LP2951-50DG4 [TI]
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS WITH SHUTDOWN; 具有关断功能可调节微功耗电压稳压器型号: | LP2951-50DG4 |
厂家: | TEXAS INSTRUMENTS |
描述: | ADJUSTABLE MICROPOWER VOLTAGE REGULATORS WITH SHUTDOWN |
文件: | 总26页 (文件大小:2761K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
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
•
•
•
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
–
–
1.4% at 25°C
–
–
–
Low-Voltage Error Signal on Falling Output
Shutdown Capability
2% Over Temperature
•
Can Be Used as a Regulator or Reference
Remote Sense Capability for Optimal
Output Regulation and Accuracy
LP2950...LP (TO-226/TO-92 PACKAGE
(BOTTOM VIEW)
LP2951...D (SOIC) PACKAGE
(TOP VIEW)
OUTPUT
GND
INPUT
1
2
3
4
8
7
6
5
OUTPUT
SENSE
FEEDBACK
V
TAP
SHUTDOWN
GND
INPUT
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.
Copyright © 2006–2007, Texas Instruments Incorporated
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
LP2950, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D–APRIL 2006–REVISED MARCH 2007
ORDERING INFORMATION(1)
VOUT
(NOM)
ORDERABLE
PART NUMBER
TA
PACKAGE(2)
TOP-SIDE MARKING
Bulk of 1000
Reel of 2000
Tube of 75
LP2950-30LP
TO-226/TO-92 – LP
SOIC – D
KY5030
LP2950-30LPR
LP2951-30D
LP2951-30DR
LP2950-33LP
LP2950-33LPR
LP2951-33D
LP2951-33DR
LP2950-50LP
LP2950-50LPR
LP2951-50D
LP2951-50DR
LP2951D
3 V
KY5130
KY5033
KY5133
Reel of 2500
Bulk of 1000
Reel of 2000
Tube of 75
TO-226/TO-92 – LP
SOIC – D
3.3 V
–40°C to 125°C
Reel of 2500
Bulk of 1000
Reel of 2000
Tube of 75
PREVIEW
KY5050
TO-226/TO-92 – LP
SOIC – D
5 V
KY5150
KY5150
Reel of 2500
Tube of 75
ADJ
SOIC-D
Reel of 2500
LP2951DR
(1) 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.
(2) 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
V
OUT
3 100 mA
OUTPUT
I
L
+
−
+
See Application
Information
ERROR
Amplifier
+
1.23-V
Reference
GND
LP2951 FUNCTIONAL BLOCK DIAGRAM
Unregulated DC
7
V
OUT
3 100 mA
I
L
+
8
1
INPUT
OUTPUT
FEEDBACK
2
SENSE
+
−
6
+
ERROR
3
See Application
Information
Amplifier
From
CMOS
or TTL
V
TAP
SHUTDOWN
330 kW
See Application Information
5
+
+
−
To CMOS
or TTL
ERROR
60 mV
+
1.235-V
Reference
4
GND
ERROR Detection Comparator
3
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LP2950, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D–APRIL 2006–REVISED MARCH 2007
Absolute Maximum Ratings(1)
over operating free-air temperature range (unless otherwise noted)
MIN
–0.3
–1.5
–1.5
–1.5
MAX UNIT
VIN
Continuous input voltage range
30
30
V
V
V
V
VSHDN
SHUTDOWN input voltage range
ERROR comparator output voltage range(2)
FEEDBACK input voltage range(2)(3)
30
VFDBK
30
D package
97
θJA
Package thermal impedance(4)(5)
°C/W
LP package
140
150
150
TJ
Operating virtual junction temperature
Storage temperature range
°C
°C
Tstg
–65
(1) 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.
(2) May exceed input supply voltage
(3) If load is returned to a negative power supply, the output must be diode clamped to GND.
(4) 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.
(5) The package thermal impedance is calculated in accordance with JESD 51-7.
Recommended Operating Conditions
MIN
MAX
30
UNIT
V
(1)
VIN
TJ
Supply input voltage
Operating virtual junction temperature
–40
125
°C
(1) 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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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)
25°C
2.970
2.940
3
3
3.030
V
VOUT
3.3-V VERSION (LP295x-33)
VOUT Output voltage
5-V VERSION (LP295x-50)
VOUT Output voltage
ALL VOLTAGE OPTIONS
Output voltage
IL = 100µA
–40°C to 125°C
3.060
25°C
3.267
3.234
3.3
3.3
3.333
V
IL = 100µA
IL = 100µA
–40°C to 125°C
3.366
25°C
4.950
4.900
5
5
5.050
V
–40°C to 125°C
5.100
Output voltage temperature
IL = 100 µA
–40°C to 125°C
20
100 ppm/°C
coefficient(1)
25°C
–40°C to 125°C
25°C
0.03
0.2
Line regulation(2)
VIN = [VOUT(NOM) + 1 V] to 30 V
%/V
0.4
0.04
50
0.2
%
Load regulation(2)
IL = 100 µA to 100 mA
IL = 100 µA
–40°C to 125°C
25°C
0.3
80
–40°C to 125°C
25°C
150
mV
450
VIN – VOUT Dropout voltage(3)
380
75
IL = 100 mA
–40°C to 125°C
25°C
600
120
µA
IL = 100 µA
–40°C to 125°C
25°C
140
IGND
GND current
8
12
IL = 100 mA
mA
14
–40°C to 125°C
25°C
110
160
170
µA
VIN = VOUT(NOM) – 0.5 V,
IL = 100 µA
Dropout ground current
–40°C to 125°C
25°C
200
200
mA
220
Current limit
VOUT = 0 V
–40°C to 125°C
25°C
Thermal regulation(4)
IL = 100 µA
0.05
430
160
0.2
%/W
CL = 1 µF (5 V only)
CL = 200 µF
Output noise (RMS),
10 Hz to 100 kHz
25°C
µV
LP2951-50: CL = 3.3 µF,
CBypass = 0.01 µF between pins 1
and 7
100
(LP2951-xx) 8-PIN VERSION ONLY ADJ
25°C
1.218
1.212
1.235
1.252
1.257
–40°C to 125°C
Reference voltage
V
VOUT = VREF to (VIN – 1 V),
VIN = 2.3 V to 30 V,
IL = 100 µA to 100 mA
–40°C to 125°C
25°C
1.200
1.272
Reference voltage
20
ppm/°C
temperature coefficient(1)
(1) Output or reference voltage temperature coefficient is defined as the worst-case voltage change divided by the total temperature range.
(2) 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.
(3) 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.
(4) 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.
5
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
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
TYP
MAX UNIT
25°C
20
40
nA
60
FEEDBACK bias current
–40°C to 125°C
FEEDBACK bias current
temperature coefficient
25°C
0.1
nA/°C
ERROR COMPARATOR
25°C
–40°C to 125°C
25°C
0.01
150
60
1
Output leakage current
Output low voltage
VOUT = 30 V
µA
2
250
mV
400
VIN = VOUT(NOM) – 0.5 V,
IOL = 400 µA
–40°C to 125°C
25°C
40
25
Upper threshold voltage
(ERROR output high)(5)
mV
–40°C to 125°C
25°C
75
95
mV
140
Lower threshold voltage
(ERROR output low)(5)
–40°C to 125°C
25°C
Hysteresis(6)
15
mV
SHUTDOWN INPUT
Low (regulator ON)
High (regulator OFF)
0.7
V
Input logic voltage
–40°C to 125°C
2
25°C
–40°C to 125°C
25°C
30
450
3
50
VTAP = 2.4 V
VTAP = 30 V
100
µA
SHUTDOWN input current
600
–40°C to 125°C
25°C
750
10
VSHUTDOWN ≥ 2 V,
Regulator output current
in shutdown
VIN ≤ 30 V, VOUT = 0,
µA
–40°C to 125°C
20
FEEDBACK tied to VTAP
(5) 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).
(6) 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).
6
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
SLVS582D–APRIL 2006–REVISED MARCH 2007
TYPICAL CHARACTERISTICS
QUIESCENT CURRENT
INPUT CURRENT
vs
INPUT VOLTAGE
vs
LOAD CURRENT
100
90
80
70
60
50
40
30
20
10
0
10
RL = ∞
1
0.1
0.01
0.0001
0.001
0.01
0.1
IL – Load Current – A
0
1
2
3
4
5
6
7
8
9
10
VIN – Input Voltage – V
INPUT CURRENT
vs
INPUT VOLTAGE
INPUT CURRENT
vs
INPUT VOLTAGE
120
110
100
90
80
70
60
50
40
30
20
10
0
200
180
160
140
120
100
80
RL = 50 Ω
RL = 50 kΩ
60
40
20
0
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
VIN – Input Voltage – V
VIN – Input Voltage – V
7
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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
5.075
5.050
5.025
5.000
4.975
4.950
4.925
4.900
120
110
100
90
80
70
60
50
40
30
20
10
0
IL = 0
IL = 100 µA
IL = 100 mA
0
1
2
3
4
5
6
7
8
-40 -25 -10
5
20 35 50 65 80 95 110 125
A – Temperature – °C
VIN – Input Voltage – V
T
QUIESCENT CURRENT
vs
QUIESCENT CURRENT
vs
INPUT VOLTAGE
INPUT VOLTAGE
8
7
6
5
4
3
2
1
120
110
100
90
IL = 100 mA
IL = 1 mA
80
70
60
50
40
30
20
10
0
0
0
0
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
VIN – Input Voltage – V
VIN – Input Voltage – V
8
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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
QUIESCENT CURRENT
vs
TEMPERATURE
TEMPERATURE
100
95
90
85
80
75
70
65
60
55
50
10
IL = 100 mA
IL = 100 µA
VIN = 6 V
9.5
9
VIN = 6 V
8.5
8
7.5
7
6.5
6
5.5
5
-40 -25 -10
5
20 35 50 65 80 95 110 125
-40 -25 -10
5
20 35 50 65 80 95 110 125
TA – Temperature – °C
TA – Temperature – °C
SHORT-CIRCUIT CURRENT
DROPOUT VOLTAGE
vs
vs
TEMPERATURE
TEMPERATURE
250
225
200
175
150
125
100
75
500
450
400
350
300
250
200
150
100
50
RL = 100 mA
RL = 100 µA
50
0
-40 -25 -10
5
20 35 50 65 80 95 110 125
-40 -25 -10
5
20 35 50 65 80 95 110 125
TA – Temperature – °C
TA – Temperature – °C
9
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
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SLVS582D–APRIL 2006–REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
DROPOUT VOLTAGE
vs
OUTPUT CURRENT
LP2951 MINIMUM OPERATING VOLTAGE
vs
TEMPERATURE
2
1.95
1.9
400
350
300
250
200
150
100
50
1.85
1.8
1.75
1.7
1.65
1.6
0
-40 -25 -10
5
20 35 50 65 80 95 110 125
0.0001
0.001
0.01
0.1
TA – Temperature – °C
IO – Output Current – A
LP2951 FEEDBACK BIAS CURRENT
LP2951 ERROR COMPARATOR OUTPUT
vs
vs
TEMPERATURE
INPUT VOLTAGE
8
7
6
5
4
3
2
1
30
25
20
15
10
5
50-kW resistor to
external 5-V supply
50-kW resistor
to VOUT
0
-5
-10
-15
-20
0
0
1
2
3
4
5
6
7
8
VIN – Input Voltage – V
-55 -30 -5
20 45 70
95 120 145
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 ERROR COMPARATOR SINK CURRENT
LINE TRANSIENT RESPONSE
vs
vs
OUTPUT LOW VOLTAGE
TIME
2
1.75
1.5
1.25
1
Input Voltage
2 V/div
TA = 125
TA = 25
Output Voltage
80 mV/div
0.75
0.5
0.25
0
TA = –40
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
LOAD TRANSIENT RESPONSE
vs
TIME
vs
TIME
(VOUT = 5 V, CL = 1 µF)
(VOUT = 5 V, CL = 10 µF)
Output Voltage
100 mV/div
Output Voltage
100 mV/div
Output Load
100 mA/div
Output Load
100 mA/div
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ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
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SLVS582D–APRIL 2006–REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
ENABLE TRANSIENT RESPONSE
ENABLE TRANSIENT RESPONSE
vs
TIME
vs
TIME
(CL = 1 µF, IL = 1 mA)
(CL = 10 µF, IL = 1 mA)
OUTPUT IMPEDANCE
vs
RIPPLE REJECTION
vs
FREQUENCY
FREQUENCY
100
10
90
80
70
60
50
40
30
20
IL = 100 µA
IL = 0
1
IL = 1 mA
IL = 100 µA
0.1
IL = 100 mA
VIN = 6 V
CL = 1 µF
0.01
10
10
100
1k
10k
100k
1M
100
1k
10k
100k
1M
f – Frequency – Hz
f – Frequency – Hz
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SLVS582D–APRIL 2006–REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
RIPPLE REJECTION
vs
RIPPLE REJECTION
vs
FREQUENCY
FREQUENCY
100
90
80
70
60
50
40
30
20
100
90
80
70
60
50
40
30
20
10
VIN = 6 V
CL = 1 µF
VIN = 6 V
CL = 1 µF
IL = 50 mA
IL = 1 mA
IL = 100 mA
IL = 10 mA
1k
10
10
100
10k
100k
1M
10
100
1k
10k
100k
1M
f – Frequency – Hz
f – Frequency – Hz
LP2951 OUTPUT NOISE
LP2951 DIVIDER RESISTANCE
vs
vs
FREQUENCY
TEMPERATURE
6
5
4
400
350
300
250
200
150
100
50
CL = 200 µF
3
2
1
0
CL = 1 µF
CL = 3.3 µF
0
-40 -25 -10
5
20 35 50 65 80 95 110 125
.
10
.
100
1k
10k
.
100k
TA – Temperature – °C
f – Frequency – Hz
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SLVS582D–APRIL 2006–REVISED MARCH 2007
TYPICAL CHARACTERISTICS (continued)
SHUTDOWN THRESHOLD VOLTAGE (OFF TO ON)
SHUTDOWN THRESHOLD VOLTAGE (ON TO OFF)
vs
vs
TEMPERATURE
TEMPERATURE
1.7
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.9
0.8
-40 -25 -10
5
20 35 50 65 80 95 110 125
TA – Temperature – °C
-40 -25 -10
5
20 35 50 65 80 95 110 125
A – Temperature – °C
T
LINE REGULATION
vs
INPUT VOLTAGE
6
5
4
3
2
1
0
-1
-2
0
5
10
15
20
25
30
VIN – Input Voltage – V
14
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LP2950, LP2951
ADJUSTABLE MICROPOWER VOLTAGE REGULATORS
WITH SHUTDOWN
www.ti.com
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.
15
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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
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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
5 V
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:
R1
ǒ 1 )
Ǔ
VOUT + VREF
* IFBR1
R2
(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.
17
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PACKAGE OPTION ADDENDUM
www.ti.com
11-Jun-2007
PACKAGING INFORMATION
Orderable Device
LP2950-30LP
LP2950-30LPR
LP2950-33LPE3
LP2950-33LPRE3
LP2950-50LPRE3
LP2951-30D
Status (1)
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
TO-92
LP
3
3
3
3
3
8
8
8
8
8
8
8
8
8
8
8
8
8
8
1000
2000
1000
2000
2000
Pb-Free
(RoHS)
CU SN
CU SN
CU SN
CU SN
CU SN
N / A for Pkg Type
N / A for Pkg Type
N / A for Pkg Type
N / A for Pkg Type
N / A for Pkg Type
TO-92
TO-92
TO-92
TO-92
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
SOIC
LP
LP
LP
LP
D
Pb-Free
(RoHS)
Pb-Free
(RoHS)
Pb-Free
(RoHS)
Pb-Free
(RoHS)
75 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2951-30DG4
LP2951-30DR
LP2951-30DRG4
LP2951-33D
D
75 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
2500 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
2500 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
75 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2951-33DG4
LP2951-33DR
LP2951-33DRG4
LP2951-50D
D
75 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
2500 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
2500 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
75 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2951-50DG4
LP2951-50DR
LP2951-50DRG4
LP2951D
D
75 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
2500 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
2500 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
D
75 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
LP2951DR
D
2500 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
(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
16-Jun-2007
Device
Package Pins
Site
Reel
Reel
A0 (mm)
B0 (mm)
K0 (mm)
P1
W
Pin1
Diameter Width
(mm) (mm) Quadrant
(mm)
330
330
330
330
(mm)
12
LP2951-30DR
LP2951-33DR
LP2951-50DR
LP2951DR
D
D
D
D
8
8
8
8
FMX
FMX
FMX
FMX
6.4
6.4
6.4
6.4
5.2
5.2
5.2
5.2
2.1
2.1
2.1
2.1
8
8
8
8
12
12
12
12
Q1
Q1
Q1
Q1
12
12
12
TAPE AND REEL BOX INFORMATION
Device
Package
Pins
Site
Length (mm) Width (mm) Height (mm)
LP2951-30DR
LP2951-33DR
LP2951-50DR
LP2951DR
D
D
D
D
8
8
8
8
FMX
FMX
FMX
FMX
342.9
342.9
342.9
342.9
336.6
336.6
336.6
336.6
20.64
20.64
20.64
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
0.022 (0,56)
0.016 (0,41)
0.016 (0,41)
0.014 (0,35)
0.104 (2,65)
FORMED LEAD OPTION
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.
1
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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)
0.748 (19,00)
0.689 (17,50)
0.433 (11,00)
0.335 (8,50)
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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