I have an application board with ADUC831BS on it. In this board, Vref(7) and Cref(8) are connected together and brought to a bypass capacitor and the base of an open collector Transistor.Emitter of the Transistor is grounded. It measures 2.5V.This Vref is used on board as ref for two more ADC channels. But if I remove the Transistor,the Voltage on Vref+Cref reads almost equal to AVdd.
Now,ADUC831BS manual states the bandgap reference of 2.5V is internal. But by above, it appears that NTC of a normal BJT needs to be connected to ADUC831BS for realising 2.5V reference. Which is true ?