input then a 0.1
F
tantalum or aluminum electrolytic capacitor should be placed
from the input to the ground.
Instability can occur if there is stray capacitance to the
SPX2955/56/57 feedback terminal (pin 7). This could cause
more problems when using a higher value of external resistors to
set the output voltage.
This problem can be fixed by adding a 100pF capacitor between
output and feedback and increasing the output capacitor to at least
3.3
F.
ERROR DETECTION COMPARATOR OUTPUT
The Comparator produces a logic low output whenever the
SPX2955/56/57 output falls out of regulation by more than around
5%. This is around 60mV offset divided by the 1.235 reference
voltage. This trip level remains 5% below normal regardless of the
programmed output voltage of the regulator. Figure 1 shows the
timing diagram depicting the ERROR signal and the regulator output
voltage as the SPX2955/56/57 input is ramped up and down. The
ERROR signal becomes low at around 1.3V input, and goes high
around 5V input (input voltage at which Vout = 4.75). Since the
SPX2955/56/57's dropout voltage is load dependent, the input voltage
trip point (around 5V) will vary with the load current. The output
voltage trip point (approx. 4.75V) does not vary with load.
The error comparator has an open-collector output, which requires an
external pull-up resistor. Depending on the system requirements the
resistor may be returned to 5V output or other supply voltage. In
determining the value of this resistor, note that the output is rated to
sink 400
A, this value adds to battery drain in a low battery
condition. Suggested values range from 100K to 1M
. If the output
is unused this resistor is not required.
PROGRAMMING THE OUTPUT VOLTAGE OF
SPX2955/56/57
The SPX2956/57 may be pin-strapped for 5V using its internal
voltage divider by tying Pin 1 (output) to Pin 2 (sense) and Pin 7
(feedback) to Pin 6 (5V Tap).
+
+
+
+
4 .7 5 V
O U T PU T
V O L T A G E
E R R O R *
_ _ _ _ _ _ _
IN P U T
V O L T A G E
1 .3 V
5 .0 V
F ig u r e 1 . E R R O R O u tp u t T im in g
_ _ _ _ _ _ _
* S e e A p p lica tio n In fo .
100K
OUTPUT
ERROR
ERROR
______
SD
V
OUT
GND
FB
+V
IN
+V
IN
1.23V
1.2 to
29V
R
1
.01uF
10uF
R
2
V
REF
3
8
5
1
4
7
SHUTDOWN
INPUT
+
Figure 2. Adjustable Regulator
SPX2955/57
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