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Altera_Forum
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10 years ago

DDR2 VREF problem

Hi, My FPGA design uses 4 ddr2 devices. And I use LP2996 to output VTT and VREF for FPGA and DDR2. However, VREF measures 1.43V other than 0.9V. After I cut the VREF output trace, I found LP299...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
10 years ago

You may have made the same mistake I did a couple of years ago. The pin labeled VREF on the LP2996 is NOT the pin that gets connected to VREF on the FPGA. It is for capacitor bypassing only. Pins VTT/VSENSE on the LP2996 get connected to the FPGA VREF pins.