Part of the Day · TPS54331 — SOIC-8 3A 28V step-down DC-DC converter (marking 54331)

Part of the Day · 2026-11-09

A step-down (buck) switching regulator that converts a 3.5~28V input into a lower voltage (down to 0.8V). The switching MOSFET is built into the chip, so it delivers up to 3A continuous and runs at 570kHz. Add an inductor, a Schottky diode, capacitors and two resistors outside, and it is widely used to turn 12V or 24V into 5V or 3.3V. The marking on the TI SOIC-8 (D) chip is 54331.

Actual size

↓ Actual size, left edge aligned to 0 on the ruler

One ruler tick = 1mm. On PC this is actual size on a 24-inch FHD monitor at 100% zoom; on iPhone it adjusts automatically. For other screens, use “Calibrate ruler” below.

Enlarged (SOIC-8 · top view · approx. 15×)

Pins 1 BOOT (bootstrap — 0.1µF to PH) · 2 VIN (input 3.5~28V) · 3 EN (on/off, enabled when left open) · 4 SS (slow-start capacitor) · 5 VSENSE (output voltage feedback) · 6 COMP (compensation network) · 7 GND (ground) · 8 PH (switch output — to inductor and diode)

Package SOIC-8 · Marking 54331

Key specifications

Values are from the Texas Instruments datasheet.

Marking and pins

Marking code 54331 · Pins 1 BOOT (bootstrap — 0.1µF to PH) · 2 VIN (input 3.5~28V) · 3 EN (on/off, enabled when left open) · 4 SS (slow-start capacitor) · 5 VSENSE (output voltage feedback) · 6 COMP (compensation network) · 7 GND (ground) · 8 PH (switch output — to inductor and diode)

Typical uses

• Board power that steps 12V or 24V down to 5V or 3.3V (5V, 12V and 24V distributed power systems)
• Power for set-top boxes, LCD monitors, peripherals and battery chargers
• Industrial and car-audio power supplies
• Battery-powered equipment that benefits from the 1µA shutdown current

Companion & similar parts

• TPS54331DR — Same chip, SOIC-8 on reel (2,500 pcs) — the TPS54331D tube holds 75
• TPS54331DDA — Same chip in SO PowerPAD-8 — heat escapes through the bottom pad (RθJA 48.7℃/W); connect the pad to GND
• TPS62933 — The part the datasheet recommends when you need 30V input, higher frequency and lower quiescent current
• B340A — External Schottky diode chosen in the datasheet design example (Diodes Inc.)

Because it is non-synchronous, an external Schottky (catch) diode between PH and GND is required — its reverse voltage must be higher than the maximum input voltage + 0.5V. Place a 0.1µF ceramic capacitor between BOOT and PH. EN enables the device when left open and disables it when pulled below 1.25V; the datasheet recommends setting the input undervoltage lockout with two resistors. At light loads, the pulse-skipping Eco-mode raises efficiency.