Monolithic Power Systems Inc. MP3900DK-LF-Z

Overview

MP3900DK-LF-Z from Monolithic Power Systems is a high-efficiency, constant-frequency peak current mode boost controller driving external N-channel MOSFETs up to 10A peak inductor current. It features 330kHz switching frequency, 0.816V internal reference, 180µA quiescent current, and lossless current sensing for V_ISENSE < 30V-enabling direct drain-sensing in low-voltage boost applications such as 25V/2A TV CCFL power supplies.

For engineers reviewing the MP3900DK-LF-Z datasheet, MP3900DK-LF-Z pinout, MP3900DK-LF-Z application, or MP3900DK-LF-Z equivalent, this controller supports multi-topology operation (Boost, SEPIC, Flyback, Forward), integrates slope compensation and cycle-by-cycle current limiting, and requires no external current sense resistor when output voltage is below 30V-reducing BOM count and conduction losses.

Technical Context

The MP3900DK-LF-Z implements a fixed-frequency (270–390kHz) peak current mode control architecture with an internal transconductance error amplifier (0.36mA/V typ), COMP/RUN node enabling soft-start and shutdown control via 0.5µA internal charge current, and a dedicated ISENSE comparator with 200mV current limit threshold. Its gate driver delivers 10V output with 4.0Ω sink / 16Ω source impedance to drive standard-threshold MOSFETs efficiently.

It integrates undervoltage lockout (8.9V turn-on, 2.3V hysteresis), thermal shutdown (150°C), and internal slope compensation to stabilize duty cycles above 50%. The FB pin regulates output voltage to 0.816V ±2.7% with 50nA bias current, while PGND and SGND separation enables precise high-side current sensing and noise isolation in high-di/dt paths.

Key Specifications

Pinout & Package

MP3900DK-LF-Z is housed in an 8-pin MSOP package (3.0mm × 3.0mm, 0.65mm pitch) with exposed thermal pad for enhanced power dissipation (θ_JA = 150°C/W). Pin 1 is marked by half-circle indentation per JEDEC MO-187 AA.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar boost controller applications.

Compared with LM5122 and TPS40210, MP3900DK-LF-Z uniquely combines lossless sensing below 30V, 10V gate drive for standard MOSFETs, and integrated slope compensation-making it optimal for high-efficiency, medium-power boost and SEPIC designs where BOM count and thermal performance are critical.

Availability

MP3900DK-LF-Z is available at Aetrix Electronics and suitable for TV backlight power generation, telecom isolated DC-DC modules, and industrial off-line controllers requiring stable component supply, RoHS-compliant packaging, and long-term production continuity.

Supply support for MP3900DK-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, and global distribution since 1997.

The MP3900 belongs to MPS's high-efficiency DC-DC controller product line, engineered specifically for non-isolated and isolated power conversion topologies requiring low quiescent current, integrated protection, and multi-topology flexibility in space-constrained applications.

FAQ

Can MP3900DK-LF-Z operate in discontinuous conduction mode (DCM)?

Yes. The MP3900DK-LF-Z supports both continuous and discontinuous conduction modes. Its peak current mode architecture automatically transitions into DCM at light loads, reducing switching losses and maintaining regulation down to zero load. No external circuitry is required to enable DCM operation.

What is the maximum allowable V_ISENSE voltage when using lossless sensing?

The absolute maximum V_ISENSE rating is +30V. For lossless sensing, the datasheet specifies direct connection to the MOSFET drain is valid only when the voltage swing remains below 30V. Exceeding this risks false triggering of the current limit comparator and unstable regulation.

How does the COMP/RUN pin implement soft-start?

An internal 0.5µA current charges the external capacitor on COMP/RUN. When voltage reaches ~0.16V, the controller begins switching with gradually increasing duty cycle. This linear ramp prevents inrush current and output overshoot-typical soft-start time is 5–10ms with 100nF capacitor.

Is the MP3900DK-LF-Z compatible with SOIC8 footprints?

No. MP3900DK-LF-Z uses the MSOP8 package (3.0mm × 3.0mm), which is physically smaller and has finer pitch (0.65mm) than SOIC8 (3.9mm × 4.9mm, 1.27mm pitch). Board layout must use the MSOP8 land pattern-SOIC8 pads will not align and cause solder bridging or open circuits.

What thermal derating applies above 25°C ambient?

With θ_JA = 150°C/W, the MSOP8 package dissipates 0.67W at 25°C. For every 1°C rise in ambient temperature, maximum allowable power drops by 4.47mW. At 70°C ambient, max continuous power is reduced to 0.42W-requiring careful MOSFET selection and board copper area optimization.

Does the FB pin require an external capacitor for stability?

No. The FB pin is designed for direct connection to a resistive divider. Stability is achieved through the COMP/RUN compensation network (R3/C3). Adding capacitance directly to FB introduces phase lag and may cause oscillation-only the COMP node should host the compensation capacitor.

Can MP3900DK-LF-Z drive a P-channel MOSFET?

No. The GATE driver is optimized for N-channel MOSFETs with source tied to PGND. Driving a P-channel device would require high-side gate drive with bootstrap or charge pump circuitry-functionality not supported by the MP3900DK-LF-Z's architecture or pinout.