Monolithic Power Systems Inc. MP8124GD-P

Overview

MP8124GD-P from Monolithic Power Systems is a 500mA integrated LNB power supply and control regulator for satellite receiver front-ends. It combines a current-mode boost converter (440kHz, 8–14V input) followed by a tracking linear regulator to deliver stable 13V/18V outputs with DiSEqC 1.x–compliant 22kHz tone modulation. Designed for coaxial cable–fed low-noise block (LNB) biasing in set-top boxes, it provides line-drop compensation, soft-start, and full protection including OCP (600mA), SCP, boost OVP (32V), and OTP (160°C).

For engineers reviewing the MP8124GD-P datasheet, MP8124GD-P pinout, MP8124GD-P application, or MP8124GD-P equivalent, key selection considerations include its dual-stage architecture (boost + tracking LDO), selectable output voltage (13V/18V), integrated 22kHz tone shaper with 0.45–0.85Vpp amplitude, LINEDROP compensation capability, and QFN-14 (2mm×3mm) thermal performance (θJA = 70°C/W).

Technical Context

The MP8124GD-P implements a fixed-frequency (440kHz typ.) peak-current-mode boost stage that generates a VBOOST rail ~1V above final VOUT, enabling minimal dropout operation of the downstream tracking linear regulator. This architecture reduces thermal stress while maintaining low-noise LDO output suitable for sensitive RF front-ends.

Its DiSEqC 1.x compliance is realized via dedicated EXTM pin processing: external 20–24kHz tone signals are internally shaped (40–60% duty, 5–15μs rise/fall) and superimposed onto VOUT without requiring external modulation circuitry. Output voltage selection (13V/18V) and line-drop compensation (±1V) are controlled via logic-level inputs referenced to BYPASS voltage.

Key Specifications

Pinout & Package

MP8124GD-P is housed in a thermally enhanced 14-pin QFN package (2mm × 3mm, 0.5mm pitch) with exposed thermal pad. The package supports high-power density mounting and efficient heat dissipation through the bottom-side pad soldered to PCB copper.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MPQ8124GD-A, the MP8124GD-P offers identical LNB regulation and tone functionality at lower cost and smaller footprint for industrial/consumer applications, while the LMX2531LQ1E trades integrated DiSEqC support for RF synthesis capability - making it unsuitable as a drop-in replacement without redesign.

Availability

MP8124GD-P is available at Aetrix Electronics and suitable for satellite set-top box manufacturing, PC card satellite receiver development, and TV-integrated tuner production requiring stable component supply, consistent parametric performance, and long-term lifecycle support.

Supply support for MP8124GD-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 core expertise in DC/DC conversion, motor drivers, and power management for consumer, industrial, and automotive markets.

The MP8124GD-P belongs to MPS's LNB power management product line, engineered specifically for satellite receiver front-end applications requiring integrated bias regulation, DiSEqC 1.x compliance, and coaxial cable compensation in minimal footprint.

FAQ

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

The TCAP pin sets the output voltage slew rate during startup and 13V/18V transitions via an external capacitor charged at 6.8μA. Its value determines VOUT rise time: C_TCAP = (13.5 × I_CHA × T_RISE) / V_OUT, where I_CHA = 6.8μA. For 18V with 13.5ms rise time, a 22nF capacitor is typical. TCAP also serves as the feedback reference voltage for both boost and LDO stages and must be decoupled with a small capacitor away from noise sources.

How does the LINEDROP function compensate for coaxial cable voltage drop?

When the LINEDROP pin is driven high (e.g., tied to BYPASS), the MP8124GD-P increases VOUT by exactly +1V to offset IR drop across long coaxial cables. This compensation is applied directly within the feedback loop and does not require external sensing resistors or op-amps. The function is disabled when LINEDROP is low or grounded, and the pin must never be left floating to ensure predictable regulation.

Can the MP8124GD-P operate without an external 22kHz tone source?

Yes - the MP8124GD-P functions as a standard LNB power regulator even with EXTM tied to GND. In this mode, it delivers clean, regulated 13V or 18V output without tone modulation. The 22kHz tone shaper is entirely optional and only active when a valid 20–24kHz square wave is applied to EXTM; no internal oscillator generates tone autonomously.

What is the role of the BST and VBOOST pins in the two-stage architecture?

BST supplies the gate drive for the internal N-MOSFET in the tracking LDO stage via a charge pump, requiring a 0.1μF capacitor to VBOOST. VBOOST is the boosted output of the upstream DC/DC converter - typically ~1V above final VOUT - and serves as the input to the LDO. This architecture minimizes LDO dropout voltage and power dissipation, enabling high efficiency across load range.

Why is a 0.1μF capacitor specified for the VOUT output instead of larger values?

A 0.1μF ceramic capacitor is specified for VOUT to preserve the integrity of the 22kHz tone signal: larger capacitances attenuate high-frequency content and distort rise/fall times beyond DiSEqC 1.x limits (5–15μs). While insufficient for bulk energy storage, this value ensures optimal tone fidelity; bulk decoupling is handled by the VBOOST capacitor upstream of the LDO.

How does the MP8124GD-P handle short-circuit conditions on the VOUT line?

Under VOUT short-circuit, the MP8124GD-P enters hiccup-mode protection: it limits output current to ~600mA for 50ms, then shuts down for 1.9 seconds before attempting restart. If the fault persists, the cycle repeats. This prevents thermal runaway and allows safe recovery once the short is removed, without requiring external current-sense resistors or latch-off circuitry.

Is the MP8124GD-P RoHS-compliant and lead-free?

Yes - the MP8124GD-P is fully RoHS-compliant, lead-free, and halogen-free per MPS green policy. It meets JEDEC J-STD-020 moisture sensitivity level (MSL) 3 requirements and is qualified for reflow soldering per IPC/JEDEC J-STD-020 standards. Full compliance documentation is available on the Monolithic Power Systems website under Quality Assurance.