Monolithic Power Systems Inc. MP157GJ-Z

Overview

MP157GJ-Z from Monolithic Power Systems is a primary-side constant-voltage (CV) off-line regulator with integrated 500V/10Ω MOSFET, supporting Buck, Buck-Boost, Boost, and Flyback topologies. It delivers up to 6W output power, achieves <100mW no-load consumption, and operates in green mode with frequency foldback and peak current compression for high light-load efficiency. It targets low-power AC/DC conversion in home appliance standby supplies.

For engineers reviewing the MP157GJ-Z datasheet, MP157GJ-Z pinout, MP157GJ-Z application, or MP157GJ-Z equivalent, key selection criteria include its TSOT23-5 package footprint, primary-side regulation eliminating optocoupler dependency, VCC UVLO hysteresis (230mV), 2.55V FB reference, and thermal shutdown at 150°C - all critical for compact, cost-sensitive, isolated/non-isolated SMPS designs.

Technical Context

The MP157GJ-Z implements primary-side CV control via feedback sampling through an internal error amplifier with 6μs delay and ramp compensation, enabling precise output regulation without secondary-side sensing. Its green-mode operation dynamically scales switching frequency and peak current (640mA typ.) with load, maintaining >75% efficiency at 10% load.

Protection architecture includes timer-based OLP (150ms delay at 37kHz), SCP triggered at 900mA, open-loop detection at 60mV FB, and thermal shutdown with auto-restart. Internal 400ns leading-edge blanking prevents false current-sense triggering during MOSFET turn-on transients.

Key Specifications

Pinout & Package

MP157GJ-Z is housed in a thermally enhanced TSOT23-5 package with exposed drain pad for improved heat dissipation. The 5-pin configuration supports minimal external component count and compact layout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with LNK3206G and UCC28910DR, MP157GJ-Z offers the smallest TSOT23-5 footprint and lowest no-load consumption (<100mW), making it optimal for space-constrained, energy-compliant applications below 6W where optocoupler elimination is prioritized over maximum power scalability.

Availability

MP157GJ-Z is available at Aetrix Electronics and suitable for home appliance control, industrial sensor powering, and IoT edge node auxiliary supplies requiring stable component supply, RoHS-compliant sourcing, and long-lifecycle support.

Supply support for MP157GJ-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 in the US, China, and Taiwan, and global manufacturing partnerships.

The MP157 belongs to MPS's primary-side regulation (PSR) controller product line, engineered specifically for compact, low-cost, and energy-efficient AC/DC converters targeting consumer, industrial, and white-goods markets.

FAQ

What topologies does MP157GJ-Z support, and which require isolation?

MP157GJ-Z supports Buck, Buck-Boost, Boost, and Flyback topologies. Only Flyback provides galvanic isolation via a transformer; the others are non-isolated and deliver referenced output voltages. Flyback is used where safety isolation is mandated (e.g., mains-connected outputs), while Buck is common for internal 5V/12V rails.

How does MP157GJ-Z achieve constant voltage regulation without an optocoupler?

It uses primary-side sensing: an RC network on the secondary side feeds back output voltage to the FB pin via a capacitor that samples and holds the output during freewheeling. The internal error amplifier compares this sampled voltage to the 2.55V reference and adjusts switching duty cycle accordingly - eliminating optocoupler drift and failure modes.

What is the minimum off-time limitation, and why is it critical for power delivery?

The MP157GJ-Z enforces a 13.1μs minimum off-time during normal operation. This directly limits maximum achievable output power in CCM mode: P_max ≈ V_OUT × t_{min_off} × I_PEAK / (2 × L). Selecting inductance too small violates this constraint, causing regulation loss at full load - per Figure 8 in the datasheet.

Can MP157GJ-Z operate with universal AC input (85–265VAC)?

Yes. Its integrated 500V MOSFET and internal high-voltage startup current source allow direct connection to rectified universal AC input. Design Example (Figure 12) validates operation from 85VAC to 265VAC delivering 12V/350mA, with input capacitors sized per half-wave (3μF/W) or full-wave (1.5–2μF/W) rectification.

What protections are implemented, and how do they reset?

MP157GJ-Z includes thermal shutdown (150°C, auto-restart), VCC UVLO (4.45V on / 4.6V off), OLP (150ms timer), SCP (900mA threshold), and open-loop detection (60mV FB). All protections except thermal shutdown use VCC discharge/recharge cycles: a 16μA internal current source discharges VCC to 2.4V before restarting, providing controlled fault recovery.

Is the TSOT23-5 package thermally adequate for 6W operation?

Yes - with proper PCB layout. The datasheet specifies θ_JA = 100°C/W for TSOT23-5 on a 4-layer board. At 6W dissipation and 25°C ambient, junction temperature rises ~600°C above ambient - but actual power dissipation is far lower due to high efficiency (>80% typical). Layout guidelines (exposed drain pad to copper pour) ensure safe operation within 150°C T_J limit.