Analog Devices Inc./Maxim Integrated DS1842N+T&R

Overview

DS1842N+T&R from Maxim Integrated is a high-voltage APD bias output stage IC with integrated switch FET, dual-ratio current mirror (10:1 and 5:1), and 2mA current clamp for avalanche photodiode monitoring in optical receivers. It delivers up to 76V boost output, supports GPON burst-mode timing with 30ns mirror rise time, and operates from -40°C to +85°C in a 3mm × 3mm 14-pin TDFN-EP package.

For engineers reviewing the DS1842N+T&R datasheet, DS1842N+T&R pinout, DS1842N+T&R application, or DS1842N+T&R equivalent, key selection criteria include its 76V maximum LX voltage, fast 50ns current mirror time constant, precise MIR1/MIR2 ratio tolerance (±1% at 1μA–1mA), CLAMP pin active-high shutdown, and thermal shutdown at +150°C - all critical for ROSA-level APD bias stability and burst-mode compliance.

Technical Context

The DS1842N+T&R functions as a high-side APD bias output stage, integrating a 3.7Ω typical R_DS(ON) switch FET (V_GS = 10V) and dual current mirrors referenced to MIRIN. Its LX node handles up to 80V with ≤1μA leakage, while CLAMP enables external overcurrent disable independent of internal 2mA current limit.

Current mirroring operates across 1μA–2mA input range with <±1% error over temperature and voltage (15V–76V), and MIR1/MIR2 outputs feature separate 30ns rise times (20%/80%) - enabling simultaneous low-gain (MIR2) and high-resolution (MIR1) monitoring paths for ADC interfacing in GPON ONU receivers.

Key Specifications

Pinout & Package

DS1842N+T&R uses a 3mm × 3mm, 14-pin TDFN-EP package with exposed pad (EP) tied to GND for thermal dissipation. Pin 7 is GND; pins 3, 4, 9–12 are no-connect (NC); EP must be soldered to PCB ground plane.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar APD bias and monitoring applications.

Compared with MAX1932 and DS1842A, DS1842N+T&R uniquely combines integrated switch FET, dual-ratio current mirroring, and active CLAMP control in one package - reducing total solution size by 40% and eliminating three external high-voltage components required by alternatives.

Availability

DS1842N+T&R is available at Aetrix Electronics and suitable for GPON ONU/OLT receivers, FTTx line cards, and SFP+ optical transceivers requiring stable component supply, RoHS-compliant packaging, and guaranteed long-term availability through 2030.

Supply support for DS1842N+T&R 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 and mixed-signal ICs for communications, computing, and industrial systems, with emphasis on high-reliability, low-power, and high-voltage solutions.

The DS1842N+T&R belongs to Maxim's optical networking product line, engineered specifically for burst-mode APD biasing and real-time current monitoring in GPON and XG-PON optical receivers.

FAQ

What is the maximum APD bias voltage supported by the DS1842N+T&R?

The DS1842N+T&R supports a maximum APD bias voltage of 76V, defined by its absolute maximum LX voltage rating of 80V and operational specification of 76V maximum boost output. This enables compatibility with standard InGaAs APDs used in GPON and XG-PON optical receivers. Exceeding 76V risks violating the device's safe operating area and may trigger thermal shutdown or permanent damage.

How does the CLAMP pin function on the DS1842N+T&R?

The CLAMP pin on the DS1842N+T&R is an active-high input that disables the MIROUT current path when driven high (≥2V). It provides external override capability for the internal 2mA current clamp, allowing system-level fault detection or precision current regulation via feedback circuitry. When CLAMP is low, the internal clamp remains active at 2mA; when high, MIROUT shuts off completely - protecting the APD during overvoltage or communication faults.

Can the DS1842N+T&R be used with APDs requiring bias voltages below 16V?

Yes, the DS1842N+T&R supports APD bias voltages from 16V to 76V, as confirmed in the Detailed Description section. While its minimum specified output is 16V, successful operation at lower voltages depends on external DC-DC controller configuration (e.g., DS1875 or MAX1932) and loop compensation. However, sub-16V operation is not characterized or guaranteed - design validation is required for such use cases.

What is the purpose of the exposed pad (EP) on the DS1842N+T&R package?

The exposed pad (EP) on the DS1842N+T&R is electrically connected to GND and serves as the primary thermal dissipation path. With a junction-to-case thermal resistance (θ_JC) of 8°C/W, proper soldering of EP to a large PCB ground plane is essential to maintain junction temperature below +150°C under continuous 2mA MIROUT operation. Leaving EP unconnected degrades thermal performance by >60%, risking premature thermal shutdown.

Does the DS1842N+T&R require external compensation components?

Yes, the DS1842N+T&R requires external compensation components - specifically C_COMP and R_COMP on the COMP pin - to stabilize the feedback loop of the external DC-DC controller it drives (e.g., DS1875). These components set loop bandwidth and phase margin; values depend on inductor selection, output capacitance, and target transient response. The Typical Application Circuit shows standard values, but optimization is necessary for each specific power stage layout.