DS3893A

The DS3893A TURBOTRANSCEIVER is designed for use in very highspeed bus systems. The bus terminal characteristics of theTURBOTRANSCEIVER are referred to as "BackplaneTransceiver Logic" (BTL). BTL is a new logic signaling stan-dard that has been developed to enhance the performanceof backplane buses. BTL compatible transceivers featurelow output capacitance drivers to minimize bus loading, a 1Vnominal signal swing for reduced power consumption andreceivers with precision thresholds for maximum noise im-munity. This new standard eliminates the settling time de-lays, that severely limit the TTL bus performance, to providesignificantly higher bus transfer rates.

The DS3893A TURBOTRANSCEIVER is compatible with the require-ments of the proposed IEEE 896 Futurebus draft standard. Itis similar to the DS3896/97 BTL TRAPEZOIDAL™ Trans-ceivers but the trapezoidal feature has been removed toimprove the propagation delay. A stripline backplane is there-fore required to reduce the crosstalk induced by the fasterrise and fall times. This device can drive a 10Ω load with atypical propagation delay of 3.5 ns for the driver and 5 ns forthe receiver.

When multiple devices are used to drive a parallel bus, thedriver enables can be tied together and used as a commoncontrol line to get on and off the bus. The driver enable delayis designed to be the same as the driver propagation delay inorder to provide maximum speed in this configuration. Thelow input current on the enable pin eases the drive requiredfor the common control line.

The DS3893A bus driver is an open collector NPN with a Schottkydiode in series to isolate the transistor output capacitancefrom the bus when the driver is in the inactive state. Theactive output low voltage is typically 1V. The bus is intendedto be operated with termination resistors (selected to matchthe bus impedance) to 2.1V at both ends. Each of theresistors can be as low as 20Ω.