1 Amp will the 7660 not manage.
Then you will have to look for an real switching converter.
Perhaps you can find someting in the powersupply cookbook: http://www.maxim-ic.com/cookbook/powersupply/
Output current is max 1 Amp, but what is the input voltage? What is the output voltage?
You could use a DC to DC converter. If output voltage is -5V, you could use, for example: http://datasheets.maxim-ic.com/en/ds/MAX774-MAX776.pdf