1.225 V shunt reference — what drives the BOM fit
The LM4041DIM7X-1.2/NOPB is a precision shunt voltage reference from Texas Instruments that delivers a fixed 1.225 V output with ±1% initial tolerance. It is designed for applications requiring a stable voltage reference in a small footprint — the SC-70-5 package (also known as SOT-353) occupies minimal board area and is suited for portable, battery-powered, and space-constrained designs. The shunt topology means it behaves like a two-terminal Zener diode: a series resistor sets the bias current from the supply, and the reference regulates the voltage across itself.
150 ppm/°C drift — the tempco budget
The temperature coefficient of 150 ppm/°C means the output voltage can shift by up to 0.15 mV per degree Celsius. For a 12-bit ADC with a 2.5 V reference, that drift contributes roughly 0.75 LSB of error — acceptable for general-purpose measurement but worth noting for high-accuracy data acquisition.
12 mA output, 70 µA cathode — current budget
The reference can source up to 12 mA of output current, which is enough to bias a single ADC reference input or a comparator threshold divider. The minimum cathode current is 70 µA — the series resistor must be chosen so that the total current through the reference (load current plus quiescent) stays above this floor to maintain regulation. A typical design with a 5 V supply and 1 mA load uses a 3.3 kΩ series resistor.