STMicroelectronics L7905CP

Overview

L7905CP from STMicroelectronics is a three-terminal fixed negative voltage regulator delivering -5 V output at up to 1.5 A, featuring thermal overload protection, short-circuit protection, and SOA-controlled output transition. It operates with input voltages down to -35 V, maintains ±2% output accuracy over load/line/temperature, and is used in split-rail power supplies for op-amp circuits, industrial control modules, and local regulation on PCBs requiring stable negative bias.

For engineers reviewing the L7905CP datasheet, L7905CP pinout, L7905CP application, or L7905CP equivalent, key selection criteria include dropout voltage (1.4 V @ 1 A), quiescent current (3 mA), supply voltage rejection (54–60 dB), output noise (100 µV RMS), and TO-220FP package thermal resistance (R_thJC = 5 °C/W).

Technical Context

The L7905CP implements a monolithic PNP pass transistor architecture with internal current limiting, thermal shutdown, and safe operating area protection. Its feedback loop stabilizes output against line variations (±50 mV line regulation) and load changes (±50 mV load regulation) while maintaining low temperature drift (-0.4 mV/°C).

Designed for fixed-output operation, it supports external circuitry for adjustable output or high-current configurations (e.g., with external pass transistor). Input-to-output differential must remain ≥1.4 V under full load to sustain regulation, and stability requires ≥2.2 µF tantalum input and ≥1 µF output capacitance.

Key Specifications

Pinout & Package

L7905CP uses the TO-220FP (Full-Pak) package: 3-pin, vertical mounting, insulated tab, plastic body with metal heat sink pad. Pin 1 = Ground, Pin 2 = Input, Pin 3 = Output - verified per Figure 2 (top view) in ST Doc ID 2149 Rev 21.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar negative fixed-voltage regulation applications.

Compared with LM7905CT and MC7905BT, the L7905CP delivers superior thermal performance in TO-220FP packaging, tighter output tolerance, lower noise, and integrated SOA protection - making it optimal for new designs demanding reliability under dynamic load conditions.

Availability

L7905CP is available at Aetrix Electronics and suitable for industrial automation, test equipment, and embedded control systems requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L7905CP 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 L79xxC series was developed specifically for cost-sensitive, high-reliability linear power regulation in industrial and embedded systems - emphasizing thermal robustness, ease of use, and compatibility with the complementary L78xx positive regulator family.

FAQ

What is the minimum input voltage required for L7905CP to regulate at full 1.5 A?

The L7905CP requires a minimum input-to-output differential of 1.4 V at 1 A and 25°C (per Table 4, V_d). To sustain 1.5 A continuously, input must be ≤ -6.4 V (i.e., -5 V – 1.4 V), with derating for temperature rise. At 125°C junction temperature, dropout increases to ~2.0 V, requiring ≤ -7.0 V input.

Can L7905CP be used in parallel for higher current?

No - L7905CP is not designed for parallel operation. Its output voltage tolerance (±2%) and thermal tracking differences cause current imbalance, risking thermal runaway. For >1.5 A, ST recommends using an external pass transistor (Figure 7 in datasheet) with current-sharing resistors and proper thermal coupling.

Is a heat sink mandatory for L7905CP at 1 A load?

Yes - at 1 A with 10 V input-to-output differential (e.g., -15 V in, -5 V out), power dissipation is 10 W. With R_thJC = 5 °C/W and R_thCA ≈ 20 °C/W (typical heatsink), junction temperature exceeds 150°C. A heatsink with ≤10 °C/W total thermal resistance is required for continuous 1 A operation at 25°C ambient.

Does L7905CP require input and output capacitors, and what types are specified?

Yes - per Figure 4 and Section 6, a minimum 2.2 µF solid tantalum capacitor is required at the input if the regulator is >10 cm from the main filter; a minimum 1 µF solid tantalum capacitor is required at the output for stability. Aluminum electrolytic capacitors may be used only if ≥10× larger (e.g., 10 µF input, 10 µF output), due to higher ESR.