Monolithic Power Systems Inc. EV157-J-00B

Overview

EV157-J-00B from Monolithic Power Systems is an evaluation board demonstrating the MP157 primary-side constant voltage buck regulator IC for universal AC input (85–265VAC, 50/60Hz), delivering regulated dual outputs: 18V/0.3A and 5V/0.1A. It implements a non-isolated buck topology with integrated 500V MOSFET, peak-current control, and multi-protection features for small-appliance power supplies.

For engineers reviewing the EV157-J-00B datasheet, EV157-J-00B pinout, EV157-J-00B application, or EV157-J-00B equivalent, this board provides verified reference design validation for cost-sensitive, low-power AC/DC conversion with IEC61000-4-5 surge immunity and EN55022 conducted EMI compliance.

Technical Context

The EV157-J-00B implements a primary-side-controlled buck regulator using the MP157GJ IC in TSOT23-5 package, eliminating optocoupler and secondary-side feedback. It employs peak-current mode control with frequency foldback and peak current compression to maintain regulation across universal AC input range.

Output cross-regulation is achieved via coupled inductor T1 (EE13 core, N1:N2 = 200:94, 1.4mH ±10%), with independent post-regulation of the 5V rail by U2 (L78L05ACUTR LDO). Protection includes SCP, OCP, OTP, and VCC UVLO - all implemented without external sensing circuitry.

Key Specifications

Availability

EV157-J-00B is available at Aetrix Electronics and suitable for small-appliance development, white-goods prototyping, and IoT edge-device power supply validation requiring stable component supply, repeatable reference designs, and pre-validated safety margins.

Supply support for EV157-J-00B 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 focus on efficiency, integration, and thermal performance in power management solutions.

The EV157-J-00B belongs to MPS's evaluation board portfolio for its MP157 primary-side CV controller family, designed specifically to accelerate adoption of low-cost, non-isolated AC/DC converters in cost-sensitive consumer and small-appliance applications.

FAQ

What is the role of the coupled inductor T1 on the EV157-J-00B?

T1 (EE13 core, 1.4mH ±10%, N1:N2 = 200:94) enables dual-output generation from a single primary-side controller. Its tightly coupled windings provide inherent cross-regulation between the 18V and 5V rails, reducing need for secondary feedback while maintaining output stability under varying load conditions.

Does the EV157-J-00B provide galvanic isolation?

No - the EV157-J-00B implements a non-isolated buck topology per MP157's primary-side control architecture. It lacks transformer isolation; safety relies on reinforced insulation design, creepage/clearance compliance, and mandatory use of an isolation transformer during lab testing as stated in the warning notice.

How is the 5V output stabilized given the primary-side control architecture?

The 5V rail is post-regulated by U2 (L78L05ACUTR), a fixed 5V linear regulator in SOT89 package. This compensates for cross-regulation drift in the coupled inductor, ensuring precise 5V ±2% tolerance under dynamic load changes - critical for MCU and digital logic supply integrity.

What protection features are implemented, and how are they triggered?

Protections include short-circuit (SCP), over-current (OCP), over-temperature (OTP), and VCC under-voltage lockout (UVLO). SCP/OCP are sensed internally via MP157's current-sense resistor and valley-current detection; OTP uses on-die thermal shutdown; UVLO disables switching below ~8.5V VCC.

Can the EV157-J-00B be used directly in end products?

No - the board is an engineering prototype evaluation tool only, not agency-certified (UL/EN62368-1). It lacks final safety approvals, conformal coating, and production-grade mechanical robustness. It serves strictly for design verification, not for deployment in certified end equipment.

What is the purpose of R7 (3.9kΩ) on the 18V output?

R7 acts as a dummy load (≈4.6mA) to improve light-load regulation and prevent output voltage overshoot when the 18V rail operates near no-load conditions. It ensures minimum conduction in the freewheeling path (D5) and stabilizes feedback loop dynamics during standby.