Analog Devices Inc./Maxim Integrated DS1842N+

Overview

DS1842N+ 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. It delivers up to 76V boost output, supports GPON burst-mode monitoring with 50ns time constant, and operates from –40°C to +85°C in a 14-pin TDFN-EP package. It is used in optical line transmission systems to precisely bias and monitor avalanche photodiodes.

For engineers reviewing the DS1842N+ datasheet, DS1842N+ pinout, DS1842N+ application, or DS1842N+ equivalent, key selection criteria include its 76V maximum LX voltage, 3.7Ω typical FET on-resistance at 10V gate drive, 1µA–2mA current mirror input range, thermal shutdown at +150°C, and compatibility with external DC-DC controllers like DS1875 and MAX1932.

Technical Context

The DS1842N+ integrates a high-voltage switching FET (RDSON = 3.7Ω typ, VDS max = 85V) and dual current mirrors optimized for APD bias feedback. Its MIRIN input accepts 1µA–2mA, while MIROUT delivers a precise ratioed output with ≤2% error across temperature and current range.

It implements three independent current-limiting methods: internal 2mA clamp, active-high CLAMP pin shutdown, and externally adjustable clamping via feedback. The device features thermal shutdown at +150°C and supports fast transient response (30ns rise time) for GPON Rx burst-mode timing compliance.

Key Specifications

Pinout & Package

DS1842N+ uses a 3mm × 3mm, 14-pin TDFN package with exposed pad (EP), designed for high thermal efficiency in compact optical modules. The exposed pad must be soldered to PCB ground for optimal thermal performance and electrical stability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX32663A and DS1842A, the DS1842N+ uniquely combines a 76V-rated internal FET, dual-ratio current mirror, and thermal shutdown in one 14-pin TDFN-enabling minimal-component, high-reliability APD biasing without microcontroller dependency or layout revision.

Availability

DS1842N+ is available at Aetrix Electronics and suitable for GPON optical line terminals, fiber-to-the-home ONUs, passive optical network test equipment, and compact SFP/XFP transceiver modules requiring stable component supply and long-term manufacturability.

Supply support for DS1842N+ 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-voltage ICs for communications, computing, and industrial applications.

The DS1842N+ belongs to Maxim's optical networking product line, engineered specifically to simplify APD bias generation and monitoring in burst-mode PON receivers while meeting stringent timing, accuracy, and reliability requirements.

FAQ

What is the maximum APD bias voltage achievable with the DS1842N+?

The DS1842N+ supports a maximum LX node voltage of +85V and is specified for 76V maximum boost output. When paired with an external DC-DC controller (e.g., DS1875 or MAX1932) and appropriate inductor, it reliably generates APD bias voltages from 16V to 76V. This range covers standard GPON and XG-PON receiver requirements. The DS1842N+ itself does not regulate the final voltage-the external controller sets duty cycle and feedback loop parameters.

How does the DS1842N+ implement current limiting for APD protection?

The DS1842N+ provides three independent current-limiting mechanisms: (1) an internal 2mA clamp triggered when MIROUT exceeds threshold, (2) an active-high CLAMP pin that forces MIROUT to zero when asserted, and (3) an externally adjustable clamp level using feedback circuitry connected to the CLAMP pin. All three methods protect the APD from overcurrent during startup, fault conditions, or temperature drift-without requiring additional ICs or complex supervision logic.

Can the DS1842N+ be used with controllers other than the DS1875?

Yes, the DS1842N+ is compatible with multiple external DC-DC boost controllers beyond the DS1875. The datasheet explicitly confirms interoperability with the MAX1932 and notes that "other DC-DC converters are also compatible." Its GATE pin accepts standard PWM or error-amplifier output signals, and LX tolerates up to 85V, enabling use with industry-standard boost controllers supporting 76V+ output rails-provided gate drive strength and timing meet DS1842N+'s 1.2MHz max switching frequency requirement.

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

The exposed pad (EP) on the DS1842N+ TDFN-EP package serves two critical functions: thermal dissipation and electrical grounding. It reduces junction-to-ambient thermal resistance to 41°C/W, allowing safe operation at up to 1951mW continuous power dissipation at +70°C. Electrically, the EP must be soldered to a low-impedance PCB ground plane to stabilize the high-voltage LX node, minimize switching noise coupling into sensitive MIRIN/MIROUT paths, and ensure reliable thermal shutdown activation.

Does the DS1842N+ support both continuous-mode and burst-mode APD operation?

Yes, the DS1842N+ supports both modes. Its 50ns time constant and 30ns mirror rise time meet GPON burst-mode timing requirements for rapid APD bias settling between optical bursts. For continuous-mode applications (e.g., CATV receivers), the device maintains stable bias with <1% mirror error over temperature and offers multiple external filtering options-including 10nF capacitors on MIR1/MIR2-to suppress ripple without degrading bandwidth. The same DS1842N+ silicon operates identically in either mode; only external RC network selection differs.