72 Mb (2M x 36 & 4M x 18)
Q7 UAD (Burst o. f 4) Synchronous SRAMs
• 2M x 36 or 4M x 18.
• On-chip delay-locked loop (DLL) for wide data
• Separate read and write ports with concurrent
read and write operations.
• Synchronous pipeline read with late write opera-
• Double data rate (DDR) interface for read and
write input ports.
• Fixed 4-bit burst for read and write operations.
• Clock stop support.
• Two input clocks (K and K) for address and con-
trol registering at rising edges only.
• Two input clocks (C and C) for data output con-
• Industrial temperature available
• Two echo clocks (CQ and CQ) that are delivered
simultaneously with data.
• +1.8V core power supply and 1.5, 1.8V VDDQ,
used with 0.75, 0.9V VREF.
• HSTL input and output levels.
• Registered addresses, write and read controls,
byte writes, data in, and data outputs.
• Full data coherency.
• Boundary scan using limited set of JTAG 1149.1
• Byte write capability.
• Fine ball grid array (FBGA) package
- 15mm x 17mm body size
- 1mm pitch
- 165-ball (11 x 15) array
• Programmable impedance output drivers via 5x
user-supplied precision resistor.
The 72Mb IS61QDB42M36 and
IS61QDB44M18 are synchronous, high-perfor-
mance CMOS static random access memory
(SRAM) devices. These SRAMs have separate I/Os,
eliminating the need for high-speed bus turnaround.
The rising edge of K clock initiates the read/write
operation, and all internal operations are self-timed.
Refer to the Timing Reference Diagram for Truth
Table on page 8 for a description of the basic opera-
tions of these QUAD (Burst of 4) SRAMs.
Read and write addresses are registered on alter-
nating rising edges of the K clock. Reads and writes
are performed in double data rate. The following are
registered internally on the rising edge of the K
• Read/write address
• Read enable
• Write enable
• Byte writes for burst addresses 1 and 3
• Data-in for burst addresses 1 and 3
The following are registered on the rising edge of
the K clock:
Integrated Silicon Solution, Inc.
• Byte writes for burst addresses 2 and 4
• Data-in for burst addresses 2 and 4
Byte writes can change with the corresponding data-
in to enable or disable writes on a per-byte basis. An
internal write buffer enables the data-ins to be regis-
tered one cycle after the write address. The first
data-in burst is clocked one cycle later than the write
command signal, and the second burst is timed to
the following rising edge of the K clock. Two full
clock cycles are required to complete a write opera-
During the burst read operation, the data-outs from
the first and third bursts are updated from output
registers off the second and fourth rising edges of
the C clock (starting 1.5 cycles later). The data-outs
from the second and fourth bursts are updated with
the third and fifth rising edges of the C clock. The K
and K clocks are used to time the data-outs when-
ever the C and C clocks are tied high. Two full clock
cycles are required to complete a read operation
The device is operated with a single +1.8V power
supply and is compatible with HSTL I/O interfaces.