CY7C1566V18, CY7C1577V18
CY7C1568V18, CY7C1570V18
Document Number: 001-06551 Rev. *E Page 19 of 28
Power Up Sequence in DDR-II+ SRAM
DDR-II+ SRAMs must be powered up and initialized in a
predefined manner to prevent undefined operations. During
power up, when the DOFF is tied HIGH, the DLL is locked after
2048 cycles of stable clock.

Power Up Sequence

■Apply power with DOFF tied HIGH (All other inputs can be
HIGH or LOW)
❐Apply VDD before VDDQ
❐Apply VDDQ before VREF or at the same time as VREF
■Provide stable power and clock (K, K) for 2048 cycles to lock
the DLL.

DLL Constraints

■DLL uses K clock as its synchronizing input. The input must
have low phase jitter, which is specified as tKC Var.
■The DLL functions at frequencies down to 120 MHz.
■If the input clock is unstable and the DLL is enabled, then the
DLL may lock on to an incorrect frequency, causing unstable
SRAM behavior. To avoid this, provide 2048 cycles stable clock
to relock to the desired clock frequency.
Power Up Waveforms
Figure 3. Power Up Waveforms

K

K

Fix HIGH (tie to VDDQ)

VDD/VDDQ

DOFF

Clock Start (Clock Starts after VDD/VDDQ is Stable)
Unstable Clock > 2048 Stable Clock Start Normal
Operation
~
~
~
~
VDD/VDDQ Stable (< + 0.1V DC per 50 ns)
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