LP38501TSX-ADJ/NOPB [TI]
LP38501/3-ADJ, LP38501A/3A-ADJ 3A FlexCap Low Dropout Linear Regulator for 2.7V to 5.5V Inputs; LP38501 / 3 -ADJ ， LP38501A / 3A - ADJ 3A FlexCap低压差线性稳压器的2.7V至5.5V输入
| 型号： | LP38501TSX-ADJ/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | LP38501/3-ADJ, LP38501A/3A-ADJ 3A FlexCap Low Dropout Linear Regulator for 2.7V to 5.5V Inputs |
| 文件： | 总22页 (文件大小：1314K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LP38501-ADJ, LP38503-ADJ
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SNVS522H –AUGUST 2007–REVISED APRIL 2013
LP38501/3-ADJ, LP38501A/3A-ADJ 3A FlexCap Low Dropout Linear Regulator for 2.7V to
5.5V Inputs
Check for Samples: LP38501-ADJ, LP38503-ADJ
1
FEATURES
DESCRIPTION
2
•
FlexCap: Stable with Ceramic, Tantalum, or
Aluminum Capacitors
TI's FlexCap LDO's feature unique compensation that
allows the use of any type of output capacitor with no
limits on minimum or maximum ESR. The LP38501/3
series of low-dropout linear regulators operates from
a +2.7V to +5.5V input supply. These ultra low
dropout linear regulators respond very quickly to step
changes in load, which makes them suitable for low
voltage microprocessor applications. Developed on a
CMOS process, (utilizing a PMOS pass transistor),
the LP38501/3 has low quiescent current that
changes little with load current.
•
•
•
•
•
•
•
•
•
Stable with 10 µF Input/Output Capacitor
Adjustable Output Voltage from 0.6V to 5V
Low Ground Pin Current
25 nA Quiescent Current in Shutdown Mode
Output Current of 3A
Available in TO-263, PFM THIN Packages
VADJ Accuracy of ±1.5% at 25°C (A Grade)
VADJ Accuracy of ±3.5% at 25°C (STD)
Ground Pin Current: Typically 2 mA at 3A load
current.
Over-Temperature and Over-Current
Protection
Disable Mode: Typically 25 nA quiescent current
when the Enable pin is pulled low.
•
•
−40°C to +125°C Operating TJ Range
Enable Pin (LP38501)
Simplified Compensation: Stable with any type of
output capacitor, regardless of ESR.
APPLICATIONS
Precision Output: "A" grade versions available with
1.5% VADJ tolerance (25°C) and 3% over line, load
and temperature.
•
ASIC Power Supplies In:
–
–
Printers, Graphics Cards, DVD Players
Set Top Boxes, Copiers, Routers
•
•
•
DSP and FPGA Power Supplies
SMPS Regulator
Conversion from 3.3V or 5V Rail
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
2
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2007–2013, Texas Instruments Incorporated
LP38501-ADJ, LP38503-ADJ
SNVS522H –AUGUST 2007–REVISED APRIL 2013
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Typical Application Circuit
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.
Connection Diagram
Top View (LP38501TS-ADJ)
Top View (LP38503TS-ADJ)
See Package Number KTT0005B (TO-263)
See Package Number KTT0005B (TO-263)
Connection Diagram
Top View (LP38501TJ-ADJ, LP38501ATJ-ADJ)
Top View (LP38503TJ-ADJ, LP38503ATJ-ADJ)
See Package Number NDQ0005A (PFM THIN)
See Package Number NDQ0005A (PFM THIN)
Pin Descriptions for TO-263 (TS) and TO-263 THIN (TJ)
Pin #
Designation
Function
Enable (LP38501 only). Pull high to enable the output, low to disable the output. This pin has
no internal bias and must be either tied to the input voltage, or actively driven.
EN
1
In the LP38503, this pin has no internal connections. It can be left floating or used for trace
routing.
N/C
2
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Pin Descriptions for TO-263 (TS) and TO-263 THIN (TJ) (continued)
Pin #
Designation
IN
Function
2
3
4
5
Input Supply Pin
Ground
GND
OUT
Regulated Output Voltage Pin
Sets output voltage
ADJ
The DAP is used as a thermal connection to remove heat from the device to the circuit board
copper clad area which acts as the heatsink. The DAP is electrically connected to the backside
of the die. The DAP must be connected to ground potential, but can not be used as the only
ground connection.
DAP
DAP
ABSOLUTE MAXIMUM RATINGS(1)
Storage Temperature Range
Lead Temperature (Soldering, 5 sec.)
ESD Rating(2)
−65°C to +150°C
260°C
±2 kV
Power Dissipation(3)
Internally Limited
−0.3V to +6.0V
−0.3V to +6.0V
−0.3V to +6.0V
Internally Limited
Input Pin Voltage (Survival)
Enable Pin Voltage (Survival)
Output Pin Voltage (Survival)
IOUT(Survival)
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but does not specific performance limits. For specifications and conditions, see the
Electrical Characteristics.
(2) The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin.
(3) Operating junction temperature must be evaluated, and derated as needed, based on ambient temperature (TA), power dissipation (PD),
maximum allowable operating junction temperature (TJ(MAX)), and package thermal resistance (θJA). See Application Information.
OPERATING RATINGS(1)
Input Supply Voltage
Enable Input Voltage
Output Current (DC)
Junction Temperature(2)
VOUT
2.7V to 5.5V
0.0V to 5.5V
0 to 3A
−40°C to +125°C
0.6V to 5V
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but does not specific performance limits. For specifications and conditions, see the
Electrical Characteristics.
(2) Operating junction temperature must be evaluated, and derated as needed, based on ambient temperature (TA), power dissipation (PD),
maximum allowable operating junction temperature (TJ(MAX)), and package thermal resistance (θJA). See Application Information.
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ELECTRICAL CHARACTERISTICS, LP38501/3–ADJ
Unless otherwise specified: VIN = 3.3V, IOUT = 10 mA, CIN = 10 µF, COUT = 10 µF, VEN = VIN, VOUT = 1.8V. Limits in standard
type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C to +125°C.
Minimum and Maximum limits are specified through test, design, or statistical correlation. Typical values represent the most
likely parametric norm at TJ = 25°C, and are provided for reference purposes only.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
2.7V ≤ VIN ≤ 5.5V
10 mA ≤ IOUT ≤ 3A
0.584
0.575
0.626
0.635
VADJ
Adjust Pin Voltage(1)
0.605
V
Adjust Pin Voltage(1)
"A" GRADE
2.7V ≤ VIN ≤ 5.5V
10 mA ≤ IOUT ≤ 3A
0.596
0.587
0.614
0.623
VADJ
IADJ
0.605
50
V
Adjust Pin Bias Current
Dropout Voltage(2)
2.7V ≤ VIN ≤ 5.5V
750
nA
mV
550
665
VDO
IOUT = 3A
420
0.04
0.05
(1)
ΔVOUT/ΔVIN
ΔVOUT/ΔIOUT
IGND
Output Voltage Line Regulation(3)
2.7V ≤ VIN ≤ 5.5V
10 mA ≤ IOUT ≤ 3A
10 mA ≤ IOUT ≤ 3A
VEN < VIL(EN)
—
—
—
—
—
—
%/V
%/A
mA
µA
0.12
0.24
Output Voltage Load Regulation(4)(1)
Ground Pin Current In Normal
Operation Mode
4
5
2
0.125
15
IDISABLED
Ground Pin Current
0.025
IOUT(PK)
ISC
Peak Output Current
Short Circuit Current
V
OUT ≥ VOUT(NOM) - 5%
6
6
A
A
VOUT = 0V
3.5
Enable Input (LP38501 Only)
VIH(EN) Enable Logic High
VIL(EN)
VOUT = ON
1.4
—
—
—
V
Enable Logic Low
Turn-off delay
VOUT = OFF
—
0.65
Time from VEN < VIL(EN) to VOUT = OFF
ILOAD = 3A
td(off)
td(on)
—
—
25
25
—
—
µs
nA
Time from VEN >VIH(EN) to VOUT = ON
ILOAD = 3A
Turn-on delay
IIH(EN)
IIL(EN)
Enable Pin High Current
Enable Pin Low Current
VEN = VIN
VEN = 0V
—
—
35
35
—
—
AC Parameters
VIN = 3.0V, IOUT = 3A
f = 120Hz
—
58
—
PSRR
Ripple Rejection
dB
VIN = 3.0V, IOUT = 3A
f = 1 kHz
—
—
—
56
1.0
100
—
—
—
ρn(l/f)
Output Noise Density
Output Noise Voltage
f = 120Hz, COUT = 10 µF CER
µV/√Hz
BW = 100Hz – 100kHz
COUT = 10 µF CER
en
µV (rms)
Thermal Characteristics
TSD
Thermal Shutdown
TJ rising
—
—
170
10
—
—
°C
ΔTSD
Thermal Shutdown Hysteresis
TJ falling from TSD
Thermal Resistance
Junction to Ambient
TO-263, PFM THIN(5)
1 sq. in. copper
θJ-A
θJ-C
37
5
°C/W
Thermal Resistance
Junction to Case
TO-263, TO-263 THIN
—
—
(1) The line and load regulation specification contains only the typical number. However, the limits for line and load regulation are included
in the output voltage tolerance specification.
(2) Dropout voltage is defined as the minimum input to output differential voltage at which the output drops 2% below the nominal value. For
any output voltage less than 2.5V, the minimum VIN operating voltage is the limiting factor.
(3) Output voltage line regulation is defined as the change in output voltage from the nominal value due to change in the voltage at the
input.
(4) Output voltage load regulation is defined as the change in output voltage from the nominal value due to change in the load current at the
output.
(5) The value of θJA for the TO-263 (TS) package and TO-263 THIN (TJ) package can range from approximately 30 to 60°C/W depending
on the amount of PCB copper dedicated to heat transfer (See Application Information).
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TYPICAL PERFORMANCE CHARACTERISTICS
Unless otherwise specified: TJ = 25°C, VIN = 2.7V, VEN = VIN, CIN = 10 µF, COUT = 10 µF, IOUT = 10 mA, VOUT = 1.8V
Noise Density
Noise Density
Figure 1.
Figure 2.
IGND(OFF)
IGND
vs
Load Current
vs
Temperature
Figure 3.
Figure 4.
VADJ
vs
Temperature
Dropout Voltage
vs
Load Current
Figure 5.
Figure 6.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Unless otherwise specified: TJ = 25°C, VIN = 2.7V, VEN = VIN, CIN = 10 µF, COUT = 10 µF, IOUT = 10 mA, VOUT = 1.8V
VEN
vs
Temperature
Turn-on Characteristics
Figure 7.
Figure 8.
Load Regulation
vs
Temperature
Turn-on Time
Figure 9.
Figure 10.
PSRR
Turn-on Time
Figure 11.
Figure 12.
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Block Diagrams
Figure 13. LP38501-ADJ Block Diagram
Figure 14. LP38503-ADJ Block Diagram
APPLICATION INFORMATION
EXTERNAL CAPACITORS
The LP3850X requires that at least 10 µF (±20%) capacitors be used at the input and output pins located within
one cm of the IC. Larger capacitors may be used without limit on size for both CIN and COUT. Capacitor
tolerances such as temperature variation and voltage loading effects must be considered when selecting
capacitors to ensure that they will provide the minimum required amount of capacitance under all operating
conditions for the application.
In general, ceramic capacitors are best for noise bypassing and transient response because of their ultra low
ESR. It must be noted that if ceramics are used, only the types with X5R or X7R dielectric ratings should be used
(never Z5U or Y5F). Capacitors which have the Z5U or Y5F characteristics will see a drop in capacitance of as
much as 50% if their temperature increases from 25°C to 85°C. In addition, the capacitance drops significantly
with applied voltage: a typical Z5U or Y5F capacitor can lose as much as 60% of it’s rated capacitance if only
half of the rated voltage is applied to it. For these reasons, only X5R and X7R ceramics should be used.
INPUT CAPACITOR
All linear regulators can be affected by the source impedance of the voltage which is connected to the input. If
the source impedance is too high, the reactive component of the source may affect the control loop’s phase
margin. To ensure proper loop operation, the ESR of the capacitor used for CIN must not exceed 0.5
Ohms. Any good quality ceramic capacitor will meet this requirement, as well as many good quality tantalums.
Aluminum electrolytic capacitors may also work, but can possibly have an ESR which increases significantly at
cold temperatures. If the ESR of the input capacitor may exceed 0.5 Ohms, it is recommended that a 2.2 µF
ceramic capacitor be used in parallel, as this will assure stable loop operation.
OUTPUT CAPACITOR
Any type of capacitor may be used for COUT, with no limitations on minimum or maximum ESR, as long as the
minimum amount of capacitance is present. The amount of capacitance can be increased without limit.
Increasing the size of COUT typically will give improved load transient response.
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SETTING THE OUTPUT VOLTAGE
The output voltage of the LP38501/3-ADJ can be set to any value between 0.6V and 5V using two external
resistors shown as R1 and R2 in Figure 15.
Figure 15.
The value of R2 should always be less than or equal to 10 kΩ for good loop compensation. R1 can be selected
for a given VOUT using the following formula:
VOUT = VADJ (1 + R1/R2) + IADJ (R1)
where
•
•
VADJ is the adjust pin voltage
IADJ is the bias current flowing into the adjust pin
(1)
STABILITY AND PHASE MARGIN
Any regulator which operates using a feedback loop must be compensated in such a way as to ensure adequate
phase margin, which is defined as the difference between the phase shift and -180 degrees at the frequency
where the loop gain crosses unity (0 dB). For most LDO regulators, the ESR of the output capacitor is required to
create a zero to add enough phase lead to ensure stable operation. The LP38501 has a unique internal
compensation circuit which maintains phase margin regardless of the ESR of the output capacitor, so any type of
capacitor may be used.
Figure 16 shows the gain/phase plot of the LP38501-ADJ with an output of 1.2V, 10 µF ceramic output capacitor,
delivering 2A of load current. It can be seen that the unity-gain crossover occurs at 300 kHz, and the phase
margin is about 40° (which is very stable).
Figure 16. Gain-Bandwidth Plot for 2A Load
Figure 17 shows the gain and phase with no external load. In this case, the only load is provided by the gain
setting resistors (about 12 kΩ total in this test). It is immediately obvious that the unity-gain frequency is
significantly lower (dropping to about 500 Hz), at which point the phase margin is 125°.
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Figure 17. Gain-Bandwidth Plot for No Load
The reduction in unity-gain bandwidth as load current is reduced is normal for any LDO regulator using a P-FET
or PNP pass transistor, because they have a pole in the loop gain function given by:
(2)
This illustrates how the pole goes to the highest frequency when RL is minimum value (maximum load current).
In general, LDO’s have maximum bandwidth (and lowest phase margin) at full load current. In the case of the
LP38501, it can be seen that it has good phase margin even when using ceramic capacitors with ESR values of
only a few milli Ohms.
LOAD TRANSIENT RESPONSE
Load transient response is defined as the change in regulated output voltage which occurs as a result of a
change in load current. Many applications have loads which vary, and the control loop of the voltage regulator
must adjust the current in the pass FET transistor in response to load current changes. For this reason,
regulators with wider bandwidths often have better transient response.
The LP38501 employs an internal feedforward design which makes the load transient response much faster than
would be predicted simply by loop speed: this feedforward means any voltage changes appearing on the output
are coupled through to the high-speed driver used to control the gate of the pass FET along a signal path using
very fast FET devices. Because of this, the pass transistor’s current can change very quickly.
Figure 18 shows the output transient response resulting from a change in load current of 0.1A – 3A, and then
3A – 0.1A with a load current slew rate of 500 mA/µs. As shown in the plots, the resulting change in output
voltage is only about 40 mV (peak), which is just slightly over 2% for the 1.8V output used for this test. This is
excellent performance for such a small output capacitor.
Figure 18. Load Transient Response: 10 µF Ceramic, 0.5A/µs di/dt
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When the load current changes much more quickly, the output voltage will show more change because the loop
and internal feedforward circuitry are not able to react as fast as the load changes. In such cases, it is the output
capacitor which must supply load current during the transition until the loop responds and changes the pass
transistor’s drive to deliver the new value of load current. As an example, the slew rate of the load current will be
increased to 75A/µs and the same test will be performed. In Figure 19, it can be seen that the peak excursion of
the output voltage during the transient has now increased to about 200 mV, which is just slightly over 11% for the
1.8V output.
Figure 19. Load Transient Response: 10 µF Ceramic, 75A/µs di/dt
A better understanding of the load transient can be obtained when the load’s rising edge is expanded in time
scale (Figure 20).
Figure 20. Rising Edge, 10 µF Ceramic, 75A/µs di/dt
It can be seen from the figure that the output voltage starts “correcting” back upwards after less than a micro
second, and has fully reversed direction after about 1.2 µs. This very rapid reaction is a result of the maximum
loop bandwidth (full load is being delivered) and the feedforward effect kicking on the drive to the FET before
feedback gets fully around the loop.
In cases where extremely fast load changes occur, and output voltage regulation better than 10% is required, the
output capacitance must be increased. When selecting capacitors, it must be understood that the better
performing ones usually cost the most. For fast changing loads, the internal parasitics of ESR (equivalent series
resistance) and ESL (equivalent series inductance) degrade the capacitor’s ability to source current quickly to the
load. The best capacitor types for transient performance are (in order):
1. Multilayer Ceramic: with the lowest values of ESR and ESL, they can have ESR values in the range of a few
milli Ohms. Disadvantage: capacitance values above about 22 µF significantly increase in cost.
2. Low-ESR Aluminum Electrolytics: these are aluminum types (like OSCON) with a special electrolyte which
provides extremely low ESR values, and are the closest to ceramic performance while still providing large
amounts of capacitance. These are cheaper (by capacitance) than ceramic.
3. Solid tantalum: can provide several hundred µF of capacitance, transient performance is slightly worse than
OSCON type capacitors, cheaper than ceramic in large values.
4. General purpose aluminum electrolytics: cheap and provide a lot of capacitance, but give the worst
performance.
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As a first example, larger values of ceramic capacitance will be tried to show how much reduction can be
obtained from the 200 mV output change (Figure 20) which was seen with only a 10 µF ceramic output capacitor.
In Figure 21, the 10 µF output capacitor is increased to 22 µF. The 200 mV transient is reduced to about 160
mV, which is from about 11% of VOUT down to about 9%.
Figure 21. 22 µF Ceramic Output Capacitor
In Figure 22, the output capacitance is increased to 47 µF ceramic. It can be seen that the output transient is
further reduced down to about 120 mV, which is still about 6.6% of the output voltage. This shows that a 5X
increase in ceramic capacitance from the original 10 µF only reduced the peak voltage transient amplitude by
about 40%.
Figure 22. 47 µF Ceramic Output Capacitor
In general, managing load transients is done by paralleling ceramic capacitance with a larger bulk capacitance.
In this way, the ceramic can source current during the rapidly changing edge and the bulk capacitor can support
the load current after the first initial spike in current.
In the next test, the same 10 µF ceramic capacitor will be paralleled with a general purpose (cheap) aluminum
electrolytic whose capacitance is 220 µF. As shown in Figure 23, there is a small improvement over the 200 mV
peak seen with the 10 µF ceramic alone. By adding the 220 µF aluminum capacitor, the peak is reduced to about
160 mV (the same peak value as seen with a 22 µF ceramic capacitor alone).
Figure 23. 10 µF Ceramic Paralleled By 220 µF Generic Aluminum Electrolytic
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A solid Tantalum should work better, so the aluminum electrolytic is replaced by a 220 µF Tantalum (Figure 24).
The peak amplitude of the output transient is now reduced to about 130 mV, just slightly worse than the value of
the 47 µF ceramic alone.
Figure 24. 10 µF Ceramic Paralleled By 220 µF Tantalum
The OSCON (ultra low ESR) aluminum electrolytic is the best of the electrolytics. Figure 25 shows the output
voltage transient is reduced down to about 90 mV (about 5% of VOUT) when a 220 µF OSCON is added to the 10
µF ceramic. This indicates that some kind of ultra-low ESR aluminum electrolytic used in parallel with some
ceramic capacitance is probably the best approach for extremely fast transients, but each application must be
dialed in for it’s specific load requirements.
Figure 25. 10 µF Ceramic Paralleled By 220 µF OSCON
PRINTED CIRCUIT BOARD LAYOUT
Good layout practices will minimize voltage error and prevent instability which can result from ground loops. The
input and output capacitors should be directly connected to the IC pins with short traces that have no other
current flowing in them (Kelvin connect).
The best way to do this is to place the capacitors very near the IC and make connections directly to the IC pins
via short traces on the top layer of the PCB. The regulator’s ground pin should be connected through vias to the
internal or backside ground plane so that the regulator has a single point ground.
The external resistors which set the output voltage must also be located very near the IC with all connections
directly tied via short traces to the pins of the IC (Kelvin connect). Do not connect the resistive divider to the load
point or DC error will be induced.
RFI/EMI SUSCEPTIBILITY
RFI (Radio Frequency Interference) and EMI (Electro-Magnetic Interference) can degrade any integrated circuit's
performance because of the small dimensions of the geometries inside the device. In applications where circuit
sources are present which generate signals with significant high frequency energy content (> 1 MHz), care must
be taken to ensure that this does not affect the IC regulator.
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If RFI/EMI noise is present on the input side of the regulator (such as applications where the input source comes
from the output of a switching regulator), good ceramic bypass capacitors must be used at the input pin of the IC
to reduce the amount of EMI conducted into the IC.
If the LP38501/3-ADJ output is connected to a load which switches at high speed (such as a clock), the high-
frequency current pulses required by the load must be supplied by the capacitors on the IC output. Since the
bandwidth of the regulator loop is less than 300 kHz, the control circuitry cannot respond to load changes above
that frequency. This means the effective output impedance of the IC at frequencies above 300 kHz is determined
only by the output capacitor(s). Ceramic capacitors provide the best performance in this type of application.
In applications where the load is switching at high speed, the output of the IC may need RF isolation from the
load. In such cases, it is recommended that some inductance be placed between the output capacitor and the
load, and good RF bypass capacitors be placed directly across the load. PCB layout is also critical in high noise
environments, since RFI/EMI is easily radiated directly into PC traces. Noisy circuitry should be isolated from
"clean" circuits where possible, and grounded through a separate path. At MHz frequencies, ground planes begin
to look inductive and RFI/EMI can cause ground bounce across the ground plane. In multi-layer PC Board
applications, care should be taken in layout so that noisy power and ground planes do not radiate directly into
adjacent layers which carry analog power and ground.
OUTPUT NOISE
Noise is specified in two ways-
Spot Noise or Output noise density is the RMS sum of all noise sources, measured at the regulator output, at
a specific frequency (measured with a 1Hz bandwidth). This type of noise is usually plotted on a curve as a
function of frequency.
Total output noise voltage or Broadband noise is the RMS sum of spot noise over a specified bandwidth,
usually several decades of frequencies. Attention should be paid to the units of measurement.
Spot noise is measured in units µV/√Hz or nV/√Hz and total output noise is measured in µV(rms). The primary
source of noise in low-dropout regulators is the internal reference. In CMOS regulators, noise has a low
frequency component and a high frequency component, which depend strongly on the silicon area and quiescent
current.
Noise can generally be reduced in two ways: increase the transistor area or increase the reference current.
However, enlarging the transisitors will increase die size, and increasing the reference current means higher total
supply current (ground pin current).
SHORT-CIRCUIT PROTECTION
The LP38501/3-ADJ contains internal current limiting which will reduce output current to a safe value if the output
is overloaded or shorted. Depending upon the value of VIN, thermal limiting may also become active as the
average power dissipated causes the die temperature to increase to the limit value (about 170°C). The hysteresis
of the thermal shutdown circuitry can result in a “cyclic” behavior on the output as the die temperature heats and
cools.
ENABLE OPERATION (LP38501-ADJ Only)
The Enable pin (EN) must be actively terminated by either a 10 kΩ pull-up resistor to VIN, or a driver which
actively pulls high and low (such as a CMOS rail to rail comparator). If active drive is used, the pull-up resistor is
not required. This pin must be tied to VIN if not used (it must not be left floating).
DROPOUT VOLTAGE
The dropout voltage of a regulator is defined as the input-to-output differential required by the regulator to keep
the output voltage within 2% of the nominal value. For CMOS LDOs, the dropout voltage is the product of the
load current and the RDS(on) of the internal MOSFET pass element.
Since the output voltage is beginning to “drop out” of regulation when it drops by 2%, electrical performance of
the device will be reduced compared to the values listed in the Electrical Characteristics table for some
parameters (line and load regulation and PSRR would be affected).
Copyright © 2007–2013, Texas Instruments Incorporated
Submit Documentation Feedback
13
Product Folder Links: LP38501-ADJ LP38503-ADJ
LP38501-ADJ, LP38503-ADJ
SNVS522H –AUGUST 2007–REVISED APRIL 2013
www.ti.com
REVERSE CURRENT PATH
The internal MOSFET pass element in the LP38501/3-ADJ has an inherent parasitic diode. During normal
operation, the input voltage is higher than the output voltage and the parasitic diode is reverse biased. However,
if the output is pulled above the input in an application, then current flows from the output to the input as the
parasitic diode gets forward biased. The output can be pulled above the input as long as the current in the
parasitic diode is limited to 200 mA continuous and 1A peak. The regulator output pin should not be taken below
ground potential. If the LP38501/3-ADJ is used in a dual-supply system where the regulator load is returned to a
negative supply, the output must be diode-clamped to ground.
POWER DISSIPATION/HEATSINKING
The maximum power dissipation (PD(MAX)) of the LP38501/3-ADJ is limited by the maximum junction temperature
of 125°C, along with the maximum ambient temperature (TA(MAX)) of the application, and the thermal resistance
(θJA) of the package. Under all possible conditions, the junction temperature (TJ) must be within the range
specified in the Operating Ratings. The total power dissipation of the device is given by:
PD = ( (VIN − VOUT) x IOUT) + (VIN x IGND
)
where
•
IGND is the operating ground current of the device (specified under Electrical Characteristics)
(3)
The maximum allowable junction temperature rise (ΔTJ) depends on the maximum expected ambient
temperature (TA(MAX)) of the application, and the maximum allowable junction temperature (TJ(MAX)):
ΔTJ = TJ(MAX)− TA(MAX)
(4)
The maximum allowable value for junction to ambient Thermal Resistance, θJA, can be calculated using the
formula:
θJA = ΔTJ / PD(MAX)
(5)
The LP38501/3-ADJ is available in the TO-263 package. The thermal resistance depends on the amount of
copper area allocated to heat transfer.
HEATSINKING TO-263, PFM THIN PACKAGES
The TO-263 package and TO-263 THIN package use the copper plane on the PCB as a heatsink. The DAP of
the package is soldered to the copper plane for heat sinking. Figure 26 shows a typical curve for the θJA of the
TO-263 package for different copper area sizes (the thermal performance of both the TO-263 and TO-263 THIN
are the same). The tests were done using a PCB with 1 ounce copper on top side only which were square in
shape.
Figure 26. θJA vs Copper Area for TO-263 Package
As shown in the figure, increasing the copper area beyond 1.5 square inch produces very little improvement.
14
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
Product Folder Links: LP38501-ADJ LP38503-ADJ
LP38501-ADJ, LP38503-ADJ
www.ti.com
SNVS522H –AUGUST 2007–REVISED APRIL 2013
REVISION HISTORY
Changes from Revision G (April 2013) to Revision H
Page
•
Changed layout of National Data Sheet to TI format .......................................................................................................... 14
Copyright © 2007–2013, Texas Instruments Incorporated
Submit Documentation Feedback
15
Product Folder Links: LP38501-ADJ LP38503-ADJ
PACKAGE OPTION ADDENDUM
www.ti.com
21-May-2013
PACKAGING INFORMATION
Orderable Device
Status Package Type Package Pins Package
Eco Plan Lead/Ball Finish
MSL Peak Temp
Op Temp (°C)
Device Marking
Samples
Drawing
Qty
(1)
(2)
(3)
(4/5)
LP38501ATJ-ADJ/NOPB
LP38501TJ-ADJ/NOPB
LP38501TS-ADJ/NOPB
LP38501TSX-ADJ/NOPB
LP38503ATJ-ADJ/NOPB
LP38503TJ-ADJ/NOPB
LP38503TS-ADJ/NOPB
LP38503TSX-ADJ/NOPB
ACTIVE
TO-263
TO-263
NDQ
5
5
5
5
5
5
5
5
1000
Green (RoHS
& no Sb/Br)
CU SN
CU SN
CU SN
CU SN
CU SN
CU SN
CU SN
CU SN
Level-1-260C-UNLIM
Level-1-260C-UNLIM
Level-3-245C-168 HR
Level-3-245C-168 HR
Level-1-260C-UNLIM
Level-1-260C-UNLIM
Level-3-245C-168 HR
Level-3-245C-168 HR
-40 to 125
LP38501A
TJ-ADJ
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
ACTIVE
NDQ
KTT
KTT
NDQ
NDQ
KTT
KTT
1000
45
Green (RoHS
& no Sb/Br)
LP38501
TJ-ADJ
DDPAK/
TO-263
Pb-Free (RoHS
Exempt)
-40 to 125
-40 to 125
-40 to 125
-40 to 125
-40 to 125
-40 to 125
LP38501
TS-ADJ
DDPAK/
TO-263
500
1000
1000
45
Pb-Free (RoHS
Exempt)
LP38501
TS-ADJ
TO-263
Green (RoHS
& no Sb/Br)
LP38503A
TJ-ADJ
TO-263
Green (RoHS
& no Sb/Br)
LP38503
TJ-ADJ
DDPAK/
TO-263
Pb-Free (RoHS
Exempt)
LP38503
TS-ADJ
DDPAK/
TO-263
500
Pb-Free (RoHS
Exempt)
LP38503
TS-ADJ
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3) MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
21-May-2013
(4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.
(5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 2
PACKAGE MATERIALS INFORMATION
www.ti.com
29-May-2013
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
B0
K0
P1
W
Pin1
Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant
(mm) W1 (mm)
LP38501ATJ-ADJ/NOPB TO-263
LP38501TJ-ADJ/NOPB TO-263
NDQ
NDQ
KTT
5
5
5
1000
1000
500
330.0
330.0
330.0
24.4
24.4
24.4
10.6
10.6
15.4
15.4
2.45
2.45
5.0
12.0
12.0
16.0
24.0
24.0
24.0
Q2
Q2
Q2
LP38501TSX-ADJ/NOPB DDPAK/
TO-263
10.75 14.85
LP38503ATJ-ADJ/NOPB TO-263
LP38503TJ-ADJ/NOPB TO-263
NDQ
NDQ
KTT
5
5
5
1000
1000
500
330.0
330.0
330.0
24.4
24.4
24.4
10.6
10.6
15.4
15.4
2.45
2.45
5.0
12.0
12.0
16.0
24.0
24.0
24.0
Q2
Q2
Q2
LP38503TSX-ADJ/NOPB DDPAK/
TO-263
10.75 14.85
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
29-May-2013
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SPQ
Length (mm) Width (mm) Height (mm)
LP38501ATJ-ADJ/NOPB
LP38501TJ-ADJ/NOPB
TO-263
TO-263
NDQ
NDQ
KTT
5
5
5
5
5
5
1000
1000
500
367.0
367.0
367.0
367.0
367.0
367.0
367.0
367.0
367.0
367.0
367.0
367.0
35.0
35.0
45.0
35.0
35.0
45.0
LP38501TSX-ADJ/NOPB DDPAK/TO-263
LP38503ATJ-ADJ/NOPB
LP38503TJ-ADJ/NOPB
TO-263
TO-263
NDQ
NDQ
KTT
1000
1000
500
LP38503TSX-ADJ/NOPB DDPAK/TO-263
Pack Materials-Page 2
MECHANICAL DATA
NDQ0005A
TJ5A (Rev F)
www.ti.com
MECHANICAL DATA
KTT0005B
TS5B (Rev D)
BOTTOM SIDE OF PACKAGE
www.ti.com
IMPORTANT NOTICE
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changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
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TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
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TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
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