STMicroelectronics LDK120M25R

Overview

LDK120M25R from STMicroelectronics is a 200 mA, 2.5 V fixed-output low-dropout linear regulator with 100 mV typical dropout at 100 mA, 100 µA max quiescent current, ±2.0% output voltage tolerance at 25 °C, and operation from 1.9 V to 5.5 V input. It delivers ultra-low noise (51 µVRMS, 10 Hz–100 kHz with 10 nF bypass) and supports ceramic output capacitors as small as 1 µF. It powers core logic rails in space-constrained, battery-operated portable electronics.

For engineers reviewing the LDK120M25R datasheet, LDK120M25R pinout, LDK120M25R application, or LDK120M25R equivalent, key selection criteria include dropout performance under 200 mA load, shutdown current <1 µA, thermal shutdown at 160 °C, compatibility with 1 µF ceramic COUT, and SOT23-5L package footprint constraints.

Technical Context

The LDK120M25R employs a PMOS pass transistor architecture enabling ultra-low dropout and near-zero gate-drive current, eliminating external compensation requirements. Its internal bandgap reference and error amplifier maintain tight regulation across –40 °C to 125 °C junction temperature while supporting fast load transient response (≤10 µs settling for 1–200 mA step).

Logic-controlled enable (EN) pin provides precise system-level power sequencing with 0.4 V logic-low threshold and 1.2 V logic-high threshold. The device integrates short-circuit constant-current limiting (400 mA typ.) and thermal foldback protection with 20 °C hysteresis, ensuring robust operation during fault conditions without external circuitry.

Key Specifications

Pinout & Package

LDK120M25R is packaged in SOT23-5L (2.95 mm × 1.60 mm × 1.45 mm), a surface-mount 5-pin package with exposed thermal pad (not electrically connected). Pin 1 is IN, Pin 2 is GND, Pin 3 is EN, Pin 4 is BYP (bypass capacitor connection for noise reduction), and Pin 5 is OUT. Pin 4 must be left floating if bypass capacitor is unused.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-noise, low-IQ LDO applications.

Compared with XC6210B252MR-G and RT9013-25GB, LDK120M25R uniquely combines sub-100 mV dropout, 51 µVRMS noise with bypass, and full thermal/short-circuit protection in SOT23-5L - making it optimal for high-reliability, noise-critical portable designs.

Availability

LDK120M25R is available at Aetrix Electronics and suitable for mobile phones, digital still cameras, Bluetooth LE audio earbuds, and industrial handheld terminals requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for LDK120M25R 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing silicon solutions for automotive, industrial, and consumer markets since 1987.

The LDK120 series was developed specifically for ultra-low-power, low-noise power management in portable battery-operated equipment - emphasizing minimal quiescent current, ceramic capacitor compatibility, and robust protection features in miniature packages.

FAQ

What is the minimum input voltage required for LDK120M25R to maintain 2.5 V output at 200 mA load?

The minimum input voltage is determined by dropout voltage. At 200 mA load and 125 °C junction temperature, maximum dropout is 300 mV per datasheet Table 4. Therefore, VIN(min) = 2.5 V + 0.3 V = 2.8 V. Operation below this risks output undervoltage and regulation loss.

Can LDK120M25R be used with a 0.47 µF ceramic output capacitor instead of the recommended 1 µF?

No. Stability testing in Figure 25 shows the minimum stable COUT is 1 µF for the fixed version. Using 0.47 µF risks oscillation and poor transient response, especially under 100–200 mA load steps. The 1 µF requirement is absolute for guaranteed stability.

Is the BYP pin on LDK120M25R required to be connected for basic operation?

No. The BYP pin is optional: it accepts a 10 nF ceramic capacitor to reduce output noise from 148 µVRMS to 51 µVRMS. If noise performance is not critical, the pin must be left floating - no routing or connection to GND or any other net is permitted.

Does LDK120M25R support reverse current blocking when input voltage drops below output voltage?

Yes. The PMOS pass transistor architecture inherently blocks reverse current flow from OUT to IN. This prevents backfeeding into upstream power sources during brown-out or hot-swap events, eliminating the need for an external blocking diode in most applications.