We seem to be unable to put the PCA82C250T/YM into standby mode. We have 5V going to the chip, nothing connected to Vref, Rs is connected to 3.3V through a 100k resistor. I have checked that there is 3.3V going to the Rs pin. Why does the device still draw ~14mA. I have even lifted pins 6, 7, 1 and 4 but still the device draws ~14mA?