K7R641884M SAMSUNG [Samsung semiconductor], K7R641884M Datasheet - Page 6

• Manufacturer Part Number: K7R641884M
• Description: 2Mx36 & 4Mx18 QDRTM II b4 SRAM
• Manufacturer: SAMSUNG [Samsung semiconductor]

K7R643684M
Echo clock operation
K7R641884M
Single Clock Mode
Depth Expansion
Separate input and output ports enables easy depth expansion.
Each port can be selected and deselected independently and read and write operation do not affect each other.
Before chip deselected, all read and write pending operations are completed.
The designer can program the SRAM's output buffer impedance by terminating the ZQ pin to V
The value of RQ (within 15%) is five times the output impedance desired.
For example, 250
Impedance updates occur early in cycles that do not activate the outputs, such as deselect cycles.
In all cases impedance updates are transparent to the user and do not produce access time "push-outs" or other anomalous
behavior in the SRAM.
There are no power up requirements for the SRAM. However, to guarantee optimum output driver impedance after power up,
K7R643684M and K7R641884M utlizes internal DLL(Delay-Locked Loops) for maximum output data valid window.
It can be placed into a stopped-clock state to minimize power with a modest restart time of 1024 clock cycles.
Circuitry automatically resets the DLL when absence of input clock is detected.
Power-Up/Power-Down Supply Voltage Sequencing
The following power-up supply voltage application is recommended: V
simultaneously, as long as V
removal sequence is recommended: V
does not exceed V
The K7R643684M and K7R641884M can be operated with the single clock pair K and K, insted of C or C for output clocks.
To operate these devices in single clock mode, C and C must be tied high during power up
and must be maintained high during operation.
After power up, this device can’t change to or from single clock mode.
System flight time and clock skew could not be compensated in this mode.
Programmable Impedance Output Buffer Operation
Clock Consideration
To assure the output tracibility, the SRAM provides the output Echo clock, pair of compliment clock CQ and CQ,
which are synchronized with internal data output.
Echo clocks run free during normal operation.
The Echo clock is triggered by internal output clock signal, and transfered to external through same structures as output driver.
the SRAM needs 1024 non-read cycles.
DD
resistor will give an output impedance of 50 .
by more than 0.5V during power-down.
DDQ
does not exceed V
IN
, V
REF
, V
DDQ
DD
, V
by more than 0.5V during power-up. The following power-down supply voltage
DD
, V
SS
- 6 -
. V
DD
2Mx36 & 4Mx18 QDR
SS
and V
, V
DD
DDQ
, V
DDQ
can be removed simultaneously, as long as V
, V
REF
, then V
SS
through a precision resistor(RQ).
IN
. V
DD
and V
TM
Preliminary
II b4 SRAM
DDQ
can be applied
Oct. 2004
Rev 0.5
DDQ