LM4128/LM4128Q
SOT-23 Precision Micropower Series Voltage Reference
General Description
Features
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 stability 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 advantage, 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.
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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
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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.
© 2008 National Semiconductor Corporation
202110
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LM4128/LM4128Q SOT-23 Precision Micropower Series Voltage Reference
October 23, 2008
LM4128/LM4128Q
Connection Diagram
Top View
20211002
SOT23-5 Package
NS Package Number MF05A
Ordering Information
Input Output Voltage
Accuracy at 25°C And
Temperature Coefficient
0.1%, 75 ppm/°C (A grade)
0.2%, 75 ppm/°C (B grade)
0.5%, 100 ppm/°C (C grade)
1.0%, 100 ppm/°C max
(D grade)
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LM4128 Supplied as
1000 units, Tape and
Reel
LM4128 Supplied as
3000 units, Tape and
Reel
Part Marking
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
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
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
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
2
Feature
0.1%, 75 ppm/°C
(AQ grade)
0.2%, 75 ppm/°C
(BQ grade)
0.5%, 100 ppm/°C
(CQ grade)
1.0%, 100 ppm/°C max
(DQ grade)
LM4128 Supplied as
1000 units, Tape and
Reel
LM4128 Supplied as
3000 units, Tape and
Reel
Part Marking
Feature
LM4128AQ1MF1.8
LM4128AQ1MFX1.8
R6AA
LM4128AQ1MF2.0
LM4128AQ1MFX2.0
R6BA
LM4128AQ1MF2.5
LM4128AQ1MFX2.5
R6CA
AEC-Q100 Grade 1
qualified. Automotive
Grade Production Flow*
LM4128AQ1MF3.0
LM4128AQ1MFX3.0
R6DA
LM4128AQ1MF3.3
LM4128AQ1MFX3.3
R6EA
LM4128AQ1MF4.1
LM4128AQ1MFX4.1
R6FA
LM4128BQ1MF1.8
LM4128BQ1MFX1.8
R6AB
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
LM4128CQ1MF1.8
LM4128CQ1MFX1.8
R6AC
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
LM4128DQ1MF1.8
LM4128DQ1MFX1.8
R6AD
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
AEC-Q100 Grade 1
qualified. Automotive
Grade Production Flow*
AEC-Q100 Grade 1
qualified. Automotive
Grade Production Flow*
AEC-Q100 Grade 1
qualified. Automotive
Grade Production Flow*
*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
3
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LM4128/LM4128Q
Input Output Voltage
Accuracy at 25°C And
Temperature Coefficient
LM4128/LM4128Q
Vapor Phase (60 sec)
Infrared (15sec)
ESD Susceptibility (Note 3)
Human Body Model
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
Output short circuit duration
Power Dissipation (TA = 25°C)
(Note 2)
Storage Temperature Range
-0.3 to 6V
Indefinite
Maximum Input Supply Voltage
Maximum Enable Input Voltage
Maximum Load Current
Junction Temperature Range (TJ)
350 mW
−65°C to 150°C
(soldering, 10sec)
2 kV
Operating Ratings
Lead Temperature
215°C
220°C
5.5V
VIN
20mA
−40°C to
+125°C
260°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
VREF
Parameter
Min
Typ
Max
(Note 4) (Note 5) (Note 4)
Unit
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 Temperature Coefficient
6)
IQ
Conditions
LM4128A-1.8
%
75
LM4128B-1.8
75
LM4128C-1.8
100
LM4128D-1.8
100
60
100
µA
Supply Current in Shutdown
EN = 0V
3
7
µA
ΔVREF/ΔVIN
Line Regulation
VREF + 400 mV ≤ VIN ≤ 5.5V
30
ΔVREF/ΔILOAD
Load Regulation
0 mA ≤ ILOAD ≤ 20 mA
25
Long Term Stability (Note 7)
1000 Hrs
50
Thermal Hysteresis (Note 8)
-40°C ≤ TJ ≤ +125°C
75
IQ_SD
ΔVREF
VIN - VREF
Supply Current
ppm / °C
ppm / V
120
ppm / mA
ppm
Dropout Voltage (Note 9)
ILOAD = 10 mA
200
VN
Output Noise Voltage
0.1 Hz to 10 Hz
170
ISC
Short Circuit Current
75
mA
VIL
Enable Pin Maximum Low Input Level
35
%V
VIH
Enable Pin Minimum High Input Level
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65
4
400
mV
µVPP
%V
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
VREF
Parameter
Min
Typ
Max
(Note 4) (Note 5) (Note 4)
Unit
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 Temperature Coefficient
6)
IQ
Conditions
LM4128A-2.0
%
75
LM4128B-2.0
75
LM4128C-2.0
100
LM4128D-2.0
100
60
100
µA
Supply Current in Shutdown
EN = 0V
3
7
µA
ΔVREF/ΔVIN
Line Regulation
VREF + 400 mV ≤ VIN ≤ 5.5V
30
ΔVREF/ΔILOAD
Load Regulation
0 mA ≤ ILOAD ≤ 20 mA
25
Long Term Stability (Note 7)
1000 Hrs
50
Thermal Hysteresis (Note 8)
-40°C ≤ TJ ≤ +125°C
75
IQ_SD
ΔVREF
VIN - VREF
Supply Current
ppm / °C
ppm / V
120
ppm / mA
ppm
Dropout Voltage (Note 9)
ILOAD = 10 mA
175
VN
Output Noise Voltage
0.1 Hz to 10 Hz
190
ISC
Short Circuit Current
75
mA
VIL
Enable Pin Maximum Low Input Level
35
%V
VIH
Enable Pin Minimum High Input Level
65
5
400
mV
µVPP
%V
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LM4128/LM4128Q
Electrical Characteristics
LM4128-2.0 (VOUT = 2.048V)
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
VREF
Parameter
Min
Typ
Max
(Note 4) (Note 5) (Note 4)
Unit
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 Temperature Coefficient
6)
IQ
Conditions
LM4128A-2.5
%
75
LM4128B-2.5
75
LM4128C-2.5
100
LM4128D-2.5
100
60
100
µA
Supply Current in Shutdown
EN = 0V
3
7
µA
ΔVREF/ΔVIN
Line Regulation
VREF + 400 mV ≤ VIN ≤ 5.5V
50
ΔVREF/ΔILOAD
Load Regulation
0 mA ≤ ILOAD ≤ 20 mA
25
Long Term Stability (Note 7)
1000 Hrs
50
Thermal Hysteresis (Note 8)
-40°C ≤ TJ ≤ +125°C
75
IQ_SD
ΔVREF
VIN - VREF
Supply Current
ppm / °C
ppm / V
120
ppm / mA
ppm
Dropout Voltage (Note 9)
ILOAD = 10 mA
175
VN
Output Noise Voltage
0.1 Hz to 10 Hz
275
ISC
Short Circuit Current
75
mA
VIL
Enable Pin Maximum Low Input Level
35
%V
VIH
Enable Pin Minimum High Input Level
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65
6
400
mV
µVPP
%V
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
VREF
Parameter
Min
Typ
Max
(Note 4) (Note 5) (Note 4)
Unit
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 Temperature Coefficient
6)
IQ
Conditions
LM4128A-3.0
%
75
LM4128B-3.0
75
LM4128C-3.0
100
LM4128D-3.0
100
60
100
µA
Supply Current in Shutdown
EN = 0V
3
7
µA
ΔVREF/ΔVIN
Line Regulation
VREF + 400 mV ≤ VIN ≤ 5.5V
70
ΔVREF/ΔILOAD
Load Regulation
0 mA ≤ ILOAD ≤ 20 mA
25
Long Term Stability (Note 7)
1000 Hrs
50
Thermal Hysteresis (Note 8)
-40°C ≤ TJ ≤ +125°C
75
IQ_SD
ΔVREF
VIN - VREF
Supply Current
ppm / °C
ppm / V
120
ppm / mA
ppm
Dropout Voltage (Note 9)
ILOAD = 10 mA
175
VN
Output Noise Voltage
0.1 Hz to 10 Hz
285
ISC
Short Circuit Current
75
mA
VIL
Enable Pin Maximum Low Input Level
35
%V
VIH
Enable Pin Minimum High Input Level
65
7
400
mV
µVPP
%V
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LM4128/LM4128Q
Electrical Characteristics
LM4128-3.0 (VOUT = 3.0V)
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
VREF
Parameter
Min
Typ
Max
(Note 4) (Note 5) (Note 4)
Unit
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 Temperature Coefficient
6)
IQ
Conditions
LM4128A-3.3
%
75
LM4128B-3.3
75
LM4128C-3.3
100
LM4128D-3.3
100
60
100
µA
Supply Current in Shutdown
EN = 0V
3
7
µA
ΔVREF/ΔVIN
Line Regulation
VREF + 400 mV ≤ VIN ≤ 5.5V
85
ΔVREF/ΔILOAD
Load Regulation
0 mA ≤ ILOAD ≤ 20 mA
25
Long Term Stability (Note 7)
1000 Hrs
50
Thermal Hysteresis (Note 8)
-40°C ≤ TJ ≤ +125°C
75
IQ_SD
ΔVREF
VIN - VREF
Supply Current
ppm / °C
ppm / V
120
ppm / mA
ppm
Dropout Voltage (Note 9)
ILOAD = 10 mA
175
VN
Output Noise Voltage
0.1 Hz to 10 Hz
310
ISC
Short Circuit Current
75
mA
VIL
Enable Pin Maximum Low Input Level
35
%V
VIH
Enable Pin Minimum High Input Level
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65
8
400
mV
µVPP
%V
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
VREF
Parameter
IQ
Min
Typ
Max
(Note 4) (Note 5) (Note 4)
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
LM4128A-4.1
75
LM4128C-4.1
100
LM4128D-4.1
100
Supply Current
ppm / °C
60
100
µA
3
7
µA
EN = 0V
ΔVREF/ΔVIN
Line Regulation
VREF + 400 mV ≤ VIN ≤ 5.5V
100
ΔVREF/ΔILOAD
Load Regulation
0 mA ≤ ILOAD ≤ 20 mA
25
Long Term Stability (Note 7)
1000 Hrs
50
Thermal Hysteresis (Note 8)
-40°C ≤ TJ ≤ +125°C
75
VIN - VREF
%
75
LM4128B-4.1
Supply Current in Shutdown
ΔVREF
Unit
Output Voltage Initial Accuracy
TCVREF / °C (Note Temperature Coefficient
6)
IQ_SD
Conditions
ppm / V
120
ppm / mA
ppm
Dropout Voltage (Note 9)
ILOAD = 10 mA
175
VN
Output Noise Voltage
0.1 Hz to 10 Hz
350
ISC
Short Circuit Current
75
mA
VIL
Enable Pin Maximum Low Input Level
35
%V
VIH
Enable Pin Minimum High Input Level
400
mV
µVPP
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.
9
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LM4128/LM4128Q
Electrical Characteristics
LM4128-4.1 (VOUT = 4.096V)
LM4128/LM4128Q
Typical Performance Characteristics for 2.5V
Output Voltage vs Temperature
Load Regulation
20211054
20211055
Line Regulation
0.1 - 10 Hz Noise
20211021
20211056
Output Voltage Noise Spectrum
Power Supply Rejection Ratio vs Frequency
20211057
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20211058
10
LM4128/LM4128Q
Dropout vs Load to 0.5% Accuracy
Typical Long Term Stability
20211008
20211030
Supply Current vs Input Voltage
Shutdown IQ vs Input Voltage
20211010
20211053
Ground Current vs Load Current
Line Transient Response
VIN = 3V to 5V
20211051
20211018
11
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LM4128/LM4128Q
Load Transient Response
ILOAD = 0 to 10mA
Short-Circuit Protection and Recovery
20211082
20211050
Start-Up Response
20211083
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12
THEORY OF OPERATION
The foundation of any voltage reference is the band-gap circuit. 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 example. 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 characteristics. See the Electrical Characteristics section and Enable
Transfer Characteristics figure for more detail. Note, the part
will not operate correctly for VEN > VIN.
20211038
FIGURE 1. Illustrative Temperature Profile
This may be expressed analytically as the following:
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 overshoot during startup. Use of an additional optional bypass
capacitor between the input and ground may help further reduce 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 capacitor 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 signals, effectively bypassing them to ground. Bypass capacitors
should be mounted close to the part. Mounting bypass capacitors close to the part will help reduce the parasitic trace
components thereby improving performance.
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 output voltage over the operating temperature range. This deviation over temperature may be illustrated as shown in Figure
2.
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.
20211039
FIGURE 2. Illustrative Temperature Coefficient Profile
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).
Temperature coefficient may be expressed analytically as the
following:
13
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LM4128/LM4128Q
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 temperature profile is shown in Figure 1.
Application Information
LM4128/LM4128Q
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:
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.
Where:
VREF is in volts (V) and VERROR is in milli-volts (mV).
Voltage error (mV) to percentage error (percent):
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 temperature.
Where:
VREF is in volts (V) and VERROR is in milli-volts (mV).
EXPRESSION OF ELECTRICAL CHARACTERISTICS
Electrical characteristics are typically expressed in mV, ppm,
or a percentage of the nominal value. Depending on the application, one expression may be more useful than the other.
To convert one quantity to the other one may apply the following:
ppm to mV error in output voltage:
PRINTED CIRCUIT BOARD and LAYOUT
CONSIDERATIONS
References in SOT packages are generally less prone to PC
board mounting than devices in Small Outline (SOIC) packages. 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. Mounting bypass capacitors close to the part will reduce the parasitic trace components thereby improving performance.
Where:
VREF is in volts (V) and VERROR is in milli-volts (mV).
Bit error (1 bit) to voltage error (mV):
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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
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LM4128/LM4128Q
Physical Dimensions inches (millimeters) unless otherwise noted
SOT23-5 Package
NS Package Number MF05A
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16
LM4128/LM4128Q
Notes
17
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LM4128/LM4128Q SOT-23 Precision Micropower Series Voltage Reference
Notes
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