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CY7C1292DV18
CY7C1294DV18
Document #: 001-00350 Rev. *A Page 16 of 23
Power-Up Sequence in QDR-II SRAM
[16]
QDR-II SRAMs must be powered up and initialized in a
predefined manner to prevent undefined operations.
Power-Up Sequence
• Apply power with DOFF
tied HIGH (All other inputs can be
HIGH or LOW)
—Apply V
DD
before V
DDQ
—Apply V
DDQ
before V
REF
or at the same time as V
REF
• Provide stable power and clock (K, K) for 1024 cycles to
lock the DLL.
DLL Constraints
• DLL uses K clock as its synchronizing input. The input
should have low phase jitter, which is specified as t
KC Var
.
• The DLL will function at frequencies down to 80 MHz.
• If the input clock is unstable and the DLL is enabled, then
the DLL may lock onto an incorrect frequency, causing
unstable SRAM behavior. To avoid this, provide 1024 cycles
stable clock to relock to the desired clock frequency.
Notes:
15.It is recommended that the DOFF
pin be pulled HIGH via a pull up resistor of 1Kohm.
16.During Power-Up, when the DOFF is tied HIGH, the DLL gets locked after 1024 cycles of stable clock.
Power-up Waveforms
> 1024 Stable clock
Start Normal
Operation
DOFF
Stable (< +/- 0.1V DC per 50ns )
Fix High (or tied to V
DDQ
)
K
K
DDQ
DD
V
V
/
DDQ
DD
V
V
/
Clock Start
(Clock Starts after Stable)
DDQ
DD
V
V
/
~
~
~
~
Unstable Clock
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