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LP2951-33-Q1, LP2951-50-Q1
SLVSAW6E – JUNE 2011 – REVISED NOVEMBER 2014
LP2951-xx-Q1 Adjustable Micropower Voltage Regulators With Shutdown
1 Features
3 Description
•
•
•
•
•
•
•
•
The LP2951-xx-Q1 devices are bipolar, low-dropout
voltage regulators that can accommodate a wide
input supply-voltage range of up to 35 V. The 8-pin
LP2951-xx-Q1 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-xxQ1 outputs a fixed 5 V and 3.3 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.
1
•
•
•
•
Qualified for Automotive Applications
Wide Input Range: Up to 35 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
Stable With Low ESR (>12 mΩ) Capacitors
Current- and Thermal-Limiting Features
8-Pin Package
– Fixed Voltages: 5 V/ADJ and 3.3 V/ADJ
– Low-Voltage Error Signal on Falling Output
– Shutdown Capability
– Remote Sense Capability for Optimal Output
Regulation and Accuracy
The 8-pin LP2951-xx-Q1 also offers additional
functionality that makes it particularly suitable for
battery-powered applications. For example, a logiccompatible 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 LP295x-xx-Q1 devices 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.
2 Applications
•
•
•
Automotive Power
– Battery to MCU Regulator
– Sensor Supply
– Infotainment
– Body Control Module
Secondary Side Regulation
Point of Load Regulation
Device Information(1)
PART NUMBER
LP2951-33-Q1
LP2591-50-Q1
LP2951-50-Q1
PACKAGE
BODY SIZE (NOM)
SOIC (8)
4.90 mm × 3.90 mm
WSON (8)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Dropout Voltage vs Temperature
500
(V IN – V OUT ) – Dropout Voltage – mV
450
400
350
RIL = 100 m A
300
250
200
150
100
RIL = 100 µA
50
0
-40 -25 -10
5
20 35
50 65
80 95 110 125
TA – Temperature – °C
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LP2951-33-Q1, LP2951-50-Q1
SLVSAW6E – JUNE 2011 – REVISED NOVEMBER 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
3
3
6.1
6.2
6.3
6.4
6.5
6.6
3
3
4
4
4
6
Absolute Maximum Ratings .....................................
Handling Ratings.......................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description ............................................ 12
7.1 Overview ................................................................. 12
7.2 LP2951-xx-Q1 Functional Block Diagram............... 13
7.3 Feature Description................................................. 14
7.4 Device Functional Modes........................................ 15
8
Application and Implementation ........................ 16
8.1 Application Information............................................ 16
8.2 Typical Application ................................................. 16
9 Power Supply Recommendations...................... 19
10 Layout................................................................... 19
10.1 Layout Guidelines ................................................. 19
10.2 Layout Example .................................................... 19
11 Device and Documentation Support ................. 19
11.1
11.2
11.3
11.4
Related Links ........................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
19
19
19
19
12 Mechanical, Packaging, and Orderable
Information ........................................................... 20
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision D (April 2013) to Revision E
•
Page
Added Handling Rating table, Feature Description section, Device Functional Modes, Application and
Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation
Support section, and Mechanical, Packaging, and Orderable Information section................................................................ 1
Changes from Revision C (February 2013) to Revision D
Page
•
Deleted unreleased devices ................................................................................................................................................... 1
•
Added the THERMAL INFORMATION table .......................................................................................................................... 4
Changes from Revision B (December 2012) to Revision C
Page
•
Deleted P/N LP2951-Q1 from page header ........................................................................................................................... 1
•
Deleted ORDERING INFORMATION table............................................................................................................................ 3
Changes from Revision A (July 2012) to Revision B
•
Page
Changed LP2951-33QDRGRQ1 From: Preview To: Active ................................................................................................... 3
Changes from Original (June, 2011) to Revision A
•
2
Page
Removed continuous from input voltage range parameter description; changed max values for VIN and VSHDN from
30 to 35................................................................................................................................................................................... 3
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Copyright © 2011–2014, Texas Instruments Incorporated
Product Folder Links: LP2951-33-Q1 LP2951-50-Q1
LP2951-33-Q1, LP2951-50-Q1
www.ti.com
SLVSAW6E – JUNE 2011 – REVISED NOVEMBER 2014
5 Pin Configuration and Functions
D Package
8-Pin SOIC
LP2591-50-Q1 Top View
OUTPUT
SENSE
SHUTDOWN
GND
DRG Package
8-Pin WSON With Exposed Thermal Pad
Top View
INPUT
FEEDBACK
6 VTAP
5 ERROR
1
8
2
3
7
4
OUTPUT
SENSE
SHUTDOWN
GND
1
2
8
7
Thermal
3
6
4
5
INPUT
FEEDBACK
VTAP
ERROR
Pin Functions
PIN
NAME
TYPE
NO.
DESCRIPTION
ERROR
5
O
Active-low open-collector error output. Goes low when VOUT drops by 6% of its
nominal value.
FEEDBACK
7
I
Determines the output voltage. Connect to VTAP (with OUTPUT tied to SENSE)
to output the fixed voltage corresponding to the part version, or connect to a
resistor divider to adjust the output voltage.
GND
4
—
INPUT
8
I
Supply input
OUTPUT
1
O
Voltage output.
SENSE
2
I
Senses the output voltage. Connect to OUTPUT (with FEEDBACK tied to VTAP)
to output the voltage corresponding to the part version.
SHUTDOWN
3
I
Active-high input. Shuts down the device.
VTAP
6
O
Tie to FEEDBACK to output the fixed voltage corresponding to the part version.
Ground
6 Specifications
6.1 Absolute Maximum Ratings (1)
over operating free-air temperature range (unless otherwise noted)
VIN
Input voltage range
VSHDN SHUTDOWN input voltage range
MIN
MAX
UNIT
–0.3
35
V
–1.5
35
V
ERROR comparator output voltage range (2)
–1.5
30
V
VFDBK
FEEDBACK input voltage range (2)
–1.5
30
V
TJ
Operating virtual-junction temperature
150
°C
(1)
(2)
(3)
(3)
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.
6.2 Handling Ratings
Tstg
MIN
MAX
UNIT
–65
150
°C
0
2000
Corner pins (1, 4, 8,
and 5)
0
1000
Other pins
0
1000
Storage temperature range
Human body model (HBM), per AEC Q100-002 (1) (2)
V(ESD)
(1)
(2)
Electrostatic discharge
Charged device model (CDM), per
AEC Q100-011
V
AEC Q100-002 indicates HBM stressing is done in accordance with the ANSI/ESDA/JEDEC JS-001 specification.
LP2951-50QDRQ1 Feedback pin survives up to 1500V HBM
Copyright © 2011–2014, Texas Instruments Incorporated
Product Folder Links: LP2951-33-Q1 LP2951-50-Q1
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6.3 Recommended Operating Conditions
MIN
VIN
Supply input voltage
TA
Operating temperature
(1)
NOM
MAX
UNIT
(1)
30
V
–40
125
°C
See
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
6.4 Thermal Information
THERMAL METRIC
LP2951-30-Q1,
LP2951-50-Q1
LP2951-50-Q1
DRG
D
UNIT
8 PINS
8 PINS
RθJA
Junction-to-ambient thermal resistance
55.7
121.6
RθJC(top)
Junction-to-case (top) thermal resistance
66.5
69.8
RθJB
Junction-to-board thermal resistance
30.2
61.9
ψJT
Junction-to-top characterization parameter
1.1
22.2
ψJB
Junction-to-board characterization parameter
30.4
61.4
RθJC(bot)
Junction-to-case (bottom) thermal resistance
10
n/a
°C/W
6.5 Electrical Characteristics
VIN = VOUT (nominal) + 1 V, IL = 100 μA, CL = 1 μF (5-V versions) or CL = 2.2 μF (3.3-V versions),
8-pin version: FEEDBACK tied to VTAP, OUTPUT tied to SENSE, VSHUTDOWN ≤ 0.7 V
PARAMETER
TEST CONDITIONS
TA
MIN
TYP
MAX
UNIT
3.3-V VERSION (LP2951-33-Q1)
VOUT
Output voltage
IL = 100 μA
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
20
100
0.03
0.2
V
5-V VERSION (LP2951-50-Q1)
VOUT
Output voltage
IL = 100 μA
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
(1)
(2)
(3)
4
Dropout ground current
VIN = VOUT(NOM) – 0.5 V,
IL = 100 μA
Current limit
VOUT = 0 V
–40°C to 125°C
25°C
–40°C to 125°C
25°C
0.4
0.04%
–40°C to 125°C
25°C
380
8
25°C
120
12
14
110
–40°C to 125°C
–40°C to 125°C
450
140
–40°C to 125°C
25°C
80
mV
600
75
–40°C to 125°C
25°C
0.2%
150
–40°C to 125°C
25°C
%/V
0.3%
50
–40°C to 125°C
25°C
ppm/°C
170
200
160
200
220
μA
mA
μA
mA
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.
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SLVSAW6E – JUNE 2011 – REVISED NOVEMBER 2014
Electrical Characteristics (continued)
VIN = VOUT (nominal) + 1 V, IL = 100 μA, CL = 1 μF (5-V versions) or CL = 2.2 μF (3.3-V versions),
8-pin version: FEEDBACK tied to VTAP, OUTPUT tied to SENSE, VSHUTDOWN ≤ 0.7 V
PARAMETER
Thermal regulation (4)
TEST CONDITIONS
IL = 100 μA
TA
MIN
25°C
CL = 1 μF (5 V only)
Output noise (RMS),
10 Hz to 100 kHz
Reference voltage (5)
CL = 200 μF
Reference voltage temperature
coefficient (1)
MAX
UNIT
0.05
0.2
%/W
430
160
25°C
LP2951-50-Q1: CL = 3.3 μF,
CBypass = 0.01 μF between pins 1 and 7
VOUT = VREF to (VIN – 1 V),
VIN = 2.3 V to 30 V,
IL = 100 μA to 100 mA
TYP
μV
100
–40°C to 125°C
1.200
1.272
25°C
20
25°C
0.01
V
ppm/°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) (6)
25°C
40
–40°C to 125°C
25
Lower threshold voltage
(ERROR output low) (6)
–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
(4)
(5)
(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
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.
For LP2951-50QDR in SOIC package, VREF is tested at VIN = 6 V and IOUT=100 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 (typical) and 7.7% (maximum).
Copyright © 2011–2014, Texas Instruments Incorporated
Product Folder Links: LP2951-33-Q1 LP2951-50-Q1
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6.6 Typical Characteristics
100
10
RL = ∞
90
1
70
Input Current – µA
Quiescent Current – mA
80
0.1
60
50
40
30
20
10
0.01
0.0001
0
0.001
0.01
0.1
0
1
2
3
4
5
6
7
8
9
10
IL – Load Current – A
VIN – Input Voltage – V
Figure 1. Quiescent Current vs Load Current
Figure 2. Input Current vs Input Voltage
200
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
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
Figure 3. Input Current vs Input Voltage
Figure 4. Input 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
6
0
20 35 50 65 80 95 110 125
0
1
2
3
4
5
6
7
8
TA – Temperature – °C
VIN – Input Voltage – V
Figure 5. Output Voltage vs Temperature
Figure 6. Quiescent Current vs Input Voltage
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SLVSAW6E – JUNE 2011 – REVISED NOVEMBER 2014
Typical Characteristics (continued)
8
IL = 100 mA
120
7
IL = 1 mA
110
Quiescent Current – mA
Quiescent Current – µA
100
90
80
70
60
50
40
30
6
5
4
3
2
20
10
1
0
0
1
2
3
4
5
6
7
8
0
0
VIN – Input Voltage – V
1
2
3
4
5
6
7
8
VIN – Input Voltage – V
Figure 7. Quiescent Current vs Input Voltage
Figure 8. Quiescent Current vs Input Voltage
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
IL = 100 µA
V IN = 6 V
5
20
35
50
65
80
50
-40 -25 -10
95 110 125
5
Figure 9. Quiescent Current vs Temperature
65
80
95 110 125
500
450
(V IN – V OUT ) – Dropout Voltage – mV
225
Short-Circuit Current – mA
35 50
Figure 10. Quiescent Current vs Temperature
250
200
175
150
125
100
75
50
-40 -25 -10
20
TA – Temperature – °C
TA – Temperature – °C
5
20
35 50
65
80
95 110 125
400
350
RIL = 100 m A
300
250
200
150
100
RIL = 100 µA
50
0
-40 -25 -10
5
20 35
50 65
80 95 110 125
TA – Temperature – °C
TA – Temperature – °C
Figure 11. Short-Circuit Current vs Temperature
Figure 12. Dropout Voltage vs Temperature
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400
2
350
1.95
Minimum Operating Voltage – V
(V IN – V OUT ) – Dropout Voltage – mV
Typical Characteristics (continued)
300
250
200
150
100
1.9
1.85
1.8
1.75
1.7
1.65
50
0
0.0001
0.001
0.01
1.6
-40 -25 -10
0.1
Figure 13. Dropout Voltage vs Output Current
20
35 50
65 80
95 110 125
Figure 14. Minimum Operating Voltage vs Temperature
30
8
25
7
50-kW resistor to
external 5-V supply
20
6
ERROR Output – V
FEEDBACK Bias Current – nA
5
TA – Temperature – °C
IO – Output Current – A
15
10
5
0
-5
5
4
3
50-kW resistor
to VOUT
2
-10
1
-15
-20
-55
0
-30
-5
20
45
70
95
0
120 145
1
2
3
4
5
6
7
8
V IN – Input Voltage – V
TA – Temperature – °C
Figure 15. Feedback Bias Current vs Temperature
Figure 16. ERROR Comparator Output vs Input Voltage
2
ISINK – Sink Current – mA
1.75
TA = 125
Input Voltage
2 V/div
1.5
1.25
TA = 25
1
0.75
TA = –40
0.5
Output Voltage
80 mV/div
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
Figure 17. ERROR Comparator Sink Current vs Output Low
Voltage
8
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Figure 18. Line Transient Response vs Time
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SLVSAW6E – JUNE 2011 – REVISED NOVEMBER 2014
Typical Characteristics (continued)
Output Voltage
100 mV/div
Output Voltage
100 mV/div
Output Load
100 mA/div
Output Load
100 mA/div
Figure 19. Load Transient Response vs Time
(VOUT = 5 V, CL = 1 μF)
Figure 20. Load Transient Response vs Time
(VOUT = 5 V, CL = 10 μF)
Figure 21. Enable Transient Response vs Time
(CL = 1 μF, IL = 1 mA)
Figure 22. Enable Transient Response vs Time
(CL = 10 μF, IL = 1 mA)
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
100
1.E+01
1.E+02
1k
1.E+03
10k
1.E+04
100k
1.E+05
1M
1.E+06
f – Frequency – Hz
f – Frequency – Hz
Figure 23. Output Impedance vs Frequency
Figure 24. Ripple Rejection vs Frequency
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Typical Characteristics (continued)
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
80
60
50
40
IL = 100 mA
30
20
IL = 10 mA
1.E+02
100
1.E+03
1k
1.E+04
10k
1.E+05
100k
IL = 50 mA
70
20
10
1.E+01
10
CL = 1 µF
10
10
1.E+01
1.E+06
1M
100
1.E+02
1k
1.E+03
100k
1.E+05
1M
1.E+06
Figure 26. Ripple Rejection vs Frequency
6
400
RP2P4 – Pin 2 to Pin 4 Resistance – k W
Figure 25. Ripple Rejection vs Frequency
5
Output Noise – µV
10k
1.E+04
f – Frequency – Hz
f – Frequency – Hz
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
0
-40 -25 -10
1.E+05
100k
5
20
35 50
65 80 95 110 125
TA – Temperature – °C
f – Frequency – Hz
Figure 27. Output Noise vs Frequency
Figure 28. Divider Resistance vs Temperature
1.7
1.7
1.6
V
–
) 1.5
N
O
o
t 1.4
F
F
O
( 1.3
e
g
ta
l 1.2
o
V
ic 1.1
g
o
L
t 1
u
p
n
I
0.9
Input Logic Voltage (ON to OFF) – V
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
-40 -25 -10
0.8
-40 -25 -10
5
20
35
50
65
80
95 110 125
5
20
35
50
65
80
95 110 125
TA – Temperature – °C
TA – Temperature – °C
Figure 29. Shutdown Threshold Voltage (OFF to ON) vs
Temperature
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Figure 30. Shutdown Threshold Voltage (ON to OFF) vs
Temperature
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Typical Characteristics (continued)
6
Output Voltage Change – mV
5
4
3
2
1
0
-1
-2
0
5
10
15
20
25
30
VIN – Input Voltage – V
Figure 31. Line Regulation vs Input Voltage
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7 Detailed Description
7.1 Overview
The LP2951-xx-Q1 devices are bipolar, low-dropout voltage regulators that can accommodate a wide input
supply-voltage range of up to 30 V. The 8-pin LP2951-xx-Q1 devices are 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-xx-Q1 devices output 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-xx-Q1 devices also offer additional functionality that makes them 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.
LP2951-xx-Q1 devices 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 lowpower voltage references or 100-mA regulators.
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7.2 LP2951-xx-Q1 Functional Block Diagram
FEEDBACK
INPUT
OUTPUT
SENSE
+
Error
Amplifier
SHUTDOWN
VTAP
+
ERROR
60 mV
1.235-V Reference
GND
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7.3 Feature Description
7.3.1
ERROR Function
The LP2951-xx-Q1 devices have 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 32 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.
Output
Voltage
4.75 V
ERROR
5V
Input
Voltage
1.3 V
Figure 32. 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.
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Feature Description (continued)
7.3.2 Programming Output Voltage
A unique feature of the LP2951-xx-Q1 devices are their 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 1:
R1 ö
æ
VOUT = VREF ´ ç 1 +
÷ - IFBR1
è R2 ø
(1)
Where:
VREF = 1.235 V applied across R2 (see Figure 33)
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-xxQ1 devices under no load.
VOUT
R1
FEEDBACK
R2
Figure 33. Adjusting the Feedback on the LP2951-xx-Q1
7.4 Device Functional Modes
7.4.1 Shutdown Mode
These devices can be placed in shutdown mode with a logic high at the SHUTDOWN pin. Return the logic level
low to restore operation or tie SHUTDOWN to ground if the feature is not being used.
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8 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The LP2951-xx-Q1 devices are used as low-dropout regulators with a wide range of input voltages.
8.2 Typical Application
330 kΩ
VOUT = 5 V
1 PF
VOUT
SENSE
8
2
7
FEEDBACK
LP2951-50
VIN = 12 V
VIN
1
1 PF
SHUTDOWN
3
6
VTAP
GND
4
5
ERROR
Figure 34. 12-V to 5-V Converter
8.2.1 Design Requirements
8.2.1.1 Input Capacitor (CIN)
A 1-μF (tantalum, ceramic, or aluminum) electrolytic capacitor should be placed locally at the input of the
LP2951-xx-Q1 device 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.
8.2.1.2 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.
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Typical Application (continued)
8.2.2 Detailed Design Procedure
8.2.2.1 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 greater 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 LP2951-xx-Q1 devices, 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-xx-Q1 is used with external
resistors to set the output voltage, a minimum load current of 1 μA is recommended through the resistor divider.
8.2.2.2 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.
8.2.2.3 CBYPASS: Noise and Stability Improvement
In the LP2951-xx-Q1 devices, 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-xx-Q1 devices. 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, where loop gain reduction is greatest.
A suitable CBYPASS is calculated as shown in Equation 2:
f(CBYPASS) ; 200 Hz ® C(BYPASS) =
1
2p ´ R1´ 200 Hz
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Typical Application (continued)
8.2.2.4 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 is always
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 an ESR that is too high could result in the zero
occurring too soon, causing the gain to roll off too slowly. This, in turn, allows a third pole to appear before unity
gain and introduces enough phase shift to cause instability. This typically limits the maximum ESR to
approximately 5 Ω.
Conversely, the lower limit of the ESR range is tied to the fact that an ESR that is too low shifts the zero too far
out, past unity gain, which allows the gain to roll off at 40 dB/decade at unity gain, resulting in a 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.
8.2.3 Application Curve
Output Voltage
100 mV/div
Output Load
100 mA/div
Figure 35. Load Transient Response vs Time (VOUT = 5 V, CL = 1 µF)
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9 Power Supply Recommendations
Maximum input voltage should be limited to 30 V for proper operation. Place input and output capacitors as close
to the device as possible to take advantage of their high frequency noise filtering properties.
10 Layout
10.1 Layout Guidelines
Make sure that traces on the input and outputs of the device are wide enough to handle the desired currents. For
this device, the output trace will need to be larger in order to accommodate the larger available current.
Place input and output capacitors as close to the device as possible to take advantage of their high frequency
noise filtering properties.
10.2 Layout Example
1 PF
1
8
2
7
1 PF
LP2951-50
3
6
4
5
ERROR can be left floating
if not used
Figure 36. LP2951-xx-Q1 Layout Example (D Package)
11 Device and Documentation Support
11.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 1. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
LP2951-33-Q1
Click here
Click here
Click here
Click here
Click here
LP2951-50-Q1
Click here
Click here
Click here
Click here
Click here
11.2 Trademarks
All trademarks are the property of their respective owners.
11.3 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.4 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
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12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LP2951-33QDRGRQ1
ACTIVE
SON
DRG
8
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
RACQ
LP2951-50QDRGRQ1
ACTIVE
SON
DRG
8
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 125
ZUFQ
LP2951-50QDRQ1
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-3-260C-168 HR
-40 to 125
KY515Q
(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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