Monolithic Power Systems Inc. MP1528DQ-LF-P

Overview

MP1528DQ-LF-P from Monolithic Power Systems is a 36V step-up white LED driver IC designed to regulate current for up to nine series-connected LEDs from a single-cell Li-ion battery (2.7–36V BIAS input). It integrates a 0.63Ω power MOSFET, features 0.4V full-scale current-sense threshold, analog/PWM brightness control via BRT pin, and open-load shutdown triggered at 40V on BIAS pin. Used in compact portable displays requiring precise 20mA per-string current regulation.

For engineers reviewing the MP1528DQ-LF-P datasheet, MP1528DQ-LF-P pinout, MP1528DQ-LF-P application, or MP1528DQ-LF-P equivalent, key selection criteria include its 9-LED series drive capability, 36V output headroom, 0.4V sense threshold enabling low-loss current sensing, thermal shutdown at 160°C, and QFN6 (3mm × 3mm) RoHS-compliant package with exposed thermal pad.

Technical Context

The MP1528DQ-LF-P employs constant off-time, variable-frequency current-mode control to regulate LED current with high efficiency across input voltages from 2.7V to 36V. Its feedback loop uses a precision 0.4V reference applied to the FB pin, derived from a 1/3-attenuated BRT voltage, enabling accurate analog dimming from 0.27V to 1.2V.

Open-circuit protection is implemented via the BIAS pin monitoring output voltage; shutdown occurs when BIAS exceeds 40V. The internal 950mA switch current limit, 330ns minimum off-time, and integrated 0.63Ω MOSFET enable stable operation driving up to nine 3.6V white LEDs (32.4V total) while maintaining >80% efficiency at 20mA.

Key Specifications

Pinout & Package

MP1528DQ-LF-P is housed in a 6-pin QFN package (3mm × 3mm, 0.95mm height) with exposed thermal pad on underside for enhanced heat dissipation. Pin 1 is marked by a dot or notch; pins are numbered counterclockwise from top-left corner in top view.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP1528DK-LF-Z, MP1528DQ-LF-P offers 62% lower θ_JA (50 vs 150°C/W) and 44% smaller footprint; versus LT3466-1EDD, it eliminates external FET, reduces component count by 3, and lowers total solution cost despite identical LED performance.

Availability

MP1528DQ-LF-P is available at Aetrix Electronics and suitable for handheld computers, digital cameras, and small LCD displays requiring stable component supply, RoHS compliance, and long-term production continuity.

Supply support for MP1528DQ-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, headquartered in Kirkland, WA, with global design and support centers.

The MP1528 product line targets portable LED lighting applications demanding high integration, minimal external components, and robust fault protection - optimized for space-constrained battery-powered devices with stringent efficiency and reliability requirements.

FAQ

What is the maximum number of white LEDs the MP1528DQ-LF-P can drive in series?

The MP1528DQ-LF-P is specified to drive up to nine (9) series-connected white LEDs, assuming typical forward voltage of 3.6V per LED (total ~32.4V), with 3.6V headroom margin before reaching its 42V absolute maximum SW-to-GND rating. Operation beyond 9 LEDs risks violating open-load shutdown threshold or exceeding internal current limit under low-input conditions.

Can the MP1528DQ-LF-P operate without connecting the BIAS pin?

No - the BIAS pin must be connected either to the top of the LED string (for open-load protection) or to the input supply (to disable protection and reduce quiescent current). Leaving BIAS floating violates Absolute Maximum Ratings and may cause erratic operation or damage due to uncontrolled internal biasing.

What is the minimum recommended sense resistor value for 20mA LED current?

Using the 0.4V FB threshold, the minimum recommended sense resistor is 20Ω (R = 0.4V / 0.02A). Lower values increase current-sense noise susceptibility and reduce regulation accuracy; higher values raise power dissipation (e.g., 50Ω dissipates 400µW) and thermal drift impact.

Does the MP1528DQ-LF-P support PWM dimming frequencies outside 100–400Hz?

No - the BRT pin's internal comparator is optimized for 100–400Hz PWM signals. Frequencies below 100Hz cause visible flicker and inconsistent current regulation; above 400Hz, the internal one-shot timer cannot reliably resolve duty cycle, leading to reduced dimming linearity and potential instability.

How does the EN pin behave during brown-out conditions?

The EN pin has 60mV hysteresis and triggers turn-on at 0.8–1.2V (rising) and turn-off at 0.74–1.14V (falling). During input brown-out, the device remains latched on until BIAS drops below 2.1V (UVLO threshold), independent of EN state - ensuring graceful shutdown without oscillation near threshold.

Is the exposed thermal pad on the QFN6 package electrically connected internally?

No - the exposed pad is a thermal-only connection with no internal electrical bond. It must be soldered to a dedicated PCB copper pour tied to GND for optimal heat transfer; floating or unconnected pads degrade thermal performance by >30% and risk premature thermal shutdown.