Monolithic Power Systems Inc. MP3430HQ-LF-Z

Overview

MP3430HQ-LF-Z from Monolithic Power Systems is a monolithic 90V step-up converter with integrated high-side avalanche photodiode (APD) current monitoring, featuring 1.3MHz fixed-frequency current-mode control, 2.7V–5.5V input range, and dual-ratio (1:10 and 1:2) APD current mirror outputs for optical receiver biasing. It delivers up to 90V output with cycle-by-cycle current limiting and thermal shutdown protection.

For engineers reviewing the MP3430HQ-LF-Z datasheet, MP3430HQ-LF-Z pinout, MP3430HQ-LF-Z application, or MP3430HQ-LF-Z equivalent, key selection criteria include APD bias voltage stability, 50ns monitor response speed, programmable APD over-current limit via RLIM, and QFN16 package thermal performance in fiber-optic transceiver modules.

Technical Context

The MP3430HQ-LF-Z employs a constant-frequency, current-mode PWM architecture with internal ramp generation and error amplifier feedback, enabling fast transient response and stable regulation across wide input/output voltage ratios. Its control loop operates at 1.3MHz with internal compensation and soft-start functionality.

It integrates a 100V/1Ω NFET switch with 0.9A current limit and a dedicated high-side APD current monitor with ±5% gain tolerance. The monitor provides two isolated current-sense outputs-MON1 (1:10 ratio) and MON2 (1:2 ratio)-each clamped to ≤3.5V and capable of sourcing up to 2.5mA.

Key Specifications

Pinout & Package

The MP3430HQ-LF-Z is housed in a thermally enhanced 3mm × 3mm QFN16 package with exposed pad (EP) soldered to PCB ground for optimal heat dissipation and EMI reduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX3865EASA+ and LT3482EDD, the MP3430HQ-LF-Z uniquely integrates a 90V switch, dual-ratio APD monitors, and programmable over-current protection in a 3×3mm QFN-reducing solution size by >40% and eliminating external compensation in high-ratio boost designs.

Availability

MP3430HQ-LF-Z is available at Aetrix Electronics and suitable for fiber-optic transceivers, lidar receiver modules, precision optical sensors, and industrial spectrometers requiring stable component supply and RoHS-compliant packaging.

Supply support for MP3430HQ-LF-Z 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

Monolithic Power Systems (MPS) is a fabless semiconductor company specializing in high-performance analog and power ICs, with core expertise in DC-DC conversion, LED drivers, and motor control.

The MP3430 product line targets high-voltage optical receiver subsystems, delivering integrated APD biasing and real-time current monitoring to simplify design of fiber-optic, lidar, and scientific instrumentation front-ends.

FAQ

What is the maximum safe APD voltage that MP3430HQ-LF-Z can deliver?

The MP3430HQ-LF-Z is rated for up to 90V output under normal operating conditions, with absolute maximum APD pin voltage specified at 100V. Operation above 90V risks violating recommended operating limits and may trigger thermal shutdown or reduce long-term reliability. Designers should maintain ≥10% headroom below 90V for worst-case line/load/temperature variation.

How does the RLIM pin set the APD over-current threshold?

The RLIM pin accepts a resistor to ground that programs the APD current limit between 0.36mA and 4.3mA. The relationship is approximately linear: I_APD,MAX ≈ (68 kΩ / R_RLIM). For example, a 27.2kΩ resistor sets a 2.5mA limit. This direct analog programming avoids digital interfaces and supports field recalibration without firmware changes.

Can MON1 and MON2 be used simultaneously without interference?

Yes - MON1 and MON2 are independently buffered current-source outputs with separate internal mirror paths. They share the same APD current sense node but drive distinct external resistors (R_MON1, R_MON2) to generate isolated voltage signals. Layout best practice requires separate AGND returns and decoupling for each monitor path to preserve accuracy.

Why does MP3430HQ-LF-Z require discontinuous conduction mode (DCM)?

Due to its high voltage conversion ratio (e.g., 3.3V → 90V), the boost topology develops a right-half-plane zero that destabilizes the control loop in continuous conduction mode (CCM). DCM operation eliminates this zero, ensuring phase margin >45° across all input/output conditions without complex external compensation.

Is the exposed pad (EP) electrically connected internally?

Yes - the exposed pad is internally connected to PGND and must be soldered to a large copper pour on the PCB. It serves as the primary thermal and electrical ground path, contributing ~70% of total θ_JA reduction. Leaving it unconnected degrades thermal performance by >40% and increases switching noise coupling into analog monitor paths.

What is the purpose of the MONIN pin, and how should it be filtered?

MONIN supplies bias to the internal APD current mirrors and must be clean to avoid gain error. It should be decoupled with a π-filter: 10µF X7R ceramic + 1µH ferrite bead + 100nF ceramic, placed adjacent to the IC. Ripple on MONIN directly modulates monitor gain, so filtering reduces gain error from <±5% to <±2.5% under heavy load transients.