CY7C1518AV18-278BZI CYPRESS [Cypress Semiconductor], CY7C1518AV18-278BZI Datasheet - Page 19

• Manufacturer Part Number: CY7C1518AV18-278BZI
• Description: 72-Mbit DDR-II SRAM 2-Word Burst Architecture
• Manufacturer: CYPRESS [Cypress Semiconductor]

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
1024 cycles of stable clock.
Power Up Sequence
■
■
Power Up Waveforms
Document Number: 001-06982 Rev. *C
Apply power with DOFF tied HIGH (all other inputs can be HIGH
or LOW)
❐
❐
Provide stable power and clock (K, K) for 1024 cycles to lock
the DLL.
Apply V
Apply V
V
DD
/
DOFF
V
DD
DDQ
DDQ
before V
K
K
before V
DDQ
REF
or at the same time as V
Unstable Clock
Clock Start (Clock Starts after
V
DD
/
V
REF
DDQ
V
Stable (< +/- 0.1V DC per 50ns )
DD
/
V
DLL Constraints
■
■
■
DDQ
DLL uses K clock as its synchronizing input. The input must
have low phase jitter, which is specified as t
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 onto an incorrect frequency, causing unstable
SRAM behavior. To avoid this, provide 1024 cycles stable clock
to relock to the desired clock frequency.
Fix High (or tied to V DDQ )
> 1024 Stable clock
Stable)
CY7C1516AV18, CY7C1527AV18
CY7C1518AV18, CY7C1520AV18
Start Normal
Operation
KC Var
Page 19 of 30
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