Analog Devices Inc./Maxim Integrated DS3922T+T

Overview

DS3922T+T from Maxim Integrated is a high-speed current mirror IC with integrated high-voltage and low-voltage FETs, designed for APD bias monitoring and burst-mode RSSI measurement in GPON/10G-PON OLT systems. It delivers ±0.5dB optical power accuracy across -32dBm to -5dBm, supports 300ns sampling, and provides three precision current mirror outputs (10%, 20%, 80%) with adjustable clamp and fast HV shutdown.

For engineers reviewing the DS3922T+T datasheet, DS3922T+T pinout, DS3922T+T application, or DS3922T+T equivalent, this device serves as a system-level solution for APD current sensing, laser/EML bias generation, and high-voltage protection - requiring attention to MIROUT capacitive loading (330–500pF), RLIM resistor selection for clamp tuning, and thermal management via the exposed-pad TQFN package.

Technical Context

The DS3922T+T integrates dual-domain circuitry: high-voltage (up to 76V) mirror and clamp circuits referenced to HVGND, plus low-voltage (2.85–3.63V) synchronous buck, inverting, and boost FET drivers referenced to LVGND. Its current mirror architecture achieves <±2.5% ratio variation over VMIRIN = 40V ±10%, with sub-1µs ILIMS response and 30ns HV FET turn-on time.

It implements three independent control paths: (1) ISRC/SHDN pin for active-high MIROUT disable and current-source adjustment, (2) RLIM-based analog current limit with status flag on ILIMS, and (3) thermal shutdown at 150°C with 20°C hysteresis. The APDV monitor output enables closed-loop APD voltage regulation by reporting (VMIRIN − VMIROUT)/2.

Key Specifications

Pinout & Package

DS3922T+T is housed in a 3.5mm × 3.5mm, 24-pin TQFN package with exposed thermal pad (EP), optimized for high-density OLT line card layouts and thermal dissipation (θJA = 5.4°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage current mirror and bias controller applications.

Compared with MAX3665AETL+ and LMH6629MF/NOPB, the DS3922T+T consolidates APD current sensing, clamp protection, HV shutdown, and multi-topology laser bias generation into one 3.5mm × 3.5mm package - reducing component count by ≥12, PCB area by 45%, and design validation effort for GPON/10G-PON OLT platforms.

Availability

DS3922T+T is available at Aetrix Electronics and suitable for GPON OLT, 10G-PON transceivers, and EML/DFB laser bias applications requiring stable component supply, long-term industrial temperature operation, and RoHS-compliant packaging.

Supply support for DS3922T+T 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) is a semiconductor company specializing in precision analog, mixed-signal, and power management ICs for communications, industrial, and computing markets.

The DS3922T+T belongs to Maxim's optical networking analog front-end product line, engineered specifically for burst-mode APD bias control and integrated laser driver support in next-generation PON infrastructure.

FAQ

What is the maximum APD bias voltage supported by the DS3922T+T?

The DS3922T+T supports APD bias voltages from 15V to 76V on the MIRIN pin, enabling compatibility with both standard GPON and extended-reach 10G-PON APDs. This range is validated across the full -40°C to +95°C operating temperature and includes built-in overvoltage protection via the integrated HV FET clamp path. The DS3922T+T maintains mirror accuracy and clamp stability throughout this range, as confirmed by the Electrical Characteristics table's VMIRIN specification.

How does the DS3922T+T achieve ±0.5dB RSSI accuracy in burst-mode operation?

The DS3922T+T achieves ±0.5dB RSSI accuracy through its precision current mirror architecture with tightly controlled ratio tolerances (±2.5% over voltage variation), ultra-fast 300ns minimum sampling period, and integrated MIRCAP filtering that stabilizes MIROUT against high-frequency noise. The device's low offset currents (e.g., 20µA VIP1 offset) and calibrated mirror ratios (KIOUT = 0.090–0.110 A/A) ensure minimal error across the -32dBm to -5dBm optical input range. This performance is guaranteed per the datasheet's Benefits and Features section and verified in Typical Operating Characteristics plots.

Can the DS3922T+T generate negative bias for EMLs without external components?

Yes, the DS3922T+T can generate negative bias for EMLs using its LVOUT2 pin, which is an open-drain pMOS output capable of swinging to -3.7V relative to LVGND. When configured with an external inductor and diode in an inverting topology, LVOUT2 delivers regulated negative voltage directly - eliminating the need for external charge pumps or dedicated inverter ICs. This capability is explicitly documented in the Electrical Characteristics table (LVOUT2 = -3.7V to VLVCC) and the Applications Information section.

What is the role of the APDV pin on the DS3922T+T and how is it used?

The APDV pin on the DS3922T+T outputs (VMIRIN − VMIROUT)/2, providing a direct measure of the voltage drop across the current mirror. This signal enables closed-loop regulation of APD bias voltage by feeding into an external op-amp comparator that adjusts the boost converter driving MIRIN. The APDV function is critical for maintaining constant APD reverse bias despite temperature drift or aging, and its design meaning is confirmed in the Detailed Description section and Figure 1 of the datasheet.

Does the DS3922T+T require external resistors for current clamp configuration, and if so, what values are supported?

Yes, the DS3922T+T requires an external resistor between RLIM and GND to set the current clamp threshold. Supported values include 25kΩ (clamp = 2.55–4.45mA) and 40kΩ (clamp = 1.37–3.21mA), with guaranteed accuracy for RISRC = 29.7–30.3kΩ. These values are specified in the Electrical Characteristics table under "Maximum MIROUT Current" and are validated across temperature. The DS3922T+T's clamp circuitry is designed exclusively for resistor-based tuning - no internal DAC or digital interface is provided.