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
(100µA 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-220-3 Package
TO-263-5 Package
TO-220-5 Package
8-Pin Surface Mount
OUTPUT
1
2
SPX2955
3
2
1
V
OUT
GND
V
IN
8
INPUT
FEEDBACK
5V/ 3.3V TAP
ERROR
SPX2956/57
SENSE
Five Lead Package Pin Functions:
SPX2956
SPX2957
1)
ERROR
2)
INPUT
3)
GND
4)
OUTPUT
5)
SHUTDOWN
ADJUST
SHUTDOWN
GND
INPUT
OUTPUT
SPX2956/57
SHUTDOWN
GROUND
ALPHA
7
SPX2955
3
AS2930
6
4
5
Front View
TO-263-3 Package
Top View
1 2 34 5
3 V
OUT
1 2 3 4 5
SPX2955
Top View
2 GND
1 V
IN
Top View
Front View
Rev. 11/21/00
SPX2955/56/57
ABSOLUTE MAXIMUM RATINGS
Power Dissipation..........................................Internally Limited
Lead Temp. (Soldering, 5 Seconds) ................................ 260°C
Storage Temperature Range .............................. -65° to +150°C
Operating Junction Temperature Range (Note 9)
SPX2955/56/57...................................... -40C° to +125°C
Operating Input Supply Voltage....................... 3.0V to +60V
Feedback Input Voltage ..................................-1.5V to +30V
Shutdown Input Voltage..................................-0.3V to +30V
Error Comparator Output ................................-0.3V to +30V
ESD Rating ............................................................ 2KV Min
ELECTRICAL CHARACTERISTICS
at V
S
=±15V,T
A
=25°C, unless otherwise specified.
Boldface
applies over the full
operating temperature range.
PARAMETER
3.3V Version
Output Voltage
-
40°C
≤T
J
≤+125°C
CONDITIONS
(Note 2)
Typ.
SPX2955/56/57A
Min
Max
3.267
3.217
3.333
3.382
SPX2955/56
Min
Max
3.234
3.185
3.366
3.415
UNITS
3.3
3.3
V
1mA
≤I
L
≤
350mA
5V Version
Output Voltage
-
40°C
≤T
J
≤+125°C
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
Output Voltage
Temperature Coefficient
Line Regulation ( Note 3)
Load Regulation ( Note 3 )
Dropout Voltage
( Note 5 )
20
(Note 1)
6V
≤
V
IN
≤30V
(Note 4)
I
L
= 1 to 350mA
I
L
= 0.1 to 1mA
I
L
= 1mA
I
L
= 100mA
I
L
= 250mA
I
L
= 350mA
Ground Current
I
L
= 1mA
I
L
= 100mA
I
L
= 250mA
I
L
= 350mA
Current Limit
Thermal Regulation
Output Noise,
10Hz to 100kHz
I
L
= 100mA
V
OUT
= 0
0.05
400
260
0.03
0.04
60
220
250
375
50
0.5
4
5
SPX2955/56/57A
100
0.1
0.40
0.20
0.30
100
150
250
300
300
420
400
500
100
150
1
2
8
10
10
15
700
800
0.2
SPX2955/56/57
150
0.20
0.80
0.30
0.50
100
150
250
300
350
420
500
600
100
150
1
2
8
10
10
15
700
800
0.2
ppm/°C
%max
%max
mV
µA
mA
mA
%/w
µV
Vrms
C
L
= 2.2µF
C
L
= 33µF
Rev. 11/21/00
SPX2955/56/57
(Continued)
PARAMETER
Adjustable Versions only
Reference Voltage
Reference Voltage
Feedback Pin Bias Current
Reference Voltage Temperature
Coefficient
Feedback Pin Bias Current
Temperature Coefficient
Over Temperature (Note 6)
20
(Note 7)
50
nA/°C
0.1
V
0H
= 30V
V
IN
= 4.5V
I
0L
= 400µA
(Note 8)
(Note 8)
(Note 8)
Low (Regulator ON)
High (Regulator OFF)
V
S
= 2.4V
V
S
= 30V
Regulator Output Current in Shutdown
0.01
150
60
75
15
40
25
95
140
1.00
2.00
250
400
40
25
95
140
1.00
2.00
250
400
µA
mV
mV
mV
mV
V
1.3
30
450
3
10
20
2.0
0.7
50
100
600
750
2.0
0.7
90
150
800
1000
15
25
µA
CONDITIONS
(Note 2)
Typ.
Typ.
1.235
SPX2955/57A
Min
Max
SPX2955/57A
1.210
1.260
1.200
1.270
1.185
1.285
40
60
SPX2955/57
Min
Max
SPX2955/57B
1.200
1.270
1.990
1.280
1.185
1.285
60
80
UNITS
V
V
NA
ppm/°C
Error Comparator
Output Leakage Current
Output Low Voltage
Upper Threshold Voltage
Lower Threshold Voltage
Hysteresis
Shutdown Input
Input logic Voltage
Shut down Pin Input Current
µA
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
= 100µA and C
L
= 1µF. 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
= 100µA 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
≤Vin≤30V,
100µA≤I
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 160°C/ 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
SPX2955/56/57
UNREGULATED DC
7
FEEDBACK
8
INPUT
1
OUTPUT
2
SENSE
+
_
FROM
CMOS OR
TTL
3
SHUTDOWN
60k
Ω
..
180k
Ω
..
ERROR
AMPLIFIER
6
5V TAP
5
______
ERROR
TO CMOS OR
TTL
4
REFERENCE
GROUND
+
1
µ
F
..
330k
Ω
..
5V @ 350mA
MAX
+
+
60 mV
+ 1.23V
+
_
ERROR DETECTION
COMPARATOR
SPX2955/56/57 Block Diagram
Rev. 11/21/00
SPX2955/56/57
APPLICATION HINTS
EXTERNAL CAPACITORS
The stability of the SPX2955/56/57 requires a 2.2µF 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 5Ω 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 0.5µF and 0.15µF 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
5µF 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 0.1µF
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
3.3µF.
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 400µA, this value adds to battery drain in a low battery
condition. Suggested values range from 100K to 1MΩ. 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
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