CY2305 Cypress Semiconductor, CY2305 Datasheet - Page 6

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

2 SDRAM DIMM Zero Delay Buffer Solution
The CY2309 is an excellent clocking solution for a system
using 2 SDRAM DIMMs. The CY2309 comes in a small
150-mil 16-pin SOIC package and is priced very aggressively
for the high volume PC market. There are two solutions for
implementing 2 SDRAM DIMMs support with the CY2309:
the first is the adjustable delay solution, and the second is the
self adjusting delay solution.
The Self Adjusting Solution:
• This solution will automatically compensate for different
• CLKOUT must drive CK0 on the SDRAM module 1 so that
SDRAM input loads (only on module 1).
CLKOUT is always fully loaded (pin 42 on the SDRAM
module).
CPUCLK
CPUCLK
Decoding
Decoding
Logic
Logic
REF
S1
S2
CY2309
Zero Delay
Buffer
REF
S1
S2
CY2309
Zero Delay
Buffer
CLKOUT
CLKOUT
CLKA1
CLKA2
CLKA3
CLKA4
CLKB1
CLKB2
CLKB3
CLKB4
CLKA1
CLKA2
CLKA3
CLKA4
CLKB1
CLKB2
CLKB3
CLKB4
6
CY2305 and CY2309 as PCI and SDRAM Buffers
The Adjustable Delay Solution:
• C
• To make the SDRAM inputs lead or lag the reference input
• Clocks are three-stated when that SDRAM module is not
• If only 1 SDRAM module is installed it must be module 1.
• If only one SDRAM module is installed it must be module 1.
• CLKA and CLKB clocks are three-stated when their re-
delay.
see the Lead or Lag Adjustments section of “Special Fea-
tures of the Cypress Zero Delay Buffers”.
present.
spective SDRAM module is not present, but CLKOUT will
continue to run.
load
C
load
must be equal to SDRAM module loading for zero
SDRAM Module 1
SDRAM Module 2
SDRAM Module 1
SDRAM Module 2
Module Sense
Module Sense
Module Sense
Module Sense