STMicroelectronics L7980ATR

Overview

L7980ATR from STMicroelectronics is a 2 A synchronous step-down DC-DC switching regulator with integrated P-channel MOSFET, operating from 4.5 V to 28 V input and delivering adjustable output down to 0.6 V. It features 250 kHz base switching frequency (programmable up to 1 MHz), internal soft-start, enable control, 100% duty-cycle low-dropout operation, and voltage feed-forward for line transient immunity - used in LCD TV power rails, FPGA core supplies, and XDSL line card DC-DC conversion.

For engineers reviewing the L7980ATR datasheet, L7980ATR pinout, L7980ATR application, or L7980ATR equivalent, key selection criteria include its 2.5 A current limit, VFQFPN3x3-8L thermal performance (R_thJA = 60 °C/W), synchronization capability via SYNCH pin, zero-load quiescent current (20–30 µA), and Type II/III compensation flexibility for stable loop design across varying ESR output capacitors.

Technical Context

The L7980ATR implements voltage-mode PWM control with a fixed-frequency sawtooth oscillator whose slope is dynamically adjusted by both input voltage (voltage feed-forward) and switching frequency (frequency feed-forward), maintaining constant PWM gain across operating conditions. Its error amplifier provides 100 dB DC gain and 4.5 MHz GBWP, with COMP pin directly accessible for external Type II or Type III compensation networks.

Synchronization is achieved via the bidirectional SYNCH pin: when floating, it outputs a 180° phase-shifted clock; when driven externally or tied to another L7980, it enables master-slave interleaving with half-period phase offset to reduce input ripple RMS current. Overcurrent protection operates in hiccup mode under regulation and pulse-skipping constant-current mode during soft-start.

Key Specifications

Pinout & Package

Package: VFQFPN 3 × 3 mm, 8-lead, exposed thermal pad (R_thJA = 60 °C/W on demo board).

Key Features

Applications

Equivalent & Alternatives

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

Compared with LM2678SD-ADJ/NOPB and TPS54202DRCT, the L7980ATR uniquely balances 2 A capability, 28 V input, VFQFPN thermal efficiency, and dual feed-forward + synchronization - making it optimal for space-constrained, multi-rail, and EMI-sensitive embedded systems requiring robust line regulation.

Availability

L7980ATR is available at Aetrix Electronics and suitable for LCD TV power subsystems, FPGA core supplies, and XDSL line card DC-DC conversion requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for L7980ATR 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, designing and manufacturing microcontrollers, power ICs, sensors, and analog chips for industrial, automotive, and consumer markets.

The L7980ATR belongs to ST's high-efficiency monolithic buck regulator product line, engineered for compact, thermally efficient DC-DC conversion in space- and reliability-critical embedded systems with wide input voltage ranges.

FAQ

What is the maximum allowable input voltage for continuous operation?

The L7980ATR supports continuous operation up to 28 V input, with absolute maximum rating of 30 V. Exceeding 28 V risks violating operational specifications including UVLO hysteresis, MOSFET SOA, and thermal limits - especially under high ambient temperatures or poor PCB copper area. The device enters undervoltage lockout below 4.4 V and resumes only after hysteresis (≥0.12 V) is satisfied.

How does the SYNCH pin behave when left unconnected?

When the SYNCH pin is left floating, it outputs a square wave at the device's internal switching frequency with a 180° phase shift relative to the power switch turn-on edge. This built-in inverted clock enables natural interleaving when two L7980ATRs are connected together - the higher-frequency unit becomes master, and the other synchronizes with half-period delay, reducing input capacitor RMS current by up to 30%.

Can the L7980ATR regulate output voltages below 0.6 V?

No - the internal 0.6 V reference is fixed and non-adjustable; the FB pin compares against this threshold, so the lowest achievable regulated output is 0.6 V (with direct connection). To achieve lower voltages, an external resistive divider with negative reference or a dedicated low-V_REF controller is required. Attempting sub-0.6 V regulation results in uncontrolled high-duty-cycle operation and potential instability.

What is the purpose of the voltage and frequency feed-forward functions?

Voltage feed-forward adjusts the sawtooth ramp slope proportionally to input voltage, while frequency feed-forward modifies it based on switching frequency - both preserve constant PWM gain across line and frequency variations. This maintains consistent loop dynamics and improves transient response to input voltage steps (e.g., battery sag) without requiring recompensation when adjusting FSW resistor value.