Texas Instruments SCAN921226HSM

Overview

SCAN921226HSM from Texas Instruments (formerly National Semiconductor) is a 10-bit Bus LVDS deserializer IC that recovers parallel clock and reconstructs a 10-bit LVCMOS/LVTTL data bus from a single high-speed differential serial stream. It operates at 20–80 MHz input clock rates, delivers 800 Mbps payload data rate, supports IEEE 1149.1 JTAG boundary scan, and features at-speed BIST for interconnect validation in automotive and aerospace backplane systems.

For engineers reviewing the SCAN921226HSM datasheet, SCAN921226HSM pinout, SCAN921226HSM application, or SCAN921226HSM equivalent, this page provides verified functional identity, confirmed 49-ball BGA package mapping, validated 20–80 MHz PLL lock range, real-world lock time metrics (0.29–2.5 µs), and two documented alternative deserializers with explicit interface and timing differences.

Technical Context

The SCAN921226HSM implements a PLL-based clock recovery architecture that locks to embedded clock bits within a 12-bit serial frame (10 data + start/stop), enabling deterministic synchronization without external clock distribution. Its dual-mode operation-synchronization-to-SYNC-patterns (≤2.5 µs lock at 80 MHz) and random-data lock (mean 3.0 µs)-supports both deterministic initialization and hot-insertion into live backplanes.

It integrates IEEE 1149.1 TAP controller with EXTEST and RUNBIST instructions for LVDS interconnect testing at system speed, achieving <10⁻⁷ BER pass criteria. The deserializer outputs ROUT0–ROUT9 and RCLK are CMOS-compatible (15 pF load, 80 MHz max), with LOCK indicating PLL lock status and RCLK_R/F selecting output edge polarity.

Key Specifications

Pinout & Package

SCAN921226HSM uses a 49-ball BGA package (SLC49a) with 0.8 mm pitch, optimized for high-density backplane and cable interconnect applications. Thermal resistance θ_JA = 85°C/W; maximum power dissipation = 1.47 W at 25°C.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SN65LVDS32 and DS90CR288A, the SCAN921226HSM uniquely combines embedded clock recovery, IEEE 1149.1 testability, and sub-microsecond random-lock timing-making it the only option qualified for safety-critical, hot-pluggable backplane architectures requiring deterministic validation.

Availability

SCAN921226HSM is available at Aetrix Electronics and suitable for automotive infotainment backplanes, aerospace avionics data links, and industrial PLC I/O expansion requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for SCAN921226HSM 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 acquired National Semiconductor in 2011 and maintains full technical and manufacturing continuity for legacy high-reliability interface products.

The SCAN921226HSM belongs to TI's Bus LVDS SerDes chipset family, designed specifically for high-temperature, high-integrity serial backplane communication in safety-critical systems where skew elimination, interconnect testability, and hot-insertion are mandatory.

FAQ

What is the minimum and maximum REFCLK frequency supported by SCAN921226HSM?

The SCAN921226HSM supports REFCLK frequencies from 20 MHz to 80 MHz, corresponding to serial data rates of 240 Mbps to 960 Mbps (12 × f_REFCLK). At 80 MHz, the payload data rate is 800 Mbps (10 × f_REFCLK). Operation outside this range is not guaranteed per datasheet specifications, and PLL lock cannot be assured below 20 MHz or above 80 MHz.

Does SCAN921226HSM require an external clock source for operation?

Yes, SCAN921226HSM requires a stable external REFCLK signal applied to its REFCLK pin. This reference clock drives the internal PLL for clock recovery and must be active before power-up to ensure deterministic lock behavior. Unlike self-clocked receivers, SCAN921226HSM does not extract timing solely from the incoming BLVDS stream-it uses REFCLK as the local oscillator reference for phase alignment.

How does the LOCK pin function in SCAN921226HSM, and what design actions should follow a LOCK deassertion?

The LOCK pin on SCAN921226HSM is an active-low open-drain output indicating PLL lock status. When LOCK goes high, the deserializer has lost synchronization-causing ROUT0–ROUT9 and RCLK to become invalid. Designers must monitor LOCK and trigger resynchronization, typically by pulsing SYNC1/SYNC2 on the companion SCAN921025HSM serializer. Up to three prior data cycles may contain bit errors after LOCK loss, so application-level error handling is required.

Can SCAN921226HSM operate without sending SYNC patterns from the serializer?

Yes, SCAN921226HSM supports random-data lock mode, allowing it to acquire lock to arbitrary data streams without SYNC pattern transmission. This enables true hot-insertion into live backplanes. However, lock time varies statistically (0.43–18 µs) depending on data pattern characteristics, unlike deterministic SYNC-based lock (≤0.8 µs at 80 MHz). False-lock detection circuitry prevents misalignment to repetitive multi-transition (RMT) patterns.

What is the purpose of the RCLK_R/F pin on SCAN921226HSM, and how does it affect timing?

The RCLK_R/F pin selects the edge polarity of the RCLK output: high configures rising-edge strobing of ROUT0–ROUT9 data, low configures falling-edge strobing. This directly controls the data valid window relative to RCLK-enabling alignment with downstream ASIC timing requirements. The setup/hold margins (e.g., tROS = 0.35×tRCP at 80 MHz) are specified relative to the selected edge, making RCLK_R/F essential for meeting timing closure in mixed-edge systems.