LP3992
Micropower 1.5V CMOS Voltage Regulator with
Shutdown Control
LP3992 Micropower 1.5V CMOS Voltage Regulator with Shutdown Control
December 2002
General Description
The LP3992 regulator is designed to meet the requirements
of portable, battery-powered systems providing an accurate
output voltage, low noise, and low quiescent current. Battery
life will be prolonged by the ability of the LP3992 to provide
a 1.5V output from the low input voltage of 1.9V. Additionally,
when switched to a shutdown mode via a logic signal at the
shutdown pin, the power consumption is reduced to virtually
zero. The LP3992 also features short-circuit and thermalshutdown protection.
The LP3992 is designed to be stable with space saving
ceramic capacitors as small as 1.0µF.
The device is available in an SOT23-5 package. Performance is specified for a -40˚C to 125˚C temperature range.
For output voltages other than 1.5V and alternative package
options, please contact your local NSC sales office.
Typical Application Circuit
Key Specifications
n 1.9 to 5.2V input range
n Accurate 1.5V
n Less than 1.5µA quiescent current in shutdown
n Stable with a 1µF output capacitor
n Guaranteed 30mA output current
n Low output voltage Noise; 300µV
±
0.09V output voltage
RMS
Features
n Operation from a low input voltage; 1.9V
n Low quiescent current; 29µA typical
n Stable with a ceramic capacitor
n Logic controlled shutdown
n Fast turn ON and OFF
n Thermal-overload and short circuit protection
n 5 pin package, SOT23
n -40˚C to +125˚C junction temperature range
20041201
© 2002 National Semiconductor Corporation DS200412 www.national.com
Pin Descriptions
LP3992
Pin No Symbol Name and Function
1V
2 GND Common Ground
3 SD Shutdown input; Disables the regulator when ≤ 0.4V.
4C
5V
Connection Diagram
OUT
OUT
IN
Voltage Supply Input
Enables the regulator when ≥ 1.15V.
Output capacitor connection. Internally Connected to V
OUT
connection. This is the recommended device connection for the
1.0µF output capacitor to guarantee a stable output.
Voltage output. Connect this output to the load circuit.
SOT23 - 5 Package (MF)
20041202
Top View
See NS package number MF05A
Ordering Information
Output
Voltage (V)
Grade
1.5 STD LP3992IMF-1.5 LP3992IMFX-1.5
1.5 STD LP3992IMF-1.5/E4000193 LP3992IMFX-1.5/S4000170
LP3992 Supplied as 1000
Units, Tape and Reel
LP3992 Supplied as 3000
Units, Tape and Reel
Package Marking
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LP3992
Absolute Maximum Ratings
(Notes 1, 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Input Voltage -0.3 to 6.5V
Output Voltage -0.3 to (V
+ 0.3V) to
IN
Thermal Resistance (Note 4)
θ
JA
220˚C/W
Maximum Power Dissipation
at 25˚C 568mW
ESD (Note 5)
Human Body Model 2KV
Machine Model 200V
6.5V (max)
Shutdown Input Voltage -0.3 to 6.5V
Junction Temperature 150˚C
Lead Temp. (Note 3) 260˚C
Storage Temperature -65 to 150˚C
Operating Conditions(Note 1)
Input Voltage 1.9 to 5.2V
Shutdown Input Voltage 0 to 6.0V
Junction Temperature -40˚C to 125˚C
Power Dissipation at 25˚C 454mW
Electrical Characteristics
Unless otherwise noted, VSD= 1.15, VIN=V
pearing in normal type apply for T
= 25˚C. Limits appearing in boldface type apply over the full temperature range for opera-
J
tion, −40 to +125˚C. (Note 13)
Symbol Parameter Conditions Typ
V
∆V
IN
OUT
Input Voltage 1.9 5.2 V
Output Voltage Tolerance Over full line and load regulation. -90 +90 mV
Line Regulation Error V
Load Regulation Error I
I
LOAD
I
Q
I
SC
Load Current (Notes 6, 7) 0 µA
Quiescent Current VSD= 1.15V, I
Short Circuit Current Limit (Note 12) 90 mA
PSRR Power Supply Rejection Ratio f = 1kHz, I
E
EN
T
SHUTDOWN
Output noise Voltage (Note 7) BW = 10Hz to 1000kHz,
Thermal Shutdown Temperature 160
Thermal Shutdown Hysteresis 20
Enable Control Characteristics
I
SD
Maximum Input Current at
SD Input
V
IL
V
IH
Low Input Threshold VIN= 1.8V to 5.2V 0.4 V
High Input Threshold VIN= 1.8 to 5.2V 1.15 V
Timing Characteristics
T
ON1
T
ON2
T
OFF1
T
OFF2
Transient
Response
Note 1: Absolute Maximum Ratings are limits beyond which damage can occur. Operating Ratings are conditions under which operation of the device is
guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the Electrical
Characteristics tables.
Note 2: All Voltages are with respect to the potential at the GND pin.
Turn On Time (Note 7) 50 to 85% of V
Turn Off Time (Note 7) 85 to 50% of V
Line Transient Response |δV
OUT|Trise=Tfall
Load Transient Response
|
|δV
OUT
+ 1.0V, CIN= 1 µF, I
OUT
OUT
= 1 mA, C
= 1 µF. Typical values and limits ap-
OUT
Limit
Min Max
=(V
IN
OUT(NOM)
= 1mA
I
OUT
= 1mA to 30mA 100 220 µV/mA
OUT
= 1.15V, I
SD
V
= 0.4V 0.003 1.5
SD
f = 20kHz, I
= 4.2V
V
IN
VEN= 0.0V and VIN= 5.2V
+ 1.0V) to 5.2V,
= 0mA 26 50
OUT
= 30mA 29 50
OUT
= 30mA 40
OUT
= 30mA 30
OUT
OUT(NOM)
(Note 8) 15
-0.27 +0.27 %/V
300 µV
0.001 µA
To 95% Level (Note 9) 40
OUT(NOM)
(Note 10) 15
95 to 5% Level (Note 11) 40
= 10µS (Note 7) 60
T
rise=Tfall
I
OUT
= 1µS
= 100µA to 5mA(Note 7)
60
Units
µAV
dB
RMS
˚C
µS
µS
mV
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Electrical Characteristics (Continued)
Note 3: The package can pass MSL (moisture sensitivity level) 1 at 260˚C.
LP3992
Additional information on lead temperature can be obtained from National Semiconductor web pages
http://www.national.com/packaging/general.html
http://www.national.com/packaging/plastic.html
Note 4: The Maximum power dissipation of the device is dependant on the maximum allowable junction temperature for the device and the ambient temperature.
This relationship is given by the formula
=(TJ-TA)/θ
P
D
Where TJis the junction temperature, TAis the ambient temperature, and θJA is the junction-to-ambient thermal resistance. The Maximum Power dissipation across
the device related to the operational conditions can be calculated using the formula
P
=(V
D
Substituting the device values gives the max power dissipation = (5.2V - 1.5V)(0.03) = 0.111W. This figure for Maximum power dissipation can be used to derive the
maximum ambient temperature. For the SOT23-5 package θ
220). This gives the maximum ambient temperature for operation as 100.6˚C, (125 - 24.4). Similarly the numbers for the absolute maximum case can be derived
using a figure of 150˚C for the junction temperature.
Note 5: The human body is 100pF discharge through 1.5kW resistor into each pin. The machine model is a 200 pF capacitor discharged directly into each pin.
Note 6: The device maintains the regulated output voltage without the load.
Note 7: This electrical specification is guaranteed by design.
Note 8: Time for V
Note 9: Time from V
Note 10: Time for V
Note 11: Time from V
Note 12: Short circuit current is measured on the input supply line at the point when the short circuit condition reduces the output voltage to 95% of its nominal value.
Note 13: All limits are guaranteed. All electrical characteristics having room-temperature limits are tested during production at T
Statistical Quality Control methods. Operation over the temperature specification is guaranteed by correlating the electrical characteristics to process and
temperature variations and applying statistical process control.
JA
IN(MAX)-VOUT(MAX)
to rise from 50 to 85% of V
OUT
= 1.15V to V
SD
OUT
SD
)*(I
to fall from 85 to 50% of V
= 0.4V to V
OUT(MAX)
OUT
OUT
)
= 95%(V
= 5%(V
OUT(nom)
OUT(nom)
OUT(nom)
OUT(nom)
= 220˚C/W, thus for this device the maximum temperature difference, (TJ-TA), is 24.4˚C, (0.111 *
JA
. (figure 1)
). (figure 1)
. (figure 1)
. (figure 1)
= 25˚C or correlated using
J
Output Capacitor, Recommended Specifications
Symbol Parameter Conditions Typ
C
o
Output Capacitor Capacitance(Note 14) 1.0 µF
ESR 5 500 mΩ
Note 14: Capacitor types recommended are X7R, Y5V, and Z5U. X7R tolerance is quoted as 15% over temperature.
Limit
Min Max
Units
FIGURE 1. Figure 1. Ton/T
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Timing Diagram
off
20041203
FIGURE 2. Figure 2. Line Transient Input Test Signal.
20041205
FIGURE 3. Figure 3. PSRR Input Test Signal.
LP3992
20041204
Typical Performance Characteristics. Unless otherwise specified, C
= 2.8V, TA= 25˚C, Shutdown pin is tied to VIN.
V
IN
Output Voltage Change vs Temperature Ground Current vs Load Current
20041207
IN=COUT
= 1.0 µF Ceramic,
20041208
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Typical Performance Characteristics. Unless otherwise specified, C
= 2.8V, TA= 25˚C, Shutdown pin is tied to VIN. (Continued)
LP3992
IN=COUT
= 1.0 µF Ceramic, V
IN
Ground Current vs V
at 25˚C Ground Current vs VINat 125˚C
IN
20041209 20041210
Short Circuit Current Short Circuit Current
20041211 20041212
Line Transient Response Line Transient Response
20041213 20041214
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LP3992
Typical Performance Characteristics. Unless otherwise specified, C
= 2.8V, TA= 25˚C, Shutdown pin is tied to VIN. (Continued)
Turn ON/OFF Timing Turn ON/OFF Timing
20041215 20041216
Ripple Rejection Load Transient Response
IN=COUT
= 1.0 µF Ceramic, V
IN
Load Transient Response
20041218
20041217
20041219
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Application Hints
LP3992
EXTERNAL CAPACITORS
In common with most regulators, the LP3992 requires external capacitors for regulator stability. The LP3992 is specifically designed for portable applications requiring minimum
board space and smallest components. These capacitors
must be correctly selected for good performance.
INPUT CAPACITOR
An input capacitor is required for stability. It is recommended
that a 1.0µF capacitor be connected between the LP3992
input pin and ground (this capacitance value may be increased without limit).
This capacitor must be located a distance of not more than
1cm from the input pin and returned to a clean analogue
ground. Any good quality ceramic, tantalum, or film capacitor
may be used at the input.
Important: Tantalum capacitors can suffer catastrophic failures due to surge current when connected to a lowimpedance source of power (like a battery or a very large
capacitor). If a tantalum capacitor is used at the input, it must
be guaranteed by the manufacturer to have a surge current
rating sufficient for the application.
There are no requirements for the ESR (Equivalent Series
Resistance) on the input capacitor, but tolerance and temperature coefficient must be considered when selecting the
capacitor to ensure the capacitance will remain ) 1.0µF over
the entire operating temperature range.
OUTPUT CAPACITOR
The LP3992 is designed specifically to work with very small
ceramic output capacitors. A 1.0µF ceramic capacitor (dielectric types Z5U, Y5V or X7R) with ESR between 5mΩ to
500mΩ, is suitable in the LP3992 application circuit.
For this device the output capacitor should be connected
between the C
connect the output capacitor directly to the V
case C
should be left open-circuit or tied directly to V
OUT
It may also be possible to use tantalum or film capacitors at
the device output, C
attractive for reasons of size and cost (see the section
Capacitor Characteristics).
The output capacitor must meet the requirement for the
minimum value of capacitance and also have an ESR value
that is within the range 5mΩ to 500mΩ for stability.
NO-LOAD STABILITY
The LP3992 will remain stable and in regulation with no
external load. This is an important consideration in some
circuits, for example CMOS RAM keep-alive applications.
pin and ground. It is also possible to
OUT
OUT
OUT
(or V
), but these are not as
OUT
pin. In this
OUT
capacitors are the smallest, least expensive and have the
lowest ESR values, thus making them best for eliminating
high frequency noise. The ESR of a typical 1µF ceramic
capacitor is in the range of 20mΩ to 40mΩ, which easily
meets the ESR requirement for stability for the LP3992.
The temperature performance of ceramic capacitors varies
by type. Most large value ceramic capacitors ( ≥ 2.2µF) are
manufactured with Z5U or Y5V temperature characteristics,
which results in the capacitance dropping by more than 50%
as the temperature goes from 25˚C to 85˚C.
A better choice for temperature coefficient in a ceramic
capacitor is X7R. This type of capacitor is the most stable
±
and holds the capacitance within
15% over the tempera-
ture range.
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
1µF to 4.7µF 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.
SHUTDOWN AND ENABLE
The LP3992 features an active low shutdown pin, V
,
SD
which turns the device off when pulled low. The device
output is enabled when the shutdown pin is pulled high. In
the shutdown mode the regulator output is off and the device
typically consumes 3nA.
If the application does not require the shutdown feature, the
pin should be tied to VINto keep the regulator output
V
SD
permanently on.
.
To ensure proper operation, the signal source used to drive
the V
input must be able to swing above and below the
SD
specified turn-on/off voltage thresholds listed in the Electrical
Characteristics section under V
and VIH.
IL
FAST TURN ON AND OFF
The controlled shutdown feature of the device provides a
fast turn off by discharging the output capacitor via an internal FET device. This discharge is current limited by the
RDS
of this switch. Fast turn-on is guaranteed by control
ON
circuitry within the reference block allowing a very fast ramp
of the output voltage to reach the target voltage.
CAPACITOR CHARACTERISTICS
The LP3992 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 1µF to 4.7µF, ceramic
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Physical Dimensions inches (millimeters)
unless otherwise noted
LP3992 Micropower 1.5V CMOS Voltage Regulator with Shutdown Control
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NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
labeling, can be reasonably expected to result in a
significant injury to the user.
National Semiconductor
Corporation
Americas
Email: support@nsc.com
www.national.com
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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