March 2005 1 M9999-031805
LM4040/4041 Micrel, Inc.
LM4040/4041
Precision Micropower Shunt Voltage Reference
General Description
Ideal for space critical applications, the LM4040 and LM4041
precision voltage references are available in the subminiature
(3mm × 1.3mm) SOT-23 surface-mount package.
The LM4040 is the available in fixed reverse breakdown
voltages of 2.500V, 4.096V and 5.000V. The LM4041 is avail-
able with a fixed 1.225V or an adjustable reverse breakdown
voltage.
The minimum operating current ranges from 60µA for the
LM4041-1.2 to 74µA for the LM4040-5.0. LM4040 versions
have a maximum operating current of 15mA. LM4041 ver-
sions have a maximum operating current of 12mA.
The LM4040 and LM4041 have bandgap reference tempera-
ture drift curvature correction and low dynamic impedance,
ensuring stable reverse breakdown voltage accuracy over a
wide range of operating temperatures and currents.
Data sheets and support documentation can be found on
Micrel’s web site at www.micrel.com.
Features
• Small SOT-23 package
• No output capacitor required
• Tolerates capacitive loads
• Fixed reverse breakdown voltages of 1.225, 2.500V,
4.096V and 5.000V
• Adjustable reverse breakdown version
• Contact Micrel for parts with extended temperature
range.
Key Specifications
• Output voltage tolerance ............................. ±0.1% (max)
• Low output noise (10Hz to 100Hz)
LM4040 ................................................. 35µVRMS (typ)
LM4041 ................................................. 20µVRMS (typ)
• Wide operating current range
LM4040 ..................................................60µA to 15mA
LM4041 ..................................................60µA to 12mA
• Industrial temperature range .................. –40°C to +85°C
• Low temperature coefficient ................ 100ppm/°C (max)
Applications
• Battery-powered equipment
• Data acquisition systems
• Instrumentation
• Process control
• Energy management
• Product testing
• Automotive electronics
• Precision audio components
Typical Applications
Figure 2. LM4041 Adjustable
Shunt Regulator Application
Figure 1. LM4040, LM4041 Fixed
Shunt Regulator Application
VO = 1.233 (R2/R1 + 1)
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
VS
RS
VR
IQ + IL
IQ
IL
LM4040
LM4041
VO
VS
LM4041
Adjustable
R1
R2
RS
VO
LM4040/4041 Micrel, Inc.
M9999-031805 2 March 2005
Pin Configuration
Example Field Code
_ _ C 3rd Character C = ±0.5%
D = ±1.0%
X = ±0.5% Pb-Free
Y = ±1.0% Pb-Free
Note: If 3rd character is omitted, container will
indicate tolerance.
Example Field Code
_ 2 _ 2nd Character 1 = 1.225V
2 = 2.500V
4 = 4.096V
5 = 5.000V
A = Adjustable
Example: R2C represents Reference, 2.500V,
±0.5% (LM4040CIM3-2.5)
Example: Y1C represents Pb-Free, 1.225V,
±0.5% (LM4040CYM3-1.2)
SOT-23 Package Markings
Example Field Code
R _ _ 1st Character R = Reference
Y _ _ 1st Character Y = Pb-Free
Ordering Information
Part Number Accuracy,
Standard Pb-Free Voltage Temp. Coefficient
LM4040CIM3-2.5 LM4040CYM3-2.5 2.500V ±0.5%, 100ppm/°C
LM4040DIM3-2.5 LM4040DYM3-2.5 2.500V ±1.0%, 150ppm/°C
LM4040CIM3-4.1 LM4040CYM3-4.1 4.096V ±0.5%, 100ppm/°C
LM4040DIM3-4.1 LM4040DYM3-4.1 4.096V ±1.0%, 150ppm/°C
LM4040CIM3-5.0 LM4040CYM3-5.0 5.000V ±0.5%, 100ppm/°C
LM4040DIM3-5.0 LM4040DYM3-5.0 5.000V ±1.0%, 150ppm/°C
LM4041CIM3-1.2 LM4041CYM3-1.2 1.225V ±0.5%, 100ppm/°C
LM4041DIM3-1.2 LM4041DYM3-1.2 1.225V ±1.0%, 150ppm/°C
LM4041CIM3-ADJ LM4041CYM3-ADJ 1.24V to 10V ±0.5%, 100ppm/°C
LM4041DIM3-ADJ LM4041DYM3-ADJ 1.24V to 10V ±1.0%, 150ppm/°C
Fixed Version
SOT-23 (M3) Package
3
Pin 3 must float or be
connected to pin 2.
Adjustable Version
SOT-23 (M3) Package
1
2
3 –
FB
+
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LM4040/4041 Micrel, Inc.
Absolute Maximum Ratings
Reverse Current ......................................................... 20mA
Forward Current ......................................................... 10mA
Maximum Output Voltage
LM4041-Adjustable .................................................... 15V
Power Dissipation at TA = 25°C (Note 2) ................ 306mW
Storage Temperature ................................ –65°C to +150°C
Lead Temperature
Vapor phase (60 seconds) ............................... +215°C
Infrared (15 seconds) ....................................... +220°C
ESD Susceptibility
Human Body Model (Note 3) ............................... 2kV
Machine Model (Note 3) .................................... 200V
Operating Ratings (Notes 1 and 2)
Temperature Range
(TMIN ≤ TA ≤ TMAX) ............................–40°C ≤ TA ≤ +85°C
Reverse Current
LM4040-2.5 ............................................60µA to 15mA
LM4040-4.1 ............................................68µA to 15mA
LM4040-5.0 ............................................74µA to 15mA
LM4041-1.2 ............................................60µA to 12mA
LM4041-ADJ .......................................... 60µA to 12mA
Output Voltage Range
LM4041-ADJ ............................................1.24V to 10V
Functional Diagram
LM4040, LM4041 Fixed
Functional Diagram
LM4041 Adjustable
Note 1. Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which
the device is functional, but do not guarantee specific performance limits. For guaranteed specification and test conditions, see the “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. The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX (maximum junction temperature), θJA
(junction to ambient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any temperature is PD-
MAX = (TJMAX – TA)/θJA or the number given in the Absolute Maximum Ratings, whichever is lower. For the LM4040 and LM4041,
TJMAX = 125°C, and the typical thermal resistance (θJA), when board mounted, is 326°C/W for the SOT-23 package.
Note 3. The human body model is a 100pF capacitor discharged through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor
discharged directly into each pin.
+
+
FB
VREF
LM4040/4041 Micrel, Inc.
M9999-031805 4 March 2005
LM4040-2.5 Electrical Characteristics (Note 4)
Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25°C. The grades C and D designate initial Reverse Break-
down Voltage tolerance of ±0.5% and ±1.0 respectively.
LM4040CIM3 LM4040DIM3
Symbol Parameter Conditions Typical Units
(Note 5) Limits Limits (Limit)
(Note 6) (Note 6)
VR Reverse Breakdown Voltage IR = 100µA 2.500 V
Reverse Breakdown Voltage IR = 100µA ±12 ±25 mV (max)
Tolerance (Note 7) ±29 ±49 mV (max)
IRMIN Minimum Operating Current 45 µA
60 65 µA (max)
65 70 µA (max)
ΔVR/ΔT Average Reverse Breakdown IR = 10mA ±20 ppm/°C
Voltage Temperature IR = 1mA ±15 ±100 ±150 ppm/°C (max)
Coefficient IR = 100µA ±15 ppm/°C (max)
ΔVR/ΔIR Reverse Breakdown Voltage IRMIN ≤ IR 1mA 0.3 mV
Change with Operating 0.8 1.0 mV (max)
Current Change 1.0 1.2 mV (max)
1mA ≤ IR 15mA 2.5 mV
6.0 8.0 mV (max)
8.0 10.0 mV (max)
ZR Reverse Dynamic Impedance IR = 1mA, f = 120Hz 0.3 Ω
IAC = 0.1 IR 0.9 1.1 Ω (max)
eN Wideband Noise IR = 100µA
10Hz ≤ f ≤ 10kHz 35 µVRMS
ΔVR Reverse Breakdown Voltage t = 1000hrs
Long Term Stability T = 25°C ±0.1°C 120 ppm
IR = 100µA
Note 4. Specification for packaged product only.
Note 5. Typicals are at TJ = 25°C and represent most likely parametric norm.
Note 6. Limits are 100% production tested at 25°C. Limits over temperature are guaranteed through correlation using Statistical Quality Control (SQL)
methods.
Note 7. The boldface (over temperature limit for Reverse Breakdown Voltage Tolerance is defined as the room temperature Reverse Breakdown Volt-
age Tolerance ±[(ΔVR/ΔT)(65°C)(VR)]. ΔVR/ΔT is the VR temperature coefficient, 65°C is the temperature range from –40°C to the reference
point of 25°C, and VR is the reverse breakdown voltage. The total over temperature tolerance for the different grades follows:
C-grade: ±1.15% = ±0.5% ±100ppm/°C × 65°C
D-grade: ±1.98% = ±1.0% ±150ppm/°C × 65°C
Example: The C-grade LM4040-2.5 has an over temperature Reverse Breakdown Voltage tolerance of ±2.5 × 1.15% = ±29mV.
March 2005 5 M9999-031805
LM4040/4041 Micrel, Inc.
LM4040-4.1 Electrical Characteristics (Note 4)
Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25°C. The grades C and D designate initial Reverse Break-
down Voltage tolerance of ±0.5% and ± 1.0% respectively.
LM4040CIM3 LM4040DIM3
Symbol Parameter Conditions Typical Units
(Note 5) Limits Limits (Limits)
(Note 6) (Note 6)
VR Reverse Breakdown Voltage IR = 100µA 4.096 V
Reverse Breakdown Voltage IR = 100µA ±20 ±41 mV (max)
Tolerance (Note 7) ±47 ±81 mV (max)
IRMIN Minimum Operating Current 50 µA
68 73 µA (max)
73 78 µA (max)
ΔVR/ΔT Average Reverse Breakdown IR = 10mA ±30 ppm/°C
Voltage Temperature IR = 1mA ±20 ±100 ±150 ppm/°C (max)
Coefficient IR = 100µA ±20 ppm/°C (max)
ΔVR/ΔIR Reverse Breakdown Voltage IRMIN ≤ IR 1mA 0.5 mV
Change with Operating 0.9 1.2 mV (max)
Current Change 1.2 1.5 mV (max)
1mA ≤ IR 15mA 3.0 mV
7.0 9.0 mV (max)
10.0 13.0 mV (max)
ZR Reverse Dynamic Impedance IR = 1mA, f = 120Hz 0.5 Ω
IAC = 0.1 IR 1.0 1.3 Ω (max)
eN Wideband Noise IR = 100µA
10Hz ≤ f ≤ 10kHz 80 µVRMS
ΔVR Reverse Breakdown Voltage t = 1000hrs
Long Term Stability T = 25°C ±0.1°C 120 ppm
IR = 100µA
Note 4. Specification for packaged product only.
Note 5. Typicals are at TJ = 25°C and represent most likely parametric norm.
Note 6. Limits are 100% production tested at 25°C. Limits over temperature are guaranteed through correlation using Statistical Quality Control (SQL)
methods.
Note 7. The boldface (over temperature limit for Reverse Breakdown Voltage Tolerance is defined as the room temperature Reverse Breakdown Volt-
age Tolerance ±[(ΔVR/ΔT)(65°C)(VR)]. ΔVR/ΔT is the VR temperature coefficient, 65°C is the temperature range from –40°C to the reference
point of 25°C, and VR is the reverse breakdown voltage. The total over temperature tolerance for the different grades follows:
C-grade: ±1.15% = ±0.5% ±100ppm/°C × 65°C
D-grade: ±1.98% = ±1.0% ±150ppm/°C × 65°C
Example: The C-grade LM4040-2.5 has an over temperature Reverse Breakdown Voltage tolerance of ±2.5 × 1.15% = ±29mV.
LM4040/4041 Micrel, Inc.
M9999-031805 6 March 2005
LM4040-5.0 Electrical Characteristics (Note 4)
Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25°C. The grades C and D designate initial Reverse Break-
down Voltage tolerance of ±0.5% and ± 1.0% respectively.
LM4040CIM3 LM4040DIM3
Symbol Parameter Conditions Typical Units
(Note 5) Limits Limits (Limits)
(Note 6) (Note 6)
VR Reverse Breakdown Voltage IR = 100µA 5.000 V
Reverse Breakdown Voltage IR = 100µA ±25 ±50 mV (max)
Tolerance (Note 7) ±58 ±99 mV (max)
IRMIN Minimum Operating Current 54 µA
74 79 µA (max)
80 85 µA (max)
ΔVR/ΔT Average Reverse Breakdown IR = 10mA ±30 ppm/°C
Voltage Temperature IR = 1mA ±20 ±100 ±150 ppm/°C (max)
Coefficient IR = 100µA ±20 ppm/°C (max)
ΔVR/ΔIR Reverse Breakdown Voltage IRMIN ≤ IR 1mA 0.5 mV
Change with Operating 1.0 1.3 mV (max)
Current Change 1.4 1.8 mV (max)
1mA ≤ IR 15mA 3.5 mV
8.0 10.0 mV (max)
12.0 15.0 mV (max)
ZR Reverse Dynamic Impedance IR = 1mA, f = 120Hz 0.5 Ω
IAC = 0.1 IR 1.1 1.5 Ω (max)
eN Wideband Noise IR = 100µA
10Hz ≤ f ≤ 10kHz 80 µVRMS
ΔVR Reverse Breakdown Voltage t = 1000hrs
Long Term Stability T = 25°C ±0.1°C 120 ppm
IR = 100µA
Note 4. Specification for packaged product only.
Note 5. Typicals are at TJ = 25°C and represent most likely parametric norm.
Note 6. Limits are 100% production tested at 25°C. Limits over temperature are guaranteed through correlation using Statistical Quality Control (SQL)
methods.
Note 7. The boldface (over temperature limit for Reverse Breakdown Voltage Tolerance is defined as the room temperature Reverse Breakdown Volt-
age Tolerance ±[(ΔVR/ΔT)(65°C)(VR)]. ΔVR/ΔT is the VR temperature coefficient, 65°C is the temperature range from –40°C to the reference
point of 25°C, and VR is the reverse breakdown voltage. The total over temperature tolerance for the different grades follows:
C-grade: ±1.15% = ±0.5% ±100ppm/°C × 65°C
D-grade: ±1.98% = ±1.0% ±150ppm/°C × 65°C
Example: The C-grade LM4040-2.5 has an over temperature Reverse Breakdown Voltage tolerance of ±2.5 × 1.15% = ±29mV.
March 2005 7 M9999-031805
LM4040/4041 Micrel, Inc.
LM4040 Typical Characteristics
Test Circuit
VIN
1Hz rate LM4040
RS
VR
LM4040/4041 Micrel, Inc.
M9999-031805 8 March 2005
LM4041-1.2 Electrical Characteristics (Note 4)
Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25°C. The grades C and D designate initial Reverse Break-
down Voltage tolerance of ±0.5% and ± 1.0%, respectively.
LM4041CIM3
Symbol Parameter Conditions Typical Units
(Note 5) Limits (Limit)
(Note 6)
VR Reverse Breakdown Voltage IR = 100µA 1.225 V
Reverse Breakdown Voltage IR = 100µA ±6 mV (max)
Tolerance (Note 7) ±14 mV (max)
IRMIN Minimum Operating Current 45 µA
60 µA (max)
65 µA (max)
ΔVR/ΔT Average Reverse Breakdown IR = 10mA ±20 ppm/°C
Voltage Temperature IR = 1mA ±15 ±100 ppm/°C (max)
Coefficient IR = 100µA ±15 ppm/°C (max)
ΔVR/ΔIR Reverse Breakdown Voltage IRMIN ≤ IR 1mA 0.7 mV
Change with Operating 1.5 mV (max)
Current Change 2.0 mV (max)
1mA ≤ IR 15mA 4.0 mV
6.0 mV (max)
8.0 mV (max)
ZR Reverse Dynamic Impedance IR = 1mA, f = 120Hz 0.5 Ω
IAC = 0.1 IR 1.5 Ω (max)
eN Wideband Noise IR = 100µA
10Hz ≤ f ≤ 10kHz 20 µVRMS
ΔVR Reverse Breakdown Voltage t = 1000hrs
Long Term Stability T = 25°C ±0.1°C 120 ppm
IR = 100µA
Note 4. Specification for packaged product only.
Note 5. Typicals are at TJ = 25°C and represent most likely parametric norm.
Note 6. Limits are 100% production tested at 25°C. Limits over temperature are guaranteed through correlation using Statistical Quality Control (SQL)
methods.
Note 7. The boldface (over temperature limit for Reverse Breakdown Voltage Tolerance is defined as the room temperature Reverse Breakdown Volt-
age Tolerance ±[(ΔVR/ΔT)(65°C)(VR)]. ΔVR/ΔT is the VR temperature coefficient, 65°C is the temperature range from –40°C to the reference
point of 25°C, and VR is the reverse breakdown voltage. The total over temperature tolerance for the different grades follows:
C-grade: ±1.15% = ±0.5% ±100ppm/°C × 65°C
D-grade: ±1.98% = ±1.0% ±150ppm/°C × 65°C
Example: The C-grade LM4040-2.5 has an over temperature Reverse Breakdown Voltage tolerance of ±2.5 × 1.15% = ±29mV.
March 2005 9 M9999-031805
LM4040/4041 Micrel, Inc.
LM4041-1.2 Electrical Characteristics (Note 4)
Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25°C. The grades C and D designate initial Reverse Break-
down Voltage tolerance of ±0.5% and ± 1.0%, respectively.
LM4041DIM3
Typical Limits Units
Symbol Parameter Conditions (Note 5) (Note 6) (Limit)
VR Reverse Breakdown Voltage IR = 100µA 1.225 V
Reverse Breakdown Voltage IR = 100µA ±12 mV (max)
Tolerance (Note 7) ±24 mV (max)
IRMIN Minimum Operating Current 45 µA
65 µA (max)
70 µA (max)
ΔVR/ΔT Average Reverse Breakdown IR = 10mA ±20 ppm/°C
Voltage Temperature IR = 1mA ±15 ±150 ppm/°C (max)
Coefficient IR = 100µA ±15 ppm/°C (max)
ΔVR/ΔIR Reverse Breakdown Voltage IRMIN ≤ IR 1mA 0.7 mV
Change with Operating 2.0 mV (max)
Current Change 2.5 mV (max)
1mA ≤ IR 15mA 2.5 mV
8.0 mV (max)
10.0 mV (max)
ZR Reverse Dynamic Impedance IR = 1mA, f = 120Hz 0.5 Ω
IAC = 0.1 IR 2.0 Ω (max)
eN Wideband Noise IR = 100µA
10Hz ≤ f ≤ 10kHz 20 µVRMS
ΔVR Reverse Breakdown Voltage t = 1000hrs
Long Term Stability T = 25°C ±0.1°C 120 ppm
IR = 100µA
Note 4. Specification for packaged product only.
Note 5. Typicals are at TJ = 25°C and represent most likely parametric norm.
Note 6. Limits are 100% production tested at 25°C. Limits over temperature are guaranteed through correlation using Statistical Quality Control (SQL)
methods.
Note 7. The boldface (over temperature limit for Reverse Breakdown Voltage Tolerance is defined as the room temperature Reverse Breakdown Volt-
age Tolerance ±[(ΔVR/ΔT)(65°C)(VR)]. ΔVR/ΔT is the VR temperature coefficient, 65°C is the temperature range from –40°C to the reference
point of 25°C, and VR is the reverse breakdown voltage. The total over temperature tolerance for the different grades follows:
C-grade: ±1.15% = ±0.5% ±100ppm/°C × 65°C
D-grade: ±1.98% = ±1.0% ±150ppm/°C × 65°C
Example: The C-grade LM4040-2.5 has an over temperature Reverse Breakdown Voltage tolerance of ±2.5 × 1.15% = ±29mV.
LM4040/4041 Micrel, Inc.
M9999-031805 10 March 2005
LM4041-Adjustable Electrical Characteristics (Note 4)
Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TJ = 25°C unless otherwise specified (SOT-23, see Note 8),
IRMIN ≤ IR < 12mA, VREF ≤ VOUT ≤ 10V. The grades C and D designate initial Reverse Breakdown Voltage tolerance of ±0.5% and ±1%,
respectively for VOUT = 5V.
LM4041CIM3 LM4041DIM3
Symbol Parameter Conditions Typical Units
(Note 5) Limits Limits (Limit)
(Note 6) (Note 6)
VREF Reference Breakdown Voltage IR = 100µA 1.233 V
VOUT = 5V
Reference Breakdown Voltage IR = 100µA ±6.2 ±12 mV (max)
Tolerance (Note 9) ±14 ±24 mV (max)
IRMIN Minimum Operating Current 45 µA
60 65 µA (max)
65 70 µA (max)
ΔVREF Reference Voltage IRMIN ≤ IR 1mA 0.7 mV
/ΔIR Change with Operating SOT-23: 1.5 2.0 mV (max)
Current Change VOUT ≥ 1.6V 2.0 2.5 mV (max)
(Note 8)
1mA ≤ IR 15mA 2 mV
SOT-23: 4 6 mV (max)
VOUT ≥ 1.6V 6 8 mV (max)
(Note 8)
ΔVREF Reference Voltage Change IR = 1mA –1.55 mV/V
/ΔVO with Output Voltage Change –2.0 –2.5 mV/V (max)
–2.5 –3.0 mV/V (max)
IFB Feedback Current 60 nA
100 150 nA (max)
120 200 nA (max)
ΔVREF Average Reference VOUT = 5V
/ΔT Voltage Temperature IR = 10mA ±20 ppm/°C
Coefficient IR = 1mA ±15 ±100 ±150 ppm/°C (max)
(Note 9) IR = 100µA ±15 ppm/°C (max)
ZOUT Dynamic Output Impedance IR = 1mA, f = 120Hz
IAC = 0.1 IR
VOUT = VREF 0.3 Ω
VOUT = 10V 2 Ω (max)
eN Wideband Noise IR = 100µA
10Hz ≤ f ≤ 10kHz 20 µVRMS
ΔVREF Reference Voltage t = 1000hrs
Long Term Stability T = 25°C ±0.1°C 120 ppm
IR = 100µA
Note 4. Specification for packaged product only.
Note 5. Typicals are at TJ = 25°C and represent most likely parametric norm.
Note 6. Limits are 100% production tested at 25°C. Limits over temperature are guaranteed through correlation using Statistical Quality Control (SQL)
methods.
Note 7. The boldface (over temperature limit for Reverse Breakdown Voltage Tolerance is defined as the room temperature Reverse Breakdown Volt-
age Tolerance ±[(ΔVR/ΔT)(65°C)(VR)]. ΔVR/ΔT is the VR temperature coefficient, 65°C is the temperature range from –40°C to the reference
point of 25°C, and VR is the reverse breakdown voltage. The total over temperature tolerance for the different grades follows:
C-grade: ±1.15% = ±0.5% ±100ppm/°C × 65°C
D-grade: ±1.98% = ±1.0% ±150ppm/°C × 65°C
Example: The C-grade LM4040-2.5 has an over temperature Reverse Breakdown Voltage tolerance of ±2.5 × 1.15% = ±29mV.
Note 8. When VOUT ≤ 1.6V, the LM4041-ADJ must operate at reduced IR. This is caused by the series resistance of the die attach between the die (–)
output and the package (–) output pin. See the Output Saturation curve in the “Typical Performance Characteristics” section.
Note 9. Reference voltage and temperature coefficient will change with output voltage. See “Typical Performance Characteristics” curves.
March 2005 11 M9999-031805
LM4040/4041 Micrel, Inc.
Test Circuit
LM4041 Typical Characteristics
RS 30k
VIN
1Hz rate LM4041-1.2
VR
LM4040/4041 Micrel, Inc.
M9999-031805 12 March 2005
LM4041 Typical Characteristics
* Output Impedance vs. Freq.
Test Circuit
‡ Large Signal Response
Test Circuit
† Reverse Characteristics
Test Circuit
* Output impedance measurement..
† Reverse characteristics measurement.
‡ Large signal response measurement.
–
+
CL
120k
FB
IR
FB
2V / step
VOUT
IR
( + )
( – )
LM4041-ADJ
V
VOUT
LM4041-ADJ
( + )
FB
( – )
100k
INPUT
+ 15V
5.1k
March 2005 13 M9999-031805
LM4040/4041 Micrel, Inc.
Applications Information
The stable operation of the LM4040 and LM4041 references
requires an external capacitor greater than 10nF connected
between the (+) and (–) pins. Bypass capacitors with values
between 100pF and 10nF have been found to cause the
devices to exhibit instabilities.
Schottky Diode
LM4040-x.x and LM4041-1.2 in the SOT-23 package have
a parasitic Schottky diode between pin 2 (–) and pin 3 (die
attach interface connect). Pin 3 of the SOT-23 package must
float or be connected to pin 2. LM4041-ADJs use pin 3 as
the (–) output.
Conventional Shunt Regulator
In a conventional shunt regulator application (see Figure 1),
an external series resistor (RS) is connected between the
supply voltage and the LM4040-x.x or LM4041-1.2 reference.
RS determines the current that flows through the load (IL)
and the reference (IQ). Since load current and supply volt-
age may vary, RS should be small enough to supply at least
the minimum acceptable IQ to the reference even when the
supply voltage is at its minimum and the load current is at
its maximum value. When the supply voltage is at its maxi-
mum and IL is at its minimum, RS should be large enough so
that the current flowing through the LM4040-x.x is less than
15mA, and the current flowing through the LM4041-1.2 or
LM4041-ADJ is less than 12mA.
RS is determined by the supply voltage (VS), the load and
operating current, (IL and IQ), and the reference’s reverse
breakdown voltage (VR):
Rs = (Vs – VR) / (IL + IQ)
Adjustable Regulator
The LM4041-ADJ’s output voltage can be adjusted to any
value in the range of 1.24V through 10V. It is a function of
the internal reference voltage (VREF) and the ratio of the ex-
ternal feedback resistors as shown in Figure 2. The output
is found using the equation:
(1) VO = VREF [ (R2/R1) + 1 ]
where VO is the desired output voltage. The actual value of
the internal VREF is a function of VO. The “corrected” VREF
is determined by:
(2) VREF´ = VO (ΔVREF / ΔVO) + VY
where VO is the desired output voltage. ΔVREF / ΔVO is found
in the “Electrical Characteristics” and is typically –1.3mV/V and
VY is equal to 1.233V. Replace the value of VREF in equation
(1) with the value VREF found using equation (2).
Note that actual output voltage can deviate from that pre-
dicted using the typical ΔVREF / ΔVO in equation (2); for C-
grade parts, the worst-case ΔVREF / ΔVO is –2.5mV/V and
VY = 1.248V.
The following example shows the difference in output volt-
age resulting from the typical and worst case values of
ΔVREF / ΔVO.
Let VO = +9V. Using the typical values of ΔVREF /ΔVO , VREF
is 1.223V. Choosing a value of R1 = 10kΩ, R2 = 63.272kΩ.
Using the worst case ΔVREF / ΔVO for the C-grade and D-
grade parts, the output voltage is actually 8.965V and 8.946V
respectively. This results in possible errors as large as
0.39% for the C-grade parts and 0.59% for the D-grade parts.
Once again, resistor values found using the typical value of
ΔVREF / ΔVO will work in most cases, requiring no further
adjustment.
Figure 4. Voltage Level DetectorFigure 3. Voltage Level Detector
Typical Application Circuits
R1
120k
R2
1M
FB
+
–
LM4041-ADJ
D1
λ
< –12V
LED ON
R3
200
–5V
D1
λ
LM4041-
ADJ
R1
120k
R2
1M
FB
–
+
R3
330
> –12V
LED ON
–5V
LM4040/4041 Micrel, Inc.
M9999-031805 14 March 2005
Figure 8. Bidirectional Adjustable Clamp
±2.4 to ±6V
Figure 7. Bidirectional Adjustable Clamp
±18V to ±2.4V
* D1 can be any LED, VF = 1.5V to 2.2V at 3mA. D1 may act as an indicator.
D1 will be on if ITHRESHOLD falls below the threshold current, except with I = O.
Figure 9. Floating Current Detector
Figure 6. Bidirectional Clamp
±2.4V
Figure 5. Fast Positive Clamp
2.4V + ∆VD1
VIN
VOUT
D1
1N914
D2
1N914
R3
240k
R4
240k
R1
I
R2
50A
LM4041-ADJ
FB
+
–
D1
1N457
R3
510k
LM4041-ADJ
D2
1N457
VOUT
R2
510k
VIN
R1
I
+
FB FB
LM4041-ADJ
+
–
–
VIN
R1
R2
390k
R3
500k
FB
+
–
LM4041-ADJ
D1
1N457
R4
390k
D2
1N457
LM4041-ADJ
FB
+
–
I
VOUT
VIN
R1I
LM4041-ADJ
D2
1N457
R3
1M
R2
330k
VOUT
LM4041-ADJ
FB
+
–
FB –
+
D1
1N457
R4
330k
0 to 20mA
R1
390Ω
± 2%
1N4002
D2
LM4041-ADJ
+
–
FB
λ
D1* 1
2
3
6
5
4
4N28
N.C.
ITHRESHOLD = + = 3.2mA
1.24V
R1
5A
4N28 GAIN
N.C.
R2
470k
CMOS
+ 5V
March 2005 15 M9999-031805
LM4040/4041 Micrel, Inc.
Figure 10. Current Source
* D1 can be any LED, VF = 1.5V to 2.2V at 3mA. D1 may act as an indicator.
D1 will be on if ITHRESHOLD falls below the threshold current, except with I = O.
Figure 11. Precision Floating Current Detector
+5V
R3
100k
CMOS
R4
10M
1
2
3
6
5
4
4N28
N.C.
R2
22k
LM4041-ADJ
+
–
R1
332Ω
±1% FB
1N914
2N2222
D1*
λ
ITHRESHOLD = = 3.7mA ± 2%
1.24V
R1
D2
1N4002
0 to 20 mA
+15V
R1
2N2905
2N
3964
R2
120k
LM4041-ADJ
FB
+
–
1.24V
R1
IOUT =
1A < IOUT = 100mA
LM4040/4041 Micrel, Inc.
M9999-031805 16 March 2005
Package Information
SOT-23 (M3)
MICREL INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2004 Micrel Incorporated
