Monolithic Power Systems Inc. MP8126DF-LF-P

Overview

MP8126DF-LF-P 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 (±1% accuracy), supports 1V line-drop compensation, and shapes 22kHz tone signals for satellite receiver RF front-ends in coaxial-fed set-top boxes.

For engineers reviewing the MP8126DF-LF-P datasheet, MP8126DF-LF-P pinout, MP8126DF-LF-P application, or MP8126DF-LF-P equivalent, key selection criteria include DiSEqC-compliant voltage switching, 8V–14V input range, thermal shutdown at 150°C, POK monitoring with ±12% tolerance, and programmable current limit via ILIMIT pin resistor.

Technical Context

The device implements a fixed-frequency (342 kHz) peak-current-mode boost stage followed by a tracking LDO that maintains minimal dropout (1.26V at 500mA) while rejecting switching noise from the RF-sensitive LNB path. Its internal 22kHz shaper meets EUTELSAT DiSEqC 1.x timing requirements-50% duty cycle, 0.4–0.8Vpp amplitude, and 8μs rise/fall times-without external modulation circuitry.

Control logic includes dual-level voltage selection (13V/18V), line-drop compensation (1V step), soft-start via TCAP capacitor, and dynamic overload protection with 50ms on-time and 2s off-time recovery. All functions are managed through dedicated digital inputs (EN, LINEDROP, 13V/18V, EXTM) referenced to SGND/PGND split grounds.

Key Specifications

Pinout & Package

MP8126DF-LF-P uses the thermally enhanced TSSOP16EP package (4.4mm × 5.0mm, 0.65mm pitch) with exposed pad for GND-connected thermal dissipation. Pin mapping is validated per MPS datasheet Rev. 1.03, Figure 5 and Pin Functions table.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP8126DF-LF-P, MP8124DN-LF-Z offers superior efficiency and tighter regulation for new designs, while LMX2531LQ1745E serves hybrid RF+power applications but demands external regulation and tone generation circuitry.

Availability

MP8126DF-LF-P is available at Aetrix Electronics and suitable for satellite set-top box manufacturing, professional broadcast receiver development, and LNB module production requiring stable component supply and long-term obsolescence management.

Supply support for MP8126DF-LF-P 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 MP8126 belongs to MPS's satellite communication power management product line, engineered specifically for DiSEqC-compliant LNB power delivery in cost-sensitive, noise-critical RF front-end applications.

FAQ

What is the maximum allowable input voltage for MP8126DF-LF-P?

The absolute maximum input voltage on the VDD pin is 16V, but the recommended operating range is strictly 8V to 14V per the datasheet. Exceeding 14V may cause premature thermal shutdown or reduce reliability due to increased power dissipation in the boost switch and LDO pass element.

How does the LINEDROP pin affect output voltage accuracy?

When LINEDROP is driven HIGH, the output voltage increases by exactly 1V across all nominal settings (e.g., 13V becomes 14V, 18V becomes 19V). This offset is trimmed and stable over temperature (±10mV), enabling precise compensation for coaxial cable voltage drop without recalibrating feedback resistors.

Can MP8126DF-LF-P operate without an external inductor?

No. The internal boost converter requires an external power inductor (typically 10–22μH) connected between SW and PGND. Omitting it prevents boost stage operation, resulting in no VBOOST generation and zero VOUT regulation-only the linear regulator's dropout behavior remains active.

What is the purpose of the TCAP pin and how is its capacitor value determined?

The TCAP pin controls soft-start time via an external capacitor charged at 7μA. To achieve a target output slew rate k (V/s), use C_SS = (15 × I_CHA) / k, where I_CHA = 7μA. For example, a 100ms rise to 18V requires C_SS ≈ 12nF. Placement must be adjacent to SGND with minimal trace length.

Is MP8126DF-LF-P RoHS compliant and lead-free?

Yes. The "-LF" suffix explicitly denotes lead-free, RoHS-compliant packaging. All MPS products meet RoHS Directive 2011/65/EU and are green-status qualified per MPS Quality Assurance documentation.

Does MP8126DF-LF-P support DiSEqC 2.x or higher protocols?

No. The device is certified only for DiSEqC 1.x (1.0 and 1.1). It lacks bidirectional communication capability, data packet parsing, or addressable command decoding required for DiSEqC 2.x/3.x/4.x. Use only in legacy or 1.x–constrained systems.

What is the thermal resistance (θ_JA) of the TSSOP16EP package in standard layout?

For the MP8126DF-LF-P in TSSOP16EP, θ_JA is 45°C/W on a 4-layer JEDEC-standard PCB (JESD51-7). With proper thermal vias to internal GND planes and connection of the exposed pad to ≥1cm² copper area, actual board-level θ_JA can improve to ~35°C/W.