STMicroelectronics L7809CP

Overview

L7809CP from STMicroelectronics is a three-terminal positive linear voltage regulator delivering a fixed 9 V output with up to 1.5 A continuous current, thermal overload and short-circuit protection, and ±2 % output voltage tolerance (A-grade). It operates across an input range of 11.5–26 V and supports industrial temperature range (−40 °C to +125 °C), commonly used in local on-card power regulation for microcontroller-based control modules.

For engineers reviewing the L7809CP datasheet, L7809CP pinout, L7809CP application, or L7809CP equivalent, key selection criteria include dropout voltage (2 V at 1 A), load regulation (≤180 mV over 5 mA–1.5 A), supply voltage rejection (55 dB at 120 Hz), quiescent current (8 mA), and thermal resistance (R_thJA = 60 °C/W in TO-220FP package).

Technical Context

The L7809CP implements a monolithic silicon voltage regulator architecture with internal current limiting, safe operating area (SOA) protection, and thermal shutdown circuitry. Its feedback loop maintains stable 9 V output under varying load and line conditions without external compensation.

Designed for fixed-output operation, it requires only two external capacitors (0.33 µF input, 0.1 µF output) for stability per standard test circuits. Minimum load current is 5 mA; dropout behavior is defined at 2 V across the input–output differential at full 1 A load and 25 °C junction temperature.

Key Specifications

Pinout & Package

Supplied in TO-220FP package - a 3-pin, through-hole, thermally enhanced variant of TO-220 with insulated tab and shorter leads for compact PCB mounting. Requires mechanical mounting to heatsink via screw or clip for sustained >500 mA operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fixed-output linear regulator applications.

Compared with LM7809CT and MC7809BD2TR4G, the L7809CP offers superior temperature range (−40 °C to +125 °C), tighter output tolerance (±2 %), and optimized thermal resistance for forced-air or moderate heatsink environments - making it preferred for ruggedized industrial control designs.

Availability

L7809CP is available at Aetrix Electronics and suitable for industrial motor drives, embedded control modules, sensor interface circuits, and legacy equipment retrofits requiring stable component supply and long-term lifecycle support.

Supply support for L7809CP 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The L78 series belongs to ST's legacy positive voltage regulator product line, engineered for robustness and ease-of-use in local regulation tasks across harsh environments - emphasizing fault resilience, wide temperature operation, and minimal external component count.

FAQ

What is the minimum input voltage required for stable 9 V output from the L7809CP?

The L7809CP requires a minimum input voltage of 11.5 V to maintain regulation at full load and temperature extremes. This accounts for its 2 V dropout voltage plus margin for line and load transients. Below 11.5 V, output drops linearly with input; operation below 11.5 V is not guaranteed per datasheet specifications.

Can the L7809CP be used without a heatsink?

Yes, at low output currents (<300 mA) and ambient temperatures <50 °C, the TO-220FP package can operate without a heatsink due to its 60 °C/W junction-to-ambient thermal resistance. At 1 A and 25 °C ambient, junction temperature rises ~60 °C above ambient - reaching 85 °C, well within the 125 °C limit. For sustained 1 A operation above 40 °C ambient, a heatsink is strongly recommended.

Does the L7809CP require input and output capacitors? If so, what values and types?

Yes: a 0.33 µF ceramic capacitor is required between input and ground, placed within 1 cm of the input pin; a 0.1 µF ceramic capacitor is required between output and ground, placed adjacent to the output pin. These prevent oscillation and improve transient response. Electrolytic or tantalum capacitors may be added in parallel for bulk energy storage, but ceramic is mandatory for high-frequency stability.

How does the L7809CP behave during short-circuit conditions?

Under short-circuit, the L7809CP limits output current to approximately 0.4 A (I_sc) while maintaining thermal shutdown protection. It does not latch off - instead, it cycles into and out of thermal shutdown if the fault persists, dissipating ~3.6 W (9 V × 0.4 A) at the die until external intervention or fault removal occurs. Peak short-circuit current reaches 2.2 A briefly before limiting engages.