STMicroelectronics LDK120M31R

Overview

LDK120M31R from STMicroelectronics is a 3.1 V fixed-output, 200 mA low-dropout linear regulator with 100 mV typical dropout at 100 mA, 100 µA max quiescent current, and 51 µV_RMS output noise (10 Hz–100 kHz) when using a 10 nF bypass capacitor. It operates from 1.9 V to 5.5 V input, supports logic-controlled shutdown (<1 µA OFF mode), and is stabilized with a 1 µF ceramic output capacitor. It targets power-sensitive subsystems in portable battery-powered devices.

For engineers reviewing the LDK120M31R datasheet, LDK120M31R pinout, LDK120M31R application, or LDK120M31R equivalent, key selection criteria include dropout voltage under load, noise performance with/without bypass, EN pin threshold stability over temperature, thermal shutdown behavior, and compatibility with ultra-small 1.2 × 1.3 mm DFN6 packaging.

Technical Context

The LDK120M31R implements a PMOS pass transistor architecture enabling ultra-low dropout and minimal quiescent current across its full operating temperature range (−40 °C to +125 °C). Its internal bandgap reference and error amplifier deliver ±2.0% output voltage accuracy at 25 °C and ±3.0% over full temperature range.

It integrates logic-level enable control (V_EN(H) = 1.2 V min, V_EN(L) = 0.4 V max), short-circuit constant-current limiting (400 mA typ.), and thermal shutdown with 20 °C hysteresis. The device is stable with 1 µF ceramic C_OUT, and optional 10 nF bypass on the BYP pin reduces output noise by >65%.

Key Specifications

Pinout & Package

LDK120M31R is available in SOT23-5L (2.95 × 1.60 mm), SOT323-5L (2.0 × 2.1 mm), and DFN6 (1.2 × 1.3 mm) packages. The SOT23-5L variant uses the standard 5-pin configuration with exposed pad for thermal enhancement.

Key Features

Applications

Equivalent & Alternatives

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

Compared with XC6210B312MR-G and ADP160ACBZ-3.1-R7, the LDK120M31R uniquely balances 200 mA drive, 100 mV dropout, and 51 µV_RMS noise - making it optimal for battery-powered systems needing both high current headroom and analog-grade cleanliness.

Availability

LDK120M31R is available at Aetrix Electronics and suitable for mobile phone power rails, digital camera sensor biasing, portable medical diagnostics, and industrial handheld scanners requiring stable component supply across long production lifecycles.

Supply support for LDK120M31R 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-noise, low-quiescent-current regulation in space- and power-constrained portable electronics, emphasizing ceramic-capacitor compatibility and wide-input flexibility.

FAQ

What is the minimum input voltage required to maintain regulated 3.1 V output at 200 mA?

The LDK120M31R requires VIN ≥ VOUT + VDROP. At 200 mA and 40–125 °C, VDROP is 150–300 mV per datasheet Table 4. Thus, minimum VIN is 3.25 V (3.1 V + 150 mV) to guarantee regulation across temperature and process variation. Below this, output drops linearly with input.

Can the BYP pin be left unconnected without affecting stability or regulation?

Yes. The BYP pin is optional for noise reduction only. When unused, it must be left floating with no PCB trace - not tied to GND or OUT. Stability and regulation depend solely on the 1 µF ceramic COUT; BYP disconnection has zero impact on basic LDO function or transient response.

Is the LDK120M31R compatible with 0.5 µF output capacitors?

No. The datasheet specifies 1 µF minimum COUT for stability across all operating conditions (Section 6, Figure 25). Using 0.5 µF risks oscillation or excessive overshoot during load transients. ST validates stability only with ≥1 µF X5R/X7R ceramics having ESR ≤100 mΩ at 100 kHz.

Does the thermal shutdown feature latch off or auto-recover?

The thermal shutdown is non-latching with 20 °C hysteresis. When junction temperature exceeds 160 °C, the LDO shuts down; it automatically resumes regulation once T_J falls below 140 °C. No external reset or EN toggle is needed - critical for unattended portable equipment.