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Altera_Forum
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15 years ago

isolation for Altera programmer

I have a situation where the ground of my FPGA circuit is at a potential a few volts below the earth ground. Normally, if my FPGA and PC grounds are the same, I use a USB Blaster to program either th...
Altera_Forum's avatar
Altera_Forum
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15 years ago

USB Blaster uses standard full speed. Commercially available isolators should generally work.

On the JTAG side, the total round-trip delay (the critical path is TCK + TDO) must not exceed 80 ns, including two isolator instances and all driver and target chip delays. Thus rather fast couplers are needed. NVE IL71x are e.g. good for this application. A DC-DC converter is required to feed the target power supply to the USB Blaster's JTAG drivers - or a modification of the USB Blaster to supply it internally with fixed 3.3 V.

I append a circuit of a 3.3V JTAG isolator that has served it's purpose in power electronics applications.