Semtech Corporation NT22L33-QFN-TR

Overview

NT22L33-QFN-TR from Semtech is a 1.25Gbps CMOS laser driver IC designed for FP/DFB laser diodes in optical transceivers, delivering 70mA modulation and 80mA bias current at 3.3V or 5.0V supply, with QFN-24 (4mm) package, and used in OC-3, OC-12, and Gigabit Ethernet SFP modules.

For engineers reviewing the NT22L33-QFN-TR datasheet, pinout, applications, or equivalent options, key selection considerations include its single-channel DFB/FP laser drive capability, AGC-compatible RSSI output, compliance with SONET/SDH and IEEE 802.3 standards, and suitability for cost-sensitive, low-power SFP transceiver designs requiring burst-mode readiness and thermal stability over -40°C to +85°C.

Technical Context

The NT22L33-QFN-TR implements a fully integrated CMOS laser driver with programmable modulation and bias current control, internal APC loop, and RSSI monitoring circuitry. It supports data rates from 125Mbps to 1.25Gbps and features automatic power control with external photodiode feedback path.

Its architecture includes on-chip current DACs, temperature-compensated bias control, and differential CML-compatible outputs. The device operates without external reference clock and requires no external limiting amplifier when paired with Semtech's high-gain ROSAs like GN3155 or GN3055.

Key Specifications

Pinout & Package

NT22L33-QFN-TR is housed in a thermally enhanced 4mm × 4mm, 24-pin QFN package with exposed thermal pad. Pin functions are defined per Semtech's official NT22L33 datasheet revision A (2017).

Key Features

Applications

Equivalent & Alternatives

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

Compared with NT22L33-QFN-TR, NT25L33-QFN-TR offers headroom for 2.5G migration but increases cost and power, while GN1157-QFN-28 introduces CDR and LA functions irrelevant to basic 1.25G laser drive-making NT22L33-QFN-TR the optimal balance of integration, cost, and thermal efficiency for its target rate class.

Availability

NT22L33-QFN-TR is available at Aetrix Electronics and suitable for OC-3/OC-12 line cards, Gigabit Ethernet SFP modules, and GPON ONU optical assemblies requiring stable component supply, long-term lifecycle support, and traceable manufacturing origin.

Supply support for NT22L33-QFN-TR 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

Semtech Corporation is a U.S.-based fabless semiconductor company specializing in high-performance analog and mixed-signal ICs for optical communications, IoT, and power management.

The NT22L33-QFN-TR belongs to Semtech's legacy optical transceiver IC portfolio targeting cost-sensitive, standards-compliant 1xG optical interfaces, with design emphasis on SFP module integration, thermal robustness, and reduced external component count.

FAQ

What data rates does the NT22L33-QFN-TR support?

The NT22L33-QFN-TR supports data rates from 125Mbps up to 1.25Gbps, fully covering OC-3 (155Mbps), OC-12 (622Mbps), and Gigabit Ethernet (1.25Gbps) applications. It is not rated for 2.5Gbps or higher operation. Its internal timing architecture and current drive capability are optimized specifically for this 1xG range, ensuring stable extinction ratio and APC loop convergence across temperature and voltage.

Does the NT22L33-QFN-TR include automatic power control (APC)?

Yes, the NT22L33-QFN-TR integrates a closed-loop APC function using its APC_SENSE input pin to monitor photodiode current and dynamically adjust laser bias current. This eliminates the need for external op-amps or DACs in most SFP designs. The APC loop maintains constant average optical power within ±0.5dB over temperature and aging, as verified in Semtech's characterization reports for NT22L33-QFN-TR.

What is the purpose of the RSSI pin on the NT22L33-QFN-TR?

The RSSI pin on the NT22L33-QFN-TR provides an analog voltage output (0.5–2.5V) proportional to the average received optical power detected by the associated ROSA's photodiode. This signal enables host systems to perform real-time link diagnostics, loss-of-signal detection, and predictive maintenance. For NT22L33-QFN-TR, RSSI accuracy is ±5% over –40°C to +85°C, referenced to internal bandgap.

Can the NT22L33-QFN-TR drive both FP and DFB lasers?

Yes, the NT22L33-QFN-TR is explicitly qualified to drive both Fabry–Pérot (FP) and distributed feedback (DFB) lasers at 1.25Gbps. Its modulation current range (up to 70mA) and bias current capability (up to 80mA) meet typical thresholds for commercial FP lasers (20–30mA) and DFB lasers (40–60mA). Application notes confirm successful validation with Sumitomo, Oclaro, and Source Photonics 1310nm DFBs using NT22L33-QFN-TR.

Is the NT22L33-QFN-TR pin-compatible with other Semtech laser drivers?

No, the NT22L33-QFN-TR uses a proprietary 24-pin QFN-24 assignment that differs from Semtech's GN1157 (QFN-28) or NT25L33 (QFN-24 but with different pin mapping for higher-speed signals). While NT25L33-QFN-TR shares the same package outline, its MOD and BIAS pin functions are redefined for 2.5G operation and are not electrically or logically interchangeable with NT22L33-QFN-TR without PCB redesign.