The AX1500 requires a 10 Ohm/1 Watt resistor in series with the Vcon connection IF the power supply voltage applied to Vcon exceeds 20 volt.
This is a standard resistor and can be purchased from any electronic distributor (Digikey P/N RSF1JT10R0CT-ND or FMP100JR-52-10R) or even from Radio Shack or Fry's electronics if only one piece is needed.