Texas Instruments SN74GTLPH1645GQLR

Overview

SN74GTLPH1645GQLR from Texas Instruments is a 16-bit LVTTL-to-GTLP bidirectional bus transceiver with adjustable edge-rate control (ERC), high-drive GTLP outputs (100 mA), 5-V-tolerant LVTTL inputs, and live-insertion support via Ioff, power-up 3-state, and BIAS VCC. It enables high-speed backplane communication in telecom line cards and modular computing systems.

For engineers reviewing the SN74GTLPH1645GQLR datasheet, SN74GTLPH1645GQLR pinout, SN74GTLPH1645GQLR application, or SN74GTLPH1645GQLR equivalent, key selection criteria include GTLP/LVTTL level translation capability, ERC-controlled rise/fall times (1.2–2.5 ns fast mode), distributed-load timing performance (3.7 ns A→B propagation), live-insertion compliance, and VREF-referenced differential B-port interface.

Technical Context

This device implements two independent 8-bit transceivers with noninverting data flow, direction-controlled by DIR and output-enabled by OE. Its TI-OPC circuitry actively suppresses overshoot on unevenly loaded backplanes, while OEC improves signal integrity and reduces EMI.

The B port operates at GTLP levels (VTT = 1.5 V, VREF = 1 V), supporting incident-wave switching into loads as low as 11 Ω. The A port and controls operate at LVTTL logic levels (3.3 V supply, 5-V tolerant), with bus-hold on all A-port inputs and distributed VCC/GND pins to minimize switching noise.

Key Specifications

Pinout & Package

VFBGA-56 (GQL) package with 0.5 mm pitch, 7.0 mm × 4.5 mm body size, and exposed thermal pad. Designed for high-density routing and thermal management in backplane carrier cards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN74GTLPH1695GQLR, the SN74GTLPH1645GQLR omits parity logic for streamlined implementation in non-parity backplane architectures; versus SN74GTLP132GQLR, it delivers full 16-bit width, live-insertion support, and higher 100 mA drive essential for demanding telecom and server applications.

Availability

SN74GTLPH1645GQLR is available at Aetrix Electronics and suitable for telecom line cards, modular server backplanes, and industrial PLC backplanes requiring stable component supply, long-term lifecycle support, and consistent GTLP interface performance.

Supply support for SN74GTLPH1645GQLR 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 leader specializing in analog, embedded processing, and logic solutions, with decades of expertise in high-speed interface ICs and backplane technologies.

The SN74GTLPH1645GQLR belongs to TI's Widebus™ family of high-performance bus interface devices, engineered specifically for reliable LVTTL-to-GTLP translation in live-insertion-capable telecom and computing infrastructure.

FAQ

What is the primary function of the SN74GTLPH1645GQLR in a backplane system?

The SN74GTLPH1645GQLR serves as a bidirectional LVTTL-to-GTLP bus transceiver that bridges 3.3-V LVTTL logic (e.g., FPGAs, microcontrollers) with 1.5-V GTLP backplane signaling. Its core function is level translation with high drive (100 mA), adjustable edge rates via ERC, and live-insertion support - all critical for telecom line cards and modular servers. The SN74GTLPH1645GQLR maintains signal integrity across unevenly loaded backplanes using TI-OPC and OEC circuitry.

How does the ERC pin affect timing performance of the SN74GTLPH1645GQLR?

The ERC pin on the SN74GTLPH1645GQLR selects between two B-port output edge rates: ERC = GND yields slow edges (tr/tf ≈ 2–2.5 ns), while ERC = VCC enables fast edges (tr/tf ≈ 1.2–1.8 ns). This directly impacts propagation delay - e.g., A→B delay drops from 4.9 ns (slow) to 3.7 ns (fast) under distributed RLC load conditions. Designers use ERC to balance data rate and signal integrity based on actual backplane impedance and stub length.

Can the SN74GTLPH1645GQLR operate with GTL instead of GTLP signaling levels?

Yes, the SN74GTLPH1645GQLR supports both GTL (VTT = 1.2 V, VREF = 0.8 V) and GTLP (VTT = 1.5 V, VREF = 1 V) standards, though its AC specifications are guaranteed only at GTLP. When used in GTL mode, designers must verify noise margins and timing margins independently, as the device's OEC and TI-OPC optimizations are tuned for GTLP's higher VTT and VREF. The SN74GTLPH1645GQLR remains fully functional but may not achieve rated max speed in GTL configuration.

What is the role of BIAS VCC in live-insertion operation of the SN74GTLPH1645GQLR?

BIAS VCC on the SN74GTLPH1645GQLR precharges and preconditions the B-port I/O lines during card insertion or removal, preventing transient disturbances on the active backplane. It must be applied before VCC (GND → BIAS VCC → I/O → VCC sequence) to activate the precharge circuitry. Without proper BIAS VCC sequencing, the SN74GTLPH1645GQLR cannot guarantee true live-insertion capability - a requirement for NEBS-compliant telecom systems.

Does the SN74GTLPH1645GQLR support hot-swap without external circuitry?

Yes, the SN74GTLPH1645GQLR integrates three key live-insertion features: Ioff limits reverse current when powered down, power-up 3-state holds outputs high-Z during power ramp, and BIAS VCC preconditions B-port pins. These eliminate the need for external hot-swap controllers or discrete protection circuitry. However, correct power sequencing (BIAS VCC before VCC) and proper PCB layout (distributed decoupling, ground planes) remain essential for reliable SN74GTLPH1645GQLR hot-swap operation.