If you are using Cypress DVK you have to set the board jumpers
to 5V and in PSOC Creator open *.cydwr file in workspace window,
pick "System" tab, and set the Vdd voltages to 5.0 V. The latter sets
up the firmware in startup for the chip to make sure various chip
settings and constants are made aware of the Vdd used.
Are you talking about a specific board (e.g. the -050 series)?
USB should deliver more than just 4V, this looks like you got a rather bad (or long) cable, it should be more of 4.7V or even higher. In that case the board can not really do anything about that (apart from using a step-up converter, maybe)
If you are using are Cypress Development kit, they all come with an external power connector, where you can attach a power supply (9-12V). Then you get proper 5V (provided the jumpers on the board are set to this voltage).
Thanks for hte answer,
But , I have to take this 5V from an external source and then linking this to the jumper, or from an internal source in the PsoC?
depends on what development kit you are using. If you are using the -050 kit you can use J10 and J11 to set up VDDD and VDDA and supply 7v-12v via the barrel conector J4 or battery via U2.
If you don't want to use external supply and work only with VUSB then you will be limited to 4.4-4.7 depending on VUSB