2.5 V shunt reference with ±0.1% initial accuracy
The LM4040AIM3X-2.5 is a precision shunt voltage reference from Texas Instruments, delivering a fixed 2.5 V output with a tight ±0.1% initial tolerance. This makes it a solid choice for biasing ADCs, DACs, or comparators where the reference voltage directly sets the conversion range or threshold — the ±0.1% band keeps the system error budget tight without external trimming.
Noise floor and temperature drift
Output noise is specified at 35 µVrms over the 10 Hz to 10 kHz band, which is low enough for most 12- to 14-bit precision applications without an additional RC filter stage.
Shunt architecture and bias current
As a shunt reference, the LM4040AIM3X-2.5 requires an external series resistor to set the cathode current. The minimum cathode current is 65 µA, and the maximum output current is 15 mA. In a typical 5 V rail design with a 2.5 V reference, the resistor value is chosen so the cathode current stays above 65 µA across the load range — a common oversight that leads to regulation dropout if the resistor is oversized.
Existing production builds can still be supported through independent distribution, but new designs should evaluate the active LM4040 family siblings — same SOT-23-3 footprint, same 2.5 V output, wider availability.