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LP3985
SNVS087AE – OCTOBER 2000 – REVISED MAY 2015
LP3985 Micropower, 150-mA Low-Noise Ultra-Low-Dropout CMOS Voltage Regulator
1 Features
3 Description
•
•
•
•
•
•
•
The LP3985 is designed for portable and wireless
applications with demanding performance and space
requirements. LP3985 performance is optimized for
battery-powered systems to deliver ultra low noise,
extremely low dropout voltage, and low quiescent
current. Regulator ground current increases only
slightly in dropout, further prolonging the battery life.
1
•
•
•
•
•
•
Input Voltage: 2.5 V to 6 V
100-mV Maximum Dropout with 150-mA Load
150-mA Verified Output
50-dB PSRR at 1 kHz at VIN = VOUT + 0.2 V
≤ 1.5-μA Quiescent Current when Shut Down
Fast Turn-On time: 200 μs (typ.)
30-μVRMS Output Noise (typical) over 10 Hz to 100
kHz
−40°C to 125°C Junction Temperature Range for
Operation
2.5-V, 2.6-V, 2.7-V, 2.8-V, 2.85-V, 2.9-V, 3-V, 3.1V, 3.2-V, 3.3-V, 4.7-V, 4.75-V, 4.8-V and 5-V
Outputs Standard
Logic Controlled Enable
Stable with Ceramic and High-Quality Tantalum
Capacitors
Fast Turnon
Thermal Shutdown and Short-Circuit Current Limit
An optional external bypass capacitor reduces the
output noise without slowing down the load transient
response. Fast startup time is achieved by utilizing an
internal power-on circuit that actively pre-charges the
bypass capacitor.
Power supply rejection is better than 50 dB at low
frequencies and starts to roll off at 1 kHz. High power
supply rejection is maintained down to low input
voltage levels common to battery operated circuits.
The device is ideal for mobile phone and similar
battery-powered wireless applications. It provides up
to 150 mA, from a 2.5-V to 6-V input. The LP3985
consumes less than 1.5 µA in disable mode and has
fast turn-on time less than 200 µs.
2 Applications
•
•
•
•
The LP3985 is stable with a small 1-µF ±30%
ceramic or high-quality tantalum output capacitor. The
DSBGA requires the smallest possible PC board area
- the total application circuit area can be less than 2
mm x 2.5 mm, a fraction of a 1206 case size.
CDMA Cellular Handsets
Wideband CDMA Cellular Handsets
GSM Cellular Handsets
Portable Information Appliances
space
The LP3985 is available with fixed output voltages
from 2.5 V to 5 V. Contact Texas Instruments Sales
for specific voltage option needs.
Simplified Schematic
1(C3)
Device Information(1)
5(C1)
IN
PART
NUMBER
OUT
1µF
1µF
LP3985
3(A1)
2(B2)
BODY SIZE
DSBGA (5)
1.502 mm x 1.045 mm (MAX)
SOT-23 (5)
2.90 mm x 1.60 mm (NOM)
(1) For all available packages, see the Package Option
Addendum at the end of the datasheet.
4(A3)
EN
LP3985
PACKAGE
BYPASS
*
Pin Numbers in parenthesis indicate DSBGA package.
* Optional Noise Reduction Capacitor.
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.
LP3985
SNVS087AE – OCTOBER 2000 – REVISED MAY 2015
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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 Performance Characteristics ........................
Detailed Description ............................................ 13
7.1 Overview ................................................................. 13
7.2 Functional Block Diagram ....................................... 13
7.3 Feature Description................................................. 13
7.4 Device Functional Modes........................................ 14
8
Application and Implementation ........................ 15
8.1 Application Information............................................ 15
8.2 Typical Application ................................................. 15
9 Power Supply Recommendations...................... 18
10 Layout................................................................... 19
10.1
10.2
10.3
10.4
Layout Guidelines .................................................
Layout Examples...................................................
DSBGA Mounting..................................................
DSBGA Light Sensitivity .......................................
19
19
19
19
11 Device and Documentation Support ................. 21
11.1
11.2
11.3
11.4
Documentation Support .......................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
21
21
21
21
12 Mechanical, Packaging, and Orderable
Information ........................................................... 21
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision AD (October 2014) to Revision AE
Page
•
Changed update pin names to TI nomenclature; replace Handling Ratings with ESD Ratings ........................................... 1
•
Deleted Voltage Options table - information in POA ............................................................................................................. 1
•
Added GND as type for ground pins ..................................................................................................................................... 3
•
Added Thermal Considerations sub-section ........................................................................................................................ 17
Changes from Revision AC (May 2013) to Revision AD
•
Added Device Information and Handling Rating tables, Feature Description, Device Functional Modes, Application
and Implementation, Power Supply Recommendations, Layout, Device and Documentation Support, and
Mechanical, Packaging, and Orderable Information sections; moved some curves to Application Curves section; add
new Thermal Information........................................................................................................................................................ 1
Changes from Revision AB (May 2013) to Revision AC
•
2
Page
Page
Changed layout of National Data Sheet to TI format ........................................................................................................... 20
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SNVS087AE – OCTOBER 2000 – REVISED MAY 2015
5 Pin Configuration and Functions
DBV Package
5 Pin SOT-23
Top View
EN
3
GND
2
IN
1
5
OUT
4
BYPASS
YZR Package
5 Pin DSBGA
Top View
BYPASS
IN
A3
C3
GND
B2
A1
C1
EN
OUT
Pin Functions
PIN
(1)
NAME
DSBGA
NUMBER (1)
SOT-23
NUMBER
TYPE
DESCRIPTION
BYPASS
A3
4
I/O
EN
A1
3
I
GND
B2
2
GND
IN
C3
1
I
Input voltage of the LDO
OUT
C1
5
O
Output voltage of the LDO
Optional bypass capacitor for noise reduction
Enable input logic, enable high
Common ground
The pin numbering scheme for the DSBGA package was revised in April 2002 to conform to JEDEC standard. Only the pin numbers
were revised. No changes to the physical location of the inputs/outputs were made. For reference purposes, the obsolete numbering
scheme had VEN as pin 1, GND as pin 2, VOUT as pin 3, VIN as pin 4, and BYPASS as pin 5.
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1) (2) (3)
MIN
MAX
IN, EN
–0.3
6.5
OUT
−0.3
(VIN + 0.3) < 6.5
Junction temperature
150
Lead temperature
235
Pad temperature
(4)
SOT-23 (5)
364
DSBGA (5)
314
Storage temperature, Tstg
(2)
(3)
(4)
(5)
V
°C
235
Maximum power dissipation
(1)
UNIT
–65
mW
150
°C
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 potential at the GND pin.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
Additional information on lead temperature and pad temperature can be found in Texas Instruments Application Note AN-1187 Leadless
Leadframe Package (LLP) (SNOA401).
The Absolute Maximum power dissipation depends on the ambient temperature and can be calculated using the formula: PD = (TJ TA)/RθJA,where TJ is the junction temperature, TA is the ambient temperature, and RθJA is the junction-to-ambient thermal resistance.
The 364-mW rating for SOT23-5 appearing under Absolute Maximum Ratings results from substituting the Absolute Maximum junction
temperature, 150°C for TJ, 70°C for TA, and 220°C/W for RθJA. More power can be dissipated safely at ambient temperatures below
70°C . Less power can be dissipated safely at ambient temperatures above 70°C. The Absolute Maximum power dissipation can be
increased by 4.5 mW for each degree below 70°C, and it must be derated by 4.5 mW for each degree above 70°C.
6.2 ESD Ratings
V(ESD)
(1)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
VALUE
UNIT
±2000
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
VIN
Supply input voltage
VEN
ON/OFF input voltage
IOUT
Output current
TJ
Operating junction temperature
(1)
MIN
MAX
2.5 (1)
6
0
−40
UNIT
V
VIN
V
150
mA
125
°C
Recommended minimum VIN is the greater of 2.5-V or VOUT(MAX) + rated dropout voltage (max) for operating load current.
6.4 Thermal Information
LP3985
THERMAL METRIC (1)
SOT-23 (DBV)
DSBGA (YZR)
UNIT
5 PINS
RθJA
Junction-to-ambient thermal resistance
220
RθJC(top)
Junction-to-case (top) thermal resistance
79.8
0.8
RθJB
Junction-to-board thermal resistance
31.6
107.9
ψJT
Junction-to-top characterization parameter
3.1
0.5
ψJB
Junction-to-board characterization parameter
31.1
107.9
RθJC(bot)
Junction-to-case (bottom) thermal resistance
N/A
N/A
(1)
4
255
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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6.5 Electrical Characteristics
Unless otherwise specified: VIN = VOUT(nom) + 0.5 V, CIN = 1 μF, IOUT = 1 mA, COUT = 1 μF, CBYPASS = 0.01 μF. Minimum (MIN)
and Maximum (MAX) values apply over –40°C ≤ TJ ≤ 125°C and typical values are TA = 25°C, unless otherwise indicated.
(1) (2)
PARAMETER
ΔVOUT
Output voltage tolerance
IOUT = 1 mA
Line regulation error
VIN = (VOUT(nom) + 0.5 V) to 6 V,
For 4.7-V to 5-V options
For all other options
Load regulation error (4)
Output AC line regulation
PSRR
IQ
TEST CONDITIONS
Power supply rejection ratio
Quiescent current
Dropout voltage (5)
–0.19
–0.1
0.19
0.1
%/V
LP3985 (DSBGA)
0.0004
0.002
%/mA
VIN = VOUT(nom) + 1 V,
IOUT = 150 mA (Figure 1)
1.5
mVP-P
VIN = VOUT(nom) + 0.2 V,
f = 1 kHz,
IOUT = 50 mA (Figure 2)
50
dB
VIN = VOUT(nom) + 0.2 V,
ƒ = 10 kHz,
IOUT = 50 mA (Figure 2)
40
dB
VEN = 1.4 V, IOUT = 0 mA
For 4.7-V to 5-V options
For all other options
100
85
165
150
VEN = 1.4 V, IOUT = 0 to 150 mA
For 4.7-V to 5-V options
For all other options
155
140
250
200
VEN = 0.4 V
0.003
1.5
IOUT = 1 mA
0.4
2
mV
IOUT = 50 mA
20
35
mV
IOUT = 100 mA
45
70
mV
IOUT = 150 mA
60
100
mV
Peak output current
VOUT ≥ VOUT(nom) – 5%
TON
Turnon time (6)
CBYPASS = 0.01 µF
Output noise voltage (7)
BW = 10 Hz to 100 kHz,
COUT = 1 µF
Output noise density
CBP = 0
IEN
Maximum input current at EN VEN = 0.4 V and VIN = 6 V
VIL
Maximum low-level input
voltage at EN
VIN = 2.5 V to 6 V
VIH
Minimum high-level input
voltage at EN
VIN = 2.5 V to 6 V
TSD
Thermal shutdown
temperature
µA
300
600
mA
550
mA
200
µs
30
µVRMS
230
nV/ √Hz
±1
nA
0.4
V
V
1.4
160
Thermal shutdown hysteresis
(7)
% of
VOUT(nom)
%/mA
IOUT(PK)
(6)
UNIT
2 (3)
3
0.005
Short circuit current limit
(2)
(3)
(4)
(5)
MAX
0.0025
ISC
(1)
TYP
IOUT = 1 mA to 150 mA
LP3985IM5 (SOT23-5)
Output Grounded
(Steady State)
en
MIN
–2 (3)
–3
20
°C
°C
All limits are verified. All electrical characteristics having room-temperature limits are tested during production with TA = 25°C or
correlated using Statistical Quality Control (SQC) methods. All hot and cold limits are specified by correlating the electrical
characteristics to process and temperature variations and applying statistical process control.
The target output voltage, which is labeled VOUT(NOM), is the desired voltage option.
TA = 25°C only.
An increase in the load current results in a slight decrease in the output voltage and vice versa.
Dropout voltage is the input-to-output voltage difference at which the output voltage is 100mV below its nominal value. This specification
does not apply for input voltages below 2.5V.
Turnon time is time measured between the enable input just exceeding VIH and the output voltage just reaching 95% of its nominal
value.
The output noise varies with output voltage option. The 30 µVRMS is measured with 2.5-V voltage option. To calculate an approximated
output noise for other options, use the equation: (30µVRMS)(X)/2.5, where X is the voltage option value.
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Figure 1. Line Transient Input Test Signal
Figure 2. PSRR Input Test Signal
6
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6.6 Typical Performance Characteristics
Unless otherwise specified, CIN = COUT = 1 µF ceramic, CBYPASS = 0.01 µF, VIN = VOUT + 0.2 V, TA = 25°C, EN pin is tied to
VIN.
VIN = VOUT + 0.5V
VOUT CHANGE (%)
0.4
0
-0.4
-0.8
-50
-25
0
25
50
75
100
125
TEMPERATURE (°C)
Figure 3. Output Voltage Change vs Temperature
Figure 4. Dropout Voltage vs Load Current
Figure 5. Ground Current vs Load Current
Figure 6. Ground Current vs VIN at 25°C
Figure 7. Ground Current vs VIN at −40°C
Figure 8. Ground Current vs VIN at 125°C
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Typical Performance Characteristics (continued)
Unless otherwise specified, CIN = COUT = 1 µF ceramic, CBYPASS = 0.01 µF, VIN = VOUT + 0.2 V, TA = 25°C, EN pin is tied to
VIN.
8
Figure 9. Short Circuit Current (DSBGA)
Figure 10. Short Circuit Current (DSBGA)
Figure 11. Short Circuit Current (SOT)
Figure 12. Short Circuit Current (SOT)
Figure 13. Short Circuit Current (SOT)
Figure 14. Short Circuit Current (SOT)
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Typical Performance Characteristics (continued)
Unless otherwise specified, CIN = COUT = 1 µF ceramic, CBYPASS = 0.01 µF, VIN = VOUT + 0.2 V, TA = 25°C, EN pin is tied to
VIN.
Figure 16. Short Circuit Current (DSBGA)
Figure 15. Short Circuit Current (DSBGA)
VIN = VOUT + 0.2 V
Figure 17. Output Noise Spectral Density
VIN = VOUT + 1 V
Figure 18. Ripple Rejection
VIN = 5 V
Figure 19. Ripple Rejection
Figure 20. Ripple Rejection
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Typical Performance Characteristics (continued)
Unless otherwise specified, CIN = COUT = 1 µF ceramic, CBYPASS = 0.01 µF, VIN = VOUT + 0.2 V, TA = 25°C, EN pin is tied to
VIN.
VIN = VOUT + 0.2 V
VIN = VOUT + 0.2 V
Figure 21. Start-up Time
VIN = 4.2 V
Figure 22. Start-up Time
VIN = VOUT + 0.2 V
Figure 23. Start-up Time
Figure 24. Start-up Time
VIN = 4.2 V
Figure 26. Line Transient Response
Figure 25. Start-up Time
10
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Typical Performance Characteristics (continued)
Unless otherwise specified, CIN = COUT = 1 µF ceramic, CBYPASS = 0.01 µF, VIN = VOUT + 0.2 V, TA = 25°C, EN pin is tied to
VIN.
VIN = 3.2 V
Figure 27. Line Transient Response
Figure 28. Load Transient Response
VIN = 4.2 V
VIN = 3.2 V
Figure 29. Load Transient Response
Figure 30. Load Transient Response
VIN = VOUT + 0.2 V
VIN = 4.2 V
Figure 31. Load Transient Response
Figure 32. Enable Response
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Typical Performance Characteristics (continued)
Unless otherwise specified, CIN = COUT = 1 µF ceramic, CBYPASS = 0.01 µF, VIN = VOUT + 0.2 V, TA = 25°C, EN pin is tied to
VIN.
VIN = VOUT + 0.2 V
VIN = 4.2 V
Figure 33. Enable Response
VIN = 4.2 V
Figure 34. Enable Response
VIN = VOUT + 0.2 V
Figure 35. Output Impedance
12
Figure 36. Output Impedance
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7 Detailed Description
7.1 Overview
The LP3985 family of fixed-output, ultra-low-dropout and low noise regulators offers exceptional, cost-effective
performance for battery powered applications. Available in output voltages from 2.5 V to 5 V, the family is
capable of delivering 150-mA continuous load current. Standard regulator features, such as overcurrent and
overtemperature protection, are also included.
The LP3985 contains several features to facilitate battery powered designs:
• Multiple voltage options
• Low dropout voltage, typical dropout of 60 mV at 150-mA load current
• Low quiescent current and low ground current, typically 140 μA at 150-mA load, and 85-μA at 0-mA load
• A shutdown feature is available, allowing the regulator to consume only 0.003 µA typically when the EN pin is
pulled low
• Overtemperature protection and overcurrent protection circuitry is designed to safeguard the device during
unexpected conditions
• Enhanced stability: The LP3985 is stable with output capacitor, which allows the use of ceramic capacitors on
the output
• Power supply rejection is better than 50 dB at low frequencies and starts to roll off at 1 kHz.
• Low noise: A BYPASS pin allows for low-noise operation, with a typical output noise of 30 µVRMS, with the use
of a 10-nF bypass capacitor.
7.2 Functional Block Diagram
IN
EN
ON t 1.4V
OUT
Vreference
1.23V
Fast Turnon
Circuit
R1
OFF d 0.4V
BYPASS
R2
Overcurrent &
Thermal Protection
GND
7.3 Feature Description
7.3.1 No-Load Stability
The LP3985 will remain stable and in regulation with no external load. This is specially important in CMOS RAM
keep-alive applications.
7.3.2 On/Off Input Operation
The LP3985 is turned off by pulling the EN pin low, and turned on by pulling it high. If this feature is not used, the
EN pin should be tied to VIN to keep the regulator output on at all time. To assure proper operation, the signal
source used to drive the EN input must be able to swing above and below the specified turnon/turnoff voltage
thresholds listed in Electrical Characteristics under VIL and VIH.
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Feature Description (continued)
7.3.3 Fast On-Time
The LP3985 output is turned on after VREF voltage reaches its final value (1.23 V, nominal). To speed up this
process, the noise reduction capacitor at the BYPASS pin is charged with an internal 70-µA current source. The
current source is turned off when the bandgap voltage reaches approximately 95% of its final value. The turnon
time is determined by the time constant of the bypass capacitor. The smaller the capacitor value, the shorter the
turn on time, but less noise gets reduced. As a result, turn on time and noise reduction need to be taken into
design consideration when choosing the value of the bypass capacitor.
7.4 Device Functional Modes
7.4.1 Operation with VOUT(TARGET) + 0.3 V ≤ VIN ≤ 6 V
The device operates if the input voltage is equal to, or exceeds, VOUT(TARGET) + 0.3 V. At input voltages below the
minimum VIN requirement, the devices does not operate correctly, and output voltage may not reach target value.
7.4.2 Operation Using the EN Pin
If the voltage on the EN pin is less than 0.4 V, the device is disabled, and in this state shutdown current does not
exceed 1.5 μA. Raising VEN above 1.4 V initiates the start-up sequence of the device.
14
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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 LP3985 can provide 150-mA output current with 2.5-V to 6-V input. It is stable with a small 1-µF ±30%
ceramic or high-quality tantalum output capacitor. The DSBGA requires the smallest possible PC board
area – the total application circuit area can be less than 2 mm x 2.5 mm, a fraction of a 1206 case size. An
optional external bypass capacitor reduces the output noise without slowing down the load transient
response. Fast startup time is achieved by utilizing an internal power-on circuit that actively pre-charges the
bypass capacitor. Typical output noise is 30 µVRMS at frequencies from 10 Hz to 100 kHz. Typical power
supply rejection is 50 dB at 1 kHz.
8.2 Typical Application
1(C3)
5(C1)
IN
OUT
1µF
1µF
LP3985
3(A1)
4(A3)
EN
BYPASS
*
2(B2)
Pin Numbers in parenthesis indicate DSBGA package.
* Optional Noise Reduction Capacitor.
Figure 37. LP3985 Typical Application
8.2.1 Design Requirements
DESIGN PARAMETERS
VALUE
Input voltage
4.2 V, ±10% provided by the DC-DC converter switching at 1 MHz
Output voltage
3 V, ±5%
Output current
150 mA (maximum)
RMS noise, 10 Hz to100 kHz
30 μVRMS
PSRR at 1 kHz
50 dB
8.2.2 Detailed Design Procedure
8.2.2.1 External Capacitors
Like any low-dropout regulator, the LP3985 requires external capacitors for regulator stability. The LP3985 is
specifically designed for portable applications requiring minimum board space and smallest components. These
capacitors must be correctly selected for good performance.
8.2.2.2 Input Capacitor
An input capacitance of approximately 1 µF is required between the LP3985 input pin and ground (the amount of
the capacitance may be increased without limit).
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This capacitor must be located a distance of not more than 1 cm from the input pin and returned to a clean
analog ground. A ceramic capacitor is recommended although a good quality tantalum or film capacitor may be
used at the input.
NOTE
Tantalum capacitors can suffer catastrophic failures due to surge current when connected
to a low-impedance source of power (like a battery or a very large capacitor). If a tantalum
capacitor is used at the input, it must be verified by the manufacturer to have a surge
current rating sufficient for the application.
There are no requirements for the ESR on the input capacitor, but tolerance and temperature coefficient must be
considered when selecting the capacitor to ensure the capacitance will remain within the operational range over
the full range of temperature and operating conditions.
8.2.2.3 Output Capacitor
Correct selection of the output capacitor is important to ensure stable operation in the intended application.
The output capacitor must meet all the requirements specified in the recommended capacitor table over all
conditions in the application. These conditions include DC-bias, frequency and temperature. Unstable operation
will result if the capacitance drops below the minimum specified value. (See the next section Capacitor
Characteristics).
The LP3985 is designed specifically to work with very small ceramic output capacitors. A 1-µF ceramic capacitor
(dialectric type X7R) with ESR between 5 mΩ to 500 mΩ is suitable in the LP3985 application circuit. X5R
capacitors may be used but have a narrower temperature range. With these and other capacitor types (Y5V,
Z6U) that may be used, selection is dependant on the range of operating conditions and temperature range for
that application. (see Capacitor Characteristics ).
It may also be possible to use tantalum or film capacitors at the output, but these are not as attractive for
reasons of size and cost (see Capacitor Characteristics).
It is also recommended that the output capacitor be placed within 1 cm from the output pin and returned to a
clean ground line.
8.2.2.4 Capacitor Characteristics
The LP3985 is designed to work with ceramic capacitors on the output to take advantage of the benefits they
offer: for capacitance values in the range of 1 µF to 4.7 µF, ceramic capacitors are the smallest, least expensive,
and have the lowest ESR values (which makes them best for eliminating high frequency noise). The ESR of a
typical 1-µF ceramic capacitor is in the range of 20 mΩ to 40 mΩ, which easily meets the ESR requirement for
stability by the LP3985.
For both input and output capacitors careful interpretation of the capacitor specification is required to ensure
correct device operation. The capacitor value can change greatly dependant on the conditions of operation and
capacitor type.
In particular the output capacitor selection should take account of all the capacitor parameters to ensure that the
specification is met within the application. Capacitance value can vary with DC bias conditions as well as
temperature and frequency of operation. Capacitor values will also show some decrease over time due to aging.
The capacitor parameters are also dependant on the particular case size with smaller sizes giving poorer
performance figures in general. As an example Figure 38 shows a typical graph showing a comparison of
capacitor case sizes in a Capacitance vs. DC Bias plot. As shown in the graph, as a result of the DC Bias
condition the capacitance value may drop below the minimum capacitance value given in the recommended
capacitor table (0.7 µF in this case). Note that the graph shows the capacitance out of spec for the 0402 case
size capacitor at higher bias voltages. It is therefore recommended that the capacitor manufacturers'
specifications for the nominal value capacitor are consulted for all conditions as some capacitor sizes (for
example, 0402) may not be suitable in the actual application.
16
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CAP VALUE (% of NOMINAL 1 PF)
www.ti.com
0603, 10V, X5R
100%
80%
60%
0402, 6.3V, X5R
40%
20%
0
1.0
2.0
3.0
4.0
5.0
DC BIAS (V)
Figure 38. Graph Showing A Typical Variation In Capacitance vs DC Bias
The ceramic capacitor's capacitance can vary with temperature. The capacitor type X7R, which operates over a
temperature range of −55°C to 125°C, will only vary the capacitance to within ±15%. The capacitor type X5R has
a similar tolerance over a reduced temperature range of −55°C to 85°C. Most large value ceramic capacitors
(around 2.2 µF) are manufactured with Z5U or Y5V temperature characteristics. Their capacitance can drop by
more than 50% as the temperature goes from 25°C to 85°C. Therefore X7R is recommended over Z5U and Y5V
in applications where the ambient temperature will change significantly above or below 25°C.
Tantalum capacitors are less desirable than ceramic for use as output capacitors because they are more
expensive when comparing equivalent capacitance and voltage ratings in the 1-µF to 4.7-µF range.
Another important consideration is that tantalum capacitors have higher ESR values than equivalent size
ceramics. This means that while it may be possible to find a tantalum capacitor with an ESR value within the
stable range, it would have to be larger in capacitance (which means bigger and more costly ) than a ceramic
capacitor with the same ESR value. It should also be noted that the ESR of a typical tantalum will increase about
2:1 as the temperature goes from 25°C down to −40°C, so some guard band must be allowed.
8.2.2.5 Noise Bypass Capacitor
Connecting a 0.01-µF capacitor between the CBYPASS pin and ground significantly reduces noise on the
regulator output. This cap is connected directly to a high impedance node in the band gap reference circuit. Any
significant loading on this node will cause a change on the regulated output voltage. For this reason, DC leakage
current through this pin must be kept as low as possible for best output voltage accuracy.
The types of capacitors best suited for the noise bypass capacitor are ceramic and film. High-quality ceramic
capacitors with either NPO or COG dielectric typically have very low leakage. Polypropolene and polycarbonate
film capacitors are available in small surface-mount packages and typically have extremely low leakage current.
Unlike many other LDOs, addition of a noise reduction capacitor does not effect the load transient response of
the device.
8.2.2.6 Thermal Considerations
CAUTION
Due to the limited power dissipation characteristics of the available SOT-23 (DBV) and
DSBGA (YZR) packages, all possible combinations of output current (IOUT), input
voltage (VIN), output voltage (VOUT), and ambient temperatures (TA) cannot be
ensured.
Power dissipation, PD is calculated from the following formula: PD = ((VIN – VOUT) × IOUT) .
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The LP3985 regulator has internal thermal limiting designed to protect the device during overload conditions. For
continuous normal conditions, the recommended maximum operating junction temperature is 125°C. It is
important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional
heat sources mounted nearby must also be considered.
For surface-mount devices, heat sinking is accomplished by using the heat-spreading capabilities of the PC
board and its copper traces. Copper board stiffeners and plated through-holes can also be used to spread the
heat generated by power devices. Example: Given an output voltage of 3.3 V, an input voltage range of 4 V to 6
V, a maximum output current of 100 mA, and a maximum ambient temperature of 50°C, what is the maximum
operating junction temperature? The power dissipated by the device is found using the formula:
PD(MAX) = ((VIN(MAX) ± VOUT) × IOUT(MAX))
where
•
•
•
IOUT(MAX) = 100 mA
VIN(MAX) = 6 V
VOUT = 3.3 V
(1)
For example, PD(MAX) = ((6 V – 3.3 V) × 100 mA ) = 0.27 W.
Using the 5-pin SOT-23 (DBV) package, the LP3985 junction-to-ambient thermal resistance (RθJA) has a rating
of 220°C/W using the standard JEDEC JESD51-7 PCB (High-K) circuit board. The junction temperature rise
above ambient is found using the formula:
TRISE = PD(MAX) × RθJA;
for example, TJ(MAX) = 50°C + 59.4°C = 109.4°C.
8.2.3 Application Curves
VIN = 4.2 V
VIN = 4.2 V
Figure 39. Start-up Time
Figure 40. Enable Response
9 Power Supply Recommendations
The LP3985 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.
18
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10 Layout
10.1 Layout Guidelines
For best overall performance, place all circuit components on the same side of the circuit board and as near as
practical to the respective LDO pin connections. Place ground return connections to the input and output
capacitor, and to the LDO ground pin as close to each other as possible, connected by a wide, component-side,
copper surface. The use of vias and long traces to create LDO circuit connections is strongly discouraged and
negatively affects system performance. This grounding and layout scheme minimizes inductive parasitics, and
thereby reduces load-current transients, minimizes noise, and increases circuit stability. A ground reference
plane is also recommended and is either embedded in the PCB itself or located on the bottom side of the PCB
opposite the components. This reference plane serves to assure accuracy of the output voltage, shield noise,
and behaves similar to a thermal plane to spread (or sink) heat from the LDO device. In most applications, this
ground plane is necessary to meet thermal requirements.
10.2 Layout Examples
VIN
VOUT
Input
Capacitor
OUT
IN
Output
Capacitor
GND
Ground
Bypass
Capacitor
EN
BYPASS
Figure 41. LP3985 SOT-23 Package Typical Layout
IN
OUT
Input
Capacitor
C3
GND
B2
Bypass
Capacitor
A3
BYPASS
Output
Capacitor
C1
A1
EN
Figure 42. LP3985 DSBGA Package Typical Layout
10.3 DSBGA Mounting
The DSBGA package requires specific mounting techniques which are detailed in Texas Instruments Application
Note 1112 DSBGA Wafer Level Chip Scale Package (SNVA009). Referring to the section Surface Mount
Technology (SMT) Assembly Considerations, it should be noted that the pad style which must be used with the
5-bump package is NSMD (non-solder mask defined) type.
For best results during assembly, alignment ordinals on the PC board may be used to facilitate placement of the
DSBGA device.
10.4 DSBGA Light Sensitivity
Exposing the DSBGA device to direct sunlight will cause mis-operation of the device. Light sources such as
halogen lamps can effect electrical performance if brought near to the device.
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LP3985
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DSBGA Light Sensitivity (continued)
The wavelengths which have most detrimental effect are reds and infra-reds, which means that the fluorescent
lighting used inside most buildings has very little effect on performance. A DSBGA test board was brought to
within 1 cm of a fluorescent desk lamp and the effect on the regulated output voltage was negligible, showing a
deviation of less than 0.1% from nominal.
20
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LP3985
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11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation, see the following:
• Texas Instruments Application Note AN-1187 Leadless Leadframe Package (LLP) (SNOA401).
• Texas Instruments Application Note AN-1112 DSBGA Wafer Level Chip Scale Package (SNVA009).
11.2 Trademarks
All trademarks are the property of their respective owners.
11.3 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
11.4 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
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30-Sep-2021
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)
LP3985IM5-2.5
NRND
SOT-23
DBV
5
1000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-40 to 125
LCSB
LP3985IM5-2.5/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCSB
LP3985IM5-2.7/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCUB
LP3985IM5-2.8/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCJB
LP3985IM5-2.9/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCYB
LP3985IM5-3.0/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCRB
LP3985IM5-3.2/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LDPB
LP3985IM5-3.3
NRND
SOT-23
DBV
5
1000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-40 to 125
LDQB
LP3985IM5-3.3/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LDQB
LP3985IM5-4.7/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LDRB
LP3985IM5-5.0/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LDSB
LP3985IM5X-2.5/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCSB
LP3985IM5X-2.8/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCJB
LP3985IM5X-285/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCXB
LP3985IM5X-3.0
NRND
SOT-23
DBV
5
3000
Non-RoHS
& Green
Call TI
Level-1-260C-UNLIM
-40 to 125
LCRB
LP3985IM5X-3.0/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LCRB
LP3985IM5X-3.3/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LDQB
LP3985IM5X-4.7/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LDRB
LP3985IM5X-5.0/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
LDSB
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
Orderable Device
30-Sep-2021
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)
LP3985ITL-2.5/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-2.6/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-2.7/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-2.8/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-2.9/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-285/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-3.0/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-3.1/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-3.3/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITL-4.8/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
LP3985ITL-5.0/NOPB
ACTIVE
DSBGA
YZR
5
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITLX-2.5/NOPB
ACTIVE
DSBGA
YZR
5
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITLX-2.7/NOPB
ACTIVE
DSBGA
YZR
5
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITLX-2.8/NOPB
ACTIVE
DSBGA
YZR
5
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITLX-285/NOPB
ACTIVE
DSBGA
YZR
5
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITLX-3.0/NOPB
ACTIVE
DSBGA
YZR
5
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITLX-3.1/NOPB
ACTIVE
DSBGA
YZR
5
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITLX-3.3/NOPB
ACTIVE
DSBGA
YZR
5
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
LP3985ITLX-5.0/NOPB
ACTIVE
DSBGA
YZR
5
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
-40 to 125
5
(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.
Addendum-Page 2
5
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
30-Sep-2021
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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