NXP Semiconductors MC88915TFN100

Overview

MC88915TFN100 from Motorola is a 5V, low-skew PLL clock driver IC designed for synchronous clock distribution in high-performance computing systems. It delivers five phase-locked Q outputs (Q0–Q4) with ≤500 ps rising-edge skew, a 180°-inverted Q5 output, a 2× frequency 2X_Q output (up to 100 MHz), and a ÷2 Q/2 output - all locked to a single SYNC input. It supports 1:2, 1:1, and 2:1 input/output frequency ratios and is used in PC/workstation motherboard clock trees requiring deterministic timing and board-level testability.

For engineers reviewing the MC88915TFN100 datasheet, MC88915TFN100 pinout, MC88915TFN100 application, or MC88915TFN100 equivalent, key selection criteria include guaranteed 100 MHz 2X_Q operation, 50 MHz Q-output maximum frequency, ±36 mA CMOS/TTL-compatible drive strength, FREQ_SEL programmable feedback division, and OE/RST-controlled 3-state outputs with sub-14 ns enable/disable timing.

Technical Context

The MC88915TFN100 implements a voltage-controlled oscillator (VCO) locked via phase detector and charge pump to a reference SYNC input, enabling precise frequency multiplication (×2), division (÷2), and phase alignment across eight outputs. Its PLL architecture supports multiple feedback configurations - including Q, Q5, Q/2, and 2X_Q - each yielding distinct input/output frequency relationships and phase offsets (0° or 180°).

It operates with dual SYNC inputs: primary SYNC for normal operation and secondary SYNC for test-mode clock injection when PLL_EN is low. The LOCK indicator asserts high within 10 ms of valid SYNC acquisition and deasserts on loss of lock or PLL_EN deactivation, providing real-time loop status for system diagnostics and power sequencing.

Key Specifications

Pinout & Package

MC88915TFN100 is housed in a 28-lead plastic leaded chip carrier (PLCC), case 776–02, with gull-wing leads and exposed die pad not electrically connected. Pin numbering follows standard top-view PLCC convention (pin 1 marked by corner notch).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PLL clock driver applications.

Compared with MC88915TFN133 and ICS552-01LFT, the MC88915TFN100 offers optimal balance of 100 MHz performance, 5V robustness, and full test-mode functionality in legacy computing platforms - making it the preferred choice where backward compatibility, thermal headroom, and board-level debugability are critical.

Availability

MC88915TFN100 is available at Aetrix Electronics and suitable for desktop PC motherboards, workstation multi-processor synchronization, and industrial embedded controller timing requiring stable component supply and long-term obsolescence management.

Supply support for MC88915TFN100 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

Motorola Semiconductor (now part of NXP Semiconductors) pioneered high-performance clock distribution ICs for computing infrastructure in the 1990s, emphasizing low skew, PLL stability, and testability.

The MC88915T family was engineered specifically for synchronous clock tree implementation in x86-based PCs and workstations, addressing timing closure challenges in multi-GHz signaling environments before widespread adoption of on-die clock generation.

FAQ

What is the maximum guaranteed operating frequency of the 2X_Q output for MC88915TFN100?

The MC88915TFN100 guarantees a maximum 2X_Q output frequency of 100 MHz under phase-locked conditions with all outputs loaded into 50 Ω terminated to VCC/2. This specification applies across the full industrial temperature range (–40°C to +85°C) and 5.0 V ±5% supply. Operation above 100 MHz is not characterized or guaranteed for MC88915TFN100.

Can MC88915TFN100 operate with a 10 MHz input clock and still generate a 100 MHz 2X_Q output?

Yes - the MC88915TFN100 can generate a 100 MHz 2X_Q output from a 10 MHz SYNC input by configuring the PLL feedback path to divide the VCO output by 2 (FREQ_SEL = low). This keeps the VCO running at 200 MHz (within its optimal 20–200 MHz range), then divides by 2 before distribution, resulting in 100 MHz at 2X_Q and 50 MHz at Q outputs.

How does the OE/RST pin affect the reset state of MC88915TFN100 outputs after being released?

When OE/RST is released (driven high), Q0–Q4 and Q/2 outputs reset to the low state, while 2X_Q resets to the inverse of the selected SYNC input. Q5 retains its 180° phase relationship. This deterministic reset behavior ensures known initial states for CPU and memory initialization sequences, and is independent of PLL lock status at release time.

Is MC88915TFN100 pin-compatible with other variants in the MC88915T family?

Yes - all MC88915T variants (including MC88915TFN55, TFN70, TFN100, TFN133, and TFN160) share identical 28-pin PLCC packaging, pinout, and DC/AC interface characteristics. Frequency ratings differ per variant, but PCB layout, power delivery, and control logic are fully interchangeable across the family.

What termination is required for the FEEDBACK input to ensure jitter-free operation of MC88915TFN100?

A 1 MΩ resistor must be connected from the FEEDBACK pin to either Analog VCC or Analog GND, as shown in Figure 2 of the datasheet. This bias network eliminates jitter caused by floating feedback node impedance and ensures stable phase detector operation. Omitting this resistor results in measurable output jitter and potential loss of lock under marginal conditions.