DP83241

Features:

· Provides 12.5 MHz and 25 MHz TTL clocks
· 12.5 MHz and 125 MHz ECL clocks
·5 phase TTL local byte clocks eliminate clock skew problems in concentrators
· Internal VCO requires no varactors, coils or adjustments
· Option for use of High Q external VCO
·125 MHz clock generated from a 12.5 MHz crystal
·External PLL synchronizing reference for concentrator configurations
·28-pin PLCC package
· BiCMOS processing


Application

An application where many of the features of the CDD device are used is a FDDI concentrator. A concentrator is used to connect several workstations and peripherals to a single node in the network. A concentrator provides the ability to easily bypass or insert multiple stations into the network. The CDD device in each station is driven from a common oscillator instead of each CDD device being driven by its own crystal. In a small concentrator, the same LBC phase can be used in each station since the data flight time from one board to another is small compared to the LBC period and the skew between the CDD devices on the two boards is minimal. In a larger concentrator configuration where this skew becomes too large, the data setup time of the downstream station will be directly impacted. One way to avoid this problem is to latch data into the next station. The strobe for the latch will be supplied by one of the LBC outputs from the upstream station's CDD device. An LBC output phase is chosen that occurs after the physical layer data is stable. Assuming that the data and LBC flight times are equal, the LBC output will latch data for the next station. The LBC output phase should be selected to give the optimum setup and hold time for the receiving station's physical layer function.


Pinout




Specifications

Storage Temperature             -65 to +150
TTL Signals
  Inputs                                    -0.5V to +5.5V
  Outputs                                 -0.5V to +5.5V
ECL Signals
  Output Current                                  -50 mA
Supplies
EXTVCC to EXTGND                    -0.5V to +7V
  DVCC to DGND                         -0.5V to +7V
  AVCC to AGND                         -0.5V to +7V
ESD Protection                                     1500V


Description

The CDD device DP83241 is a clock generation and distribution device intended for use in FDDI (Fiber Distributed Data Interface) networks. The DP83241 provides the complete set of clocks required to convert byte wide data to serial format for fiber medium transmission and to move byte wide data between the PLAYERTM and BMACTM devices in various station configurations. 12.5 MHz and 125 MHz differential ECL clocks are generated for the conversion of data to serial format and 12.5 MHz and 25 MHz TTL clocks are generated for the byte wide data transfers.