Members of the Texas Instruments

Widebus? Family

UBT ? Transceivers Combine D-Type

Latches and D-Type Flip-Flops for

Operation in Transparent, Latched, or

Clocked Mode

Support Mixed-Mode Signal Operation (5-V

Input and Output Voltages With 3.3-V VCC)

Support Unregulated Battery Operation

Down to 2.7 V

Typical VOLP (Output Ground Bounce)

<0.8 V at VCC = 3.3 V, TA = 25°C

Ioff and Power-Up 3-State Support Hot

Insertion

Bus Hold on Data Inputs Eliminates the

Need for External Pullup/Pulldown

Resistors

Distributed VCC and GND Pins Minimize

High-Speed Switching Noise

Flow-Through Architecture Optimizes PCB

Layout

Latch-Up Performance Exceeds 500 mA Per

JESD 17

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 ’LVTH16500 devices are 18-bit universal bus

transceivers designed for low-voltage (3.3-V) VCC

operation, but with the capability to provide a TTL

interface to a 5-V system environment.

Data flow in each direction is controlled by output-enable (OEAB and OEBA), latch-enable (LEAB and LEBA),

and clock (CLKAB and CLKBA) inputs. For A-to-B data flow, the devices operate in the transparent mode when

LEAB is high. When LEAB is low, the A data is latched if CLKAB is held at a high or low logic level. If LEAB is

low, the A data is stored in the latch/flip-flop on the high-to-low transition of CLKAB. OEAB is active high. When

OEAB is high, the B-port outputs are active. When OEAB is low, the B-port outputs are in the high-impedance

state.

Data flow for B to A is similar to that of A to B, but uses OEBA, LEBA, and CLKBA. The output enables are

complementary (OEAB is active high and OEBA is active low).

Active bus-hold circuitry holds unused or undriven inputs at a valid logic state. Use of pullup or pulldown resistors

with the bus-hold circuitry is not recommended.

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

However, to ensure the high-impedance state above 1.5 V, OE should be tied to VCC through a pullup resistor

and OE should be tied to GND through a pulldown resistor; the minimum value of the resistor is determined by

the current-sinking/current-sourcing capability of the driver.

These devices are fully specified for hot-insertion applications using Ioff and power-up 3-state. The Ioff circuitry

disables the outputs, preventing damaging current backflow through the devices when they are powered down.

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

which prevents driver conflict.