Cypress CY7C1245V18 Manual De Usuario

Document Number: 001-06365 Rev. *D

Page 20 of 28

QDR-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.

■

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 2048 cycles to lock 
the DLL.

■

DLL uses K clock as its synchronizing input. The input must
have low phase jitter, which is specified as t

KC 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 onto an incorrect frequency, causing unstable 
SRAM behavior. To avoid this, provide 2048 cycles stable clock 
to relock to the clock frequency you want.

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)