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LP3982
SNVS185F – FEBRUARY 2002 – REVISED APRIL 2017
LP3982 Micropower, Ultra-Low-Dropout, Low-Noise, 300-mA CMOS Regulator
1 Features
3 Description
•
•
The LP3982 low-dropout (LDO) CMOS linear
regulator is available in 1.8-V, 2.5-V, 2.82-V, 3-V,
3.3-V, and adjustable versions. They deliver 300 mA
of output current. Packaged in an 8-pin VSSOP, the
LP3982 is pin- and package-compatible with Maxim's
MAX8860. The LM3982 is also available in the small
footprint WSON package.
1
•
•
•
•
•
•
•
•
•
•
•
2.5-V to 6-V Input Range
MAX8860 Pin, Package, and Specification
Compatible
300-mA Output Current
120-mV Typical Dropout at 300 mA
90-μA Typical Quiescent Current
1-nA Typical Shutdown Mode
60-dB Typical PSRR
120-μs Typical Turnon Time
Stable With Small Ceramic Output Capacitors
37-μVRMS Output Voltage Noise
(10 Hz to 100 kHz)
Overtemperature/Overcurrent Protection
±2% Output Voltage Tolerance
Create a Custom Design Using the LP3982 With
the WEBENCH® Power Designer
The LP3982 suits battery-powered applications
because of its shutdown mode (1 nA typical), low
quiescent current (90 μA typical), and LDO voltage
(120 mV typical). The low dropout voltage allows for
more utilization of a battery’s available energy by
operating closer to its end-of-life voltage. The LP3982
device's PMOS output transistor consumes relatively
no drive current compared to PNP LDO regulators.
This PMOS regulator is stable with small ceramic
capacitive loads (2.2 μF typical).
These devices also include regulation fault detection,
a bandgap voltage reference, constant current
limiting, and thermal-overload protection.
2 Applications
•
•
•
•
Device Information(1)
Wireless Handsets
DSP Core Power
Battery Powered Electronics
Portable Information Appliances
PART NUMBER
LP3982
PACKAGE
BODY SIZE (NOM)
WSON (8)
2.50 mm × 3.00 mm
VSSOP (8)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the data sheet.
Application Circuit (Fixed VOUT Version)
VO
VIN
OUT
IN
2.2 PF
100
kŸ
SHDN
2.2 PF
CERAMIC
FAULT
GND
CC
33 nF
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.
LP3982
SNVS185F – FEBRUARY 2002 – REVISED APRIL 2017
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
4
6.1
6.2
6.3
6.4
6.5
6.6
4
4
4
4
5
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Conditions.......................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 9
7.1
7.2
7.3
7.4
Overview ................................................................... 9
Functional Block Diagram ......................................... 9
Feature Description................................................... 9
Device Functional Modes........................................ 10
8
Application and Implementation ........................ 11
8.1 Application Information............................................ 11
8.2 Typical Application ................................................. 11
9 Power Supply Recommendations...................... 16
10 Layout................................................................... 17
10.1 Layout Guidelines ................................................. 17
10.2 Layout Example .................................................... 17
10.3 WSON Mounting ................................................... 17
11 Device and Documentation Support ................. 18
11.1
11.2
11.3
11.4
11.5
11.6
Documentation Support .......................................
Receiving Notification of Documentation Updates
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
18
18
18
18
18
19
12 Mechanical, Packaging, and Orderable
Information ........................................................... 19
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision E (October 2015) to Revision F
•
Page
Added links for Webench and changed top navigator icon for TI Designs ........................................................................... 1
Changes from Revision D (April 2013) to Revision E
Page
•
Added Device Information and Pin Configuration and Functions sections, ESD Ratings table, Feature Description,
Device Functional Modes, Application and Implementation, Power Supply Recommendations, Layout, Device and
Documentation Support, and Mechanical, Packaging, and Orderable Information sections; update Thermal Information... 1
•
Deleted lead temperature from Abs Max table (in POA); revised wording for footnote 4 ..................................................... 4
Changes from Revision C (April 2013) to Revision D
•
2
Page
Changed layout of National Data Sheet to TI format ............................................................................................................. 9
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SNVS185F – FEBRUARY 2002 – REVISED APRIL 2017
5 Pin Configuration and Functions
DGK Package
8-Pin VSSOP
Top View
OUT
IN
GND
OUT
1
8
2
7
3
6
4
5
FAULT
SHDN
CC
SET *
The SET pin is internally disconnected for the fixed versions.
NGM Package
8-Pin WSON With Thermal Pad
Top View
OUT
1
IN
2
8
FAULT
7
SHDN
DAP
GND
3
6
CC
OUT
4
5
SET*
The SET pin is internally disconnected for the fixed versions.
Pin Functions
PIN
NAME
NO.
I/O
DESCRIPTION
Connect a capacitor between CC pin and ground to reduce the output noise. The optimum
value for CC is 33 nF.
CC
6
—
FAULT
8
Output
FAULT pin goes low during out of regulation conditions like current limit and thermal
shutdown, or when it approaches dropout. Requires a pullup resistor because it is an activelow, open-drain output.
GND
3
Ground
Ground
IN
2
Input
OUT
1, 4
Output
SET
5
Input
In the adjustable version a resistor divider connected to this pin sets the output voltage. The
SET pin is internally disconnected for the fixed versions.
SHDN
7
Input
The SHDN pin allows the part to be turned to an ON or OFF state by pulling SHDN pin high
or low.
DAP
√
—
WSON Only - The DAP (Die Attached Pad) is an exposed pad that does not have an internal
connection; it functions as a thermal relief when soldered to a copper plane. It is recommend
that the DAP be connected to GND. See WSON Mounting section for more information.
This is the input supply voltage to the regulator.
Regulated output voltage
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1) (2) (3)
VIN, VOUT, VSHDN, VSET, VCC, VFAULT
MIN
MAX
UNIT
−0.3
6.5
V
20
mA
150
°C
160
°C
Fault sink current
See (4)
Power dissipation
Junction temperature, TJ
Storage temperature, Tstg
(1)
(2)
(3)
(4)
–65
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltages are with respect to the potential at the GND pin.
If Military/Aerospace-specified devices are required, contact Texas Instruments Sales Office/Distributors for availability and
specifications.
In applications where high power dissipation and/or poor thermal resistance is present, the maximum ambient temperature may have to
be derated. Maximum ambient temperature (TA(MAX)) is dependant on the maximum operating junction temperature (TJ(MAX-OP)), the
maximum power dissipation (PD(MAX)), and the junction-to-ambient thermal resistance in the application (RθJA). This relationship is given
by: TA(MAX) = TJ(MAX-OP) − (PD(MAX) × RθJA).The value of the RθJA for the WSON package is specifically dependent on the PCB trace
area, trace material, and the number of layers and thermal vias. For improved thermal resistance and power dissipation for the WSON
package, refer to TI Application Note AN-1187 Leadless Leadframe Package (LLP) (SNOA401).
6.2 ESD Ratings
V(ESD)
(1)
Electrostatic discharge
VALUE
UNIT
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2000
V
Machine model
±200
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions (1) (2)
MIN
NOM
MAX
UNIT
Operating temperature
–40
85
°C
Supply voltage
2.5
6
V
(1)
(2)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
All voltages are with respect to the potential at the GND pin.
6.4 Thermal Information
LP3982
THERMAL METRIC (1)
DGK (VSSOP)
NGM (WSON) (2)
UNIT
8 PINS
8 PINS
RθJA (3)
Junction-to-ambient thermal resistance, High-K
175.2
52.6
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
66.0
66.2
°C/W
RθJB
Junction-to-board thermal resistance
95.6
16.7
°C/W
ψJT
Junction-to-top characterization parameter
9.7
1.9
°C/W
ψJB
Junction-to-board characterization parameter
94.2
16.7
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
n/a
11.1
°C/W
(1)
(2)
(3)
4
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
The PCB for the WSON/NGN package RθJA includes thermal vias under the exposed thermal pad per EIA/JEDEC JESD51-5.
Thermal resistance value RθJA is based on the EIA/JEDEC High-K printed circuit board defined by: JESD51-7 - High Effective Thermal
Conductivity Test Board for Leaded Surface Mount Packages.
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6.5 Electrical Characteristics
Unless otherwise specified, all limits are specified for VIN = VOUT + 0.5 V (1), VSHDN = VIN, CIN = COUT = 2.2 μF, CCC = 33 nF, TJ
= 25°C.
PARAMETER
VIN
Input voltage
ΔVOUT
Output voltage tolerance
Output adjust range
VOUT
Maximum output current
IOUT
MIN (2)
TEST CONDITIONS
2.5
6
100 μA ≤ IOUT ≤ 300 mA
VIN = VOUT + 0.5 V (1)
SET = OUT for the ADJ Versions
−2
2
For operating temperature extremes:
−40°C to 85°C
−3
3
ADJ version only;
for operating temperature extremes:
−40°C to 85°C
1.25
6
Average DC current rating;
For operating temperature extremes:
−40°C and 85°C
300
VDO
Dropout voltage
ΔVOUT
en
Line regulation
V
mA
330
90
IOUT = 300 mA
(1) (4)
% of VOUT
mA
IOUT = 0 mA;
for operating temperature extremes:
−40°C to 85°C
Shutdown supply current
V
770
For operating temperature extremes:
−40°C to 85°C
Supply current
UNIT
(NOM)
IOUT = 0 mA
IQ
MAX (2)
For operating temperature extremes:
−40°C to 85°C
Output current limit
ILIMIT
TYP (3)
270
μA
1
μA
225
VO = 0 V, SHDN = GND
0.001
IOUT = 1 mA
0.4
IOUT = 200 mA
80
IOUT = 200 mA;
for operating temperature extremes:
−40°C to 85°C
IOUT = 300 mA
120
IOUT = 1 mA,
(VOUT + 0.5 V) ≤ VI ≤ 6 V (1)
0.01
IOUT = 1 mA, (VOUT + 0.5 V) ≤ VI ≤ 6
V (1);
for operating temperature extremes:
−40°C to 85°C
mV
220
%/V
−0.1
0.1
Load regulation
100 μA ≤ IOUT ≤ 300 mA
0.002
%/mA
Output voltage noise
IOUT = 10 mA, 10 Hz ≤ f ≤ 100 kHz
37
μVRMS
Output voltage noise density
10 Hz ≤ f ≤ 100 kHz, COUT = 10 μF
190
nV/√Hz
(1)
VSHDN
SHDN input threshold
VIH, (VOUT + 0.5 V) ≤ VIN ≤ 6 V ;
for operating temperature extremes:
−40°C to 85°C
2
V
VIL, (VOUT + 0.5 V) ≤ VIN ≤ 6 V (1);
for operating temperature
extremes:−40°C to 85°C
0.4
ISHDN
SHDN input bias current
SHDN = GND or IN
0.1
100
nA
ISET
SET input leakage
SET = 1.3 V, ADJ version only (5)
0.1
2.5
nA
(1)
(2)
(3)
(4)
(5)
Condition does not apply to input voltages below 2.5 V because this is the minimum input operating voltage.
All limits are verified by testing or statistical analysis.
Typical values represent the most likely parametric norm.
Dropout voltage is measured by reducing VIN until VOUT drops 100 mV from its nominal value at VIN – VOUT = 0.5 V. Dropout voltage
does not apply to the 1.8-V version.
The SET pin is not externally connected for the fixed versions.
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Electrical Characteristics (continued)
Unless otherwise specified, all limits are specified for VIN = VOUT + 0.5 V(1), VSHDN = VIN, CIN = COUT = 2.2 μF, CCC = 33 nF, TJ
= 25°C.
PARAMETER
TEST CONDITIONS
VO ≥ 2.5 V, IOUT = 200 mA (6)
FAULT detection voltage
VFAULT
IFAULT
TSD
TON
(6)
6
TYP (3)
FAULT output low voltage
ISINK = 2 mA;
for operating temperature extremes:
−40°C to 85°C
FAULT off-leakage current
FAULT = 3.6 V, SHDN = 0 V
Thermal shutdown temperature
MAX (2)
280
0.25
0.1
100
10
COUT = 10 μF, VOUT at 90% of final
value
mV
0.115
160
Thermal shutdown hysteresis
UNIT
120
VOUT ≥ 2.5 V, IOUT = 200 mA (6);
for operating temperature extremes:
−40°C to 85°C
ISINK = 2 mA
Start-up time
MIN (2)
120
V
nA
°C
μs
The FAULT detection voltage is specified for the input-to-output voltage differential at which the FAULT pin goes active low.
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6.6 Typical Characteristics
Unless otherwise specified, VIN = VO + 0.5 V, CIN = COUT = 2.2 μF, CCC = 33 nF, TJ = 25°C, VSHDN = VIN.
160
140
VO = 2.77V
140
25°C
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
120
100
VO = 2.5V
80
VO = 3.3V
60
40
120
85°C
100
80
-40°C
60
40
20
20
0
0
0
50
100
200
150
250
300
0
100
150
200
250
300
LOAD CURRENT (mA)
LOAD CURRENT (mA)
Figure 1. Dropout Voltage vs Load Current
(for Different Output Voltages)
Figure 2. Dropout Voltage vs Load Current
(for Different Output Temperatures)
240
180
IL = 0mA
220
160
200
140
SUPPLY CURRENT (PA)
FAULT DETECT THRESHOLD (mV)
50
FAULT = HIGH
120
100
80
FAULT = LOW
60
40
180
TA = 85°C
160
TA = 25°C
140
120
100
80
60
TA = -40°C
40
20
20
0
0
0
50
100
150
200
250
300
0
1
2
3
4
5
6
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
Figure 3. FAULT Detect Threshold vs Load Current
Figure 4. Supply Current vs Input Voltage
0
250
85°C
25°C
-20
PSRR (dB)
SUPPLY CURRENT (PA)
-10
200
150
-40°C
100
-30
-40
-50
50
-60
0
0
50
250
200
150
100
LOAD CURRENT (mA)
300
Figure 5. Supply Current vs Load Current
-70
10
10k
100
1k
FREQUENCY (Hz)
100k
Figure 6. Power Supply Rejection Ratio vs Frequency
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Typical Characteristics (continued)
Unless otherwise specified, VIN = VO + 0.5 V, CIN = COUT = 2.2 μF, CCC = 33 nF, TJ = 25°C, VSHDN = VIN.
NOISE (PV/ Hz)
10
100 PV/DIV
1
COUT = 10PF
0.1
COUT = 2.2PF
0.01
100
10
k
FREQUENCY (Hz)
100k
1k
1 ms/DIV
Figure 8. Output Noise (10 Hz to 100 kHz)
Figure 7. Output Noise Spectral Density
2
2 V/DIV
1.6
VSHDN
1.4
0V
1.2
1
0.8
VOUT
0.6
1 V/DIV
OUTPUT IMPEDANCE (:)
1.8
0.4
0.2
0
10
100
1k
10k
0V
100k
500 Ps/DIV
FREQUENCY (Hz)
Figure 10. Shutdown Response
VIN
1 V/DIV
VIN
VO
2 V/DIV
FAULT
1 V/DIV
2 V/DIV
Figure 9. Output Impedance vs Frequency
FAULT
VIN
VO
VIN
VO
VO
5 ms/DIV
5 mS/DIV
Figure 12. Power-Down Response
Figure 11. Power-Up Response
8
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7 Detailed Description
7.1 Overview
The LP3982 is package, pin, and performance compatible with Maxim's MAX8860, excluding reverse battery
protection and dual-mode function (fixed and adjustable combined).
A 1.25-V bandgap reference, an error amplifier, and a PMOS pass transistor perform voltage regulation while
being supported by shutdown, fault, and the usual temperature and current protection circuitry (see Functional
Block Diagram).
The regulator topology is the classic type with negative feedback from the output to one of the inputs of the error
amplifier. Feedback resistors R1 and R2 are either internal or external to the device, depending on whether it is
the fixed-voltage version or the adjustable version. The negative feedback and high open loop gain of the error
amplifier cause the two inputs of the error amplifier to be virtually equal in voltage. If the output voltage changes
due to load changes, the error amplifier provides the appropriate drive to the pass transistor to maintain the error
amplifier's inputs as virtually equal. In short, the error amplifier keeps the output voltage constant in order to keep
its inputs equal.
7.2 Functional Block Diagram
IN
OUT
FAST
START-UP
CIRCUIT
CURRENT
LIMIT
FAULT
FAULT
COMPARATORS
R1
+
SET
-
CC
ERROR
AMP
OFF
SHDN
R2
THERMAL
PROTECTION
1.25-V
BANDGAP
GND
7.3 Feature Description
7.3.1 No-Load Stability
The LP3982 remains stable during no-load conditions, a necessary feature for CMOS RAM keep-alive
applications.
7.3.2 Fast Start-Up
The LP3982 provides fast start-up time for better system efficiency. The start-up speed is maintained when using
the optional noise bypass capacitor. An internal 500-μA current source charges the capacitor until it reaches
about 90% of its final value.
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7.4 Device Functional Modes
7.4.1 Shutdown
The LP3982 goes into sleep mode when the SHDN pin is in a logic low condition. During this condition, the pass
transistor, error amplifier, and bandgap are turned off, reducing the supply current to 1 nA typical. The maximum
voltage for a logic low at the SHDN pin is 0.4 V. A minimum voltage of 2 V at the SHDN pin turns the LP3982
back on. The SHDN pin may be directly tied to VIN to keep the part on. The SHDN pin may exceed VIN but not
the maximum of 6.5 V.
Figure 13 shows an application that uses the SHDN pin. It detects when the battery is too low and disconnects
the load by turning off the regulator. A micropower comparator (LMC7215) and reference (LM385) are combined
with resistors to set the minimum battery voltage. At the minimum battery voltage, the comparator output goes
low and tuns off the LP3982 and corresponding load. Hysteresis is added to the minimum battery threshold to
prevent the battery's recovery voltage from falsely indicating an above minimum condition. When the load is
disconnected from the battery, it automatically increases in terminal voltage because of the reduced IR drop
across its internal resistance. The minimum battery detector of Figure 13 has a low detection threshold (VLT) of
3.6 V that corresponds to the minimum battery voltage. The upper threshold (VUT) is set for 4.6 V to exceed the
recovery voltage of the battery.
VB
OUT
IN
R1
768k
R4
180k
+
4 Cells
NiMH
R2
2.2PF
2.74M
100k
2.2PF
CERAMIC
VB
LMC7215
FAULT
SHDN
GND
R3
301k
LP3982
VREF
LM385A-1.2V
Figure 13. Minimum Battery Detector that Disconnects the Load Via the SHDN Pin of the LP3982
Resistor value for VUT and VLT are determined as follows:
GT =
1
+
1
+
R2
R1
1
R3
VUT = R1 (VREF) GT
VLT = R1 // R2 (VREF) GT
(1)
(The application of Figure 13 used a GT of 5 μ mho.)
R1 =
VUT1
VREF (GT)
1
R2 =
VREF (GT)
VLT
(2)
-
1
R1
(3)
1
R3 =
GT -
1
1
+
R2
R1
(4)
The above procedure assumes a rail-to-rail output comparator. Essentially, R2 is in parallel with R1 prior to
reaching the lower threshold, then R2 becomes parallel with R3 for the upper threshold. Note that the application
requires rail-to-rail input as well.
The resistor values shown in Figure 13 are the closest practical to calculated values.
10
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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 LP3982 can provide 300-mA output current with 2.5-V to 6-V input. It is stable with a 2.2-μF ceramic output
capacitor. An optional external bypass capacitor reduces the output noise without slowing down the load
transient response. Typical output noise is 37 μVRMS at frequencies from 10 Hz to 100 kHz. Typical PSSR is
60 dB at 1 kHz.
8.2 Typical Application
VO
VIN
OUT
IN
2.2 PF
100
kŸ
SHDN
2.2 PF
CERAMIC
FAULT
GND
CC
33 nF
Figure 14. LP3982 Typical Application (Fixed VOUT Version)
8.2.1 Design Requirements
For typical ultra low-dropout CMOS-regulator applications, use the parameters listed in Table 1.
Table 1. Design Parameters
DESIGN PARAMETER
EXAMPLE VALUE
Minimum input voltage
VOUT + 0.5 V
Nominal output voltage
3.3 V
Maximum output current
300 mA
RMS noise, 10 Hz to 100 kHz
37 µVRMS
PSRR at 1 kHz
60 dB
8.2.2 Detailed Design Procedure
8.2.2.1 Custom Design With WEBENCH® Tools
Click here to create a custom design using the LP3982 device with the WEBENCH® Power Designer.
1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
3. Compare the generated design with other possible solutions from Texas Instruments.
The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time
pricing and component availability.
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In most cases, these actions are available:
• Run electrical simulations to see important waveforms and circuit performance
• Run thermal simulations to understand board thermal performance
• Export customized schematic and layout into popular CAD formats
• Print PDF reports for the design, and share the design with colleagues
Get more information about WEBENCH tools at www.ti.com/WEBENCH.
8.2.2.2 Output Voltage Setting (ADJ Version Only)
The output voltage is set according to the amount of negative feedback (the pass transistor inverts the feedback
signal.) Figure 15 simplifies the topology of the LP3982. This type of regulator can be represented as an op amp
configured as non-inverting amplifier and a fixed DC Voltage (VREF) for its input signal. The special characteristic
of this op amp is its extra-large output transistor that only sources current. In terms of its non-inverting
configuration, the output voltage equals VREF times the closed loop gain:
VO = VREF
R1
R2
+1
(5)
Use Equation 6 for adjusting the output to a particular voltage:
é V
ù
R1 = R2 ê O - 1ú
ë1.25V û
(6)
Choose R2 = 100 kΩ to optimize accuracy, power supply rejection, noise, and power consumption.
VIN
VREF
+
VOUT
-
R1
R2
Figure 15. Regulator Topology Simplified
Similarity in the output capabilities exists between op amps and linear regulators. Just as rail-to-rail output op
amps allow their output voltage to approach the supply voltage, low dropout regulators (LDOs) allow their output
voltage to operate close to the input voltage. Both achieve this by the configuration of their output transistors.
Standard operational amplifiers and regulator outputs are at the source (or emitter) of the output transistor. Railto-rail op amp and LDO regulator outputs are at the drain (or collector) of the output transistor. This replaces the
threshold (or diode drop) limitations on the output with the less restrictive source-to-drain (or VSAT) limitations.
There is a trade-off; the output impedance become significantly higher, thus providing a critically lower pole when
combined with the capacitive load. That is why rail-to-rail operational amplifiers are usually poor at driving
capacitive loads and a series output resistor recommended when doing so. LDOs require the same series
resistance except that the internal resistance of the output capacitor will usually suffice. Refer to the Output
Capacitance section for more information.
8.2.2.3 Output Capacitance
The LP3982 is specifically designed to employ ceramic output capacitors as low as 2.2 μF. Ceramic capacitors
below 10 μF offer significant cost and space savings, along with high frequency noise filtering. Higher values and
other types and of capacitor may be used, but their equivalent series resistance (ESR) must be maintained below
0.5 Ω.
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Ceramic capacitor of the value required by the LP3982 are available in the following dielectric types: Z5U, Y5V,
X5R, and X7R. The Z5U and Y5V types exhibit a 50% or more drop in capacitance value as their temperature
increases from 25°C, an important consideration. The X5R generally maintain their capacitance value within
±20%. The X7R type are desirable for their tighter tolerance of 10% over temperature.
Ceramic capacitors pose a challenge because of their relatively low ESR. Like most other LDOs, the LP3982
relies on a zero in the frequency response to compensate against excessive phase shift in the feedback loop of
the regulator. If the phase shift reaches 360° (that is, becomes positive), the regulator oscillates. This
compensation usually resides in the zero generated by the combination of the output capacitor with its ESR. The
zero is intended to cancel the effects of the pole generated by the load capacitance (CL) combined with the
parallel combination of the load resistance (RL) and the output resistance (RO) of the regulator. The challenge
posed by low ESR capacitors is that the zero it generates can be too high in frequency for the pole it is intended
to compensate. The LP3982 overcomes this challenge by internally generating a strategically placed zero.
-
LOOP
GAIN
RO
VREF
ESR
+
CL
RL
Figure 16. Simplified Model of Regulator Loop Gain Components
Figure 16 shows a basic model for the linear regulator that helps describe what happens to the output signal as it
is processed through its feedback loop; that is, describe its loop gain (LG). The LG includes two main transfer
functions: the error amplifier and the load. The error amplifier provides voltage gain and a dominant pole, while
the load provides a zero and a pole. The LG of the model in Figure 16 is described by Equation 7:
LG (jω) =
AO
ω
1+j ω
POLE
1 + jω (ESR x CL)
*
1 + jω ((ESR + RO // RL) CL)
(7)
The first term of Equation 7 expresses the voltage gain (numerator) and a single pole role-off (denominator) of
the error amplifier. The second term expresses the zero (numerator) and pole (denominator) of the load in
combination with the RO of the regulator.
Figure 17 shows a Bode plot that represents a case where the zero contributed by the load is too high to cancel
the effect of the pole contributed by the load and RO. The solid line represents the loop gain while the dashed
line represents the corresponding phase shift. Notice that the phase shift at unity gain is a total 360°, the criteria
for oscillation.
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ERROR AMP
POLE: ZPOLE
0 dB
LOOP PHASE
SHIFT
LOOP GAIN
-180°
LOAD POLE
1/(2S (ESR + RO // RL)CL)
-360°
LOAD ZERO
1/(2S (ESR x CL)
Figure 17. Loop Gain Bode Plot Illustrating Inadequately High Zero for Stability Compensation
The LP3982 generates an internal zero that makes up for the inadequately high zero of the low ESR ceramic
output capacitor. This internally generated zero is strategically placed to provide positive phase shift near unity
gain, thus providing a stable phase margin.
8.2.2.4 Input Capacitor
The LP3982 requires a minimum input capacitance of about 1 μF. The value may be increased indefinitely. The
type is not critical to stability. However, instability may occur with bench set-ups where long supply leads are
used, particularly at near dropout and high current conditions. This is attributed to the lead inductance coupling to
the output through the gate oxide of the pass transistor; thus, forming a pseudo LCR network within the loop
gain. A 10-μF tantalum input capacitor remedies this non-situ condition; its larger ESR acts to dampen the
pseudo-LCR network. This may only be necessary for some bench setups. A 1-μF ceramic input capacitor are
fine for most end-use applications.
If a tantalum input capacitor is intended for the final application, it is important to consider their tendency to fail in
short circuit mode, thus potentially damaging the part.
8.2.2.5 Noise Bypass Capacitor
The noise bypass capacitor (CC) significantly reduces output noise of the LP3982. It connects between pin 6 and
ground. The optimum value for CC is 33 nF.
Pin 6 directly connects to the high impedance output of the bandgap. The DC leakage of the CC capacitor must
be considered; loading down the reference reduces the output voltage. NPO and COG ceramic capacitors
typically offer very low leakage. Polypropylene and polycarbonate film carbonate capacitor offer even lower
leakage currents.
CC does not affect the transient response; however, it does affect turnon time. The smaller the CC value, the
faster the turnon time.
8.2.2.6 Fault Detection
The LP3982 provides a FAULT pin that goes low during out of regulation conditions like current limit and thermal
shutdown, or when it approaches dropout. The latter monitors the input-to-output voltage differential and
compares it against a threshold that is slightly above the dropout voltage. This threshold also tracks the dropout
voltage as it varies with load current. Refer to Figure 3 in the Typical Characteristics section.
The FAULT pin requires a pullup resistor because it is an open-drain output. This resistor must be large in value
to reduce energy drain. A 100-kΩ pullup resistor works well for most applications.
Figure 18 shows the LP3982 with delay added to the FAULT pin for the reset pin of a microprocessor. The
output of the comparator stays low for a preset amount of time after the regulator comes out of a fault condition.
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VIN
VO = 3V
OUT
IN
LP3982
SHDN
+
FAULT
CDELAY
GND
CC
0.1PF
LMC7225
RESET
-
MICROPROCESSOR
RP
100k
Figure 18. Power-On Delayed Reset Application
The delay time for the application of Figure 18 is set by Equation 8:
CDELAY =
-t
RPln 1 -
VREF
VO
(8)
The application is set for a reset delay time of 8.8 ms. The comparator must have high impedance inputs so as
to not load down the VREF at the CC pin of the LP3982.
8.2.2.7 Power Dissipation
Knowing the device power dissipation and proper sizing of the thermal plane connected to the tab or pad is
critical to ensuring reliable operation. Device power dissipation depends on input voltage, output voltage, and
load conditions and can be calculated with Equation 9:
PD(MAX) = (VIN(MAX) – VOUT) × IOUT(MAX)
(9)
Power dissipation can be minimized, and greater efficiency can be achieved, by using the lowest available
voltage drop option that would still be greater than the dropout voltage (VDO). However, keep in mind that higher
voltage drops result in better dynamic (that is, PSRR and transient) performance. On the WSON (NGM)
package, the primary conduction path for heat is through the exposed power pad to the PCB. To ensure the
device does not overheat, connect the exposed pad, through thermal vias, to an internal ground plane with an
appropriate amount of copper PCB area. On the VSSOP (DGK) package, the primary conduction path for heat is
through the pins to the PCB. The maximum allowable junction temperature (TJ(MAX)) determines maximum power
dissipation allowed (PD(MAX)) for the device package. Power dissipation and junction temperature are most often
related by the junction-to-ambient thermal resistance (RθJA) of the combined PCB and device package and the
temperature of the ambient air (TA), according to Equation 10 or Equation 11:
(TJ(MAX) = TA(MAX) + (RθJA ×PD(MAX))
PD(MAX) = (TJ(MAX) – TA(MAX)) / RθJA
(10)
(11)
RθJA is highly dependent on the heat-spreading capability of the particular PCB design, and therefore varies
according to the total copper area, copper weight, and location of the planes. The RθJA recorded in Thermal
Information is determined by the specific EIA/JEDEC JESD51-7 standard for PCB and copper-spreading area,
and is to be used only as a relative measure of package thermal performance. For a well-designed thermal
layout, RθJA is the sum of the package junction-to-case (bottom) thermal resistance (RθJCbot) plus the thermal
resistance contribution by the PCB copper area acting as a heat sink.
Improvements and absolute measurements of the RθJA can be estimated by utilizing the thermal shutdown
circuitry that is internal to the device. The thermal shutdown turns off the pass transistor of the device when its
junction temperature reaches 160°C (typical). The pass transistor does not turn on again until the junction
temperature drops about 10°C (hysteresis).
Using the thermal shutdown circuit to estimate, RθJA can be as follows: with a low input-to-output voltage
differential, set the load current to 300 mA. Increase the input voltage until the thermal shutdown begins to cycle
on and off. Then slowly decrease VIN (100-mV increments) until the device stays on. Record the resulting voltage
differential (VD) and use it in Equation 12:
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RTJA
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(160 - TA)
(0.300 x VD)
(12)
8.2.2.8 Estimating Junction Temperature
The EIA/JEDEC standard recommends the use of psi (Ψ) thermal characteristics to estimate the junction
temperatures of surface mount devices on a typical PCB board application. These characteristics are not true
thermal resistance values, but rather package specific thermal characteristics that offer practical and relative
means of estimating junction temperatures. These psi metrics are determined to be significantly independent of
copper-spreading area. The key thermal characteristics (ΨJT and ΨJB) are given in Thermal Information and are
used in accordance with Equation 13 or Equation 14.
TJ(MAX) = TTOP + (ΨJT × PD(MAX))
where
•
•
PD(MAX) is explained in Equation 9.
TTOP is the temperature measured at the center-top of the device package.
(13)
TJ(MAX) = TBOARD + (ΨJB × PD(MAX))
where
•
•
PD(MAX) is explained in Equation 9.
TBOARD is the PCB surface temperature measured 1-mm from the device package and centered on the
package edge.
(14)
For more information about the thermal characteristics ΨJT and ΨJB, see the TI Application Report Semiconductor
and IC Package Thermal Metrics (SPRA953), available for download at www.ti.com.
For more information about measuring TTOP and TBOARD, see the TI Application Report Using New Thermal
Metrics (SBVA025), available for download at www.ti.com.
For more information about the EIA/JEDEC JESD51 PCB used for validating RθJA, see the TI Application Report
Thermal Characteristics of Linear and Logic Packages Using JEDEC PCB Designs (SZZA017), available for
download at www.ti.com.
IL =
300mA
4.3V
20 mV/DIV
VIN (V)
8.2.3 Application Curves
IL =
300mA
VOUT
100 mA/DIV
VO (10 mV/DIV)
3.3V
500 Ps/DIV
IOUT
500 Ps/DIV
Figure 19. Line Transient Response
Figure 20. Load Transient
9 Power Supply Recommendations
The LP3982 is designed to operate from an input voltage supply range between 2.5 V and 6 V. The input voltage
range provides adequate headroom in order for the device to have a regulated output. This input supply must be
well regulated. If the input supply is noisy, additional input capacitors with low ESR can help to improve the
output noise performance.
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10 Layout
10.1 Layout Guidelines
Best performance is achieved by placing CIN, COUT, and CCC on the same side of the PCB as the LP3982 device,
and as close as is practical to the package. The ground connections for CIN and COUT must be back to the
LP3982 device GND pin using as wide and as short of a copper trace as is practical.
Avoid connections using long trace lengths and narrow trace widths. These add parasitic inductances and
resistance that results in inferior performance especially during transient conditions.
10.2 Layout Example
VIA connect to ground layer
VIA connect to VOUT
COUT
RPULLUP
OUT
IN
1
2
8
FAULT
7
SHDN
DAP
(GND)
CIN
CCC
GND
3
6
CC
OUT
4
5
SET
R1
R2
Figure 21. WSON Package Adjustable Version (Not to Scale)
10.3 WSON Mounting
The WSON package requires specific mounting techniques which are detailed in TI Application Report Leadless
Leadframe Package (LLP) (SNOA401). Referring to the section PCB Design Recommendations, the pad style
which must be used with the WSON package is the NSMD (non-solder mask defined) type. Additionally, it is
recommended the PCB terminal pads be 0.2 mm longer than the package pads to create a solder fillet to
improve reliability and inspection. The thermal dissipation of the WSON package is directly related to the printed
circuit board construction and the amount of additional copper area connected to the DAP. The DAP (exposed
pad) on the bottom of the WSON package is connected to the die substrate with a conductive die attach
adhesive. The DAP has no direct electrical (wire) connection to any of the pins. There is a parasitic PN junction
between the die substrate and the device ground. As such, it is strongly recommend that the DAP be connected
directly to the ground at device pin 3 (GND). Alternately, but not recommended, the DAP may be left floating (no
electrical connection). The DAP must not be connected to any potential other than ground.
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11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For additional information, see the following:
• AN-1187 Leadless Leadframe Package (LLP)
• Semiconductor and IC Package Thermal Metrics
• Using New Thermal Metrics
• Thermal Characteristics of Linear and Logic Packages Using JEDEC PCB Designs
11.1.2 Development Support
11.1.2.1 Custom Design With WEBENCH® Tools
Click here to create a custom design using the LP3982 device with the WEBENCH® Power Designer.
1. Start by entering the input voltage (VIN), output voltage (VOUT), and output current (IOUT) requirements.
2. Optimize the design for key parameters such as efficiency, footprint, and cost using the optimizer dial.
3. Compare the generated design with other possible solutions from Texas Instruments.
The WEBENCH Power Designer provides a customized schematic along with a list of materials with real-time
pricing and component availability.
In most cases, these actions are available:
• Run electrical simulations to see important waveforms and circuit performance
• Run thermal simulations to understand board thermal performance
• Export customized schematic and layout into popular CAD formats
• Print PDF reports for the design, and share the design with colleagues
Get more information about WEBENCH tools at www.ti.com/WEBENCH.
11.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
11.3 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
11.4 Trademarks
E2E is a trademark of Texas Instruments.
WEBENCH is a registered trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
11.5 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.
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11.6 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
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
4-Sep-2022
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)
Samples
(4/5)
(6)
LP3982ILD-1.8/NOPB
ACTIVE
WSON
NGM
8
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
LNB
Samples
LP3982ILD-2.5/NOPB
ACTIVE
WSON
NGM
8
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
LPB
Samples
LP3982ILD-3.0/NOPB
ACTIVE
WSON
NGM
8
1000
RoHS & Green
NIPDAU | SN
Level-3-260C-168 HR
-40 to 85
LTB
Samples
LP3982ILD-3.3/NOPB
ACTIVE
WSON
NGM
8
1000
RoHS & Green
NIPDAU | SN
Level-3-260C-168 HR
-40 to 85
LUB
Samples
LP3982ILD-ADJ/NOPB
ACTIVE
WSON
NGM
8
1000
RoHS & Green
NIPDAU | SN
Level-3-260C-168 HR
-40 to 85
LVB
Samples
LP3982ILDX-1.8/NOPB
ACTIVE
WSON
NGM
8
4500
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
LNB
Samples
LP3982ILDX-3.3/NOPB
ACTIVE
WSON
NGM
8
4500
RoHS & Green
NIPDAU | SN
Level-3-260C-168 HR
-40 to 85
LUB
Samples
LP3982ILDX-ADJ/NOPB
ACTIVE
WSON
NGM
8
4500
RoHS & Green
NIPDAU | SN
Level-3-260C-168 HR
-40 to 85
LVB
Samples
LP3982IMM-1.8/NOPB
ACTIVE
VSSOP
DGK
8
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LENB
Samples
LP3982IMM-2.5/NOPB
ACTIVE
VSSOP
DGK
8
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LEPB
Samples
LP3982IMM-3.0
NRND
VSSOP
DGK
8
1000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-40 to 85
LETB
LP3982IMM-3.0/NOPB
ACTIVE
VSSOP
DGK
8
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LETB
LP3982IMM-3.3
NRND
VSSOP
DGK
8
1000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-40 to 85
LEUB
LP3982IMM-3.3/NOPB
ACTIVE
VSSOP
DGK
8
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LEUB
Samples
LP3982IMM-ADJ
ACTIVE
VSSOP
DGK
8
1000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-40 to 85
LEVB
Samples
LP3982IMM-ADJ/NOPB
ACTIVE
VSSOP
DGK
8
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LEVB
Samples
LP3982IMMX-1.8/NOPB
ACTIVE
VSSOP
DGK
8
3500
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LENB
Samples
LP3982IMMX-2.5/NOPB
ACTIVE
VSSOP
DGK
8
3500
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LEPB
Samples
LP3982IMMX-2.82/NOPB
ACTIVE
VSSOP
DGK
8
3500
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 85
LESB
Samples
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
Orderable Device
4-Sep-2022
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
RoHS & Green
SN
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
LP3982IMMX-ADJ/NOPB
ACTIVE
VSSOP
DGK
8
3500
Level-1-260C-UNLIM
-40 to 85
LEVB
(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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