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How to Decode ON Semi's Rectifier Part Numbers — MURA, MURS, MBRS and What They Actually Mean

2026/8/3 13:47:28

How to Decode ON Semi's Rectifier Part Numbers - MURA, MURS, MBRS and What They Actually Mean

The short answer: MURA = ultrafast, SMA. MURS = ultrafast, SMC/SMB. MBRS = Schottky, SMB. The number after the letters encodes voltage and current. Decode it in two seconds and you know the technology, package, and ratings. Misread it and you order a 40V Schottky for a 200V rail.

Three identical-looking SMB packages. One marked MURA110, one MURS360, one MBRS3200. Different prices, different thermal behaviour, completely different failure modes. If you've ever stared at a BOM and wondered whether BT3G and T3G are the same part — this is for you.

ON Semi Surface-Mount Rectifier Portfolio - Technology × Voltage × Package

MURA (Ultrafast)SMA, 50–600V, 1–2A

MURS (Ultrafast)SMB/SMC, 200–600V, 1–4A

MBRS (Schottky)SMB, 20–200V, 1–4A

Part Number Decoder: MURA110T3G, Letter by Letter

ON Semi rectifier part numbers follow a consistent scheme. Once you learn it, you can read any of them at a glance.

Position	Example	Meaning
Prefix (1–4 letters)	MURA, MURS, MBRS	Technology + series family
Voltage code	110 = 100V, 360 = 600V	MURA/MURS: last 2 digits × 10. MBRS: last 3 digits
Package code	T3G, BT3G, T3	T3G = SMC Pb-free. BT3G = SMB Pb-free. G = RoHS
Optional prefix	SURA, SURS, NRVB	S = AEC-Q101 automotive. NRVB = automotive + PPAP

MURA110T3G breaks down as: MURA (ultrafast, SMA) + 110 (100V) + T3G (Pb-free, RoHS). For MURA parts the "G" just means green/RoHS — the package stays SMA. For MURS parts, BT3G = SMB and T3G = SMC. The suffix meaning depends on the family. Always check the datasheet.

Is your head spinning yet? Here's the trick. Ignore what the family letter "should" mean for package. Read the suffix. BT3G always means SMB. T3G always means SMC. No suffix or just "T3" means older non-RoHS. This one rule prevents half the wrong-package orders we see.

The Three Families, Side by Side

What actually differentiates MURA, MURS, and MBRS? Not just the package.

	MURA	MURS	MBRS
Technology	Ultrafast (P-N junction)	Ultrafast (P-N junction)	Schottky (metal-semiconductor)
Speed	30–90ns t_rr	25–75ns t_rr	~0ns (majority carrier)
V_F range	875mV–1.5V	875mV–1.25V	500mV–950mV
Leakage @ hot	~50–150µA	~150µA	~50–100mA ⚠️
Voltage range	50–600V	200–600V	20–200V
Primary package	SMA	SMC (SMB for BT3G)	SMB
Use when	Low power, need speed	High voltage, high current	Low V_F, moderate temp

But here's what datasheets don't tell you. In Shenzhen distribution, MURA parts overwhelmingly go into auxiliary supplies and gate-drive bias rails. MURS dominates AC-DC output rectification and PFC. MBRS goes into 12–48V DC-DC outputs where every millivolt of V_F counts double.

The Suffix Trap: BT3G vs T3G vs T3

The most common ordering mistake? Confusing package suffixes.

T3G - SMC (DO-214AB), Pb-free, active. The larger package with lower R_θJA. Use this for sustained 3A in warm enclosures.
BT3G - SMB (DO-214AA), Pb-free, active. Smaller footprint, same silicon. Better for space-constrained layouts where you can afford the copper for heat spreading.
T3 - Older, non-RoHS. Obsolete for new designs. If your BOM still says T3, update to T3G or BT3G.

Same silicon in SMB vs SMC. Same specs. Different R_θJA. At 3A, that thermal gap is the difference between running cool at 65°C and throttling at 85°C. Sealed enclosure, high ambient? Pay the extra board space for SMC.

Typical R_θJA by Package (min pad, FR-4) - lower is cooler

SMA (MURA)~216°C/W

SMB (BT3G)~85°C/W

SMC (T3G)~55°C/W

Automotive? Add an S

Need AEC-Q101 paperwork? Prefix the part number with S:

MURA110T3G → SURA8110T3G (note: voltage code changes format slightly for automotive variants)
MURS360BT3G → SURS8360BT3G
MBRS3200T3G → NRVBS3200NT3G (Schottky automotive uses NRVB prefix)

Same silicon, same package, same specs. The only difference: PPAP documentation. And most engineers don't realize the standard datasheets already show AEC-Q101 test results. The S-prefix parts don't test differently — they just come with the formal paperwork.

So Which One Do You Actually Need?

Three questions, thirty seconds:

What's your rail voltage? >150V → MURS. ≤150V → keep going.
How hot does it get? >85°C and blocking >100V → MURS or MURA (ultrafast). Cooler → keep going.
How fast are you switching? ≥200kHz and low voltage → MBRS (Schottky, zero recovery). Slower → MURA or MURS.

And one last question: do you actually need 600V? On a 48V rail, MURS360 costs more and switches slower than MURS320 (200V, 25ns). Spec'ing the highest voltage "just to be safe" costs you efficiency. Buy the rating your rail needs plus margin. Not the biggest number on the datasheet.