TI announces replacements for discontinued Agere translators

Texas Instruments Inc. (TI) introduced seven pseudo emitter-coupled logic (PECL) and translator/transistor logic (TTL) drivers and receivers, including one of the industry's first 3.3V PECL translators and five devices that, according to TI, are direct replacements for translators discontinued by Agere Systems Inc.

The devices translate between differential input logic levels and TTL output logic levels. Designed for handling digital data or clock signals over balanced transmission lines, they are suitable for telecommunications and medical imaging applications.

The 3.3V TB3R1 and TB3R2 quad differential PECL receivers offer a low-voltage migration path for designers who have previously used 5V supply PECL devices. TI said the five other devices: TB5D1M, TB5D2H, TB5R1, TB5R2 and TB5T1, have combined features to replace nine former Agere PECL devices, and match the original Agere pinouts, allowing for plug-in replacement. Each device offers 3kV HBM and 2kV CDM electrostatic discharge (ESD) protection and an operating temperature range between -40°C and 85°C.

Main features of the TB5D1M and TB5D2H include a 5V or 3.3V supply operation, three-state output with a third-state level of <0.1V, surge protection on differential outputs (TB5D1M), no line loading when Vcc = 0 (TB5D2H) and logic inputs that include internal pull-up resistors of approximately 40 kiloohms that are connected to Vcc to ensure a logical high level input if the inputs are open circuited.

Translating PECL input levels to TTL output logic levels, the TB5R1, TB5R2, TB3R1 and TB3R2 feature power supplies of 5V (TB5R1 and TB5R2) and 3.3V (TB3R1 and TB3R2), hysterisis of 50mV (TB5R1 and TB3R1), and preferred state output (TB5R2 and TB3R2). The power-down loading characteristics of the receiver input circuit are approximately 8 kiloohms relative to the power supplies to prevent loading the transmission line when the device is powered down. Additionally, the enable inputs include internal pull-up resistors of approximately 40 kiloohms connected to Vcc to ensure a logical high level input if the inputs are open circuited.

With a 5V supply, the TB5T1 dual differential PECL driver/receiver translates TTL input levels to differential PECL output levels (driver) or converts PECL input levels to TTL output levels (receiver). And like the TB5D1M and TB5D2H, this device also has internal pull-up resistors of approximately 40 kiloohms. In addition, the power-down loading characteristics of the receiver input circuit are approximately 8 kiloohms relative to the power supplies to prevent loading the transmission line when the device is powered down, and each pair has its own common-mode enable control, allowing serial data and a control clock to be transmitted and received on a single circuit. In circuits with termination resistors, the line remains impedance-matched when the circuit is powered down.