Monolithic Power Systems Inc. MP8125EF-LF-Z

Overview

MP8125EF-LF-Z from Monolithic Power Systems is a DiSEqC 1.x–compliant LNB power supply and control voltage regulator integrating a current-mode boost converter and tracking linear regulator. It delivers up to 550mA output at selectable 13V/18V (±0.4V load regulation), supports 22kHz tone modulation via EXTM pin, provides 1V line-drop compensation, and operates from 8V–14V input. It powers satellite RF LNBs in set-top boxes via coaxial cable.

For engineers reviewing the MP8125EF-LF-Z datasheet, MP8125EF-LF-Z pinout, MP8125EF-LF-Z application, or MP8125EF-LF-Z equivalent, key selection criteria include DiSEqC-compliant 22kHz tone generation, programmable current limit (600–1100mA), ±12% POK monitoring, thermal shutdown at 150°C, and dual-package availability (TSSOP-16 with exposed pad / QFN24).

Technical Context

The MP8125EF-LF-Z implements a fixed-frequency (352kHz) peak-current-mode boost stage followed by a tracking LDO that maintains minimal dropout voltage while rejecting switching noise-critical for preserving LNB RF signal integrity. Its internal 22kHz oscillator synchronizes to the boost frequency (16× ratio) and modulates onto VOUT only when EXTM is high.

It features dual digital control inputs: 13V/18V selects polarization voltage level, and LINEDROP enables +1V output offset for coaxial cable drop compensation. The ILIMIT pin programs overcurrent threshold via external resistor, and TCAP sets soft-start slew rate using a capacitor charged at 7μA.

Key Specifications

Pinout & Package

MP8125EF-LF-Z is packaged in thermally enhanced TSSOP-16 with exposed pad (pin 17 connected to SGND/PGND). The package supports high-power dissipation (2.8W @ TA=25°C) and requires PCB copper area under the exposed pad for thermal management.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LNB power supply and control applications.

Compared with MP8124EF-LF-Z, the MP8125EF-LF-Z offers identical DiSEqC functionality but with higher quiescent current and narrower temperature rating; compared with LMX2531, it delivers full power regulation instead of just bias control-making it the sole integrated solution for standard STB LNB supply.

Availability

MP8125EF-LF-Z is available at Aetrix Electronics and suitable for satellite set-top box manufacturing, DiSEqC multi-switch distribution systems, Unicable LNB interface modules, and professional broadcast receiver development requiring stable component supply and long-lifecycle support.

Supply support for MP8125EF-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 design centers in the US, China, and Taiwan.

The MP8125 belongs to MPS's satellite power management product line, engineered specifically for DiSEqC-compliant LNB supply in consumer and professional satellite reception equipment.

FAQ

What is the function of the TCAP pin?

The TCAP pin sources a precise 7μA current to charge an external capacitor, controlling the soft-start rise time of VOUT. This limits inrush current during power-up and prevents overshoot. The capacitor must be placed close to TCAP and SGND, with routing kept away from noisy nodes like SW to avoid coupling.

Can MP8125EF-LF-Z drive a 550mA LNB continuously?

Yes, it delivers 550mA continuously under specified conditions: VIN = 12V, TA ≤ +85°C, and proper PCB thermal design (exposed pad soldered to ≥2 cm² copper). At full load, thermal shutdown activates above 150°C junction temperature, with automatic recovery after cooling to ~130°C.

How does the LINEDROP pin affect output voltage?

When LINEDROP is driven high, the output voltage increases by exactly +1V relative to the base setting (e.g., 13.2V → 14.2V or 18.14V → 19.14V). This compensates for IR drop across long coaxial cables, ensuring the LNB receives sufficient voltage even at 550mA load over 50m runs.

Is the 22kHz tone generated internally or externally?

The 22kHz tone is generated entirely internally by a dedicated oscillator synchronized to the 352kHz boost clock (16× ratio). It is modulated directly onto the VOUT rail only when the EXTM pin is high, with activation/deactivation latency limited to 1.5 tone periods (≤68μs) per DiSEqC timing requirements.

What is the purpose of the POK pin?

The POK (Power OK) pin is an open-drain output that goes low when VOUT falls outside ±12% of its nominal value (e.g., below 11.6V or above 14.8V for 13V mode). It provides real-time fault indication to the host controller, enabling system-level diagnostics without requiring external voltage monitors.

Why does MP8125EF-LF-Z use both boost and linear regulation?

The boost stage generates a clean, regulated VBOOST that tracks VOUT, allowing the linear post-regulator to operate with minimal dropout voltage (≤0.9V at 500mA). This architecture rejects switching noise from reaching the LNB-preserving RF signal-to-noise ratio-while maintaining high efficiency and low output ripple.

What package variants are offered for MP8125?

MP8125 is offered in two thermally enhanced packages: TSSOP-16 with exposed pad (MP8125EF) and 24-pin QFN (4mm × 4mm) (MP8125DR). The EF variant supports –20°C to +85°C ambient; the DR variant extends to –40°C to +85°C and offers slightly higher power dissipation (2.9W vs 2.8W).