SPX2920
400mA Low Drop Out Voltage Regulator with Shutdown
FEATURES
■
Output 3.3V, 5.0V, at 400mA Output
■
Very Low Quiescent Current
■
Low Dropout Voltage
■
Extremely Tight Load and Line Regulation
■
Very Low Temperature Coefficient
■
Current & Thermal Limiting
■
Error Flag Warns of Output Dropout
(for SO-8)
■
Logic-Controlled Electronic Shutdown
(for SO-8)
■
Output Programmable from 1.24V to 20V
(for SO-8)
■
Equivalent Replacement for MIC2920A and
MIC2904
0.1
µF
ON
+V
IN
8
+V
IN
V
OUT
1
1.2V to 20V
+
100K
SPX2920
SHUTDOWN
INPUT
OFF
FB
7
R
1
0.01µF
10µF
3
SD
GND
4
______
ERROR
ERROR
5
R
2
V
REF
OUTPUT
Adjustable Regulator
V
IN
5V
IN
OUT
SPX2920
+
GND
+
2.2
µF
IG
5V Regulator Circuit
Now Available in Lead Free Packaging
DESCRIPTION
The SPX2920 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 SPX2920 features very low quiescent current (140µA Typical) and very low dropout voltage. This
includes a tight initial tolerance of 1% maximum and very low output temperature coefficient, making
the SPX2920 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 from batteries. Another feature is the logic-compatible shutdown input which
enables the regulator to be switched on and off. The SPX2920 is offered in 3-pin TO-220 package,
surface mount SO-8 (same pin out as SPX2951), SOT-223, and 3-pin TO-263 packages.
The regulator output voltage (of the SO-8) may be pin-strapped for a 3.3V and 5.0V or programmed
from 1.24V to 20V with an external pair of resistors.
TO-220-3 (U)
GND
GND
V
OUT
1
2
3
4
8
7
TO-263-3 (T)
8-Pin Surface Mount
GND
V
IN
FEEDBACK
5V/ 3.3V TAP
ERROR
SOT-223 (M3)
SPX2920
SPX2920
1
2
3
SENSE
SPX2920
1
2
3
1
2
3
SHUTDOWN
GND
SPX2920
6
5
V
IN
GND V
OUT
V
IN
GND
V
OUT
V
IN
GND V
OUT
Front View
Top View
Top View
Top View
Date: 03/02/06
SPX2920 400mA Low Drop Out Voltage Regulator with Shutdown
©Copyright 2006 Sipex Corporation
1
ABSOLUTE MAXIMUM RATINGS
Power Dissipation ........................................................ Internally Limited
Lead Temp. (Soldering, 5 Seconds) .............................................. 260°C
Storage Temperature Range ......................................... -65°C to +150°C
Operating Junction Temperature Range ...................... -40°C to +125°C
Input Supply Voltage ......................................................... -20V to +20V
Feedback Input Voltage ..................................................... -1.5V to +20V
Shutdown Input Voltage .................................................... -0.3V to +20V
Error Comparator Output ................................................... -0.3V to +20V
ESD Rating ........................................................................................ 2kV
ELECTRICAL CHARACTERISTICS
Electrical characteristics at V
IN
=V
O
+1V, I
O
= 1mA, C
OUT
= 2.2µF, T
A
= 25°C, unless otherwise specified.
Boldface
applies over the full operating temperature range.
PARAMETER
3.3V Version
Output Voltage
5.0V Version
Output Voltage
All Voltage Options
Output Voltage
Temperature Coefficient
Line Regulation (Note 4)
Load Regulation (Note 3)
Dropout Voltage (Note5)
1mA ≤ I
L
≤ 400mA
CONDITIONS
(Note 2)
TYP
MIN
MAX
UNITS
3.3
3.3
5.0
5.0
20
3.267
3.217
4.950
4.880
3.333
3.382
5.050
5.120
100
20
20
30
100
150
400
500
200
300
2
2.5
9
12
15
25
800
0.2
V
V
1mA ≤ I
L
≤ 400mA
ppm/°C
mV
mV
mV
(Note1)
6V ≤ V
IN
≤ 20V
I
L
=1 to 400mA
I
L
=1mA
I
L
=400mA
1.5
5
60
370
140
1.3
3.4
6
Ground Current
I
L
=1mA
I
L
=100mA
I
L
=250mA
I
L
=400mA
µA
mA
mA
mA
mA
%/W
µV Vrms
Current Limit
Thermal Regulation
Output Noise, 10Hz to 100kHz
I
L
=100mA
Adjustable 8-Pin Version only
Reference Voltage
Reference Voltage
Feedback Pin Bias Current
Reference Voltage Temperature
Coefficient
V
OUT
=0
C
L
=10µF
0.05
400
260
1.235
1.210
1.185
C
L
=100µF
Over Temperature
20
20
1.260
1.285
40
60
V
V
nA
ppm/°C
Date: 03/02/06
SPX2920 400mA Low Drop Out Voltage Regulator with Shutdown
©Copyright 2006 Sipex Corporation
2
Electrical characteristics at V
IN
= V
O
+1V, I
O
= 1mA, C
OUT
= 2.2µF, T
A
= 25°C, unless otherwise specified.
Boldface
applies over the full operating temperature range.
PARAMETER
Feedback Pin Bias Current
Temperature Coefficient
Error Comparator
Output Leakage Current
Output Low Voltage
Upper Threshold Voltage
Lower Threshold Voltage
Hysteresis
Shutdown Input
Input Logic Voltage
Low (Regulator ON)
Shutdown Pin Input Current
High (Regulator OFF)
V
S
=2.4V
V
S
=20V
Regulator Output Current
in Shutdown
Thermal Resistance Theta JA
TO-220-3
TO-263-3
NSOIC-8
SOT-223
(Note 7)
2.0
30
450
3
10
20
29.4
31.4
128.4
62.3
ºC/W
50
100
600
750
µA
µA
V
0UT
=20V
V
IN
=4.5V
I
OUT
=400µA
(Note 6)
(Note 6)
(Note 6)
CONDITIONS
(Note 2)
TYP
0.1
MIN
MAX
UNITS
nA/°C
ELECTRICAL CHARACTERISTICS
0.01
150
60
75
15
1.3
40
25
1
2
250
400
µA
mV
mV
95
140
mV
mV
0.7
V
Note 1:
Output or reference voltage temperature coefficients defined as the worst case voltage change divided by
the total temperature range.
Note 2:
Additional conditions for the 8-pin versions are feedback tied to 5V/3.3V 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 SPX2920 is tested at 150°C for I
L
= 1 mA. For T
J
= 125°C, line regulation is guar-
anteed by design.
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:
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 7:
V
SHUTDOWN
≥ 2V, V
IN
≤ 20V, V
OUT
= 0, Feedback pin tied to 5V/3.3V Tap.
Date: 03/02/06
SPX2920 400mA Low Drop Out Voltage Regulator with Shutdown
©Copyright 2006 Sipex Corporation
3
BLOCK DIAGRAM
UNREGULATED DC
5V @ 400mA
MAX
+
7
8
1
2
+
_
FROM
TTL
180k
Ω
..
ERROR
AMPLIFIER
60k
Ω
..
6
330k
Ω
..
3
+
60 mV
+ 1.23V
5
+
1 uF
TO CMOS OR
TTL
+
_
ERROR DETECTION
COMPARATOR
REFERENCE
4
SPX2920-5.0 Block Diagram
APPLICATION HINTS
External Capacitors
The stability of the SPX2920 requires a
2.2µF or greater capacitor between output
and ground. Oscillation could occur without
this capacitor. Most types of tantalum or
aluminum electrolytic capacitors work fine
here. For operations of below -25°C, solid
tantalum is recommended since many of the
aluminum types have electrolytes that 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 capaci-
tor can be reduced to 0.5µF and 0.15µF for
1mA. More output capacitance is needed
for the 8-pin version at voltages below 5V
since it runs the error amplifier at lower
gain. At worst case, 4.7µF or greater must
be used for the condition of 250mA load at
1.23V output.
The SPX2920, unlike other low dropout
regulators, will remain stable and in regula-
tion with no load in addition to the internal
voltage divider. This feature is especially
important in applications like CMOS RAM
keep-alive.
If there is more than 10 inches of wire be-
tween 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 capaci-
tance to the SPX2920 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.
©Copyright 2006 Sipex Corporation
Date: 03/02/06
SPX2920 400mA Low Drop Out Voltage Regulator with Shutdown
4
Error Detection Comparator Output
The Comparator produces a logic low output
whenever the SPX2920 output falls out of
regulation by more than about 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 ER-
ROR signal and the regulator output voltage
as the SPX2920 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 V
OUT
= 4.75V).
Since the SPX2920’s dropout voltage is
load dependent, the input voltage trip point
(around 5V) will vary with the load current.
The output voltage trip point (approximately
4.75V) does not vary with load.
The error comparator has an open-col-
lector 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
SPX2920
The SPX2920 may be pin-strapped for 5V
or 3.3V using its internal voltage divider by
tying Pin 1 (output) to Pin 2 (sense) and Pin
7 (feedback) to Pin 6 (5V/3.3V Tap).
Also, it may be programmed for any output
voltage between its 1.235V reference and
its 20V maximum rating. As seen on the
front page, an external pair of resistors is
required.
Refer to the equation below for the program-
ming of the output voltage:
V
OUT
= V
REF
x ( 1 + R
1
/ R
2
)+ I
FB
R
1
The V
REF
is 1.235 and I
FB
is the feedback
bias current, nominally -20nA. The minimum
Date: 03/02/06
recommended load current of 1µA forces an
upper limit of 1.2MΩ on the value of R
2
. If no
load is presented, the I
FB
produces an error
of typically 2% in V
OUT
, which may be elimi-
nated at room temperature by trimming R
1
.
To improve the accuracy choose the value of
R
2
= 100kΩ; this reduces the error by 0.17%
and increases the resistor program current
by 12µA. Since the SPX2920 typically draws
60µA at no load with Pin 2 open-circuited,
this is a small price to pay.
Reducing Output Noise
It may be an advantage to reduce the AC
noise present at the output. One way is to
reduce the regulator bandwidth by increas-
ing the size of the output capacitor. This
is the only way that noise can be reduced
on the 3 lead SPX2920 but it is relatively
inefficient; as increasing the capacitor from
1µF to 220µF only decreases the noise
from 430µV to 160µV Vrms for a 100kHz
bandwidth at 5V output.
Noise could also be reduced fourfold by
a bypass capacitor across R
1
, since it re-
duces the high frequency gain from 4 to
unity. Pick
C
BYPASS
≅1
/ 2πR
1
x 200 Hz
or choose 0.01µF. When doing this, the
output capacitor must be increased to 3.3µF
to maintain stability. These changes reduce
the output noise from 430µV to 100µV Vrms
for a 100kHz bandwidth at 5V output. With
the bypass capacitor added, noise no longer
scales with output voltage so that improve-
ments are more dramatic at higher output
4.75V
OUTPUT
VOLTAGE
_______
ERROR*
+
5.0V
INPUT
VOLTAGE
+
1.3V
+
+
* See Application Info.
Figure 1. ERROR Output Timing
©Copyright 2006 Sipex Corporation
SPX2920 400mA Low Drop Out Voltage Regulator with Shutdown
5
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