I have a mobile phone wall charger which is a usb connection and wondering if I can use it to charge my sansa clip the values on the charger are as follows

ac input       100-240v-50/60Hz 0.3A

dc output     5.4Vdc 0.7A  3.78W

 any help at all, as the wall chargers I have seen for sale for the sansa clip seem to be 500mA or 1000mA and wouldn't wish to cause harm if the one I have is too high an output.........