Monolithic Power Systems Inc. MP8124GD-Z

Overview

MP8124GD-Z 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–compatible 22kHz tone modulation. It provides full protection including OCP (600mA), SCP, boost OVP (32V), and OTP (160°C shutdown), and operates in coaxial cable–fed satellite set-top boxes.

For engineers reviewing the MP8124GD-Z datasheet, MP8124GD-Z pinout, MP8124GD-Z application, or MP8124GD-Z equivalent, this device is selected for LNB biasing where low-noise output, precise 22kHz tone shaping, dynamic line-drop compensation, and robust short-circuit recovery are required - not for generic DC-DC conversion or non-satellite power applications.

Technical Context

The MP8124GD-Z implements a two-stage architecture: a fixed-frequency (440kHz typ.) peak-current-mode boost regulator supplies VBOOST at ~1V above final VOUT, enabling minimal dropout operation of the downstream tracking LDO. The LDO regulates VOUT to either 13V or 18V via logic-controlled 13V/18V pin, while simultaneously modulating the output with a shaped 22kHz tone derived from EXTM input.

It integrates analog functions including LINEDROP voltage compensation (+1V boost when asserted), TCAP-based soft-start (6.8μA charging current), and dual-stage protection: fast-cycle boost OCP (3.75A typ.), and LDO sink-current limiting with 9ms on-time / 450ms off-time hiccup behavior. Thermal shutdown activates at 160°C with 20°C hysteresis.

Key Specifications

Pinout & Package

MP8124GD-Z is housed in a thermally enhanced QFN-14 package (2mm × 3mm, 0.5mm pitch) with exposed thermal pad. Pin 1 is marked by dot; top-side marking includes "AMM" product code, year code, and lot number.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MAX22026ATB+T and LMX2594RHBR, MP8124GD-Z delivers complete DiSEqC-ready functionality in one package - integrating tone shaping, line-drop compensation, and multi-level protection - reducing system-level validation effort and improving field reliability in satellite consumer electronics.

Availability

MP8124GD-Z is available at Aetrix Electronics and suitable for satellite set-top box manufacturing, PC-based TV tuner development, and professional multiswitch distribution systems requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for MP8124GD-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 emphasis on efficiency, integration, and thermal robustness.

The MP8124 belongs to MPS's satellite communication power management product line, designed specifically to replace multi-component LNB supply solutions with a single IC that meets DiSEqC 1.x, ETSI, and IEC 60747 standards.

FAQ

What is the purpose of the TCAP pin, and how does it affect startup?

The TCAP pin sets the output voltage slew rate via an external capacitor charged at 6.8μA. Its voltage serves as the feedback reference for both boost and LDO stages. A larger TCAP capacitor increases startup time and smooths 13V↔18V transitions, preventing inrush current and LNB reset glitches. Typical value is 22nF for ~100ms rise time at 18V.

Can MP8124GD-Z operate without an external inductor?

No. The boost stage requires an external inductor (typically 10μH) to store and transfer energy. Omitting it prevents VBOOST generation, causing the LDO to fail - the IC will not regulate VOUT. Inductor DCR must be low (<150mΩ) to maintain efficiency and avoid thermal derating.

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

When LINEDROP is pulled high (to BYPASS), the IC increases VOUT by exactly 1V - e.g., from 18V to 19V - to offset IR drop across long coaxial cables. This ensures the LNB receives nominal voltage at its input despite losses up to ~1.5V over 100m RG-6 cable at 500mA.

What happens if the EXTM pin is left floating?

Leaving EXTM floating violates the absolute maximum rating (–0.3V to 6.5V) and may cause erratic tone injection or latch-up. It must be tied to GND if unused. Pulling it to BYPASS or VIN risks exceeding logic high voltage limits and damaging the input structure.

Is MP8124GD-Z compatible with DiSEqC 2.0 or higher protocols?

No. MP8124GD-Z implements only DiSEqC 1.x tone signaling (22kHz on/off keying). It lacks the bidirectional data communication, message framing, and collision detection required for DiSEqC 2.0/3.0. For those protocols, a microcontroller-based solution with separate tone generator and UART interface is required.

What is the recommended layout practice for minimizing noise on VOUT?

Place the 0.1μF LDO output capacitor (C4) directly between VOUT and AGND, with shortest possible traces. Route AGND separately from PGND and tie them at a single point near the IC. Keep TCAP, COMP, and BYPASS capacitors away from SW and PGND loops to prevent coupling of switching noise into regulation feedback.

Does MP8124GD-Z support automatic polarity switching during channel changes?

Yes - by toggling the 13V/18V pin under MCU control, the IC switches output voltage within ~10ms (governed by TCAP discharge). Combined with LINEDROP assertion, it enables synchronized polarization and line-drop compensation updates - essential for seamless H/V channel transitions in modern STBs.