TI LP2950

LP2950,, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D – APRIL 2006 – REVISED MARCH 2007
FEATURES
•
•
•
•
•
•
•
•
Wide Input Range…up to 30 V
Rated Output Current of 100 mA
Low Dropout…380 mV (Typ) at 100 mA
Low Quiescent Current…75 µA (Typ)
Tight Line Regulation…0.03% (Typ)
Tight Load Regulation…0.04% (Typ)
High VO Accuracy
– 1.4% at 25°C
– 2% Over Temperature
Can Be Used as a Regulator or Reference
LP2950...LP (TO-226/TO-92 PACKAGE
(BOTTOM VIEW)
OUTPUT
GND
INPUT
•
•
•
•
Stable With Low ESR (>12 mΩ) Capacitors
Current- and Thermal-Limiting Features
LP2950 Only (3-Pin Package)
– Fixed-Output Voltages of 5 V, 3.3 V,
and 3 V
LP2951 Only (8-Pin Package)
– Fixed- or Adjustable-Output Voltages:
5 V/ADJ, 3.3 V/ADJ, and 3 V/ADJ
– Low-Voltage Error Signal on Falling Output
– Shutdown Capability
– Remote Sense Capability for Optimal
Output Regulation and Accuracy
LP2951...D (SOIC) PACKAGE
(TOP VIEW)
OUTPUT
SENSE
SHUTDOWN
GND
1
8
2
7
3
6
4
5
INPUT
FEEDBACK
VTAP
ERROR
DESCRIPTION/ORDERING INFORMATION
The LP2950 and LP2951 devices are bipolar, low-dropout voltage regulators that can accommodate a wide input
supply-voltage range of up to 30 V. The easy-to-use, 3-pin LP2950 is available in fixed-output voltages of 5 V,
3.3 V, and 3 V. However, the 8-pin LP2951 is able to output either a fixed or adjustable output from the same
device. By tying the OUTPUT and SENSE pins together, and the FEEDBACK and VTAP pins together, the
LP2951 outputs a fixed 5 V, 3.3 V, or 3 V (depending on the version). Alternatively, by leaving the SENSE and
VTAP pins open and connecting FEEDBACK to an external resistor divider, the output can be set to any value
between 1.235 V to 30 V.
The 8-pin LP2951 also offers additional functionality that makes it particularly suitable for battery-powered
applications. For example, a logic-compatible shutdown feature allows the regulator to be put in standby mode
for power savings. In addition, there is a built-in supervisor reset function in which the ERROR output goes low
when VOUT drops by 6% of its nominal value for whatever reasons – due to a drop in VIN, current limiting, or
thermal shutdown.
The LP2950 and LP2951 are designed to minimize all error contributions to the output voltage. With a tight
output tolerance (0.5% at 25°C), a very low output voltage temperature coefficient (20 ppm typical), extremely
good line and load regulation (0.3% and 0.4% typical), and remote sensing capability, the parts can be used as
either low-power voltage references or 100-mA regulators.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006–2007, Texas Instruments Incorporated
LP2950,, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D – APRIL 2006 – REVISED MARCH 2007
ORDERING INFORMATION (1)
TA
VOUT
(NOM)
TO-226/TO-92 – LP
3V
SOIC – D
TO-226/TO-92 – LP
3.3 V
–40°C to 125°C
SOIC – D
TO-226/TO-92 – LP
5V
SOIC – D
ADJ
(1)
(2)
2
ORDERABLE
PART NUMBER
PACKAGE (2)
SOIC-D
TOP-SIDE MARKING
Bulk of 1000
LP2950-30LP
Reel of 2000
LP2950-30LPR
Tube of 75
LP2951-30D
Reel of 2500
LP2951-30DR
Bulk of 1000
LP2950-33LP
Reel of 2000
LP2950-33LPR
Tube of 75
LP2951-33D
Reel of 2500
LP2951-33DR
Bulk of 1000
LP2950-50LP
PREVIEW
Reel of 2000
LP2950-50LPR
KY5050
Tube of 75
LP2951-50D
Reel of 2500
LP2951-50DR
Tube of 75
LP2951D
Reel of 2500
LP2951DR
KY5030
KY5130
KY5033
KY5133
KY5150
KY5150
For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
website at www.ti.com.
Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines are available at
www.ti.com/sc/package.
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LP2950,, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D – APRIL 2006 – REVISED MARCH 2007
LP2950 FUNCTIONAL BLOCK DIAGRAM
Unregulated DC
+
INPUT
VOUT
IL 3 100 mA
OUTPUT
+
−
+
ERROR
Amplifier
+
See Application
Information
1.23-V
Reference
GND
LP2951 FUNCTIONAL BLOCK DIAGRAM
Unregulated DC
+
VOUT
IL 3 100 mA
7
8
1
INPUT
FEEDBACK
OUTPUT
2
SENSE
+
−
ERROR
Amplifier
3
From
CMOS
or TTL
SHUTDOWN
6
VTAP
330 kW
5
+
+
ERROR
60 mV
−
+
See Application
Information
See Application Information
To CMOS
or TTL
+
1.235-V
Reference
4
GND
ERROR Detection Comparator
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3
LP2950,, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
Absolute Maximum Ratings (1)
over operating free-air temperature range (unless otherwise noted)
MIN
MAX
VIN
Continuous input voltage range
–0.3
30
V
VSHDN
SHUTDOWN input voltage range
–1.5
30
V
–1.5
30
V
–1.5
30
V
ERROR comparator output voltage
VFDBK
range (2)
FEEDBACK input voltage range (2) (3)
θJA
Package thermal impedance (4) (5)
TJ
Operating virtual junction temperature
Tstg
Storage temperature range
(1)
(2)
(3)
(4)
(5)
D package
97
LP package
140
–65
UNIT
°C/W
150
°C
150
°C
Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings
only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating
conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
May exceed input supply voltage
If load is returned to a negative power supply, the output must be diode clamped to GND.
Maximum power dissipation is a function of TJ(max), θJA, and TA. The maximum allowable power dissipation at any allowable ambient
temperature is PD = (TJ(max) – TA)/θJA. Operating at the absolute maximum TJ of 150°C can affect reliability.
The package thermal impedance is calculated in accordance with JESD 51-7.
Recommended Operating Conditions
VIN
Supply input voltage
TJ
Operating virtual junction temperature
(1)
4
Minimum VIN is the greater of:
a. 2 V (25°C), 2.3 V (over temperature), or
b. VOUT(MAX) + Dropout (Max) at rated IL
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MIN
MAX
(1)
30
UNIT
V
–40
125
°C
LP2950,, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D – APRIL 2006 – REVISED MARCH 2007
Electrical Characteristics
VIN = VOUT (nominal) + 1 V, IL = 100 µA, CL = 1 µF (5-V versions) or CL = 2.2 µF (3-V and 3.3-V versions),
8-pin version: FEEDBACK tied to VTAP, OUTPUT tied to SENSE, VSHUTDOWN ≤ 0.7 V
PARAMETER
TEST CONDITIONS
TJ
MIN
TYP
MAX
UNIT
3-V VERSION (LP295x-30)
VOUT
Output voltage
IL = 100µA
25°C
2.970
3
3.030
–40°C to 125°C
2.940
3
3.060
V
3.3-V VERSION (LP295x-33)
VOUT
Output voltage
IL = 100µA
25°C
3.267
3.3
3.333
–40°C to 125°C
3.234
3.3
3.366
25°C
4.950
5
5.050
–40°C to 125°C
4.900
5
5.100
V
5-V VERSION (LP295x-50)
VOUT
Output voltage
IL = 100µA
V
ALL VOLTAGE OPTIONS
Output voltage temperature
coefficient (1)
IL = 100 µA
Line regulation (2)
VIN = [VOUT(NOM) + 1 V] to 30 V
Load regulation (2)
IL = 100 µA to 100 mA
IL = 100 µA
VIN – VOUT Dropout voltage (3)
IL = 100 mA
IL = 100 µA
IGND
GND current
IL = 100 mA
Dropout ground current
VIN = VOUT(NOM) – 0.5 V,
IL = 100 µA
Current limit
VOUT = 0 V
Thermal regulation (4)
–40°C to 125°C
20
25°C
0.03
–40°C to 125°C
25°C
0.04
0.2
0.3
25°C
50
–40°C to 125°C
25°C
380
–40°C to 125°C
%/V
%
80
150
450
mV
600
25°C
75
–40°C to 125°C
120
140
25°C
8
–40°C to 125°C
12
14
25°C
110
–40°C to 125°C
170
200
25°C
160
–40°C to 125°C
200
220
25°C
0.05
CL = 1 µF (5 V only)
Output noise (RMS),
10 Hz to 100 kHz
0.2
0.4
–40°C to 125°C
IL = 100 µA
100 ppm/°C
0.2
µA
mA
µA
mA
%/W
430
CL = 200 µF
160
µV
25°C
LP2951-50: CL = 3.3 µF,
CBypass = 0.01 µF between pins 1
and 7
100
(LP2951-xx) 8-PIN VERSION ONLY ADJ
Reference voltage
VOUT = VREF to (VIN – 1 V),
VIN = 2.3 V to 30 V,
IL = 100 µA to 100 mA
25°C
1.218
–40°C to 125°C
1.212
1.257
–40°C to 125°C
1.200
1.272
(3)
(4)
1.252
V
Reference voltage
temperature coefficient (1)
(1)
(2)
1.235
25°C
20
ppm/°C
Output or reference voltage temperature coefficient is defined as the worst-case voltage change divided by the total temperature range.
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.
Dropout voltage is defined as the input-to-output differential at which the output voltage drops 100 mV, below the value measured at 1-V
differential. The minimum input supply voltage of 2 V (2.3 V over temperature) must be observed.
Thermal regulation is defined as the change in output voltage at a time (T) after a change in power dissipation is applied, excluding load
or line regulation effects. Specifications are for a 50-mA load pulse at VIN = 30 V, VOUT = 5 V (1.25-W pulse) for t = 10 ms.
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
Electrical Characteristics (continued)
VIN = VOUT (nominal) + 1 V, IL = 100 µA, CL = 1 µF (5-V versions) or CL = 2.2 µF (3-V and 3.3-V versions),
8-pin version: FEEDBACK tied to VTAP, OUTPUT tied to SENSE, VSHUTDOWN ≤ 0.7 V
PARAMETER
TEST CONDITIONS
TJ
MIN
25°C
FEEDBACK bias current
TYP
MAX
20
40
–40°C to 125°C
FEEDBACK bias current
temperature coefficient
60
25°C
0.1
25°C
0.01
UNIT
nA
nA/°C
ERROR COMPARATOR
Output leakage current
VOUT = 30 V
Output low voltage
VIN = VOUT(NOM) – 0.5 V,
IOL = 400 µA
–40°C to 125°C
2
25°C
150
–40°C to 125°C
250
400
Upper threshold voltage
(ERROR output high) (5)
25°C
40
–40°C to 125°C
25
Lower threshold voltage
(ERROR output low) (5)
–40°C to 125°C
25°C
Hysteresis (6)
1
60
75
mV
mV
95
140
25°C
µA
15
mV
mV
SHUTDOWN INPUT
Input logic voltage
Low (regulator ON)
High (regulator OFF)
VTAP = 2.4 V
SHUTDOWN input current
VTAP = 30 V
Regulator output current
in shutdown
(5)
(6)
6
VSHUTDOWN ≥ 2 V,
VIN ≤ 30 V, VOUT = 0,
FEEDBACK tied to VTAP
–40°C to 125°C
25°C
0.7
2
30
–40°C to 125°C
25°C
–40°C to 125°C
25°C
–40°C to 125°C
50
100
450
V
600
µA
750
3
10
20
µA
Comparator thresholds are expressed in terms of a voltage differential equal to the nominal reference voltage (measured at
VIN – VOUT = 1 V) minus FEEDBACK terminal voltage. To express these thresholds in terms of output voltage change, multiply by the
error amplifier gain = VOUT/VREF = (R1 + R2)/R2. For example, at a programmed output voltage of 5 V, the ERROR output is specified to
go low when the output drops by 95 mV × 5 V/1.235 V = 384 mV. Thresholds remain constant as a percentage of VOUT (as VOUT is
varied), with the low-output warning occurring at 6% below nominal (typ) and 7.7% (max).
Comparator thresholds are expressed in terms of a voltage differential equal to the nominal reference voltage (measured at
VIN – VOUT = 1 V) minus FEEDBACK terminal voltage. To express these thresholds in terms of output voltage change, multiply by the
error amplifier gain = VOUT/VREF = (R1 + R2)/R2. For example, at a programmed output voltage of 5 V, the ERROR output is specified to
go low when the output drops by 95 mV × 5 V/1.235 V = 384 mV. Thresholds remain constant as a percentage of VOUT (as VOUT is
varied), with the low-output warning occurring at 6% below nominal (typ) and 7.7% (max).
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
TYPICAL CHARACTERISTICS
QUIESCENT CURRENT
vs
LOAD CURRENT
INPUT CURRENT
vs
INPUT VOLTAGE
100
10
RL = ∞
80
1
Input Current – µA
Quiescent Current – mA
90
0.1
70
60
50
40
30
20
10
0.01
0.0001
0.001
0.01
0.1
0
IL – Load Current – A
0
1
2
3
4
5
6
7
8
9
10
8
9
10
VIN – Input Voltage – V
INPUT CURRENT
vs
INPUT VOLTAGE
200
INPUT CURRENT
vs
INPUT VOLTAGE
120
RL = 50 kΩ
RL = 50 Ω
110
180
100
160
Input Current – mA
Input Current – µA
90
140
120
100
80
60
80
70
60
50
40
30
40
20
20
10
0
0
1
2
3
4
5
6
7
8
9
10
0
0
VIN – Input Voltage – V
1
2
3
4
5
6
7
VIN – Input Voltage – V
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
OUTPUT VOLTAGE
vs
TEMPERATURE
QUIESCENT CURRENT
vs
INPUT VOLTAGE
5.100
120
110
IL = 0
5.075
5.050
5.025
Quiescent Current – µA
VOUT – Output Voltage – V
100
IL = 100 µA
5.000
IL = 100 m A
4.975
4.950
90
80
70
60
50
40
30
20
4.925
10
4.900
-40 -25 -10 5
0
0
20 35 50 65 80 95 110 125
1
2
3
4
5
TA – Temperature – °C
VIN – Input Voltage – V
QUIESCENT CURRENT
vs
INPUT VOLTAGE
QUIESCENT CURRENT
vs
INPUT VOLTAGE
6
7
8
6
7
8
8
120
IL = 100 mA
IL = 1 mA
110
7
90
Quiescent Current – µA
Quiescent Current – µA
100
80
70
60
50
40
30
20
6
5
4
3
2
1
10
0
0
0
1
2
3
4
5
6
7
8
0
2
3
4
5
VIN – Input Voltage – V
VIN – Input Voltage – V
8
1
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
QUIESCENT CURRENT
vs
TEMPERATURE
QUIESCENT CURRENT
vs
TEMPERATURE
100
10
9.5
IL = 100 m A
V IN = 6 V
95
90
Quiescent Current – µA
Quiescent Current – mA
9
8.5
8
7.5
7
6.5
85
80
75
70
65
6
60
5.5
55
5
-40 -25 -10
5
20
35
50
65
80
50
-40 -25 -10
95 110 125
5
20
35 50
65
80
TA – Temperature – °C
TA – Temperature – °C
SHORT-CIRCUIT CURRENT
vs
TEMPERATURE
DROPOUT VOLTAGE
vs
TEMPERATURE
250
450
(V IN – V OUT ) – Dropout Voltage – mV
200
175
150
125
100
75
50
-40 -25 -10
95 110 125
500
225
Short-Circuit Current – A
IL = 100 µA
V IN = 6 V
5
20
35 50
65
80
95 110 125
400
350
RL = 100 m A
300
250
200
150
100
RL = 100 µA
50
0
-40 -25 -10
TA – Tem perature – °C
5
20 35
50 65
80 95 110 125
TA – Temperature – °C
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
LP2951 MINIMUM OPERATING VOLTAGE
vs
TEMPERATURE
400
2
350
1.95
Minimum Operating Voltage – V
(V IN – V OUT ) – Dropout Voltage – mV
DROPOUT VOLTAGE
vs
OUTPUT CURRENT
300
250
200
150
100
50
1.9
1.85
1.8
1.75
1.7
1.65
0
0.0001
0.001
0.01
1.6
-40 -25 -10
0.1
30
8
25
7
20
6
15
10
5
0
-5
4
3
1
-15
0
50-kW resistor
to VOUT
0
45
70
95
120 145
TA – Temperature – °C
10
95 110 125
5
-10
20
65 80
50-kW resistor to
external 5-V supply
2
-5
35 50
LP2951 ERROR COMPARATOR OUTPUT
vs
INPUT VOLTAGE
ERROR Output – V
FEEDBACK Bias Current – nA
LP2951 FEEDBACK BIAS CURRENT
vs
TEMPERATURE
-30
20
TA – Temperature – °C
IO – Output Current – A
-20
-55
5
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1
2
3
4
5
V IN – Input Voltage – V
6
7
8
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
LP2951 ERROR COMPARATOR SINK CURRENT
vs
OUTPUT LOW VOLTAGE
LINE TRANSIENT RESPONSE
vs
TIME
2
ISINK – Sink Current – mA
1.75
TA = 125
Input Voltage
2 V/div
1.5
1.25
TA = 25
1
Output Voltage
80 mV/div
0.75
TA = –40
0.5
0.25
0
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
VOL – Output Low Voltage – V
LOAD TRANSIENT RESPONSE
vs
TIME
(VOUT = 5 V, CL = 1 µF)
Output Voltage
100 mV/div
LOAD TRANSIENT RESPONSE
vs
TIME
(VOUT = 5 V, CL = 10 µF)
Output Voltage
100 mV/div
Output Load
100 mA/div
Output Load
100 mA/div
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
ENABLE TRANSIENT RESPONSE
vs
TIME
(CL = 1 µF, IL = 1 mA)
ENABLE TRANSIENT RESPONSE
vs
TIME
(CL = 10 µF, IL = 1 mA)
OUTPUT IMPEDANCE
vs
FREQUENCY
RIPPLE REJECTION
vs
FREQUENCY
100
90
Power-Supply Ripple Rejection – dB
Ω
Output Impedance – Ohm
IL = 100 µA
10
1
IL = 1 m A
0.1
IL = 100 m A
0.01
10
1.E+01
100
1.E+02
1k
1.E+03
10k
1.E+04
100k
1.E+05
1M
1.E+06
80
IL = 0
70
60
50
IL = 100 µA
40
30
V IN = 6 V
CL = 1 µF
20
10
1.E+01
100
1.E+02
1k
1.E+03
10k
1.E+04
f – Frequency – Hz
f – Frequency – Hz
12
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100k
1.E+05
1M
1.E+06
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SLVS582D – APRIL 2006 – REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
RIPPLE REJECTION
vs
FREQUENCY
RIPPLE REJECTION
vs
FREQUENCY
100
100
VIN = 6 V
90
Power-Supply Ripple Rejection – dB
Power-Supply Ripple Rejection – dB
VIN = 6 V
CL = 1 µF
90
80
70
60
50
IL = 1 mA
40
30
20
CL = 1 µF
80
IL = 50 mA
70
60
50
40
IL = 100 mA
30
20
IL = 10 mA
10
1.E+01
10
1.E+02
100
1.E+03
1k
1.E+04
10k
1.E+05
100k
10
10
1.E+01
1.E+06
1M
100
1.E+02
1k
1.E+03
f – Frequency – Hz
100k
1.E+05
1M
1.E+06
f – Frequency – Hz
LP2951 OUTPUT NOISE
vs
FREQUENCY
LP2951 DIVIDER RESISTANCE
vs
TEMPERATURE
400
RP2P4 – Pin 2 to Pin 4 Resistance – k W
6
5
Output Noise – µV
10k
1.E+04
4
CL = 200 µF
3
CL = 1 µF
2
1
350
300
250
200
150
100
50
CL = 3.3 µF
0
1.E+01
10
1.E+02
100
1.E+03
1k
1.E+04
10k
1.E+05
100k
0
-40 -25 -10
5
20
35 50
65 80 95 110 125
TA – Temperature – °C
f – Frequency – Hz
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www.ti.com
SLVS582D – APRIL 2006 – REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
SHUTDOWN THRESHOLD VOLTAGE (ON TO OFF)
vs
TEMPERATURE
1.7
1.7
1.6
1.6
Input Logic Voltage (ON to OFF) – V
Input Logic Voltage (OFF to ON) – V
SHUTDOWN THRESHOLD VOLTAGE (OFF TO ON)
vs
TEMPERATURE
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
-40 -25 -10
5
20
35
50
65
80
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
-40 -25 -10
95 110 125
TA – Temperature – °C
5
20
35
50
65
TA – Temperature – °C
LINE REGULATION
vs
INPUT VOLTAGE
6
Output Voltage Change – mV
5
4
3
2
1
0
-1
-2
0
5
10
15
20
VIN – Input Voltage – V
14
Submit Documentation Feedback
25
30
80
95 110 125
www.ti.com
LP2950,, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
SLVS582D – APRIL 2006 – REVISED MARCH 2007
APPLICATION INFORMATION
Input Capacitor (CIN)
A 1-µF (tantalum, ceramic, or aluminum) electrolytic capacitor should be placed locally at the input of the
LP2950 or LP2951 if there is, or will be, significant impedance between the ac filter capacitor and the input; for
example, if a battery is used as the input or if the ac filter capacitor is located more than 10 in away. There are
no ESR requirements for this capacitor, and the capacitance can be increased without limit.
Output Capacitor (COUT)
As with most PNP LDOs, stability conditions require the output capacitor to have a minimum capacitance and an
ESR that falls within a certain range.
Capacitance Value
For VOUT ≥ 5 V, a minimum of 1 µF is required. For lower VOUT, the regulator’s loop gain is running closer to
unity gain and, thus, has lower phase margins. Consequently, a larger capacitance is needed for stability. For
VOUT = 3 V or 3.3 V, a minimum of 2.2 µF is recommended. For worst case, VOUT = 1.23 V (using the ADJ
version), a minimum of 3.3 µF is recommended. COUT can be increased without limit and only improves the
regulator stability and transient response. Regardless of its value, the output capacitor should have a resonant
frequency less than 500 kHz.
The minimum capacitance values given above are for maximum load current of 100 mA. If the maximum
expected load current is less than 100 mA, then lower values of COUT can be used. For instance, if IOUT < 10
mA, then only 0.33 µF is required for COUT. For IOUT < 1 mA, 0.1 µF is sufficient for stability requirements. Thus,
for a worst-case condition of 100-mA load and VOUT = VREF = 1.235 V (representing the highest load current and
lowest loop gain), a minimum COUT of 3.3 µF is recommended.
For the LP2950, no load stability is inherent in the design — a desirable feature in CMOS circuits that are put in
standby (such as RAM keep-alive applications). If the LP2951 is used with external resistors to set the output
voltage, a minimum load current of 1 µA is recommended through the resistor divider.
ESR Range
The regulator control loop relies on the ESR of the output capacitor to provide a zero to add sufficient phase
margin to ensure unconditional regulator stability; this requires the closed-loop gain to intersect the open-loop
response in a region where the open-loop gain rolls off at 20 dB/decade. This ensures that the phase always is
less than 180° (phase margin greater than 0°) at unity gain. Thus, a minimum-maximum range for the ESR must
be observed.
The upper limit of this ESR range is established by the fact that too high an ESR could result in the zero
occurring too soon, causing the gain to roll off too slowly, which, in turn allows a third pole to appear before unity
gain and introduce enough phase shift to cause instability. This typically limits the max ESR to approximately
5 Ω.
Conversely, the lower limit of the ESR is tied to the fact that too low an ESR shifts the zero too far out (past
unity gain) and, thus, allows the gain to roll off at 40 dB/decade at unity gain, with a resulting phase shift of
greater than 180°. Typically, this limits the minimum ESR to approximately 20 mΩ to 30 mΩ.
For specific ESR requirements, see Typical Characteristics.
Submit Documentation Feedback
15
LP2950,, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D – APRIL 2006 – REVISED MARCH 2007
APPLICATION INFORMATION (continued)
Capacitor Types
Most tantalum or aluminum electrolytics are suitable for use at the input. Film-type capacitors also work, but at
higher cost. When operating at low temperature, care should be taken with aluminum electrolytics, as their
electrolytes often freeze at –30°C. For this reason, solid tantalum capacitors should be used at temperatures
below –25°C.
Ceramic capacitors can be used, but due to their low ESR (as low as 5 mΩ to 10 mΩ), they may not meet the
minimum ESR requirement previously discussed. If a ceramic capacitor is used, a series resistor between 0.1 Ω
to 2 Ω must be added to meet the minimum ESR requirement. In addition, ceramic capacitors have one glaring
disadvantage that must be taken into account — a poor temperature coefficient, where the capacitance can vary
significantly with temperature. For instance, a large-value ceramic capacitor (≥2.2 µF) can lose more than half of
its capacitance as temperature rises from 25°C to 85°C. Thus, a 2.2-µF capacitor at 25°C drops well below the
minimum COUT required for stability as ambient temperature rises. For this reason, select an output capacitor
that maintains the minimum 2.2-µF required for stability for the entire operating temperature range.
CBYPASS: Noise and Stability Improvement
In the LP2951, an external FEEDBACK pin directly connected to the error amplifier noninverting input can allow
stray capacitance to cause instability by shunting the error amplifier feedback to GND, especially at high
frequencies. This is worsened if high-value external resistors are used to set the output voltage, because a high
resistance allows the stray capacitance to play a more significant role; i.e., a larger RC time delay is introduced
between the output of the error amplifier and its FEEDBACK input, leading to more phase shift and lower phase
margin. A solution is to add a 100-pF bypass capacitor (CBYPASS) between OUTPUT and FEEDBACK; because
CBYPASS is in parallel with R1, it lowers the impedance seen at FEEDBACK at high frequencies, in effect
offsetting the effect of the parasitic capacitance by providing more feedback at higher frequencies. More
feedback forces the error amplifier to work at a lower loop gain, so COUT should be increased to a minimum of
3.3 µF to improve the regulator’s phase margin.
CBYPASS can be also used to reduce output noise in the LP2951. This bypass capacitor reduces the closed loop
gain of the error amplifier at the high frequency, so noise no longer scales with the output voltage. This
improvement is more noticeable with higher output voltages, because loop gain reduction is greatest. A suitable
CBYPASS is calculated as shown in Equation 1:
1
f (CBYPASS) ] 200 Hz ³ CBYPASS +
2p R1 200 Hz
(1)
On the 3-pin LP2950, noise reduction can be achieved by increasing the output capacitor, which causes the
regulator bandwidth to be reduced, therefore, eliminating high-frequency noise. However, this method is
relatively inefficient, as increasing COUT from 1 µF to 220 µF only reduces the regulator’s output noise from
430 µV to 160 µV (over a 100-kHz bandwidth).
ERROR Function (LP2951 Only)
The LP2951 has a low-voltage detection comparator that outputs a logic low when the output voltage drops by
≈6% from its nominal value, and outputs a logic high when VOUT has reached ≈95% of its nominal value. This
95% of nominal figure is obtained by dividing the built-in offset of ≈60 mV by the 1.235-V bandgap reference,
and remains independent of the programmed output voltage. For example, the trip-point threshold (ERROR
output goes high) typically is 4.75 V for a 5-V output and 11.4 V for a 12-V output. Typically, there is a hysteresis
of 15 mV between the thresholds for high and low ERROR output.
A timing diagram is shown in Figure 1 for ERROR vs VOUT (5 V), as VIN is ramped up and down. ERROR
becomes valid (low) when VIN ≈ 1.3 V. When VIN ≈ 5 V, VOUT = 4.75 V, causing ERROR to go high. Because the
dropout voltage is load dependent, the output trip-point threshold is reached at different values of VIN, depending
on the load current. For instance, at higher load current, ERROR goes high at a slightly higher value of VIN, and
vice versa for lower load current. The output-voltage trip point remains at ≈4.75 V, regardless of the load. Note
that when VIN ≤ 1.3 V, the ERROR comparator output is turned off and pulled high to its pullup voltage. If VOUT is
used as the pullup voltage, rather than an external 5-V source, ERROR typically is ≈1.2 V. In this condition, an
equal resistor divider (10 kΩ is suitable) can be tied to ERROR to divide down the voltage to a valid logic low
during any fault condition, while still enabling a logic high during normal operation.
16
Submit Documentation Feedback
LP2950,, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D – APRIL 2006 – REVISED MARCH 2007
APPLICATION INFORMATION (continued)
Output
Voltage
4.75 V
ERROR
5V
Input
Voltage
1.3 V
Figure 1. ERROR Output Timing
Because the ERROR comparator has an open-collector output, an external pullup resistor is required to pull the
output up to VOUT or another supply voltage (up to 30 V). The output of the comparator is rated to sink up to
400 µA. A suitable range of values for the pullup resistor is from 100 kΩ to 1 MΩ. If ERROR is not used, it can
be left open.
Programming Output Voltage (LP2951 Only)
A unique feature of the LP2951 is its ability to output either a fixed voltage or an adjustable voltage, depending
on the external pin connections. To output the internally programmed fixed voltage, tie the SENSE pin to the
OUTPUT pin and the FEEDBACK pin to the VTAP pin. Alternatively, a user-programmable voltage ranging from
the internal 1.235-V reference to a 30-V max can be set by using an external resistor divider pair. The resistor
divider is tied to VOUT, and the divided-down voltage is tied directly to FEEDBACK for comparison against the
internal 1.235-V reference. To satisfy the steady-state condition in which its two inputs are equal, the error
amplifier drives the output to equal Equation 2:
V OUT + V REF
ǒ 1 ) R1
Ǔ*I
R2
FB
R1
(2)
Where:
VREF = 1.235 V applied across R2
IFB = FEEDBACK bias current, typically 20 nA
A minimum regulator output current of 1 µA must be maintained. Thus, in an application where a no-load
condition is expected (for example, CMOS circuits in standby), this 1-µA minimum current must be provided by
the resistor pair, effectively imposing a maximum value of R2 = 1.2 MΩ (1.235 V/1.2 MΩ ≈ 1 µA).
IFB = 20 nA introduces an error of ≈0.02% in VOUT. This can be offset by trimming R1. Alternatively, increasing
the divider current makes IFB less significant, thus, reducing its error contribution. For instance, using R2 = 100
kΩ reduces the error contribution of IFB to 0.17% by increasing the divider current to ≈12 µA. This increase in the
divider current still is small compared to the 600-µA typical quiescent current of the LP2951 under no load.
Submit Documentation Feedback
17
PACKAGE OPTION ADDENDUM
www.ti.com
11-Jun-2007
PACKAGING INFORMATION
Orderable Device
Status (1)
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
LP2950-30LP
ACTIVE
TO-92
LP
3
1000
Pb-Free
(RoHS)
CU SN
N / A for Pkg Type
LP2950-30LPR
ACTIVE
TO-92
LP
3
2000
Pb-Free
(RoHS)
CU SN
N / A for Pkg Type
LP2950-33LPE3
ACTIVE
TO-92
LP
3
1000
Pb-Free
(RoHS)
CU SN
N / A for Pkg Type
LP2950-33LPRE3
ACTIVE
TO-92
LP
3
2000
Pb-Free
(RoHS)
CU SN
N / A for Pkg Type
LP2950-50LPRE3
ACTIVE
TO-92
LP
3
2000
Pb-Free
(RoHS)
CU SN
N / A for Pkg Type
LP2951-30D
ACTIVE
SOIC
D
8
75
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-30DG4
ACTIVE
SOIC
D
8
75
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-30DR
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-30DRG4
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-33D
ACTIVE
SOIC
D
8
75
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-33DG4
ACTIVE
SOIC
D
8
75
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-33DR
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-33DRG4
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-50D
ACTIVE
SOIC
D
8
75
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-50DG4
ACTIVE
SOIC
D
8
75
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-50DR
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951-50DRG4
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951D
ACTIVE
SOIC
D
8
Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
LP2951DR
ACTIVE
SOIC
D
8
2500 Green (RoHS &
no Sb/Br)
CU NIPDAU
Level-1-260C-UNLIM
75
Lead/Ball Finish
MSL Peak Temp (3)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
11-Jun-2007
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
16-Jun-2007
TAPE AND REEL INFORMATION
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
Device
16-Jun-2007
Package Pins
Site
Reel
Diameter
(mm)
Reel
Width
(mm)
A0 (mm)
B0 (mm)
K0 (mm)
P1
(mm)
W
Pin1
(mm) Quadrant
LP2951-30DR
D
8
FMX
330
12
6.4
5.2
2.1
8
12
Q1
LP2951-33DR
D
8
FMX
330
12
6.4
5.2
2.1
8
12
Q1
LP2951-50DR
D
8
FMX
330
12
6.4
5.2
2.1
8
12
Q1
LP2951DR
D
8
FMX
330
12
6.4
5.2
2.1
8
12
Q1
TAPE AND REEL BOX INFORMATION
Device
Package
Pins
Site
Length (mm)
Width (mm)
Height (mm)
LP2951-30DR
D
8
FMX
342.9
336.6
20.64
LP2951-33DR
D
8
FMX
342.9
336.6
20.64
LP2951-50DR
D
8
FMX
342.9
336.6
20.64
LP2951DR
D
8
FMX
342.9
336.6
20.64
Pack Materials-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
16-Jun-2007
Pack Materials-Page 3
MECHANICAL DATA
MSOT002A – OCTOBER 1994 – REVISED NOVEMBER 2001
LP (O-PBCY-W3)
PLASTIC CYLINDRICAL PACKAGE
0.205 (5,21)
0.175 (4,44)
0.165 (4,19)
0.125 (3,17)
DIA
0.210 (5,34)
0.170 (4,32)
Seating
Plane
0.157 (4,00) MAX
0.050 (1,27)
C
0.500 (12,70) MIN
0.104 (2,65)
FORMED LEAD OPTION
0.022 (0,56)
0.016 (0,41)
0.016 (0,41)
0.014 (0,35)
STRAIGHT LEAD OPTION
D
0.135 (3,43) MIN
0.105 (2,67)
0.095 (2,41)
0.055 (1,40)
0.045 (1,14)
1
2
3
0.105 (2,67)
0.080 (2,03)
0.105 (2,67)
0.080 (2,03)
4040001-2 /C 10/01
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Lead dimensions are not controlled within this area
D. FAlls within JEDEC TO -226 Variation AA (TO-226 replaces TO-92)
E. Shipping Method:
Straight lead option available in bulk pack only.
Formed lead option available in tape & reel or ammo pack.
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
1
MECHANICAL DATA
MSOT002A – OCTOBER 1994 – REVISED NOVEMBER 2001
LP (O-PBCY-W3)
PLASTIC CYLINDRICAL PACKAGE
0.539 (13,70)
0.460 (11,70)
1.260 (32,00)
0.905 (23,00)
0.650 (16,50)
0.610 (15,50)
0.020 (0,50) MIN
0.098 (2,50)
0.384 (9,75)
0.335 (8,50)
0.748 (19,00)
0.217 (5,50)
0.433 (11,00)
0.335 (8,50)
0.748 (19,00)
0.689 (17,50)
0.114 (2,90)
0.094 (2,40)
0.114 (2,90)
0.094 (2,40)
0.169 (4,30)
0.146 (3,70)
DIA
0.266 (6,75)
0.234 (5,95)
0.512 (13,00)
0.488 (12,40)
TAPE & REEL
4040001-3 /C 10/01
NOTES: A. All linear dimensions are in inches (millimeters).
B. This drawing is subject to change without notice.
C. Tape and Reel information for the Format Lead Option package.
2
POST OFFICE BOX 655303
• DALLAS, TEXAS 75265
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