Analog Devices Inc./Maxim Integrated MAX3840ETJ+TG035

Overview

MAX3840ETJ+TG035 from Maxim Integrated is a dual 2×2 asynchronous CML crosspoint switch designed for OC-48 SDH/SONET and DWDM transport systems requiring serial data loop-through and protection channel switching. It supports 2.7Gbps data and 2.7GHz clock signals, delivers ≤2ps_RMS random jitter and 6ps channel-to-channel skew, and operates from a single +3.3V supply across –40°C to +85°C.

For engineers reviewing the MAX3840ETJ+TG035 datasheet, MAX3840ETJ+TG035 pinout, MAX3840ETJ+TG035 application, or MAX3840ETJ+TG035 equivalent, key selection criteria include CML I/O compatibility, output enable/power-down control per channel, deterministic jitter (≤7ps_P-P), thermal performance in the 5mm × 5mm TQFN package, and integration with MAX3876 CDR circuits.

Technical Context

The MAX3840ETJ+TG035 implements two independent 2×2 crosspoint matrices-Channel A (A0/A1) and Channel B (B0/B1)-each controlled by dedicated TTL-select (SELAx/SELBx) and TTL-enable (ENA_x/ENB_x) inputs. Signal routing is fully asynchronous and does not require clock synchronization between input and output paths.

All eight CML I/Os (four differential inputs, four differential outputs per channel) feature on-die 50Ω terminations to V_CC, enabling direct AC-coupled interfacing with LVPECL sources without external resistors. Each CML output stage can be independently powered down via its enable pin, reducing supply current from 190mA (all outputs enabled) to as low as ~40mA (no outputs enabled).

Key Specifications

Pinout & Package

The MAX3840ETJ+TG035 is housed in a 32-pin exposed-pad thin QFN (TQFN) package with 5mm × 5mm footprint and 0.5mm pitch. The exposed pad (EP) must be soldered to PCB ground for thermal dissipation and signal reference integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed CML crosspoint switching applications.

Compared with MAX3840EGJ, the MAX3840ETJ+TG035 offers marginally better thermal performance in space-constrained modules; versus MAX3841ETJ+, it delivers lower power and proven stability in deployed OC-48 infrastructure where 2.7Gbps headroom suffices.

Availability

MAX3840ETJ+TG035 is available at Aetrix Electronics and suitable for SDH/SONET transport systems, DWDM add-drop multiplexers, and high-speed telecom backplanes requiring stable component supply, long-lifecycle support, and guaranteed lead-free compliance.

Supply support for MAX3840ETJ+TG035 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

Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and high-speed ICs for communications, computing, and industrial applications.

The MAX3840ETJ+TG035 belongs to Maxim's high-speed optical transport product line, engineered specifically for OC-48/STM-16 line interface units requiring low-jitter, low-power, and TTL-controllable signal routing.

FAQ

What is the maximum data rate supported by the MAX3840ETJ+TG035?

The MAX3840ETJ+TG035 supports a maximum data rate of 2.7Gbps, validated for OC-48 (2.488Gbps) SDH/SONET systems with forward error correction. This rating is specified under full-load conditions with all outputs enabled and measured using a 2²³–1 PRBS pattern at V_CC = +3.3V and T_A = +25°C. The MAX3840ETJ+TG035 maintains signal integrity up to this rate with ≤2ps_RMS random jitter and ≤7ps_P-P deterministic jitter.

Does the MAX3840ETJ+TG035 require external termination resistors for CML I/Os?

No, the MAX3840ETJ+TG035 integrates on-die 50Ω terminations for all CML inputs and outputs referenced to V_CC, eliminating the need for external resistors. This simplifies PCB layout, reduces component count, and improves signal integrity by minimizing stub reflections. The MAX3840ETJ+TG035 is designed to drive and receive directly into 50Ω-controlled impedance traces, supporting reliable operation up to 15cm on standard FR4.

How does the power-down feature work on the MAX3840ETJ+TG035?

The MAX3840ETJ+TG035 provides individual TTL-compatible enable inputs (ENA0, ENA1, ENB0, ENB1) that power down each CML output driver when driven low. When disabled, the corresponding output enters high-impedance state with leakage <1µA, reducing total supply current from 190mA (all outputs active) to ~40mA (all outputs disabled). This feature is essential for hitless protection switching in telecom systems using the MAX3840ETJ+TG035.

Is the MAX3840ETJ+TG035 compatible with LVPECL signal sources?

Yes, the MAX3840ETJ+TG035 CML inputs accept AC-coupled LVPECL signals without level-shifting circuitry. Its CML input voltage range (V_CC – 0.8V to V_CC + 0.5V) and 300–2000mV_P-P differential swing tolerance align with standard LVPECL output specifications. Application Note HFAN-01.0 from Maxim confirms interoperability, and the MAX3840ETJ+TG035 has been validated in systems using MAX3876 CDR outputs driving into MAX3840ETJ+TG035 inputs.

What is the thermal design requirement for the MAX3840ETJ+TG035 in continuous operation?

The MAX3840ETJ+TG035 requires the exposed pad (EP) to be soldered to a solid PCB ground plane with ≥4 thermal vias (0.3mm diameter) to ensure junction temperature stays within –55°C to +150°C. At full power (460mW), its thermal resistance θ_JA is 30°C/W in the TQFN package. For ambient temperatures up to +85°C, this yields a worst-case junction temperature of ~113°C - within specification. The MAX3840ETJ+TG035 datasheet specifies derating of 21.3mW/°C above +85°C ambient.