SN54FB2033, SN74FB2033 8-BIT TTL/BTL REGISTERED TRANSCEIVERS

SCBS174B - NOVEMBER 1991 - REVISED MAY 1994

features

• TTL A Port, Backplane Transceiver Logic (BTL) B\ Port
• Open-Collector B\-Port Outputs Sink 100 mA
• Isolated Logic-Ground and Bus-Ground Pins Reduce Noise
• BIAS V_CC Pin Minimizes Signal Distortion During Live Insertion/Withdrawal
• Available in Plastic Quad Flatpack (RC) and Ceramic Flatpack (WD) Packages
• B\-Port Biasing Network Preconditions the Connector and PC Trace to the Backplane Transceiver Logic High-Level Voltage
• TTL-Input Structures Incorporate Active Clamping Networks to Aid in Line Termination

  NC - No internal connection

description

The ´FB2033 is an 8-bit transceiver featuring a split input (AI) and output (AO) bus on the TTL-level A port. The common-I/O, open-collector B\ port operates at backplane transceiver logic (BTL) signal levels.

The logic element for data flow in each direction is configured by two mode inputs (IMODE1 and IMODE0 for B-to-A, OMODE1 and OMODE0 for A-to-B) as a buffer, a D-type flip-flop, or a D-type latch. When configured in the buffer mode, the inverted input data appears at the output port. In the flip-flop mode, data is stored on the rising edge of the appropriate clock input (CLKAB/LEAB or CLKBA/LEBA). In the latch mode, the clock pins serve as active-high transparent latch enables.

Data flow in the B-to-A direction, regardless of the logic element selected, is further controlled by the LOOPBACK input. When LOOPBACK is low, B\-port data is the B-to-A input. When LOOPBACK is high, the output of the selected A-to-B logic element (prior to inversion) is the B-to-A input.

The AO port-enable/-disable control is provided by OEA. When OEA is low or when V_CC is less than 2.5 V, the AO port is in the high-impedance state. When OEA is high, the AO port is active (high or low logic levels).

The B\ port is controlled by OEB and OEB\. If OEB is low or OEB\ is high or when V_CC is typically less than 2.5V, the B\ port is inactive. If OEB is high and OEB\ is low, the B port is active.

BG V_CC and BG GND are the bias generator reference inputs.

The A-to-B and B-to-A logic elements are active regardless of the state of their associated outputs. The logic elements can enter new data (in flip-flop and latch modes) or retain previously stored data while the associated outputs are in the high-impedance (AO port) or inactive (B\ port) states.

Output clamps are provided on the BTL outputs to reduce switching noise. One clamp reduces inductive ringing effects on V_OH during a low-to-high transition. The other clamps out ringing below the BTL V_OL voltage of 0.75 V. Both these clamps are active only during AC switching and do not affect the BTL outputs during steady-state conditions.

BIAS V_CC establishes a voltage between 1.62 V and 2.1 V on the BTL outputs when V_CC is not connected.

The SN54FB2033 is characterized for operation over the full military temperature range of -55°C to 125°C. The SN74FB2033 is characterized for operation from 0°C to 70°C.

View more information about generic part numbers:SN74FB2033

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