Monolithic Power Systems Inc. MP26085DJ-LF-Z

Overview

MP26085DJ-LF-Z from Monolithic Power Systems is a precision CC/CV controller IC for secondary-side feedback in isolated flyback and forward converters, integrating dual op-amps, a 1.223V ±1% voltage reference, a programmable current source (1.25mA typ.), and opto-coupler drive capability - used in battery chargers, LED drivers, and AC/DC adapters requiring tight output regulation.

For engineers reviewing the MP26085DJ-LF-Z datasheet, MP26085DJ-LF-Z pinout, MP26085DJ-LF-Z application, or MP26085DJ-LF-Z equivalent, this device supports accurate constant-current and constant-voltage control via external resistor dividers on VFB and IREF pins, with ICON-enabled current offset for adaptive charge termination and analog/digital dimming in LED systems.

Technical Context

The MP26085 implements two independent error amplifiers - one for voltage regulation (VFB vs. VREF) and one for current limiting (IFB vs. IREF) - whose outputs are OR'ed at the COMP pin to drive an opto-coupler LED, enabling closed-loop control of the primary-side PWM controller. Its internal bandgap reference provides stable 1.223V with 60–100 ppm/°C drift over –40°C to +85°C.

The current source is enabled/disabled via the ICON pin (active-low logic), generating a precise 1.25mA (R3+R4 = 44kΩ) that offsets the IFB sense voltage through an external resistor (Rif), allowing dynamic adjustment of charge current without changing RSEN - critical for multi-stage battery charging and LED dimming.

Key Specifications

Pinout & Package

MP26085DJ-LF-Z is housed in an 8-pin TSOT23 package (3.0mm × 3.0mm × 0.9mm), optimized for high-density secondary-side placement in compact AC/DC adapters and battery chargers.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar CC/CV secondary-side regulation applications.

Compared with UCC3803D and TL431-based solutions, MP26085DJ-LF-Z reduces component count by ≥4 parts, improves CV accuracy by 2×, and adds hardware-programmable current offset - making it optimal for space-constrained, multi-profile power supplies demanding tight regulation and flexible current control.

Availability

MP26085DJ-LF-Z is available at Aetrix Electronics and suitable for battery chargers, LED drivers, and universal AC/DC adapters requiring stable component supply, RoHS-compliant packaging, and long-term production continuity.

Supply support for MP26085DJ-LF-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.

The MP26085 belongs to MPS's secondary-side regulation product line, engineered specifically for isolated DC/DC converters needing integrated CC/CV control, opto-coupler interface, and minimal external components in compact form factors.

FAQ

What is the minimum recommended input voltage for MP26085DJ-LF-Z?

The absolute minimum operating input voltage is 7V on the IN pin, as specified in the Recommended Operating Conditions table. Below 7V, the internal reference and op-amps may not stabilize, causing erratic CV/CC regulation or COMP output dropout. Designs using auxiliary windings should ensure worst-case winding voltage remains ≥7V under all load and line conditions.

How does the ICON pin affect current regulation accuracy?

When ICON is grounded, the internal current source (1.25mA) flows through Rif to generate an offset voltage (V_OFFSET = I_SOURCE × Rif) that subtracts from the IFB sense voltage - effectively lowering the current limit. This offset introduces no additional error beyond Rif tolerance and I_SOURCE tempco (100 ppm/°C), preserving ±2% overall CC accuracy if Rif is 1% metal-film.

Can MP26085DJ-LF-Z replace TL431 in existing designs?

Yes, but only with circuit modifications: TL431 designs lack current sensing, so adding IFB, IREF, and ICON connections is required. The MP26085's dual op-amps and current source enable true CC/CV operation where TL431 provides only CV - replacement delivers enhanced functionality but is not drop-in.

What is the maximum allowable voltage on the COMP pin?

The COMP pin has an absolute maximum rating of –0.3V to +22V. However, for reliable opto-coupler LED drive, the recommended operating range is 0.5V to 5V. Sustained voltages above 5V risk excessive current through the internal op-amp output stage and may degrade long-term reliability.

Does MP26085DJ-LF-Z support synchronous rectification control?

No. MP26085DJ-LF-Z is a secondary-side feedback controller only - it provides voltage and current error signals to the primary-side PWM via opto-coupler, but does not generate gate drive signals for synchronous rectifiers. Devices like MP6902 must be used alongside it for SR control.

What is the purpose of the 44kΩ total resistance on R3+R4?

The 44kΩ sum sets the nominal current source value to 1.25mA (I_SOURCE = VREF × Ki / (R3 + R4), where Ki = 45). Deviating from 44kΩ changes I_SOURCE proportionally - e.g., 22kΩ yields 2.5mA - altering the magnitude of current offset applied via Rif, which must be recalculated for target V_OFFSET.

Is thermal shutdown integrated into MP26085DJ-LF-Z?

No. MP26085DJ-LF-Z has no internal thermal shutdown circuit. Protection relies on system-level measures: the 0.45W power dissipation limit at TA = 25°C and θJA = 220°C/W implies junction temperature must stay below +125°C. PCB layout, copper area, and airflow must be designed to maintain TJ ≤ 125°C under worst-case load.