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CY7C1618KV18 データシート(PDF) 20 Page - Cypress Semiconductor |
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CY7C1618KV18 データシート(HTML) 20 Page - Cypress Semiconductor |
20 / 32 page Document Number: 001-44274 Rev. *N Page 20 of 32 CY7C1618KV18/CY7C1620KV18 Power Up Sequence in DDR II SRAM DDR II SRAMs must be powered up and initialized in a predefined manner to prevent undefined operations. Power Up Sequence ■ Apply power and drive DOFF either high or low (all other inputs can be high or low). ❐ Apply VDD before VDDQ. ❐ Apply VDDQ before VREF or at the same time as VREF. ❐ Drive DOFF high. ■ Provide stable DOFF (high), power and clock (K, K) for 20 s to lock the PLL PLL Constraints ■ PLL uses K clock as its synchronizing input. The input must have low phase jitter, which is specified as tKC Var. ■ The PLL functions at frequencies down to 120 MHz. ■ If the input clock is unstable and the PLL is enabled, then the PLL may lock onto an incorrect frequency, causing unstable SRAM behavior. To avoid this, provide 20 s of stable clock to relock to the desired clock frequency. Figure 4. Power Up Waveforms > 20μs Stable clock Start Normal Operation DOFF Stable (< +/- 0.1V DC per 50ns ) Fix HIGH (or tie to VDDQ) K K DDQ DD V V / DDQ DD V V / Clock Start (Clock Starts after Stable) DDQ DD V V / Unstable Clock |
同様の部品番号 - CY7C1618KV18 |
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同様の説明 - CY7C1618KV18 |
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