Infineon Technologies CY7B951-SXCT

Overview

CY7B951-SXCT from Cypress Semiconductor is a SONET/SDH and ATM-compatible local area network transceiver IC that recovers clock and data from 51.84-MHz or 155.52-MHz NRZ/NRZI serial streams, provides differential transmit buffering (TOUT±), and delivers ECL-100K–compatible recovered outputs (RCLK±, RSER±, ROUT±). It operates on a single +5V supply in 24-pin SOIC packaging and supports fiber, coaxial, and twisted-pair media.

For engineers reviewing the CY7B951-SXCT datasheet, CY7B951-SXCT pinout, CY7B951-SXCT application, or CY7B951-SXCT equivalent, key selection criteria include its dual-rate PLL-based clock/data recovery (±1% frequency agility), REFCLK×8 multiplication architecture, carrier detect–controlled lock behavior, and integrated loopback testing capability for ATM/SONET physical layer validation.

Technical Context

The CY7B951-SXCT implements two independent PLLs: a Receive CDR PLL that locks to RIN± using REFCLK×8 as center-frequency reference, and a Transmit frequency multiplier PLL that synthesizes TCLK± at exactly 8×REFCLK. Both PLLs support selectable 51.84 MHz (MODE = GND) or 155.52 MHz (MODE = VCC) operation with ±1% frequency agility.

Its receiver includes a transition detector (512-bit-time timeout), Out-of-Lock detection, and Carrier Detect (CD)-gated LFI output with TTL-level status signaling. The LOOP pin enables internal TSER±→Receive-PLL routing for full-system loopback testing excluding only RIN± inputs and TOUT± drivers.

Key Specifications

Pinout & Package

Package: 24-pin Small Outline Integrated Circuit (SOIC), surface-mount, 300-mil body width, standard JEDEC MS-013AC footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SONET/ATM transceiver applications.

Compared with PM5345-SUNI and ICS873001AGI, the CY7B951-SXCT uniquely integrates dual-rate PLLs, carrier-aware lock control, hardware loopback, and unified LFI signaling - reducing system-level complexity for SONET/ATM edge equipment where flexibility and diagnostics are critical.

Availability

CY7B951-SXCT is available at Aetrix Electronics and suitable for SONET STS-1/STS-3 line interfaces, ATM physical layer transceivers, and copper-based broadband access nodes requiring stable component supply and long-term lifecycle support.

Supply support for CY7B951-SXCT 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

Cypress Semiconductor (now part of Infineon Technologies) designs high-performance mixed-signal ICs for communications, computing, and industrial applications, with emphasis on integration, reliability, and system-level simplification.

The CY7B951 belongs to Cypress's legacy telecom transceiver product line, engineered specifically for SONET/SDH and ATM physical layer implementations requiring embedded clock/data recovery, low-jitter outputs, and diagnostic visibility in space-constrained edge equipment.

FAQ

What is the function of the MODE pin, and how does it affect operation?

The MODE pin is a three-level input that selects the device's operating frequency: HIGH enables 155.52 MHz (STS-3) mode with 19.44 MHz REFCLK; LOW enables 51.84 MHz (STS-1) mode with 6.48 MHz REFCLK; floating activates test mode. This selection configures both the Receive CDR and Transmit PLLs simultaneously, ensuring synchronized clock/data recovery and generation across the full signal chain.

How does the Carrier Detect (CD) pin influence clock recovery behavior?

When CD is driven ECL HIGH, the Receive PLL locks normally to RIN±. When CD is pulled ECL LOW, the PLL aligns to REFCLK×8 instead, RSER± is forced LOW, and LFI asserts LOW - indicating invalid link. If CD is TTL LOW (<0.8 V), the transition detector disables and LFI reflects only Out-of-Lock status. An internal pull-down ensures safe default behavior when CD is unconnected.

Can the CY7B951-SXCT operate with a single-ended TTL clock source?

Yes. The REFCLK± inputs accept either differential PECL or single-ended TTL sources: when one REFCLK pin is held at TTL LOW, the other becomes a TTL-level input. This allows direct connection to low-cost crystal oscillators without level-shifting circuitry, while maintaining full PLL performance and frequency accuracy within ±1%.

What happens to power consumption when outputs are disabled?

Each ECL output pair (e.g., RCLK±, RSER±, TOUT±) draws ~4 mA when active. Tying both pins of an output pair to VCC (or leaving them unconnected) disables that driver and saves ~4 mA per pair. Disabling both RCLK± and RSER± powers down the entire Receive PLL; disabling TCLK± powers down the Transmit PLL - enabling granular power optimization in standby or partial-operation modes.