The MCP1525 is a simple, 3 pin voltage reference that provides a 2.5V output voltage reference.
The MCP1541 is basically the same part, with an output of 4.1V.
These devices are simple options for providing a reliable voltage reference (aref) for A/D conversions - whether an Arduino or MCP3008 ADC chip.
IMPORTANT: The output pin MUST have a load capacitor of 1uF to 10uF between output and ground.
If the voltage reference is reading .24V instead of 2.5V, check the capacitor.
With the flat facing forward, the pins from left to right are:
====
1 2 3
1=VSS (GND)
2=Vout
3=Vin
Absolute max input is 7.0V.
MCP1525 output is rated for an input range of 2.7V to 5.5V - so this would work for either 3.3V or 5V supply.
Current output by the device is limited to 20mA.
Continuous power dissipation is 140mW.
Note that at low temp, voltage will fall off. At -50C, output is rated for 2.495V instead of 2.50V.
At ~20C to 100C, the output voltage should be solid at 2.50V.