STMicroelectronics L7980

Overview

L7980 from STMicroelectronics is a 2 A step-down switching regulator with integrated P-channel MOSFET, designed for DC-DC conversion in space-constrained power rails. It operates from 4.5 V to 28 V input, delivers adjustable output down to 0.6 V, features 250 kHz–1 MHz programmable switching frequency, internal soft-start, and supports 100% duty cycle for low-dropout operation - used in LCD TV power supplies, FPGA core voltage regulation, and industrial DC-DC modules.

For engineers reviewing the L7980 datasheet, L7980 pinout, L7980 application, or L7980 equivalent, key selection criteria include input voltage range (4.5–28 V), output current capability (2 A continuous), thermal resistance (40 °C/W in HSOP8), voltage-mode control architecture, and synchronization capability via SYNCH pin for multi-phase designs.

Technical Context

The L7980 implements voltage-mode PWM control with a fixed-frequency sawtooth oscillator whose slope is dynamically adjusted via voltage feed-forward (input-dependent) and frequency feed-forward (FSW-resistor dependent) to maintain constant loop gain across operating conditions. Its error amplifier features 100 dB open-loop gain, 4.5 MHz GBWP, and rail-to-rail output swing (0–3.3 V).

Overcurrent protection uses peak-current sensing with 200 ns blanking time and dual-mode response: hiccup mode under regulated output conditions and pulse-skipping constant-current limiting during soft-start. Thermal shutdown activates at 150 °C with 30 °C hysteresis, and enable logic supports 0.3 V OFF / 1.2 V ON thresholds with <30 µA standby current.

Key Specifications

Pinout & Package

Available in VFQFPN 3 × 3 mm – 8L and HSOP8 packages, both with exposed thermal pads. HSOP8 achieves lower R_thJA (40 °C/W) than VFQFPN (60 °C/W), making it preferred for higher-power applications requiring minimal heatsinking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar step-down regulator applications.

Compared with LM2678-ADJ and TPS54202, the L7980 uniquely combines voltage-mode stability, 100% duty cycle, voltage/frequency feed-forward, and dual-package thermal optimization - making it optimal for industrial and consumer applications demanding robust line regulation and flexible thermal management.

Availability

L7980 is available at Aetrix Electronics and suitable for LCD TV power supplies, FPGA core regulators, and industrial PLC I/O modules requiring stable component supply, long-term lifecycle support, and traceable sourcing from STMicroelectronics.

Supply support for L7980 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, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The L7980 belongs to ST's high-efficiency monolithic buck regulator product line, engineered for compact, thermally resilient DC-DC conversion in space- and reliability-constrained applications such as set-top boxes, networking equipment, and programmable logic systems.

FAQ

What is the maximum achievable output current for L7980 in HSOP8 package at 70 °C ambient?

The L7980 delivers up to 2 A continuous output current in HSOP8 when ambient temperature is ≤70 °C, assuming proper PCB layout with thermal pad soldered to ≥200 mm² copper area and airflow >0.5 m/s. At 70 °C ambient, junction temperature remains below 125 °C due to R_thJA = 40 °C/W and typical power dissipation of ~0.5 W at 12 V_IN/3.3 V_OUT/2 A.

Can L7980 operate with input voltage below 4.5 V?

No - the absolute minimum input voltage is 4.5 V per datasheet specifications. Below this, the internal UVLO circuit disables the device (V_CCON = 4.4 V typ., hysteresis 0.12–0.35 V). Attempting operation at 4.2 V will result in unstable startup or complete disablement; no guaranteed regulation or current delivery occurs below 4.5 V.

How does the SYNCH pin behave when left unconnected?

When the SYNCH pin is left floating, it outputs a square wave synchronized to the internal oscillator with 180° phase shift relative to the power switch turn-on edge. This signal can drive a second L7980's SYNCH pin to establish master-slave interleaving with half-period phase offset - reducing input capacitor RMS current without external clock source.

Is external compensation mandatory for stable operation?

Yes - the COMP pin requires an external Type II or Type III compensation network connected between COMP, FB, and GND. The error amplifier is intentionally uncompensated; omitting compensation causes oscillation or poor transient response. Selection depends on output capacitor ESR: Type II for high-ESR electrolytics, Type III for low-ESR ceramics (see Section 6.4 of datasheet DocID15181 Rev 7).