FEATURES

· TI-OPC™ Circuitry Limits Ringing on

Unevenly Loaded Backplanes

· OEC™ Circuitry Improves Signal Integrity and

Reduces Electromagnetic Interference

· Bidirectional Interface Between GTLP Signal

Levels and LVTTL Logic Levels

· Split LVTTL Port Provides a Feedback Path

for Control and Diagnostics Monitoring

· Y Outputs Have Equivalent 26-W Series

Resistors, So No External Resistors Are

Required

· LVTTL Interfaces Are 5-V Tolerant

· High-Drive GTLP Outputs (100 mA)

· LVTTL Outputs (–12 mA/12 mA)

· Variable Edge-Rate Control (ERC) Input

Selects GTLP Rise and Fall Times for Optimal

Data-Transfer Rate and Signal Integrity in

Distributed Loads

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

Live Insertion

· Polarity Control Selects True or

Complementary Outputs

· 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 SN74GTLP21395 is two 1-bit, high-drive, 3-wire bus transceivers that provide LVTTL-to-GTLP and

GTLP-to-LVTTL signal-level translation for applications, such as primary and secondary clocks, that require

individual output-enable and true/complement controls. The device allows for transparent and inverted

transparent modes of data transfer with separate LVTTL input and LVTTL output pins, which provide a feedback

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

at LVTTL logic levels and a backplane operating at GTLP signal levels and is designed especially to work with

the Texas Instruments 3.3-V 1394 backplane physical-layer controller. High-speed (about three times faster than

standard LVTTL or TTL) backplane operation is a direct result of GTLP reduced output swing (<1 V), reduced

input threshold levels, improved differential input, OEC™ circuitry, and TI-OPC™ circuitry. Improved GTLP OEC

and TI-OPC circuitry minimizes bus settling time, and have been designed and tested using several backplane

models. The high drive allows incident-wave switching in heavily loaded backplanes, with equivalent load

impedance down to 11 W.

The Y outputs, which are designed to sink up to 12 mA, include equivalent 26-W resistors to reduce overshoot

and undershoot.

GTLP is the Texas Instruments derivative of the Gunning Transceiver Logic (GTL) JEDEC standard JESD 8-3.

The ac specification of the SN74GTLP21395 is given only at the preferred higher noise margin GTLP, but the

user has the flexibility of using this device at either GTL (VTT = 1.2 V and VREF = 0.8 V) or GTLP (VTT = 1.5 V and

VREF = 1 V) signal levels. For information on using GTLP devices in FB+/BTL applications, refer to TI application

reports, Texas Instruments GTLP Frequently Asked Questions, literature number SCEA019, and GTLP in BTL

Applications, literature number SCEA017.

Normally, the B port operates at GTLP signal levels. The A-port and control inputs operate at LVTTL logic levels,

but are 5-V tolerant and are compatible with TTL or 5-V CMOS devices. VREF is the B-port differential input

reference voltage.

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

circuitry disables the outputs, preventing damaging current backflow through the device when it is 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. 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.

This GTLP device features TI-OPC circuitry, which actively limits the overshoot caused by improperly terminated

backplanes, unevenly distributed cards, or empty slots during low-to-high signal transitions. This improves signal

integrity, which allows adequate noise margin to be maintained at higher frequencies.

High-drive GTLP backplane interface devices feature adjustable edge-rate control (ERC). Changing the ERC

input voltage between low and high adjusts the B-port output rise and fall times. This allows the designer to

optimize system data-transfer rate and signal integrity to the backplane load.

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, the output-enable (OE) input should be tied to VCC

through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the

driver.