April 2000
LM4121
Precision Micropower Low Dropout Voltage Reference
LM4121 Precision Micropower Low Dropout Voltage Reference
General Description
The LM4121 is a precision bandgap voltage reference available in a fixed 1.25V and adjustable version with up to 5 mA
current source and sink capability.
This series reference operates with input voltages as low as
1.8V and up to 12Vconsuming 160 µA (Typ.) supply current.
In power down mode, device current drops to less than 2 µA.
The LM4121 comes in two grades A and Standard. The best
grade devices (A) have an initial accuracy of 0.2%, while the
standard have an initial accuracy of 0.5%, both with a
tempco of 50ppm/˚C guaranteed from −40˚C to +125˚C.
The very low operating voltage, low supply current and
power-down capability of the LM4121 makes this product an
ideal choice for battery powered and portable applications.
The device performance is guaranteed over the industrial
temperature range (−40˚C to +85˚C), while certain specs are
guaranteed over the extended temperature range (−40˚C to
+125˚C). Please contact National for full specifications over
the extended temperature range. The LM4121 is available in
a standard 5-pin SOT-23 package.
Features (LM4121-1.2)
n Small SOT23-5 package
n Low voltage operation
n High output voltage accuracy: 0.2%
n Source and Sink current output:
n Supply current: 160 µA Typ.
n Low Temperature Coefficient: 50 ppm/˚C
n Enable pin
n Output voltages: 1.25V and Adjustable
n Industrial temperature Range: −40˚C to +85˚C
n (For extended temperature range, −40˚C to 125˚C,
contact National Semiconductor)
±
5mA
Applications
n Portable, battery powered equipment
n Instrumentation and process control
n Automotive & Industrial
n Test equipment
n Data acquisition systems
n Precision regulators
n Battery chargers
n Base stations
n Communications
n Medical equipment
Block Diagram Connection Diagrams
DS101291-2
Refer to the Ordering Information Table in this Data Sheet for Specific
Part Number
SOT23-5 Surface Mount Package
DS101291-1
*
Resistors are removed on the LM4121-ADJ
†
LM4121-ADJ only
LM4121-1.2 Block Diagram
DS101291-35
© 2001 National Semiconductor Corporation DS101291 www.national.com
Ordering Information
LM4121
Industrial Temperature Range (−40˚C to + 85˚C)
Initial Output Voltage Accuracy at 25˚C
And Temperature Coefficient
0.2%, 50 ppm/˚C max (A grade)
0.5%, 50 ppm/˚C max
LM4121 Supplied as
1000 Units, Tape and
Reel
LM4121AIM5-1.2 LM4121AIM5X-1.2 R19A
LM4121AIM5-ADJ LM4121AIM5X-ADJ R20A
LM4121IM5-1.2 LM4121IM5X-1.2 R19B
LM4121IM5-ADJ LM4121IM5X-ADJ R20B
SOT-23 Package Marking Information
Only four fields of marking are possible on the SOT-23’s small surface. This
table gives the meaning of the four fields.
Field Information
First Field:
R = Reference
Second and third Field:
19 = 1.250V Voltage Option
20 = Adjustable
Fourth Field:
A-B = Initial Reference Voltage Tolerance
±
A=
0.2%
±
B=
0.5%
LM4121 Supplied as
3000 Units, Tape and
Reel
Top
Marking
www.national.com 2
LM4121
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Lead Temperature:
Soldering, (10 sec.) +260˚C
Vapor Phase (60 sec.) +215˚C
Infrared (15 sec.) +220˚C
Maximum Voltage on input or
enable pins −0.3V to 14V
Output Short-Circuit Duration Indefinite
Power Dissipation (T
MA05B package − θ
= 25˚C) (Note 2):
A
JA
280˚C/W
Operating Range (Note 1)
Storage Temperature Range −65˚C to +150˚C
Ambient Temperature Range −40˚C to +85˚C
Junction Temperature Range −40˚C to +125˚C
Power Dissipation 350 mW
ESD Susceptibility (Note 3)
Human Body Model
Machine Model
2kV
200V
Electrical Characteristics
LM4121-1.250V
standard typeface are for T
Symbol Parameter Conditions Min (Note 5) Typ (Note 4) Max (Note 5) Units
V
OUT
TCV
∆V
∆V
Min-V
V
I
I
V
V
I
I
I
/˚C Temperature Coefficient −40˚C ≤ TA≤ +125˚C 14 50 ppm/˚c
OUT
/∆V
OUT
/∆I
OUT
IN
N
S
SS
H
L
H
L
SC
Hyst Thermal Hysteresis
∆V
OUT
Output Voltage Initial
Accuracy
LM4121A-1.250
LM4121-1.250
Line Regulation 1.8V ≤ VIN≤ 12V 0.0007 0.009
IN
Load Regulation
LOAD
Minimum Operating Voltage I
Output Noise Voltage 0.1 Hz to 10 Hz 20 µV
Supply Current 160 250
Power-down Supply Current VIN= 12V
Logic High Input Voltage 1.6 1.5 V
Logic Low Input Voltage 0.4 V
Logic High Input Current 7 15 µA
Logic Low Input Current 0.1 µA
Short Circuit Current
(Note 8)
Long Term Stability
(Note 9)
Unless otherwise specified VIN= 3.3V, I
= 25˚C, and limits in boldface type apply over the −40˚C ≤ TA≤ +85˚C temperature range.
j
LOAD
=0,C
= 0.01µF, TA=Tj= 25˚C. Limits with
OUT
1.250
±
0.2
±
0.5
0.012
0mA≤I
≤ 1 mA 0.03 0.08
LOAD
0.17
1mA≤I
≤ 5 mA 0.01 0.04
LOAD
0.1
−1 mA ≤ I
−5 mA ≤ I
= 5mA 1.5 1.8 V
LOAD
≤ 0 mA 0.04 0.12
LOAD
≤ −1 mA 0.01
LOAD
10 Hz to 10 kHz 30 µV
275
Enable = 0.4V
Enable = 0.2V
1
2
0.2
V
IN
= 3.3V, V
=0 15
OUT
630
V
= 12V, V
IN
=0 17
OUT
630
−40˚C ≤ T
≤ 125˚C 0.5 mV/V
A
1000 hrs.@25˚C 100 ppm
%
%/V
%/mA
PP
RMS
µA
µA
mA
www.national.com3
Electrical Characteristics
LM4121-ADJ
LM4121
its with standard typeface are for T
range.
Symbol Parameter Conditions Min (Note 5) Typ (Note 4) Max (Note 5) Units
V
OUT=VREF
TCV
/˚C Temperature Coefficient −40˚C ≤ TA≤ +125˚C 14 50 ppm/˚c
REF
∆V
/∆V
REF
IN
∆V
/∆I
OUT
LOAD
Min-V
IN
V
N
I
S
I
SS
I
BIAS
V
H
V
L
I
H
I
L
I
SC
Hyst Thermal Hysteresis
∆V
OUT
Note 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 do not guarantee specific performance limits. For guaranteed specifications and test conditions, see Electrical Characteristics. The
guaranteed specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed
test conditions.
Note 2: Without PCB copper enhancements. The maximum power dissipation must be de-rated at elevated temperatures and is limited by T
junction temperature), θ
=(T
JMAX−TA
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged
directly into each pin.
Note 4: Typical numbers are at 25˚C and represent the most likely parametric norm.
Note 5: Limits are 100% production tested at 25˚C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control
(SQC) methods. The limits are used to calculate National’s Averaging Outgoing Quality Level (AOQL).
Note 6: Output noise for 1.25V option. Noise is proportional to V
Note 7: Bias Current flows out of the Adjust pin.
Note 8: Thermal hysteresis is defined as the change in +25˚C output voltage before and after exposing the device to temperature extremes.
Note 9: Long term stability is change in V
)/θ
J-A
Unless otherwise specified VIN= 3.3V, V
= 25˚C, and limits in boldface type apply over the −40˚C ≤ TA≤ +85˚C temperature
j
OUT=VREF,ILOAD
=0,C
= 0.01µF, TA=Tj= 25˚C. Lim-
OUT
Output Voltage Initial
±
Accuracy
1.216
0.2
LM4121A-ADJ
LM4121-ADJ
±
0.5
Line Regulation 1.8V ≤ VIN≤ 12V 0.0007 0.009
0.012
0mA≤I
≤ 1 mA 0.03 0.08
LOAD
0.17
Load Regulation
Minimum Operating Voltage I
1mA≤I
−1 mA ≤ I
−5 mA ≤ I
=5mA 1.5 1.8 V
LOAD
≤ 5 mA 0.01 0.04
LOAD
≤ 0 mA 0.04 0.12
LOAD
≤ −1 mA 0.01
LOAD
0.1
Output Noise Voltage (Note 6) 0.1 Hz to 10 Hz 20 µV
10 Hz to 10 kHz 30 µV
Supply Current 160 250
275
Power-down Supply Current VIN= 12V
Enable = 0.4V
Enable = 0.2V
1
2
Reference Pin Bias Current (Note 7) 15 40 nA
Logic High Input Voltage 1.6 1.5 V
Logic Low Input Voltage 0.4 V
0.2
Logic High Input Current 7 15 µA
Logic Low Input Current 0.1 µA
=0 15
V
OUT
Short Circuit Current
V
= 12V, V
IN
=0 17
OUT
630
630
−40˚C ≤ T
≤ 125˚C 0.5 mV/V
A
(Note 8)
Long Term Stability
1000 hrs.@25˚C 100 ppm
(Note 9)
(junction to ambient thermal resistance) and TA(ambient temperature). The maximum power dissipation at any temperature is: PDiss
J-A
up to the value listed in the Absolute Maximum Ratings.
.
OUT
at 25˚C measured continuously during 1000 hrs.
REF
JMAX
%
%/V
%/mA
PP
RMS
µA
µA
mA
(maximum
MAX
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LM4121
LM4121- (All Options) Typical Operating Characteristics Unless otherwise specified, V
= 3.3V, V
Minimum Input Voltage vs Temperature
GND Pin Current at No Load
vs Temperature
OUT
= 1.25V, I
LOAD
=0,C
= 0.022µF, TA= 25˚C and VEN=VIN.
OUT
GND Pin Current vs V
DS101291-12
GND Pin Current vs Load
IN
DS101291-13
IN
DS101291-14
DS101291-15
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LM4121- (All Options) Typical Operating Characteristics Unless otherwise specified,
V
IN
LM4121
= 3.3V, V
OUT
= 1.25V, I
LOAD
=0,C
= 0.022µF, TA= 25˚C and VEN=VIN. (Continued)
OUT
Short Circuit vs Temperature
PSRR vs Frequency
DS101291-33
Output Impedance vs Frequency
DS101291-17
Enable Pin Current
DS101291-18
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DS101291-19
LM4121- (All Options) Typical Operating Characteristics Unless otherwise specified,
V
= 3.3V, V
IN
OUT
= 1.25V, I
LOAD
=0,C
= 0.022µF, TA= 25˚C and VEN=VIN. (Continued)
OUT
LM4121
Start-Up Response
Load Step Response
DS101291-21
Enable Response
DS101291-22
Load Step Response
DS101291-23
DS101291-24
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LM4121- (All Options) Typical Operating Characteristics Unless otherwise specified,
V
IN
LM4121
= 3.3V, V
OUT
= 1.25V, I
LOAD
=0,C
= 0.022µF, TA= 25˚C and VEN=VIN. (Continued)
OUT
Line Step Response
Noise Spectural Density (10Hz-10kHz)
DS101291-25
Noise Spectural Density (0.1Hz-10Hz)
DS101291-26
Thermal Hysteresis
DS101291-27
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DS101291-46
LM4121
LM4121-1.25 Typical Operating Characteristics Unless otherwise specified, V
= 1.25V, I
Typical Temperature Drift
Line Regulation
LOAD
=0,C
= 0.022µF, TA= 25˚C and VEN=VIN.
OUT
DS101291-28
Long Term Drift
Load Regulation
= 3.3V, V
IN
DS101291-29
OUT
DS101291-30
DS101291-31
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LM4121-ADJ Typical Operating Characteristics Unless otherwise specified, V
= 1.2V, I
LM4121
Typical Temperature Drift
LOAD
=0,C
= 0.022µF, TA= 25˚C and VEN=VIN.
OUT
Long Term Drift
= 3.3V, V
IN
OUT
Dropout Voltage vs Output Error
DS101291-16
DS101291-47
DS101291-36
Dropout Voltage vs Load Current
DS101291-48
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LM4121
LM4121-ADJ Typical Operating Characteristics Unless otherwise specified, V
= 1.2V, I
Line Regulation
Adjust Pin Bias Current
LOAD
=0,C
= 0.022µF, TA= 25˚C and VEN=VIN. (Continued)
OUT
Load Regulation
DS101291-37
Change In Reference Voltage vs Output Voltage
= 3.3V, V
IN
DS101291-38
OUT
DS101291-39
DS101291-40
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LM4121-ADJ Typical Operating Characteristics Unless otherwise specified, V
= 1.2V, I
LM4121
LOAD
=0,C
= 0.022µF, TA= 25˚C and VEN=VIN. (Continued)
OUT
= 3.3V, V
IN
OUT
Bode Plot
DS101291-41
Bode Plot
DS101291-42
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Pin Functions
Output (Pin 5): Reference Output.
Input (Pin 4):Positive Supply.
Ground (Pin 2):Negative Supply or Ground Connection.
Enable (Pin 3):Pulled to input for normal operation. Forcing
this pin to ground will turn-off the output.
REF (Pin 1):REF Pin (1.25V option only). This pin should be
left unconnected for 1.25V option.
Adj (Pin 1):V
Adj Pin (Adjustable option only). See Ap-
OUT
plication Hints section.
Application Hints
The standard application circuit for the LM4121 is shown in
Figure 1
resistors, according to the following formula:
Values for R1 and R2 should be chosen to be less than 1
MΩ.I
and I
table. For best accuracy, be sure to take into account the
variation of V
The LM4121 is designed to be stable with ceramic output
capacitors in the range of 0.022µF to 0.047µF. Note that
0.022µF is the minimum required output capacitor. These
capacitors typically have an ESR of about 0.1 to 0.5Ω.
Smaller ESR can be tolerated, however larger ESR can not.
The output capacitor can be increased to improve load transient response, up to about 1µF. However, values above
0.047µF must be tantalum. With tantalum capacitors, in the
1µF range, a small capacitor between the output and the
reference (Adj) pin is required. This capacitor will typically be
in the 50pF range. Care must be taken when using output
capacitors of 1µF or larger. These application must be thoroughly tested over temperature, line and load. Also, when
the LM4121 is used as a controller, with external active
components, each application must be carefully tested to
ensure a stable design. The adjust pin is sensitive to noise
and capacitive loading. The trace to this pin must be as short
as possible and the feedback resistiors should be close to
this pin. Also, a single point ground to the LM4121 will help
ensure good accuracy at high load currents.
An input capacitor is typically not required. However, a 0.1µF
ceramic can be used to help prevent line transients from
entering the LM4121. Larger input capacitors should be
tantalum or aluminium.
The enable pin is an analog input with very little hysteresis.
About 6µA into this pin is required to turn the part on, and it
must be taken close to GND to turn the part off (see spec.
table for thresholds). There is a
pin of about 0.003V/µS to prevent glitches on the output. All
of these conditions can easily be met with ordinary CMOS or
TTL logic. If the shutdown feature is not required, then this
pin can safely be connected directly to the input supply.
Floating this pin is not recommended.
. The output voltage is set with the two feedback
V
=[V
OUT
typically flows out of the adjust pin. Values for V
bias
are found in the Electrical Characteristics Spec.
bias
REF
(1+ R1/R2] − I
ref
with input voltage, load and output voltage.
minimum
R1
•
bias
slew rate on this
LM4121
DS101291-32
DS101291-43
ref
Printed Circuit Board Layout Consideration
The mechanical stress due to PC board mounting can cause
the output voltage to shift from its initial value. References in
SOT packages are generally less prone to assembly stress
than devices in Small Outline (SOIC) package.
To reduce the stress-related output voltage shifts, mount the
reference on the low flex areas of the PC board such as near
to the edge or the corner of the PC board.
FIGURE 1. Standard Application Circuit
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Typical Application Circuits
LM4121
Voltage Reference with Negative Output
100mA Quasi-LDO Regulator
Voltage Reference with Complimentary Output
DS101291-6
Two Terminal Constant Current Source
DS101291-3
Boosted Output Current with
Negative Voltage Reference
DS101291-7
Precision Voltage Reference
with Force and Sense Output
DS101291-4
DS101291-9
DS101291-5
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LM4121
Typical Application Circuits
(Continued)
Programmable Current Source
DS101291-10
Precision Comparator with Hysteresis
Li + Low Battery Detector
DS101291-44
Flasher Circuit
Power Supply Splitter
DS101291-11
DS101291-45
DS101291-20
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Physical Dimensions inches (millimeters) unless otherwise noted
LM4121 Precision Micropower Low Dropout Voltage Reference
LIFE SUPPORT POLICY
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
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.
National Semiconductor
Europe
Fax: +49 (0) 180-530 85 86
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +44 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
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.
National Semiconductor
Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: ap.support@nsc.com
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Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
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