Monolithic Power Systems Inc. MP1518DJ-LF-P

Overview

MP1518DJ-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 reference, and features open-load shutdown at 28V on the OV pin. Used in compact portable displays requiring high efficiency (up to 87%) and low EMI.

For engineers reviewing the MP1518DJ-LF-P datasheet, MP1518DJ-LF-P pinout, MP1518DJ-LF-P application, or MP1518DJ-LF-P equivalent, key selection criteria include its 1.0–1.5MHz fixed switching frequency, TSOT23-6 package footprint, 104mV FB threshold for precision current sensing, thermal/UVLO protection, and PWM/DC analog dimming support.

Technical Context

The MP1518DJ-LF-P implements a peak-current-mode, constant-frequency boost converter architecture with internal 1.3MHz oscillator and stabilizing ramp compensation to prevent subharmonic oscillation above 50% duty cycle. Its error amplifier compares FB voltage against a trimmed 104mV reference to control PWM comparator timing.

Protection functions are hardware-based and autonomous: OV pin monitors output voltage for open-circuit detection (28V threshold), UVLO disables operation below 2.25V (with 92mV hysteresis), and thermal shutdown activates at 160°C. Soft-start ramps current limit over 120µs to limit inrush.

Key Specifications

Pinout & Package

MP1518DJ-LF-P is packaged in a 6-pin TSOT23 (0.95 mm pitch, 1.45 mm max height), optimized for space-constrained handheld PCBs. Pin mapping is validated per Monolithic Power Systems' Rev. 1.61 datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP1518DJ-LF-P, the MP1518DJE offers lower EMI at the cost of marginal efficiency loss, while RT9397B reduces IC cost but increases design complexity and BOM count due to missing integrated OV protection.

Availability

MP1518DJ-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 MP1518DJ-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.

The MP1518 belongs to MPS's White LED Driver product line, engineered specifically for space- and efficiency-constrained portable backlighting applications where integrated protection and minimal external components are critical.

FAQ

What is the maximum number of white LEDs the MP1518DJ-LF-P can drive?

The MP1518DJ-LF-P is rated to drive up to 6 series white LEDs, assuming typical forward voltage of 3.2V per LED and a 25V maximum output capability. At 3.6V input, it supports 6 LEDs with ~85% efficiency; total output voltage must remain ≤25V to avoid OV pin shutdown.

Can the MP1518DJ-LF-P operate from a 3.3V supply?

Yes-its 2.5V to 6V input range fully supports 3.3V regulated supplies. At 3.3V input, it can drive 3–4 white LEDs (9.6–12.8V output) with >85% efficiency. Ensure input capacitance is ≥1µF ceramic and placed within 2mm of the IN pin.

How does the 104mV feedback voltage improve system efficiency?

The 104mV FB reference reduces power dissipation in the current-sense resistor by over 50% compared to standard 200mV references. For a 20mA LED current, power loss drops from 4µW to 2.08µW-critical for thermal management in sealed, fanless handheld enclosures.

Is an external Schottky diode required, and what rating is recommended?

Yes-an external Schottky diode is mandatory for boost topology operation. MPS recommends diodes rated for ≥100mA average current and ≥25V reverse voltage (e.g., CMDSH-3). Low forward voltage (<0.35V) and fast recovery (<10ns) minimize conduction and switching losses.

Does the MP1518DJ-LF-P support analog dimming, and how is it implemented?

Yes-it supports analog dimming via DC voltage injection into the FB node using a resistor divider (R2/R3 in Figure 6). A 0–2V control voltage linearly scales LED current from 0mA to full scale, enabling smooth brightness control without PWM-induced flicker in camera viewfinders.

What happens during an open LED condition, and how is it handled?

When an LED opens, output voltage rises until the OV pin detects >28V, triggering immediate latch-off shutdown. The device remains off until power is cycled-no automatic retry. This prevents capacitor overvoltage and ensures system safety without firmware intervention.

Is thermal derating required for continuous operation in a 60°C ambient environment?

Yes-using the TSOT23-6 package (θ_JA = 220°C/W), maximum continuous power dissipation at 60°C ambient is ~0.3W. At full load (e.g., 25mA × 15V = 375mW), PCB copper area and airflow must be increased or thermal vias added to avoid entering thermal shutdown.