CY2305 Cypress Semiconductor, CY2305 Datasheet - Page 7

• Manufacturer Part Number: CY2305
• Description: CY2305 and CY2309 as PCI and SDRAM Buffers
• Manufacturer: Cypress Semiconductor

3 SDRAM DIMM Zero Delay Buffer Solution
The CY2305 and CY2309 are excellent clocking solutions for
a system using 3 SDRAM DIMMs. The CY2305 comes in a
small 150-mil 8-pin SOIC package and the CY2309 comes in
a small 150-mil 16-pin SOIC. Both buffers are priced very
aggressively for the high volume PC market. There are two
solutions for implementing 3 SDRAM DIMMs support with the
CY2305 and CY2309: the first is the adjustable delay solution,
and the second is the self adjusting delay solution.
CPUCLK
Decoding
Logic
REF
REF
S1
S2
CY2305
Zero Delay
Buffer
CY2309
Zero Delay
Buffer
CLKOUT
CLKOUT
CLKA1
CLKA2
CLKA3
CLKA4
CLKB1
CLKB2
CLKB3
CLKB4
CLK4
CLK3
CLK2
CLK1
7
CY2305 and CY2309 as PCI and SDRAM Buffers
The Adjustable Delay Solution:
• C
• To make the SDRAM inputs lead or lag the reference input
• SDRAM modules must be installed in order (module 1 first
• Module 2 and 3 clocks are three-stated when those
• Module 1 clocks can only be three-stated by three-stating
for zero delay.
see the Lead or Lag Adjustments section of “Special Fea-
tures of the Cypress Zero Delay Buffers”.
and module 3 last).
SDRAM modules are not present, but CLKOUT will
continue to run.
CPUCLK which will also three-state modules 2 and 3.
C
C
load1
load1
load2
SDRAM Module 1
SDRAM Module 2
SDRAM Module 3
and C
load2
Module Sense
Module Sense
must be equal to SDRAM module loading