Applying Vdd and Vddq during QDRII/DDRII power up sequence

Question: The QDR datasheet recommends that during power up sequence to apply Vdd before Vddq. Is it mandatory during the power up sequence to apply Vdd before Vddq?



Response: It is recommended to apply Vdd before Vddq during QDRII/DDRII power up sequence. However, it is not a requirement to apply the Vdd before the Vddq for Cypress QDRII/DDRII devices and has been specified in the Cypress datasheets to accommodate the requirements of other vendors  in the QDR consortium. Vdd and Vddq can be applied simultaneously during power up, as long as Vddq does not exceed Vdd by more than 0.5V during power-up.