Monolithic Power Systems Inc. MP38870DL-LF-Z

Overview

MP38870DL-LF-Z from Monolithic Power Systems is a synchronous step-down DC-DC converter with integrated 80mΩ high-side MOSFET and external low-side gate driver, delivering 3A continuous output current across 4.5V–14V input range, fixed 600kHz switching frequency, and adjustable 0.8V–(VIN−3V) output voltage. It targets point-of-load regulation in digital set-top boxes and flat-panel displays.

For engineers reviewing the MP38870DL-LF-Z datasheet, MP38870DL-LF-Z pinout, MP38870DL-LF-Z application, or MP38870DL-LF-Z equivalent, key selection criteria include its synchronizable 250kHz–1.5MHz external clock interface, cycle-by-cycle overcurrent protection, thermal shutdown at 150°C, power-good indicator, and compatibility with low-ESR ceramic output capacitors.

Technical Context

The MP38870 operates in fixed-frequency peak-current-mode control with internal 0.8V reference and error amplifier driving COMP node for loop stability. Its PWM comparator initiates each cycle via internal oscillator, terminating conduction when sensed switch current reaches COMP-set threshold or duty exceeds 90%.

It integrates a 5V internal regulator powering core logic and BG driver bias (VCC), with bootstrap circuitry (BST/SW) enabling floating gate drive for external synchronous MOSFET. UVLO triggers at 4.1V rising threshold and 3.2V hysteresis, while soft-start ramps internal reference from 0V to 1.2V to prevent output overshoot.

Key Specifications

Pinout & Package

MP38870DL-LF-Z is housed in a thermally enhanced 3mm × 4mm, 14-pin QFN package with exposed thermal pad connected to GND. The package supports high-power density designs and requires PCB land pattern per MPS MO-229 VGED-3 specification.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP2315DJ-LF-Z and RT7297CGJ8F, MP38870DL-LF-Z uniquely combines integrated high-side switch, external low-side gate driver, power-good signaling, and full-frequency synchronization-making it optimal for mid-power, system-integrated applications demanding reliability, compactness, and EMI control.

Availability

MP38870DL-LF-Z is available at Aetrix Electronics and suitable for digital set-top boxes, flat-panel television logic supplies, personal video recorders, and broadband communications equipment requiring stable component supply and long-term manufacturability.

Supply support for MP38870DL-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, headquartered in California and serving global industrial, computing, and consumer markets since 1997.

The MP38870 belongs to MPS's synchronous buck controller product line, designed specifically for compact, high-efficiency point-of-load conversion in space-constrained video and communication systems where integration, thermal robustness, and EMI control are critical.

FAQ

What is the minimum recommended output capacitance for stable operation?

The MP38870DL-LF-Z is optimized for ceramic output capacitors with total capacitance ≥10µF and low ESR. Stability is maintained across 10µF–100µF range; using <10µF may cause phase margin degradation and output oscillation under transient load steps.

Can the MP38870DL-LF-Z operate without an external synchronous MOSFET?

No. The MP38870DL-LF-Z requires an external low-side MOSFET driven by the BG pin. It does not include a body diode or internal rectifier; omitting the external FET results in no output regulation and potential damage due to reverse current flow during dead time.

How does the EN/SYNC pin function in synchronization mode?

In sync mode, the EN/SYNC pin accepts TTL/CMOS-compatible external clock signals from 250kHz to 1.5MHz. The internal oscillator locks to the rising edge of the external clock, overriding the 600kHz internal frequency. EN remains functional: pulling low disables regulation regardless of sync signal presence.

What is the purpose of the BST capacitor and what value is recommended?

The BST capacitor forms a charge pump with the SW node to generate a floating voltage ≥V_IN + 5V for driving the external MOSFET gate above its source. A 0.1µF to 1µF X7R ceramic capacitor placed between BST and SW is recommended; 0.22µF is typical for 3.3V/5V outputs with <65% duty cycle.

Does the MP38870DL-LF-Z support adjustable soft-start time?

No. Soft-start is internal and fixed at approximately 1ms ramp time from 0V to 1.2V. There is no external pin or resistor option to modify this duration; the ramp is generated by internal current source charging an internal capacitor.

What failure modes trigger latch-off versus automatic recovery?

Latch-off occurs only during output undervoltage (FB < 0.56V for >100µs), indicating sustained short-circuit or severe overload. Thermal shutdown and cycle-by-cycle current limit recover automatically when fault condition clears. Latch-off requires cycling EN or VIN to reset.

Is the exposed thermal pad electrically connected internally?

Yes. The exposed pad is internally connected to GND and must be soldered to a dedicated PCB thermal pad tied to the main GND plane. Failure to connect it degrades thermal resistance by >30°C/W and risks thermal shutdown under 3A load.