STMicroelectronics L4987CPT33TR

Overview

L4987CPT33TR from STMicroelectronics is a 3.3 V fixed-output, very low-dropout linear voltage regulator in PPAK package, featuring 0.25 V typical dropout at 200 mA, 90 µA quiescent current in OFF mode, and an open-collector dropout control flag. It delivers up to 200 mA output current with ±2% output voltage accuracy at 25°C and supports automotive-grade input dump protection up to 40 V.

For engineers reviewing the L4987CPT33TR datasheet, L4987CPT33TR pinout, L4987CPT33TR application, or L4987CPT33TR equivalent, key selection criteria include dropout behavior under low-V_IN, flag logic timing for battery status monitoring, thermal shutdown response, and stability with 2.2 µF ceramic output capacitance.

Technical Context

The L4987CPT33TR employs a PNP pass transistor architecture enabling ultra-low dropout (0.25 V typ. at 200 mA) and high PSRR (70 dB typ. at 120 Hz). Its internal current and thermal limiting functions operate independently of external components.

The open-collector control flag (pin 3) asserts low when V_IN ≤ V_OUT + V_DROP, during current limit, or under thermal saturation - with no hysteresis and TTL-compatible shutdown input (pin 2) requiring ≤10 µA control current.

Key Specifications

Pinout & Package

PPAK (Power Package) thermally enhanced surface-mount package with exposed thermal pad; 3-pin configuration optimized for high-power density and low R_thJA (100 °C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-dropout regulator applications.

Compared with LDL1133PU33R and TLD1133EP, the L4987CPT33TR uniquely combines automotive-grade transient robustness, open-collector flag signaling, and ultra-low dropout - making it optimal for cost-sensitive car audio and industrial field equipment where fault visibility and battery utilization are design priorities.

Availability

L4987CPT33TR is available at Aetrix Electronics and suitable for automotive infotainment systems, portable medical monitors, and industrial PLC I/O modules requiring stable component supply across extended temperature and transient-voltage conditions.

Supply support for L4987CPT33TR 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 L4987 series belongs to ST's automotive-qualified linear regulator product line, engineered specifically for low-noise, low-power, and high-transient-immunity applications in car audio, body electronics, and battery-powered industrial controls.

FAQ

What is the minimum input voltage required for regulation at 200 mA load?

The L4987CPT33TR maintains 3.3 V output regulation down to an input voltage of 3.55 V at 200 mA load, based on its 0.25 V typical dropout voltage. At worst-case 0.5 V dropout (per datasheet max), minimum V_IN is 3.8 V. Operation below this threshold activates the FLAG output and may cause output collapse.

How should the FLAG pin be interfaced with a 3.3 V microcontroller GPIO?

Connect a 10 kΩ pull-up resistor from FLAG to the 3.3 V microcontroller supply. This ensures V_HIGH ≥ 2.2 V (exceeding CMOS logic high threshold) while limiting sink current to ≤0.33 mA when FLAG is active low. Do not pull up to a higher voltage rail - that risks invalid HIGH state during brownout.

Can the L4987CPT33TR replace the L4987CPT50TR in a 5 V design?

No - the L4987CPT33TR is factory-trimmed for 3.3 V output and cannot be adjusted. Its internal feedback network fixes V_OUT at 3.3 V ±2%. Substituting it for a 5 V regulator would underpower downstream 5 V logic, causing functional failure. Use L4987CPT50TR or redesign the power tree.

Is thermal derating required when operating at 125°C ambient in a sealed enclosure?

Yes - with R_thJA = 100 °C/W, 125°C ambient limits continuous power dissipation to 0.25 W (ΔT = 25°C). At 200 mA load and 12 V input, power dissipation is (12 − 3.3) × 0.2 = 1.74 W - exceeding safe limits. A minimum 200 mm² copper pour under the thermal pad and forced airflow are mandatory to sustain full load at high ambient.