Monolithic Power Systems Inc. MP1518DG-LF-P

Overview

MP1518DG-LF-P from Monolithic Power Systems is a fixed-frequency, current-mode boost LED driver IC designed to drive up to 6 series white LEDs from a 2.5V–6V input (e.g., single-cell Li-ion). It integrates a 0.5Ω power MOSFET switch, regulates LED current via a 104mV feedback voltage, operates at 1.0–1.5MHz, and includes open-load shutdown (28V OV threshold), UVLO (2.45V turn-on), and thermal shutdown (160°C). Used in compact portable displays.

For engineers reviewing the MP1518DG-LF-P datasheet, MP1518DG-LF-P pinout, MP1518DG-LF-P application, or MP1518DG-LF-P equivalent, key selection criteria include its 104mV FB reference for low-loss current sensing, QFN8 (2mm × 2mm) package thermal performance (θJA = 80°C/W), 1.3MHz typical switching frequency, and integrated protections: OV, UVLO, thermal shutdown, and internal current limit.

Technical Context

The MP1518DG-LF-P implements a constant-frequency peak-current-mode boost architecture with an internal 0.5Ω N-channel MOSFET switch and dedicated OV monitoring pin tied to the LED string anode. Its error amplifier compares FB voltage against a precise 104mV reference to control PWM duty cycle.

Soft-start ramps current limit over 120µs (in 40µs steps), while the stabilizing ramp prevents subharmonic oscillation above 50% duty cycle. Open-circuit protection triggers shutdown when OV exceeds 28V, and EN enables/disables operation with 1.35V typical threshold and 90mV hysteresis.

Key Specifications

Pinout & Package

MP1518DG-LF-P is housed in an 8-pin QFN package (2mm × 2mm, 0.4mm height) with exposed thermal pad. Pin 1 is marked by a dot or beveled corner; the exposed paddle must be soldered to PCB ground for optimal thermal performance (θJC = 16°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar white LED boost driver applications.

Compared with MP1518DJE, MP1518DG-LF-P offers higher EMI tolerance in dense layouts but less inherent noise suppression; versus RT9397B, it delivers integrated open-load protection and tighter FB reference tolerance (±10mV vs. ±15mV), simplifying design validation for portable LED systems.

Availability

MP1518DG-LF-P is available at Aetrix Electronics and suitable for cell phones, digital still cameras, and handheld computers requiring stable component supply, RoHS-compliant packaging, and long-term production continuity.

Supply support for MP1518DG-LF-P 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 MP1518 belongs to MPS's white LED driver product line, engineered specifically for space- and efficiency-constrained portable electronics that demand integrated protection, minimal external components, and stable current regulation across battery voltage variation.

FAQ

What is the recommended inductor value and type for MP1518DG-LF-P?

A 22µH shielded power inductor with low DCR (<300mΩ) is recommended. Shielded construction minimizes EMI coupling; low DCR preserves efficiency at 20–350mA LED currents. Typical part numbers include Coilcraft MSS5131-223ML or Würth Elektronik 744040220.

Can MP1518DG-LF-P drive more than 6 white LEDs?

No-driving more than 6 standard white LEDs (3.2V VF each) exceeds the 25V maximum output voltage rating. At VIN = 3.6V, 6 LEDs require ~19.2V, leaving ~5.8V headroom; adding a seventh LED would exceed safe operating limits and trigger OV shutdown.

How does analog dimming work on the FB pin?

Analog dimming injects current into FB via a resistor divider from a DC control voltage. Since the regulator maintains 104mV at FB, injected current reduces LED current proportionally (ILED = 104mV/R_SENSE – I_INJ). This enables smooth, flicker-free brightness control without PWM frequency constraints.

Is the NC pin (Pin 8) required to be grounded or left floating?

Pin 8 is a true no-connect-neither bonded nor functional. It must remain unconnected: no trace, no solder, no via. Routing or grounding it may cause mechanical stress or unintended coupling; the datasheet explicitly prohibits connection.

What thermal derating applies above +25°C ambient?

With θJA = 80°C/W, junction temperature rises 80°C per watt of dissipated power. At TA = 85°C, maximum allowable power dissipation drops to (125°C – 85°C)/80°C/W = 0.5W. For continuous 20mA output, power loss is typically <0.15W-well within safe margin.

Does MP1518DG-LF-P support PWM dimming above 1kHz?

Yes-but not directly on EN. Above 1kHz, EN toggling triggers repeated soft-start cycles, causing instability. Instead, use filtered PWM (RC low-pass) applied to FB for analog dimming, or implement external PWM gating of the LED cathode path while keeping MP1518 enabled continuously.

What is the minimum input capacitance required?

A minimum 1µF X5R/X7R ceramic capacitor placed ≤2mm from IN and GND pins is mandatory. This suppresses high-frequency switching noise and prevents VIN droop during peak current pulses; larger values (2.2–4.7µF) improve transient response under dynamic load changes.