Monolithic Power Systems Inc. MP158GJ-Z

Overview

MP158GJ-Z from Monolithic Power Systems is a primary-side constant-voltage (CV) off-line regulator with integrated 500V MOSFET, supporting Buck, Buck-Boost, Boost, and Flyback topologies. It delivers up to 2W output power, achieves <30mW no-load consumption, and operates across -40°C to +125°C junction temperature - enabling compact, low-cost standby power supplies for home appliances and white goods.

For engineers reviewing the MP158GJ-Z datasheet, MP158GJ-Z pinout, MP158GJ-Z application, or MP158GJ-Z equivalent, key selection criteria include its green-mode frequency foldback, primary-side CV regulation without optocoupler, TSOT23-5 package footprint, 5.3–5.6V VCC operating range, and thermal shutdown with auto-restart behavior.

Technical Context

The MP158GJ-Z implements primary-side regulation using internal sampling of the feedback voltage (VFB = 2.55V ±100mV) referenced to the SOURCE pin, eliminating optocoupler dependency. Its green-mode operation dynamically reduces both peak current (down to ~16mA at no load) and switching frequency under light loads via off-time extension and peak-current compression.

Protection logic includes timer-based overload protection (120ms delay), short-circuit detection (SCP threshold 150–290mA), open-loop detection (<60mV VFB), and thermal shutdown at 150°C with 30°C hysteresis. The IC self-starts from the DRAIN pin and manages VCC via internal high-voltage regulator with UVLO (5.3V turn-on / 5.6V turn-off) and latch-off discharge (~16μA).

Key Specifications

Pinout & Package

MP158GJ-Z is housed in a 5-pin TSOT23-5 package (JEDEC MO-193 AA), optimized for high-voltage isolation and thermal dissipation via exposed DRAIN pad connection. Pin 1 is VCC, Pin 2 is FB, Pins 3 and 4 are SOURCE (internally tied), and Pin 5 is DRAIN.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar primary-side off-line regulator applications.

Compared with MP158GJ-Z, MP157GJ-Z offers lower no-load consumption but sacrifices 0.5W output headroom, while LNK304DG-TL trades adaptive efficiency for fixed-frequency simplicity and lacks primary-side CV precision - making MP158GJ-Z optimal for cost-sensitive, space-limited, and energy-regulated applications requiring balanced performance.

Availability

MP158GJ-Z is available at Aetrix Electronics and suitable for smart appliance control boards, IoT sensor hub power supplies, and white goods standby power systems requiring stable component supply, RoHS-compliant packaging, and long-term lifecycle support.

Supply support for MP158GJ-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 across Asia and North America and global manufacturing partnerships.

The MP158 product line targets cost-sensitive, space-constrained off-line AC/DC conversion in consumer and industrial applications - emphasizing primary-side regulation, ultra-low no-load power, and integrated protection for simplified, compliant power supply design.

FAQ

What is the maximum continuous output power achievable with MP158GJ-Z in TSOT23-5 package?

The MP158GJ-Z supports up to 2W continuous output power in TSOT23-5 package under typical conditions (TA = 25°C, adequate PCB copper area). Derating applies above 70°C ambient due to θJA = 100°C/W; at 85°C ambient, maximum sustainable power drops to ~1.3W to maintain TJ ≤ 125°C.

Does MP158GJ-Z require an external optocoupler for output voltage regulation?

No. MP158GJ-Z implements primary-side constant-voltage regulation using internal sampling of the output via a feedback capacitor network. This eliminates the need for an optocoupler or secondary-side shunt regulator, reducing BOM cost and improving reliability in isolated flyback designs.

How does the green-mode operation reduce no-load power consumption?

Green-mode operation reduces no-load power by dynamically lowering both switching frequency and peak current limit as load decreases. At no load, frequency drops below 10kHz and peak current compresses toward ~16mA, minimizing switching and conduction losses - enabling <30mW total input power with proper dummy load tuning.

What is the function of the two SOURCE pins (3 and 4) in TSOT23-5 package?

Pins 3 and 4 are internally bonded together as the SOURCE terminal of the integrated 500V MOSFET and serve as the ground reference for both VCC and FB circuits. They must be connected to a low-impedance PCB ground plane to ensure stable regulation and accurate current sensing - splitting them externally degrades performance and may cause instability.

Can MP158GJ-Z operate in continuous conduction mode (CCM)?

Yes. MP158GJ-Z supports both CCM and DCM operation depending on inductor value and load. Maximum CCM output current is <70mA; exceeding this forces transition to DCM. Designers select inductance to target desired mode - CCM improves light-load regulation but increases size/cost, while DCM simplifies EMI filtering.

What protection features are implemented and how do they reset?

MP158GJ-Z includes thermal shutdown (OTP), short-circuit protection (SCP), overload protection (OLP), open-loop detection, and VCC UVLO. All except OTP are auto-restarting: after fault removal, VCC discharges to ~2.4V then recharges to 5.6V to initiate soft-start. OTP recovery requires junction cooling to 120°C before restart.

Is the TSOT23-5 package thermally adequate for 2W operation?

Yes, with proper PCB layout. The TSOT23-5 package has θJA = 100°C/W on a 4-layer board per JESD51-7. For 2W dissipation and TA = 25°C, junction rise is ~200°C - exceeding rating. Therefore, 2W requires ≥2 cm² of 2-oz copper connected to SOURCE/DRAIN pads and thermal vias to inner layers to achieve effective θJA ≤ 50°C/W.