LM4040 Reference Tables, Pins & Specifications

Pin reference

Signal names, electrical functions and connection guidance

TO-92

Physical pin numbers3 pins

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LM4040 pin functions and connections
Signal	Type	Function & connection
DNC	Float or connect to anode	This package lead must not be used as an input or output. Connection guidance Leave floating in the example. TI also permits an anode connection and recommends it in noisy environments. TO-92 pin 1; SOT-23 pin 3. No adjustment function.
K	Cathode / reference node	Positive shunt-current terminal and nominal 2.5 V output. Connection guidance Feed through a resistor from the source; connect a high-impedance load to this node. TO-92 pin 2; SOT-23 pin 1. Keep reference current within its operating range.
A	Anode / common return	Negative reference terminal, normally grounded. Connection guidance Connect to supply return and the measurement ground. TO-92 pin 3; SOT-23 pin 2.

A-grade 2.5 V industrial devices

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Through-hole order	LM4040AIZ-2.5/NOPB	TO-92 LP; straight leads
SMD order	LM4040AIM3-2.5/NOPB	SOT-23 DBZ; body code R2A
TO-92 front-view pins	1 DNC; 2 cathode; 3 anode	Flat face toward viewer
SOT-23 top-view pins	1 cathode; 2 anode; 3 DNC	DNC must float or connect to anode
Active terminals	Cathode and anode	No adjustment or enable input
Selected accuracy / temperature	A grade / I range	Not C, D, E or automotive limits

The TO-92 manufacturer drawing is a bottom view; the page labels its viewing orientation.

IR=100 µA unless noted

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Nominal breakdown voltage	2.5 V	Reverse operation
Initial A-grade error	±2.5 mV maximum	±0.1%; 25°C
Full-temperature A-grade error	±19 mV maximum	−40 to 85°C; 2.481–2.519 V
Average temperature coefficient	±100 ppm/°C maximum	Full specified temperature span
Typical temperature coefficient	±15 ppm/°C	100 µA or 1 mA
Typical coefficient at 10 mA	±20 ppm/°C	Characterization, not a maximum

Initial accuracy is not the complete overtemperature error.

Preserve current for both load and reference

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Minimum operating current at 25°C	45 µA typical; 60 µA maximum	Use the maximum requirement for design
Minimum over full temperature	65 µA maximum	Reference current after subtracting load
Maximum operating reverse current	15 mA	Respect package heating
Reverse-current absolute maximum	20 mA	Stress only
Forward-current absolute maximum	10 mA	Not normal reference operation
Dynamic impedance	0.3 Ω typical; 0.8 Ω maximum	IR1 mA, 120 Hz, AC current 10% of IR

A shunt reference draws the current left over by the load.

Source test conditions retained

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Voltage change: IRmin to 1 mA	0.3 mV typ.; 0.8 mV max. at 25°C	1 mV maximum over temperature
Voltage change: 1–15 mA	2.5 mV typ.; 6 mV max. at 25°C	8 mV maximum over temperature
Wideband noise	35 µV RMS typical	IR100 µA, 10 Hz–10 kHz
Long-term stability	120 ppm typical	1000 h; 25°C±0.1°C; IR100 µA
Thermal hysteresis	0.08% typical	Manufacturer −40 to125°C cycle test
External stabilization capacitor	Not required	Capacitive loads tolerated; system filtering may still help

Typical noise and aging figures are not guaranteed maximum errors.

Calculated example, not a power regulator

Manufacturer-referenced values7 parameters

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Parameter	Value	Conditions / notes
Feed resistor	2.49 kΩ, 1%, ≥0.25 W	From 5 V source to cathode
Test load	10 kΩ, 1%, ≥0.25 W	From cathode to anode/ground
Nominal feed current	(5−2.5)/2490=1.004 mA	Supplies load plus reference
Nominal load current	2.5/10000=250 µA	0.625 mW load power
Nominal reference current	754 µA	1.004 mA−250 µA
Nominal reference dissipation	2.5×0.754 mA≈1.89 mW	Feed resistor dissipates approximately 2.51 mW
Worst-case low-source budget	At 4.75 V, VR2.519 V, RS+1%, RL−1%: IR≈633 µA	Still above 65 µA before additional system loads

A high-impedance measurement input is preferable to a heavy load.

Board-dependent thermal metrics

Manufacturer-referenced values6 parameters

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Parameter	Value	Conditions / notes
Ambient operating range	−40 to85°C	Selected industrial temperature grade
Maximum junction temperature	125°C	Use the operating and power-derating guidance
TO-92 θJA	166°C/W	TI thermal-information reference board
SOT-23 θJA	291.9°C/W	TI thermal-information reference board
Reference loss at 15 mA	37.5 mW nominal	2.5 V×15 mA
Layout	Short reference and return paths	Keep load-return drops out of sensitive measurements

Thermal resistance depends on assembly; older lead-length estimates are not interchangeable with reference-board metrics.