LM4128
LM4128/LM4128Q SOT-23 Precision Micropower Series Voltage Reference
Literature Number: SNVS475D
LM4128/LM4128Q
February 23, 2009
SOT-23 Precision Micropower Series Voltage Reference
General Description
Ideal for space critical applications, the LM4128 precision
voltage reference is available in the SOT-23 surface-mount
package. The LM4128’s advanced design eliminates the
need for an external stabilizing capacitor while ensuring sta-
bility with capacitive loads up to 10 µF, thus making the
LM4128 easy to use.
Series references provide lower power consumption than
shunt references, since they do not have to idle the maximum
possible load current under no load conditions. This advan-
tage, the low quiescent current (60 µA), and the low dropout
voltage (400 mV) make the LM4128 ideal for battery-powered
solutions.
The LM4128 is available in four grades (A, B, C, and D) for
greater flexibility. The best grade devices (A) have an initial
accuracy of 0.1% with guaranteed temperature coefficient of
75 ppm/°C or less, while the lowest grade parts (D) have an
initial accuracy of 1.0% and a tempco of 100 ppm/°C.
Features
■Output voltage initial accuracy 0.1%
■Low temperature coefficient 75 ppm/°C
■Low Supply Current, 60 µA
■Enable pin allowing a 3 µA shutdown mode
■Up to 20 mA output current
■Voltage options 1.8V, 2.048V, 2.5V, 3.0V, 3.3V, 4.096V
■Custom voltage options available (1.8V to 4.096V)
■VIN range of VREF + 400 mV to 5.5V @10 mA
■Stable with low ESR ceramic capacitors
■SOT23-5 Package
■−40°C to 125°C junction temperature range
■LM4128AQ/BQ/CQ/DQ are AEC-Q100 Grade 1 qualified
and are manufactured on an Automotive Grade Flow
Applications
■Instrumentation & Process Control
■Test Equipment
■Data Acquisition Systems
■Base Stations
■Servo Systems
■Portable, Battery Powered Equipment
■Automotive & Industrial Electronics
■Precision Regulators
■Battery Chargers
■Communications
■Medical Equipment
Typical Application Circuit
20211001
*Note: The capacitor CIN is required and the capacitor COUT is optional.
© 2009 National Semiconductor Corporation 202110 www.national.com
LM4128/LM4128Q SOT-23 Precision Micropower Series Voltage Reference
Connection Diagram
Top View
20211002
SOT23-5 Package
NS Package Number MF05A
Ordering Information
Input Output Voltage
Accuracy at 25°C And
Temperature Coefficient
LM4128 Supplied as
1000 units, Tape and
Reel
LM4128 Supplied as
3000 units, Tape and
Reel
Part Marking Feature
0.1%, 75 ppm/°C (A grade)
LM4128AMF-1.8 LM4128AMFX-1.8 R5AA
LM4128AMF-2.0 LM4128AMFX-2.0 R5BA
LM4128AMF-2.5 LM4128AMFX-2.5 R5CA
LM4128AMF-3.0 LM4128AMFX-3.0 R5DA
LM4128AMF-3.3 LM4128AMFX-3.3 R5EA
LM4128AMF-4.1 LM4128AMFX-4.1 R5FA
0.2%, 75 ppm/°C (B grade)
LM4128BMF-1.8 LM4128BMFX-1.8 R5AB
LM4128BMF-2.0 LM4128BMFX-2.0 R5BB
LM4128BMF-2.5 LM4128BMFX-2.5 R5CB
LM4128BMF-3.0 LM4128BMFX-3.0 R5DB
LM4128BMF-3.3 LM4128BMFX-3.3 R5EB
LM4128BMF-4.1 LM4128BMFX-4.1 R5FB
0.5%, 100 ppm/°C (C grade)
LM4128CMF-1.8 LM4128CMFX-1.8 R5AC
LM4128CMF-2.0 LM4128CMFX-2.0 R5BC
LM4128CMF-2.5 LM4128CMFX-2.5 R5CC
LM4128CMF-3.0 LM4128CMFX-3.0 R5DC
LM4128CMF-3.3 LM4128CMFX-3.3 R5EC
LM4128CMF-4.1 LM4128CMFX-4.1 R5FC
1.0%, 100 ppm/°C max
(D grade)
LM4128DMF-1.8 LM4128DMFX-1.8 R5AD
LM4128DMF-2.0 LM4128DMFX-2.0 R5BD
LM4128DMF-2.5 LM4128DMFX-2.5 R5CD
LM4128DMF-3.0 LM4128DMFX-3.0 R5DD
LM4128DMF-3.3 LM4128DMFX-3.3 R5ED
LM4128DMF-4.1 LM4128DMFX-4.1 R5FD
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LM4128/LM4128Q
Input Output Voltage
Accuracy at 25°C And
Temperature Coefficient
LM4128 Supplied as
1000 units, Tape and
Reel
LM4128 Supplied as
3000 units, Tape and
Reel
Part Marking Feature
0.1%, 75 ppm/°C
(AQ grade)
LM4128AQ1MF1.8 LM4128AQ1MFX1.8 R6AA AEC-Q100 Grade 1
qualified. Automotive
Grade Production Flow*
LM4128AQ1MF2.0 LM4128AQ1MFX2.0 R6BA
LM4128AQ1MF2.5 LM4128AQ1MFX2.5 R6CA
LM4128AQ1MF3.0 LM4128AQ1MFX3.0 R6DA
LM4128AQ1MF3.3 LM4128AQ1MFX3.3 R6EA
LM4128AQ1MF4.1 LM4128AQ1MFX4.1 R6FA
0.2%, 75 ppm/°C
(BQ grade)
LM4128BQ1MF1.8 LM4128BQ1MFX1.8 R6AB AEC-Q100 Grade 1
qualified. Automotive
Grade Production Flow*
LM4128BQ1MF2.0 LM4128BQ1MFX2.0 R6BB
LM4128BQ1MF2.5 LM4128BQ1MFX2.5 R6CB
LM4128BQ1MF3.0 LM4128BQ1MFX3.0 R6DB
LM4128BQ1MF3.3 LM4128BQ1MFX3.3 R6EB
LM4128BQ1MF4.1 LM4128BQ1MFX4.1 R6FB
0.5%, 100 ppm/°C
(CQ grade)
LM4128CQ1MF1.8 LM4128CQ1MFX1.8 R6AC AEC-Q100 Grade 1
qualified. Automotive
Grade Production Flow*
LM4128CQ1MF2.0 LM4128CQ1MFX2.0 R6BC
LM4128CQ1MF2.5 LM4128CQ1MFX2.5 R6CC
LM4128CQ1MF3.0 LM4128CQ1MFX3.0 R6DC
LM4128CQ1MF3.3 LM4128CQ1MFX3.3 R6EC
LM4128CQ1MF4.1 LM4128CQ1MFX4.1 R6FC
1.0%, 100 ppm/°C max
(DQ grade)
LM4128DQ1MF1.8 LM4128DQ1MFX1.8 R6AD AEC-Q100 Grade 1
qualified. Automotive
Grade Production Flow*
LM4128DQ1MF2.0 LM4128DQ1MFX2.0 R6BD
LM4128DQ1MF2.5 LM4128DQ1MFX2.5 R6CD
LM4128DQ1MF3.0 LM4128DQ1MFX3.0 R6DD
LM4128DQ1MF3.3 LM4128DQ1MFX3.3 R6ED
LM4128DQ1MF4.1 LM4128DQ1MFX4.1 R6FD
*Automotive Grade (Q) product incorporates enhanced manufacturing and support processes for the automotive market, including defect detection methodologies.
Reliability qualification is compliant with the requirements and temperature grades defined in the AEC-Q100 standard. Automotive grade products are identified
with the letter Q. For more information go to http://www.national.com/automotive.
Pin Descriptions
Pin # Name Function
1 N/C No connect pin, leave floating
2 GND Ground
3 EN Enable pin
4 VIN Input supply
5 VREF Reference output
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LM4128/LM4128Q
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Maximum Voltage on any input -0.3 to 6V
Output short circuit duration Indefinite
Power Dissipation (TA = 25°C)
(Note 2) 350 mW
Storage Temperature Range −65°C to 150°C
Lead Temperature (soldering, 10sec) 260°C
Vapor Phase (60 sec) 215°C
Infrared (15sec) 220°C
ESD Susceptibility (Note 3)
Human Body Model 2 kV
Operating Ratings
Maximum Input Supply Voltage 5.5V
Maximum Enable Input Voltage VIN
Maximum Load Current 20mA
Junction Temperature Range (TJ) −40°C to
+125°C
Electrical Characteristics
LM4128-1.8 (VOUT = 1.8V) Limits in standard type are for TJ = 25°C only, and limits in boldface type apply over
the junction temperature (TJ) range of -40°C to +125°C unless otherwise specified. Minimum and Maximum limits are guaranteed
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. Unless otherwise specified VIN = 5V and ILOAD = 0A.
Symbol Parameter Conditions Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Unit
VREF Output Voltage Initial Accuracy
LM4128A-1.8 (A Grade - 0.1%) -0.1 +0.1 %
LM4128B-1.8 (B Grade - 0.2%) -0.2 +0.2
LM4128C-1.8 (C Grade - 0.5%) -0.5 +0.5
LM4128D-1.8 (D Grade - 1.0%) -1.0 +1.0
TCVREF / °C (Note
6)
Temperature Coefficient LM4128A-1.8 75
ppm / °C
LM4128B-1.8 75
LM4128C-1.8 100
LM4128D-1.8 100
IQSupply Current 60 100 µA
IQ_SD Supply Current in Shutdown EN = 0V 3 7µA
ΔVREF/ΔVIN Line Regulation VREF + 400 mV ≤ VIN ≤ 5.5V 30 ppm / V
ΔVREF/ΔILOAD Load Regulation 0 mA ≤ ILOAD ≤ 20 mA 25 120 ppm / mA
ΔVREF Long Term Stability (Note 7) 1000 Hrs 50 ppm
Thermal Hysteresis (Note 8) -40°C ≤ TJ ≤ +125°C 75
VIN - VREF Dropout Voltage (Note 9) ILOAD = 10 mA 200 400 mV
VNOutput Noise Voltage 0.1 Hz to 10 Hz 170 µVPP
ISC Short Circuit Current 75 mA
VIL Enable Pin Maximum Low Input Level 35 %V
VIH Enable Pin Minimum High Input Level 65 %V
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LM4128/LM4128Q
Electrical Characteristics
LM4128-2.0 (VOUT = 2.048V) Limits in standard type are for TJ = 25°C only, and limits in boldface type apply
over the junction temperature (TJ) range of -40°C to +125°C unless otherwise specified. Minimum and Maximum limits are
guaranteed 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. Unless otherwise specified VIN = 5V and ILOAD = 0A.
Symbol Parameter Conditions Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Unit
VREF Output Voltage Initial Accuracy
LM4128A-2.0 (A Grade - 0.1%) -0.1 +0.1 %
LM4128B-2.0 (B Grade - 0.2%) -0.2 +0.2
LM4128C-2.0 (C Grade - 0.5%) -0.5 +0.5
LM4128D-2.0 (D Grade - 1.0%) -1.0 +1.0
TCVREF / °C (Note
6)
Temperature Coefficient LM4128A-2.0 75
ppm / °C
LM4128B-2.0 75
LM4128C-2.0 100
LM4128D-2.0 100
IQSupply Current 60 100 µA
IQ_SD Supply Current in Shutdown EN = 0V 3 7µA
ΔVREF/ΔVIN Line Regulation VREF + 400 mV ≤ VIN ≤ 5.5V 30 ppm / V
ΔVREF/ΔILOAD Load Regulation 0 mA ≤ ILOAD ≤ 20 mA 25 120 ppm / mA
ΔVREF Long Term Stability (Note 7) 1000 Hrs 50 ppm
Thermal Hysteresis (Note 8) -40°C ≤ TJ ≤ +125°C 75
VIN - VREF Dropout Voltage (Note 9) ILOAD = 10 mA 175 400 mV
VNOutput Noise Voltage 0.1 Hz to 10 Hz 190 µVPP
ISC Short Circuit Current 75 mA
VIL Enable Pin Maximum Low Input Level 35 %V
VIH Enable Pin Minimum High Input Level 65 %V
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LM4128/LM4128Q
Electrical Characteristics
LM4128-2.5 (VOUT = 2.5V) Limits in standard type are for TJ = 25°C only, and limits in boldface type apply over
the junction temperature (TJ) range of -40°C to +125°C unless otherwise specified. Minimum and Maximum limits are guaranteed
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. Unless otherwise specified VIN = 5V and ILOAD = 0A.
Symbol Parameter Conditions Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Unit
VREF Output Voltage Initial Accuracy
LM4128A-2.5 (A Grade - 0.1%) -0.1 +0.1 %
LM4128B-2.5 (B Grade - 0.2%) -0.2 +0.2
LM4128C-2.5 (C Grade - 0.5%) -0.5 +0.5
LM4128D-2.5 (D Grade - 1.0%) -1.0 +1.0
TCVREF / °C (Note
6)
Temperature Coefficient LM4128A-2.5 75
ppm / °C
LM4128B-2.5 75
LM4128C-2.5 100
LM4128D-2.5 100
IQSupply Current 60 100 µA
IQ_SD Supply Current in Shutdown EN = 0V 3 7µA
ΔVREF/ΔVIN Line Regulation VREF + 400 mV ≤ VIN ≤ 5.5V 50 ppm / V
ΔVREF/ΔILOAD Load Regulation 0 mA ≤ ILOAD ≤ 20 mA 25 120 ppm / mA
ΔVREF Long Term Stability (Note 7) 1000 Hrs 50 ppm
Thermal Hysteresis (Note 8) -40°C ≤ TJ ≤ +125°C 75
VIN - VREF Dropout Voltage (Note 9) ILOAD = 10 mA 175 400 mV
VNOutput Noise Voltage 0.1 Hz to 10 Hz 275 µVPP
ISC Short Circuit Current 75 mA
VIL Enable Pin Maximum Low Input Level 35 %V
VIH Enable Pin Minimum High Input Level 65 %V
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LM4128/LM4128Q
Electrical Characteristics
LM4128-3.0 (VOUT = 3.0V) Limits in standard type are for TJ = 25°C only, and limits in boldface type apply over
the junction temperature (TJ) range of -40°C to +125°C unless otherwise specified. Minimum and Maximum limits are guaranteed
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. Unless otherwise specified VIN = 5V and ILOAD = 0A.
Symbol Parameter Conditions Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Unit
VREF Output Voltage Initial Accuracy
LM4128A-3.0 (A Grade - 0.1%) -0.1 +0.1 %
LM4128B-3.0 (B Grade - 0.2%) -0.2 +0.2
LM4128C-3.0 (C Grade - 0.5%) -0.5 +0.5
LM4128D-3.0 (D Grade - 1.0%) -1.0 +1.0
TCVREF / °C (Note
6)
Temperature Coefficient LM4128A-3.0 75
ppm / °C
LM4128B-3.0 75
LM4128C-3.0 100
LM4128D-3.0 100
IQSupply Current 60 100 µA
IQ_SD Supply Current in Shutdown EN = 0V 3 7µA
ΔVREF/ΔVIN Line Regulation VREF + 400 mV ≤ VIN ≤ 5.5V 70 ppm / V
ΔVREF/ΔILOAD Load Regulation 0 mA ≤ ILOAD ≤ 20 mA 25 120 ppm / mA
ΔVREF Long Term Stability (Note 7) 1000 Hrs 50 ppm
Thermal Hysteresis (Note 8) -40°C ≤ TJ ≤ +125°C 75
VIN - VREF Dropout Voltage (Note 9) ILOAD = 10 mA 175 400 mV
VNOutput Noise Voltage 0.1 Hz to 10 Hz 285 µVPP
ISC Short Circuit Current 75 mA
VIL Enable Pin Maximum Low Input Level 35 %V
VIH Enable Pin Minimum High Input Level 65 %V
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LM4128/LM4128Q
Electrical Characteristics
LM4128-3.3 (VOUT = 3.3V) Limits in standard type are for TJ = 25°C only, and limits in boldface type apply over
the junction temperature (TJ) range of -40°C to +125°C unless otherwise specified. Minimum and Maximum limits are guaranteed
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. Unless otherwise specified VIN = 5V and ILOAD = 0A.
Symbol Parameter Conditions Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Unit
VREF Output Voltage Initial Accuracy
LM4128A-3.3 (A Grade - 0.1%) -0.1 +0.1 %
LM4128B-3.3 (B Grade - 0.2%) -0.2 +0.2
LM4128C-3.3 (C Grade - 0.5%) -0.5 +0.5
LM4128D-3.3 (D Grade - 1.0%) -1.0 +1.0
TCVREF / °C (Note
6)
Temperature Coefficient LM4128A-3.3 75
ppm / °C
LM4128B-3.3 75
LM4128C-3.3 100
LM4128D-3.3 100
IQSupply Current 60 100 µA
IQ_SD Supply Current in Shutdown EN = 0V 3 7µA
ΔVREF/ΔVIN Line Regulation VREF + 400 mV ≤ VIN ≤ 5.5V 85 ppm / V
ΔVREF/ΔILOAD Load Regulation 0 mA ≤ ILOAD ≤ 20 mA 25 120 ppm / mA
ΔVREF Long Term Stability (Note 7) 1000 Hrs 50 ppm
Thermal Hysteresis (Note 8) -40°C ≤ TJ ≤ +125°C 75
VIN - VREF Dropout Voltage (Note 9) ILOAD = 10 mA 175 400 mV
VNOutput Noise Voltage 0.1 Hz to 10 Hz 310 µVPP
ISC Short Circuit Current 75 mA
VIL Enable Pin Maximum Low Input Level 35 %V
VIH Enable Pin Minimum High Input Level 65 %V
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LM4128/LM4128Q
Electrical Characteristics
LM4128-4.1 (VOUT = 4.096V) Limits in standard type are for TJ = 25°C only, and limits in boldface type apply
over the junction temperature (TJ) range of -40°C to +125°C unless otherwise specified. Minimum and Maximum limits are
guaranteed 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. Unless otherwise specified VIN = 5V and ILOAD = 0A.
Symbol Parameter Conditions Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Unit
VREF Output Voltage Initial Accuracy
LM4128A-4.1 (A Grade - 0.1%) -0.1 +0.1 %
LM4128B-4.1 (B Grade - 0.2%) -0.2 +0.2
LM4128C-4.1 (C Grade - 0.5%) -0.5 +0.5
LM4128D-4.1 (D Grade - 1.0%) -1.0 +1.0
TCVREF / °C (Note
6)
Temperature Coefficient LM4128A-4.1 75
ppm / °C
LM4128B-4.1 75
LM4128C-4.1 100
LM4128D-4.1 100
IQSupply Current 60 100 µA
IQ_SD Supply Current in Shutdown EN = 0V 3 7µA
ΔVREF/ΔVIN Line Regulation VREF + 400 mV ≤ VIN ≤ 5.5V 100 ppm / V
ΔVREF/ΔILOAD Load Regulation 0 mA ≤ ILOAD ≤ 20 mA 25 120 ppm / mA
ΔVREF Long Term Stability (Note 7) 1000 Hrs 50 ppm
Thermal Hysteresis (Note 8) -40°C ≤ TJ ≤ +125°C 75
VIN - VREF Dropout Voltage (Note 9) ILOAD = 10 mA 175 400 mV
VNOutput Noise Voltage 0.1 Hz to 10 Hz 350 µVPP
ISC Short Circuit Current 75 mA
VIL Enable Pin Maximum Low Input Level 35 %V
VIH Enable Pin Minimum High Input Level 65 %V
Note 1: Absolute Maximum Ratings indicate limits beyond which damage may occur to the device. Operating Ratings indicate conditions for which the device is
intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications, see Electrical Characteristics.
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. θJ-A for SOT23-5 package is 220°C/W, TJMAX = 125°C.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 4: Limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality
Control.
Note 5: Typical numbers are at 25°C and represent the most likely parametric norm.
Note 6: Temperature coefficient is measured by the "Box" method; i.e., the maximum ΔVREF is divided by the maximum ΔT.
Note 7: Long term stability is VREF @25°C measured during 1000 hrs.
Note 8: Thermal hysteresis is defined as the change in +25°C output voltage before and after cycling the device from (-40°C to 125°C).
Note 9: Dropout voltage is defined as the minimum input to output differential at which the output voltage drops by 0.5% below the value measured with a 5V
input.
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LM4128/LM4128Q
Typical Performance Characteristics for 2.5V
Output Voltage vs Temperature
20211054
Load Regulation
20211055
Line Regulation
20211056
0.1 - 10 Hz Noise
20211021
Output Voltage Noise Spectrum
20211057
Power Supply Rejection Ratio vs Frequency
20211058
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LM4128/LM4128Q
Dropout vs Load to 0.5% Accuracy
20211008
Typical Long Term Stability
20211030
Supply Current vs Input Voltage
20211053
Shutdown IQ vs Input Voltage
20211010
Ground Current vs Load Current
20211018
Line Transient Response
VIN = 3V to 5V
20211051
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LM4128/LM4128Q
Load Transient Response
ILOAD = 0 to 10mA
20211050
Short-Circuit Protection and Recovery
20211082
Start-Up Response
20211083
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LM4128/LM4128Q
Application Information
THEORY OF OPERATION
The foundation of any voltage reference is the band-gap cir-
cuit. While the reference in the LM4128 is developed from the
gate-source voltage of transistors in the IC, principles of the
band-gap circuit are easily understood using a bipolar exam-
ple. For a detailed analysis of the bipolar band-gap circuit,
please refer to Application Note AN-56.
SUPPLY AND ENABLE VOLTAGES
To ensure proper operation, VEN and VIN must be within a
specified range. An acceptable range of input voltages is
VIN > VREF + 400 mV (ILOAD ≤ 10 mA)
The enable pin uses an internal pull-up current source
(IPULL_UP ≊ 2 µA) that may be left floating or triggered by an
external source. If the part is not enabled by an external
source, it may be connected to VIN. An acceptable range of
enable voltages is given by the enable transfer characteris-
tics. See the Electrical Characteristics section and Enable
Transfer Characteristics figure for more detail. Note, the part
will not operate correctly for VEN > VIN.
COMPONENT SELECTION
A small ceramic (X5R or X7R) capacitor on the input must be
used to ensure stable operation. The value of CIN must be
sized according to the output capacitor value. The value of
CIN must satisfy the relationship CIN ≥ COUT. When no output
capacitor is used, CIN must have a minimum value of 0.1 µF.
Noise on the power-supply input may affect the output noise.
Larger input capacitor values (typically 4.7 µF to 22 µF) may
help reduce noise on the output and significantly reduce over-
shoot during startup. Use of an additional optional bypass
capacitor between the input and ground may help further re-
duce noise on the output. With an input capacitor, the LM4128
will drive any combination of resistance and capacitance up
to VREF/20 mA and 10 µF respectively.
The LM4128 is designed to operate with or without an output
capacitor and is stable with capacitive loads up to 10 µF.
Connecting a capacitor between the output and ground will
significantly improve the load transient response when
switching from a light load to a heavy load. The output ca-
pacitor should not be made arbitrarily large because it will
effect the turn-on time as well as line and load transients.
While a variety of capacitor chemistry types may be used, it
is typically advisable to use low esr ceramic capacitors. Such
capacitors provide a low impedance to high frequency sig-
nals, effectively bypassing them to ground. Bypass capacitors
should be mounted close to the part. Mounting bypass ca-
pacitors close to the part will help reduce the parasitic trace
components thereby improving performance.
SHORT CIRCUITED OUTPUT
The LM4128 features indefinite short circuit protection. This
protection limits the output current to 75 mA when the output
is shorted to ground.
TURN ON TIME
Turn on time is defined as the time taken for the output voltage
to rise to 90% of the preset value. The turn on time depends
on the load. The turn on time is typically 33.2 µs when driving
a 1µF load and 78.8 µs when driving a 10 µF load. Some users
may experience an extended turn on time (up to 10 ms) under
brown out conditions and low temperatures (-40°C).
THERMAL HYSTERESIS
Thermal hysteresis is defined as the change in output voltage
at 25ºC after some deviation from 25ºC. This is to say that
thermal hysteresis is the difference in output voltage between
two points in a given temperature profile. An illustrative tem-
perature profile is shown in Figure 1.
20211038
FIGURE 1. Illustrative Temperature Profile
This may be expressed analytically as the following:
Where
VHYS = Thermal hysteresis expressed in ppm
VREF = Nominal preset output voltage
VREF1 = VREF before temperature fluctuation
VREF2 = VREF after temperature fluctuation.
The LM4128 features a low thermal hysteresis of 190 µV from
-40°C to 125°C.
TEMPERATURE COEFFICIENT
Temperature drift is defined as the maximum deviation in out-
put voltage over the operating temperature range. This devi-
ation over temperature may be illustrated as shown in Figure
2.
20211039
FIGURE 2. Illustrative Temperature Coefficient Profile
Temperature coefficient may be expressed analytically as the
following:
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LM4128/LM4128Q
TD = Temperature drift
VREF = Nominal preset output voltage
VREF_MIN = Minimum output voltage over operating
temperature range
VREF_MAX = Maximum output voltage over operating
temperature range
ΔT = Operating temperature range.
The LM4128 features a low temperature drift of 75 ppm (max)
to 100 ppm (max), depending on the grade, from -40°C to
125°C.
LONG TERM STABILITY
Long-term stability refers to the fluctuation in output voltage
over a long period of time (1000 hours). The LM4128 features
a typical long-term stability of 50 ppm over 1000 hours. The
measurements are made using 5 units of each voltage option,
at a nominal input voltage (5V), with no load, at room tem-
perature.
EXPRESSION OF ELECTRICAL CHARACTERISTICS
Electrical characteristics are typically expressed in mV, ppm,
or a percentage of the nominal value. Depending on the ap-
plication, one expression may be more useful than the other.
To convert one quantity to the other one may apply the fol-
lowing:
ppm to mV error in output voltage:
Where:
VREF is in volts (V) and VERROR is in milli-volts (mV).
Bit error (1 bit) to voltage error (mV):
VREF is in volts (V), VERROR is in milli-volts (mV), and n is the
number of bits.
mV to ppm error in output voltage:
Where:
VREF is in volts (V) and VERROR is in milli-volts (mV).
Voltage error (mV) to percentage error (percent):
Where:
VREF is in volts (V) and VERROR is in milli-volts (mV).
PRINTED CIRCUIT BOARD and LAYOUT
CONSIDERATIONS
References in SOT packages are generally less prone to PC
board mounting than devices in Small Outline (SOIC) pack-
ages. To minimize the mechanical stress due to PC board
mounting that can cause the output voltage to shift from its
initial value, mount the reference on a low flex area of the PC
board, such as near the edge or a corner.
The part may be isolated mechanically by cutting a U shape
slot on the PCB for mounting the device. This approach also
provides some thermal isolation from the rest of the circuit.
Bypass capacitors must be mounted close to the part. Mount-
ing bypass capacitors close to the part will reduce the para-
sitic trace components thereby improving performance.
www.national.com 14
LM4128/LM4128Q
Typical Application Circuits
20211026
FIGURE 3. Voltage Reference with Complimentary Output
20211027
FIGURE 4. Precision Voltage Reference with Force and Sense Output
20211028
FIGURE 5. Programmable Current Source
15 www.national.com
LM4128/LM4128Q
Physical Dimensions inches (millimeters) unless otherwise noted
SOT23-5 Package
NS Package Number MF05A
www.national.com 16
LM4128/LM4128Q
Notes
17 www.national.com
LM4128/LM4128Q
Notes
LM4128/LM4128Q SOT-23 Precision Micropower Series Voltage Reference
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