The 1.5KE43CA is a transient voltage suppressor (TVS) diode which is RoHS compliant (Restriction of Hazardous Substances), manufactured by the company Yageo. This type of diode is used to guard against electrical loops or transient events, protecting the connected device from over-voltage. The diode is constructed in a DO-201 package, and has break over voltages of 59.3V, 40.9V, and 36.8V.