Texas Instruments SN74GTLPH1655DGG

Overview

SN74GTLPH1655 from Texas Instruments is a 16-bit universal bus transceiver (UBT) enabling bidirectional LVTTL-to-GTL+ and GTL+-to-LVTTL level translation. It operates in transparent, latched, or clocked modes with dual 8-bit partitions, 100 mA GTL+ drive capability, 5-V-tolerant LVTTL I/O, and adjustable edge-rate control via ERC pin. It targets high-speed backplane interfaces in modular computing systems.

For engineers reviewing the SN74GTLPH1655 datasheet, SN74GTLPH1655 pinout, SN74GTLPH1655 application, or SN74GTLPH1655 equivalent, key selection criteria include GTL+/GTL signal-level compatibility, live-insertion support (Ioff, power-up 3-state, BIAS VCC), bus-hold on A-port inputs, distributed VCC/GND for noise reduction, and ERC-controlled B-port rise/fall times (0.6 V to 1.3 V).

Technical Context

The SN74GTLPH1655 integrates D-type latches and D-type flip-flops per 8-bit channel, supporting independent latch-enable (LEAB/LEBA) and output-enable (OEAB/OEBA) control with a shared CLK. Its dual-word architecture enables simultaneous but separately timed A-to-B and B-to-A data flow under common clock synchronization.

It implements GTL+ signaling (VTT = 1.5 V, VREF = 1 V) on the B port while maintaining LVTTL compatibility (VIH = 2 V, VIL = 0.8 V) and 5-V tolerance on A-port and control inputs. Edge-rate control is achieved by biasing the ERC pin to GND (fast) or VCC (slow), directly adjusting B-port output transition times without external components.

Key Specifications

Pinout & Package

SN74GTLPH1655 is housed in a 64-pin plastic thin shrink small-outline package (DGG), with distributed VCC and GND pins to minimize high-speed switching noise. Pin numbering follows top-view orientation as defined in TI SCES294.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar universal bus transceiver applications.

Compared with SN74GTL1655DGG and SN74GTLPH16623DGGR, the SN74GTLPH1655DGG uniquely combines per-byte latch control, full live-insertion support, and adjustable edge-rate tuning - making it the only option among the three qualified for high-reliability, hot-pluggable backplane systems requiring both timing flexibility and robust physical layer management.

Availability

SN74GTLPH1655 is available at Aetrix Electronics and suitable for modular server backplanes, telecom line cards, high-density computing racks, and industrial control backplanes requiring stable component supply across extended product lifecycles.

Supply support for SN74GTLPH1655 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor company specializing in analog, embedded processing, and logic solutions, with decades of leadership in interface and level-shifting technologies.

The SN74GTLPH1655 belongs to TI's GTL+ Universal Bus Transceiver (UBT) product line, designed specifically for high-speed, hot-pluggable backplane interconnects in telecom, computing, and industrial infrastructure.

FAQ

What is the primary function of the SN74GTLPH1655 in a backplane system?

The SN74GTLPH1655 serves as a bidirectional LVTTL-to-GTL+ and GTL+-to-LVTTL level translator, enabling high-speed communication between LVTTL-based modules and GTL+-compliant backplanes. Its 100 mA B-port drive supports double-terminated low-impedance traces, while ERC-controlled edge rates optimize signal integrity. The SN74GTLPH1655 is explicitly designed for this role in modular systems requiring incident-wave switching and live insertion.

How does the ERC pin affect SN74GTLPH1655 performance in real-world layouts?

The ERC pin on the SN74GTLPH1655 directly controls B-port output rise and fall times: tying ERC to GND yields fast transitions (~0.8 ns), while tying it to VCC produces slower edges (~1.5 ns). This allows designers to tune timing margins and reduce ringing or crosstalk on specific backplane loads without redesigning PCBs. Real measurements confirm these values under 30 pF load and 1.5 V swing (0.6 V to 1.3 V), as validated in TI SCES294 Figure 3 test conditions.

Does the SN74GTLPH1655 support both GTL and GTL+ signaling standards?

Yes, the SN74GTLPH1655 supports both GTL (VTT = 1.2 V, VREF = 0.8 V) and GTL+ (VTT = 1.5 V, VREF = 1 V) signaling. Its AC specifications are fully characterized for GTL+, but DC and functional operation are verified across both standards. The device's input thresholds and output drive remain compliant under either configuration, allowing flexible deployment across legacy and newer backplane architectures - a capability confirmed in the "description (continued)" section of SCES294.

What live-insertion features does the SN74GTLPH1655 implement, and how do they protect the system?

The SN74GTLPH1655 implements three coordinated live-insertion features: Ioff circuitry disables outputs when VCC = 0 V to prevent damaging backflow current; power-up 3-state forces all I/O into high-Z during power ramp-up/down to avoid bus conflicts; and BIAS VCC precharges B-port lines before VCC is applied, eliminating glitches on active backplanes. These functions are tested per SCES294 Sections 8–9 and ensure safe hot-swap operation in carrier-card systems - a requirement explicitly called out in the device's functional description.

Can the SN74GTLPH1655 replace older transceivers like the '16245 or '16623, and what are the trade-offs?

Yes, the SN74GTLPH1655 is documented in Table 1 of SCES294 as a functional replacement for '16245 (transceiver), '16623 (registered transceiver), and others. Unlike '16245, it adds GTL+ compatibility, ERC control, and live-insertion support. Compared to '16623, it provides per-byte latch enable (LEAB/LEBA) instead of global register control - enabling finer-grained timing. These differences are specified in the "functional description" and "Table 1" sections of the official datasheet.