1FEATURES

• Member of the Texas Instruments Widebus™

Family

• UBT™ Transceiver Combines D-Type Latches

and D-Type Flip-Flops for Operation in

Transparent, Latched, or Clocked Modes

• OEC™ Circuitry Improves Signal Integrity and

Reduces Electromagnetic Interference (EMI)

• Compliant With VME64, 2eVME, and 2eSST

Protocol

• Bus Transceiver Split LVTTL Port Provides a

Feedback Path for Control and Diagnostics

Monitoring

• I/O Interfaces Are 5-V Tolerant

• B-Port Outputs (–48 mA/64 mA)

• Y and A-Port Outputs (–12 mA/12 mA)

• Ioff, Power-Up 3-State, and BIAS VCC Support

Live Insertion

• Bus Hold on 3A-Port Data Inputs

• 26-Ω Equivalent Series Resistor on 3A Ports

and Y Outputs

• Flow-Through Architecture Facilitates Printed

Circuit Board Layout

• Distributed VCC and GND Pins Minimize

High-Speed Switching Noise

• Latch-Up Performance Exceeds 100 mA Per

JESD 78, Class II

• ESD Protection Exceeds JESD 22

– 2000-V Human-Body Model (A114-A)

– 200-V Machine Model (A115-A)

– 1000-V Charged-Device Model (C101)

DESCRIPTION/ORDERING INFORMATION

The SN74VMEH22501 8-bit universal bus transceiver has two integral 1-bit three-wire bus transceivers and is

designed for 3.3-V VCC operation with 5-V tolerant inputs. The UBT™ transceiver allows transparent, latched, and

flip-flop modes of data transfer, and the separate LVTTL input and outputs on the bus transceivers provide a

feedback path for control and diagnostics monitoring. This device provides a high-speed interface between cards

operating at LVTTL logic levels and VME64, VME64x, or VME320(1) backplane topologies.

(1) VME320 is a patented backplane construction by Arizona Digital, Inc.

High-speed backplane operation is a direct result of the improved OEC™ circuitry and high drive that has been

designed and tested into the VME64x backplane model. The B-port I/Os are optimized for driving large capacitive

loads and include pseudo-ETL input thresholds (½ VCC ± 50 mV) for increased noise immunity. These

specifications support the 2eVME protocols in VME64x (ANSI/VITA 1.1) and 2eSST protocols in VITA 1.5. With

proper design of a 21-slot VME system, a designer can achieve 320-Mbyte transfer rates on linear backplanes

and, possibly, 1-Gbyte transfer rates on the VME320 backplane.

All inputs and outputs are 5-V tolerant and are compatible with TTL and 5-V CMOS inputs.

Active bus-hold circuitry holds unused or undriven 3A-port inputs at a valid logic state. Bus-hold circuitry is not

provided on 1A or 2A inputs, any B-port input, or any control input. Use of pullup or pulldown resistors with the

bus-hold circuitry is not recommended.

This device is fully specified for live-insertion applications using Ioff, power-up 3-state, and BIAS VCC. The Ioff

circuitry prevents damaging current to backflow through the device when it is powered off/on. The power-up

3-state circuitry places the outputs in the high-impedance state during power up and power down, which prevents

driver conflict. The BIAS VCC circuitry precharges and preconditions the B-port input/output connections,

preventing disturbance of active data on the backplane during card insertion or removal, and permits true

live-insertion capability.

When VCC is between 0 and 1.5 V, the device is in the high-impedance state during power up or power down.

However, to ensure the high-impedance state above 1.5 V, output-enable (OE and OEBY) inputs should be tied

to VCC through a pullup resistor and output-enable (OEAB) inputs should be tied to GND through a pulldown

resistor; the minimum value of the resistor is determined by the drive capability of the device connected to this

input.