Monolithic Power Systems Inc. MP26121DQ-LF-Z

Overview

MP26121DQ-LF-Z from Monolithic Power Systems is a linear single-cell Li-ion/Li-polymer battery charger IC with 28V input surge tolerance, programmable 200mA–1A charge current, 1% battery voltage regulation accuracy, 10% battery-full threshold, and integrated NTC thermistor interface for temperature-safe charging in portable electronics.

For engineers reviewing the MP26121DQ-LF-Z datasheet, MP26121DQ-LF-Z pinout, MP26121DQ-LF-Z application, or MP26121DQ-LF-Z equivalent, key selection criteria include its 28V VIN surge protection, flexible NTC resistor compatibility, thermal foldback behavior above 105°C, and open-drain CHG/ACOK status signaling for system-level battery management.

Technical Context

The MP26121 operates in three sequential charge phases-trickle (≤2.6V), constant-current (CC), and constant-voltage (CV)-with automatic recharge triggered at 4.0V and termination at 10% of programmed I_CHG. Its internal oscillator (5.4Hz with 2.2μF TMR capacitor) governs both trickle-timeout (32768 cycles) and total-charge timeout (262144 cycles).

Thermal management is implemented via die-temperature-dependent current reduction starting at 105°C, with hard shutdown at 135°C. The NTC interface uses a dual-threshold window comparator (V_{NTC_UP} = 2.735V, V_{NTC_LOW} = 1.197V) configurable with external resistors to match diverse NTC curves across –40°C to +85°C ambient.

Key Specifications

Pinout & Package

MP26121DQ-LF-Z is housed in a thermally enhanced QFN-10 package (3mm × 3mm, 0.5mm pitch) with exposed thermal pad requiring solder connection to PCB ground plane for θ_JA = 50°C/W performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar linear Li+ battery charging applications.

Compared with BQ24075RGTR and TP4056, MP26121DQ-LF-Z uniquely combines 28V surge tolerance, 10% programmable full-charge threshold, and field-configurable NTC interface-making it optimal for unregulated adapter inputs and JEITA-compliant thermal charging in consumer portables.

Availability

MP26121DQ-LF-Z is available at Aetrix Electronics and suitable for smartphones, digital cameras, portable media players, and PDAs requiring stable component supply, long-lifecycle availability, and RoHS-compliant packaging.

Supply support for MP26121DQ-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 mixed-signal ICs for power management, motor drive, and automotive applications.

The MP26121 belongs to MPS's linear battery charger product line, designed specifically for compact, thermally constrained portable devices requiring robust input surge protection, precise Li+ termination, and flexible battery temperature monitoring.

FAQ

What is the maximum allowable input voltage for MP26121DQ-LF-Z?

The MP26121DQ-LF-Z has an absolute maximum VIN rating of +28V, with built-in proprietary surge protection that allows direct connection to unregulated wall adapters. Normal operation requires 3.5V–6.5V input; charging disables automatically if VIN falls below 3V or rises above 7.3V due to its internal OVP circuit.

How does the 10% battery-full threshold function during CV mode?

The 10% threshold triggers charge termination when sensed charge current drops to 10% of the programmed I_CHG value (e.g., 50mA for 500mA setting). This occurs during CV mode as battery impedance rises near full state, and is enforced by an internal comparator independent of external timing-ensuring accurate end-of-charge detection.

Can the NTC interface accommodate custom thermistor curves?

Yes-the NTC pin implements a dual-threshold window comparator (1.197V low, 2.735V high) configurable using two external resistors (RT1, RT2) to match virtually any NTC resistance vs. temperature curve. Example values for EWTF03-103J31H are provided in the datasheet, enabling JEITA-compliant 0°C–50°C charging windows.

What happens when the die temperature exceeds 105°C?

At 105°C, the MP26121 begins proportional thermal foldback-reducing average charge current to limit further temperature rise. Foldback continues until 135°C, where hard thermal shutdown occurs. Recovery requires die cooling below 120°C and a power cycle or SHDN toggle to re-enable charging.

Is an external blocking diode required between VIN and BATT?

No-MP26121DQ-LF-Z integrates reverse-current protection, limiting battery-to-VIN leakage to <1μA when disabled or unpowered. This eliminates the 0.3–0.7V forward drop and board space of a discrete Schottky diode, improving efficiency and simplifying layout.

How is the charge timer configured and what safety functions does it provide?

The timer is set via a 2.2μF capacitor on the TMR pin, establishing a 5.4Hz internal clock. It enforces two safety limits: 32768 cycles (~1hr) for trickle-charge timeout and 262144 cycles (~8hrs) for total-charge timeout-preventing excessive charging of defective or deeply depleted batteries.

What is the purpose of the ACOK pin and how is it used in system design?

ACOK is an open-drain output indicating valid input power: pulled high when 3V < VIN < 7V, otherwise floating. It serves as a hardware "power good" signal to the host processor, enabling system-level decisions like display wake-up, USB enumeration, or battery gauge initialization upon adapter insertion.