Monolithic Power Systems Inc. MP8128GQ-Z

Overview

MP8128GQ-Z from Monolithic Power Systems is a 1A LNB voltage regulator with integrated I²C interface and DiSEqC 2.x support, designed for satellite receiver antenna port power and control. It delivers low-noise 13–18V output via a boost + tracking LDO architecture, provides 22kHz tone generation/detection, and supports programmable current limiting (up to 1.43A), OCP/SCP/OVP/OTP, and selectable internal/external tone source - enabling precise LNB biasing in set-top boxes and PC card receivers.

For engineers reviewing the MP8128GQ-Z datasheet, MP8128GQ-Z pinout, MP8128GQ-Z application, or MP8128GQ-Z equivalent, key selection criteria include DiSEqC 2.x compliance, I²C-configurable output voltage (10.33V–18V), 8–14V input range, QFN-20 thermal performance, and dual-tone signal handling (generation + detection) for satellite LNB control systems.

Technical Context

The MP8128GQ-Z implements a two-stage regulation architecture: a 440kHz fixed-frequency boost converter (R_DS(ON) = 200mΩ) supplies VBOOST to a tracking linear regulator, maintaining ≤1.1V dropout while rejecting switching noise. Its DiSEqC 2.x functionality integrates tone detection (TDI/TDO pins), bidirectional bus compatibility, and configurable tone sourcing (internal generator or external EXTM input).

I²C interface (400kHz max) enables full digital control of output voltage (VLINE bits), current limit (ILIMT resistor), tone enable (TEN), tone source (TCTRL), and protection flags (IRQ open-drain fault indicator). The device operates across –40°C to +125°C junction temperature and includes thermal shutdown (150°C) with 20°C hysteresis.

Key Specifications

Pinout & Package

MP8128GQ-Z is housed in a thermally enhanced QFN-20 (3mm × 3mm) package with an exposed PGND pad. Pin 1 is SW (boost switch node); pin 20 is PGND; the exposed pad must be soldered to PGND with thermal vias for optimal thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar LNB voltage regulation and DiSEqC interface applications.

Compared with MAX2181AETL+ and STV0900, MP8128GQ-Z uniquely combines regulated LNB power delivery, DiSEqC 2.x transceiver functionality, and I²C configurability in one QFN-20 package - reducing bill-of-materials, board space, and firmware complexity for next-generation satellite receivers.

Availability

MP8128GQ-Z is available at Aetrix Electronics and suitable for satellite set-top box manufacturing, PC card satellite receiver design, and smart TV frontend development requiring stable component supply and long-term production continuity.

Supply support for MP8128GQ-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 power management ICs for consumer, computing, industrial, and automotive markets.

The MP8128 belongs to MPS's satellite communication power product line, engineered specifically to integrate LNB voltage regulation, DiSEqC 2.x signaling, and digital control into a single chip for compact, low-noise satellite receiver designs.

FAQ

What is the maximum allowable VOUT rating for MP8128GQ-Z?

The MP8128GQ-Z has a 40V absolute maximum rating on the VOUT pin, allowing it to safely withstand transient backfeed voltages from LNBs during hot-plug or cable disconnect events without damage. This rating exceeds EN 50494 requirements and enables robust field operation in unshielded coaxial environments.

How does the ILIMT pin configure output current limit?

The ILIMT pin accepts a resistor to ground to set the output current limit: 6.98kΩ yields 1.43A, 14kΩ yields 650mA, and 19.1kΩ yields 475mA. The relationship is linear and specified across temperature; no calibration is required, and the pin must never be left floating to avoid undefined current limiting.

Can MP8128GQ-Z operate with DiSEqC 2.x tone detection and generation simultaneously?

Yes - the device supports concurrent tone generation (via EXTM or internal source) and tone detection (via TDI/TDO) in real time. When TCTRL=1 and TEN=1, EXTM carries outgoing DiSEqC pulses while TDI monitors incoming pulses on the same coaxial line, enabling full-duplex DiSEqC 2.x communication.

What is the purpose of the TCAP pin and how is it used?

The TCAP pin sets soft-start time via an external capacitor to ground. A typical 100nF capacitor yields ~10ms rise time for VOUT, preventing inrush current into large LNB output capacitors. TCAP voltage also serves as the feedback reference, so the capacitor must be placed away from noisy nodes to avoid regulation instability.

Does MP8128GQ-Z require external compensation components?

No external compensation is needed for the LDO stage. However, the COMP pin requires a type-2 compensation network (typically 10kΩ + 1nF to ground) for the boost regulator loop stability, as specified in the datasheet Figure 29. Omitting this network risks oscillation under light-load conditions.

How is I²C address selected on MP8128GQ-Z?

I²C address is set via the ADDR pin: grounding selects 0001000 (0x28), 27kΩ to GND selects 0001001 (0x29), 47kΩ to GND selects 0001010 (0x2A), and floating selects 0001011 (0x2B). Address detection current is 45–55μA, ensuring reliable recognition across voltage and temperature ranges.

What thermal management practices are recommended for QFN-20 layout?

Connect the exposed thermal pad directly to a solid PGND plane using ≥4 thermal vias (0.3mm diameter, 0.8mm pitch). Keep high-current paths (SW, VOUT, PGND) short and wide; place BYPASS (0.22μF) and TCAP capacitors within 2mm of their respective pins to minimize inductance and ensure stable regulation.