LM4121
LM4121 Precision Micropower Low Dropout Voltage Reference
Literature Number: SNVS073B
LM4121
Precision Micropower Low Dropout Voltage Reference
General Description
Features (LM4121-1.2)
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.
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This series reference operates with input voltages as low as
1.8V and up to 12V consuming 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.
Small SOT23-5 package
Low voltage operation
High output voltage accuracy:
0.2%
± 5 mA
Source and Sink current output:
Supply current:
160 µA Typ.
Low Temperature Coefficient:
50 ppm/˚C
Enable pin
Output voltages:
1.25V and Adjustable
Industrial temperature Range:
−40˚C to +85˚C
(For extended temperature range, −40˚C to 125˚C,
contact National Semiconductor)
Applications
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Portable, battery powered equipment
Instrumentation and process control
Automotive & Industrial
Test equipment
Data acquisition systems
Precision regulators
Battery chargers
Base stations
Communications
Medical equipment
Block Diagram
10129101
* Resistors are removed on the LM4121-ADJ
†LM4121-ADJ only
LM4121-1.2 Block Diagram
© 2004 National Semiconductor Corporation
DS101291
www.national.com
LM4121 Precision Micropower Low Dropout Voltage Reference
April 2000
LM4121
Connection Diagrams
10129102
10129135
Refer to the Ordering Information Table in this Data Sheet for Specific
Part Number
SOT23-5 Surface Mount Package
Ordering Information
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
LM4121 Supplied as
3000 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%
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Top
Marking
2
Lead Temperature:
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Maximum Voltage on input or
enable pins
−0.3V to 14V
Output Short-Circuit Duration
Indefinite
Power Dissipation
+260˚C
Vapor Phase (60 sec.)
+215˚C
Infrared (15 sec.)
+220˚C
Operating Range (Note 1)
Storage Temperature
Range
−65˚C to +150˚C
350 mW
Ambient Temperature
Range
−40˚C to +85˚C
2 kV
200V
Junction Temperature
Range
−40˚C to +125˚C
Power Dissipation (TA = 25˚C) (Note 2):
MA05B package − θJA
Soldering, (10 sec.)
280˚C/W
ESD Susceptibility (Note 3)
Human Body Model
Machine Model
Electrical Characteristics
LM4121-1.250V Unless otherwise specified VIN = 3.3V, ILOAD = 0, COUT = 0.01µF, TA = Tj = 25˚C. Limits with
standard typeface are for Tj = 25˚C, and limits in boldface type apply over the −40˚C ≤ TA ≤ +85˚C temperature range.
Symbol
VOUT
Parameter
Conditions
Min (Note 5)
Output Voltage Initial
Accuracy
LM4121A-1.250
Typ (Note
4)
Max (Note
5)
1.250
± 0.2
Temperature
Coefficient
−40˚C ≤ TA ≤ +125˚C
∆VOUT/∆VIN
Line Regulation
1.8V ≤ VIN ≤ 12V
Load Regulation
%
± 0.5
LM4121-1.250
TCVOUT/˚C
∆VOUT/∆ILOAD
Units
14
50
ppm/˚c
0.0007
0.009
0.012
%/V
0 mA ≤ ILOAD ≤ 1 mA
0.03
0.08
0.17
1 mA ≤ ILOAD ≤ 5 mA
0.01
0.04
0.1
−1 mA ≤ ILOAD ≤ 0 mA
0.04
0.12
−5 mA ≤ ILOAD ≤ −1 mA
0.01
ILOAD = 5mA
1.5
Min-VIN
Minimum Operating
Voltage
VN
Output Noise Voltage 0.1 Hz to 10 Hz
IS
Supply Current
ISS
Power-down Supply
Current
1.8
20
10 Hz to 10 kHz
VIN = 12V
Enable = 0.4V
Enable = 0.2V
VH
Logic High Input
Voltage
1.6
VL
Logic Low Input
Voltage
0.4
IH
Logic High Input
Current
7
IL
Logic Low Input
Current
0.1
V
µVPP
30
160
%/mA
µVRMS
250
275
µA
1
2
µA
1.5
V
V
0.2
3
15
µA
µA
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LM4121
Absolute Maximum Ratings (Note 1)
LM4121
Electrical Characteristics
LM4121-1.250V Unless otherwise specified VIN = 3.3V, ILOAD = 0, COUT = 0.01µF, TA = Tj = 25˚C. Limits with
standard typeface are for Tj = 25˚C, and limits in boldface type apply over the −40˚C ≤ TA ≤ +85˚C temperature
range. (Continued)
Symbol
Parameter
Conditions
Min (Note 5)
Typ (Note
4)
Max (Note
5)
Units
0.2
VIN = 3.3V, VOUT = 0
15
6
30
mA
ISC
Short Circuit Current
Hyst
Thermal Hysteresis
(Note 8)
−40˚C ≤ TA ≤ 125˚C
0.5
mV/V
∆VOUT
Long Term Stability
(Note 9)
1000 hrs. @ 25˚C
100
ppm
VIN = 12V, VOUT = 0
17
6
30
Electrical Characteristics
LM4121-ADJ Unless otherwise specified VIN = 3.3V, VOUT = VREF, ILOAD = 0, COUT = 0.01µF, TA = Tj = 25˚C. Limits
with standard typeface are for Tj = 25˚C, and limits in boldface type apply over the −40˚C ≤ TA ≤ +85˚C temperature range.
Symbol
VOUT = VREF
Parameter
Conditions
Min (Note 5)
Output Voltage Initial
Accuracy
LM4121A-ADJ
Typ (Note
4)
Max (Note
5)
1.216
± 0.2
Temperature
Coefficient
−40˚C ≤ TA ≤ +125˚C
∆VREF/∆VIN
Line Regulation
1.8V ≤ VIN ≤ 12V
Min-VIN
Load Regulation
Minimum Operating
Voltage
%
± 0.5
LM4121-ADJ
TCVREF/˚C
∆VOUT/∆ILOAD
Units
14
50
ppm/˚c
0.0007
0.009
0.012
%/V
0 mA ≤ ILOAD ≤ 1 mA
0.03
0.08
0.17
1 mA ≤ ILOAD ≤ 5 mA
0.01
0.04
0.1
−1 mA ≤ ILOAD ≤ 0 mA
0.04
0.12
−5 mA ≤ ILOAD ≤ −1 mA
0.01
ILOAD = 5 mA
1.5
1.8
%/mA
V
Output Noise Voltage 0.1 Hz to 10 Hz
(Note 6)
10 Hz to 10 kHz
20
µVPP
30
µVRMS
IS
Supply Current
160
ISS
Power-down Supply
Current
VIN = 12V
Enable = 0.4V
Enable = 0.2V
IBIAS
Reference Pin Bias
Current
(Note 7)
VH
Logic High Input
Voltage
VL
Logic Low Input
Voltage
0.4
Logic High Input
Current
7
VN
IH
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250
275
µA
1
2
µA
15
40
nA
1.6
1.5
V
V
0.2
4
15
µA
with standard typeface are for Tj = 25˚C, and limits in boldface type apply over the −40˚C ≤ TA ≤ +85˚C temperature
range. (Continued)
Symbol
IL
Parameter
Conditions
Min (Note 5)
Typ (Note
4)
Logic Low Input
Current
Max (Note
5)
0.1
VOUT = 0
Units
µA
15
6
30
mA
ISC
Short Circuit Current
Hyst
Thermal Hysteresis
(Note 8)
−40˚C ≤ TA ≤ 125˚C
0.5
mV/V
∆VOUT
Long Term Stability
(Note 9)
1000 hrs. @ 25˚C
100
ppm
VIN = 12V, VOUT = 0
17
6
30
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 TJMAX (maximum
junction temperature), θJ-A (junction to ambient thermal resistance) and TA (ambient temperature). The maximum power dissipation at any temperature is: PDissMAX
= (TJMAX − TA)/θJ-A up to the value listed in the Absolute Maximum Ratings.
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 VOUT.
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 VREF at 25˚C measured continuously during 1000 hrs.
LM4121- (All Options) Typical Operating Characteristics
Unless otherwise specified, VIN = 3.3V, VOUT = 1.25V,
ILOAD = 0, COUT = 0.022µF, TA = 25˚C and VEN = VIN.
Minimum Input Voltage vs Temperature
GND Pin Current vs VIN
10129113
10129112
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LM4121
Electrical Characteristics
LM4121-ADJ Unless otherwise specified VIN = 3.3V, VOUT = VREF, ILOAD = 0, COUT = 0.01µF, TA = Tj = 25˚C. Limits
LM4121
LM4121- (All Options) Typical Operating Characteristics
Unless otherwise specified,
VIN = 3.3V, VOUT = 1.25V, ILOAD = 0, COUT = 0.022µF, TA = 25˚C and VEN = VIN. (Continued)
GND Pin Current at No Load
vs Temperature
GND Pin Current vs Load
10129115
10129114
Short Circuit vs Temperature
Output Impedance vs Frequency
10129133
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10129117
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Unless otherwise specified,
PSRR vs Frequency
Enable Pin Current
10129119
10129118
Start-Up Response
Enable Response
10129121
10129122
Load Step Response
Load Step Response
10129123
10129124
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LM4121
LM4121- (All Options) Typical Operating Characteristics
VIN = 3.3V, VOUT = 1.25V, ILOAD = 0, COUT = 0.022µF, TA = 25˚C and VEN = VIN. (Continued)
LM4121
LM4121- (All Options) Typical Operating Characteristics
Unless otherwise specified,
VIN = 3.3V, VOUT = 1.25V, ILOAD = 0, COUT = 0.022µF, TA = 25˚C and VEN = VIN. (Continued)
Line Step Response
Noise Spectural Density (0.1Hz-10Hz)
10129125
10129126
Noise Spectural Density (10Hz-10kHz)
Thermal Hysteresis
10129127
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10129146
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LM4121
LM4121-1.25 Typical Operating Characteristics
Unless otherwise specified, VIN = 3.3V, VOUT = 1.25V,
ILOAD = 0, COUT = 0.022µF, TA = 25˚C and VEN = VIN.
Typical Temperature Drift
Long Term Drift
10129128
10129129
Line Regulation
Load Regulation
10129130
10129131
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LM4121
LM4121-ADJ Typical Operating Characteristics
Unless otherwise specified, VIN = 3.3V, VOUT = 1.2V,
ILOAD = 0, COUT = 0.022µF, TA = 25˚C and VEN = VIN.
Typical Temperature Drift
Long Term Drift
10129116
10129136
Dropout Voltage vs Output Error
Dropout Voltage vs Load Current
10129148
10129147
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= 1.2V, ILOAD = 0, COUT = 0.022µF, TA = 25˚C and VEN = VIN. (Continued)
Line Regulation
Load Regulation
10129138
10129137
Adjust Pin Bias Current
Change In Reference Voltage vs Output Voltage
10129139
10129140
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LM4121
LM4121-ADJ Typical Operating Characteristics Unless otherwise specified, VIN = 3.3V, VOUT
LM4121
LM4121-ADJ Typical Operating Characteristics Unless otherwise specified, VIN = 3.3V, VOUT
= 1.2V, ILOAD = 0, COUT = 0.022µF, TA = 25˚C and VEN = VIN. (Continued)
Bode Plot
Bode Plot
10129142
10129141
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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):VOUT Adj Pin (Adjustable option only). See Application Hints section.
Application Hints
The standard application circuit for the LM4121 is shown in
Figure 1. The output voltage is set with the two feedback
resistors, according to the following formula:
VOUT = [Vref(1+ R1/R2] − Ibias • R1
10129132
Values for R1 and R2 should be chosen to be less than 1
MΩ. Ibias typically flows out of the adjust pin. Values for Vref
and Ibias are found in the Electrical Characteristics Spec.
table. For best accuracy, be sure to take into account the
variation of VREF with input voltage, load and output voltage.
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.
10129143
FIGURE 1. Standard Application Circuit
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.
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LM4121
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 minimum slew rate on this
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.
Pin Functions
LM4121
Typical Application Circuits
Voltage Reference with Complimentary Output
Voltage Reference with Negative Output
10129106
Two Terminal Constant Current Source
10129103
100mA Quasi-LDO Regulator
10129107
Precision Voltage Reference
with Force and Sense Output
10129104
Boosted Output Current with
Negative Voltage Reference
10129109
Programmable Current Source
10129105
10129110
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LM4121
Typical Application Circuits
Flasher Circuit
(Continued)
Precision Comparator with Hysteresis
10129111
10129145
Power Supply Splitter
10129120
Li + Low Battery Detector
10129144
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LM4121 Precision Micropower Low Dropout Voltage Reference
Physical Dimensions
inches (millimeters)
unless otherwise noted
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.
For the most current product information visit us at www.national.com.
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