MURS220T3G vs MBRS3100T3G — Ultrafast vs Schottky Rectifier Selection Guide | ICMASS

MURS220T3G vs MBRS3100T3G: Side-by-Side Comparison

* Conduction loss at rated current: MURS220 is lower in absolute watts (1.9W vs 2.37W) because its rated current is 2A, not 3A. At 2A load, MBRS3100 V_F drops further (typ ~0.7V), giving ~1.4W — lower than MURS220. The Schottky wins on efficiency at any given current below its rating.

Key Differences

1. Reverse Recovery: 35ns vs Zero

The MURS220T3G is a PN ultrafast diode. At turn-off, stored charge takes 35ns to clear. During those 35ns, the diode conducts in reverse — current meant for the load flows backward. At 200kHz that's 0.7% of the period. It's not huge, but it's measurable on a thermal camera.

The MBRS3100T3G is a Schottky. No PN junction, no stored charge. It doesn't inject minority carriers — nothing to sweep out. Switches off instantly. At high frequencies, this eliminates a loss mechanism entirely — no snubber needed, cleaner waveforms. But how? The metal-semiconductor junction doesn't inject minority carriers. Nothing to sweep out.

2. Forward Voltage: 0.95V vs 0.79V

At rated current, the Schottky drops 0.16V less — 17% lower conduction loss. At 2A load: MURS220 ~1.9W, MBRS3100 ~1.4W. The Schottky saves about half a watt. At partial load the gap widens further as the Schottky's V_F drops more with decreasing current.

At elevated temperature the gap widens. MURS220 V_F: 0.77V at 150°C. MBRS3100 V_F: 0.62V at 125°C. The Schottky's advantage holds at 0.15–0.18V. In a thermally stressed design, that half-watt is the margin between reliable and overheating.

3. Reverse Leakage: The Schottky's Weakness

At 125°C and full reverse voltage, the MBRS3100T3G leaks 5mA. The MURS220T3G leaks 50µA at 150°C. Factor of 100. In a bridge at 85°C ambient, four Schottkys leak 2–5mA combined — over 0.5W when reverse-biased.

If your rectifier is reverse-biased most of each cycle, the Schottky's leakage may erase its V_F advantage. You're in a bridge at temperature? Don't assume Schottky wins — run the numbers.

So why does this matter? The leakage-vs-V_F crossover depends on duty cycle and temperature. Forward converter (70% forward-biased): Schottky wins. Bridge rectifier (50% reverse-biased) at 85°C: ultrafast may pull ahead. Run the thermal numbers for your operating point.

4. Surge Capability: 40A vs 130A

The MBRS3100T3G handles 3× the surge current (130A vs 40A). For motor drives, capacitor banks, hot-plug events — skip the NTC limiter. The Schottky's metal contact acts as a heat spreader during short pulses, absorbing energy that would fuse a PN junction.

When to Choose MURS220T3G / When to Choose MBRS3100T3G

Choose MURS220T3G (Ultrafast) when: Rail is 65–120V DC. Rectifier spends significant time reverse-biased at high temp. Leakage current matters more than V_F. Replacing an existing ultrafast without re-validating for leakage. Layout fits SMB but not SMC.

Choose MBRS3100T3G (Schottky) when: Rail ≤48V. Switching above 100kHz where recovery loss is real. Forward-biased most of the cycle (buck catch, flyback secondary, OR-ing). High inrush or surge expected. SMC footprint fits and you want the best thermals.

Frequently Asked Questions

Q1: Can I use MBRS3100T3G where MURS220T3G is spec'd?

A: Only if the rail is under ~65V and the thermal analysis accounts for higher leakage. Electrically, the Schottky has lower V_F and zero recovery — both improvements. But the 100V rating vs 200V gives less headroom, and the 5mA leakage at temperature may cause thermal issues in reverse-biased configurations. Check both before swapping.

Q2: Which runs cooler at 2A in a sealed 85°C enclosure?

A: The MBRS3100T3G, assuming it's forward-biased most of the time. At 2A, the Schottky's V_F is ~0.75V (typical at temperature) = 1.5W vs MURS220's 0.77V × 2A = 1.54W. Nearly identical conduction loss. But the Schottky's 11°C/W R_θJL beats the MURS220's 13°C/W. And zero recovery means zero switching loss. Net: Schottky runs a few degrees cooler. If reverse-biased more than ~30% of the cycle, the leakage penalty may reverse this — run the numbers.

Q3: Why would I ever choose ultrafast over Schottky?

A: Voltage rating and leakage current. Schottky diodes top out around 200V for silicon. Ultrafast PN diodes go to 600V+. And at high temperature with reverse bias, Schottky leakage can exceed conduction losses in bridge configurations. If your rectifier sees 100V+ reverse bias at 85°C+ ambient, the ultrafast may actually run cooler overall. The crossover point depends on duty cycle and temperature — there's no universal rule.

Q4: What's the BOM cost difference?

A: Negligible at production volumes. Both are ON Semi catalog parts in high-volume surface-mount packages. Pricing is within a few cents of each other at 1k+ quantities. The decision is technical, not cost-driven. Contact ICMASS for current pricing on your specific quantity.

Q5: Can I parallel two MURS220T3Gs to match the MBRS3100's 3A rating?

A: Yes, but with current-sharing resistors. Ultrafast diodes have a negative V_F temperature coefficient — the hotter diode drops less voltage, draws more current, gets hotter, and hogs the load. Without ballast resistors (typically 10–50mΩ each), one diode takes most of the current. Two MBRS3100s in parallel have the same issue but with positive tempco Schottkys, the V_F drops less dramatically with temperature, making sharing more even. Either way, one properly-rated single diode is simpler than two paralleled ones.

Related Products

• MURS220T3G — 200V/2A Ultrafast SMB — full product page
• MBRS3100T3G — 100V/3A Schottky SMC — full product page
• MBRS3200T3G — 200V/3A Schottky — higher voltage Schottky option
• MURS320T3G — 200V/3A Ultrafast SMC — higher current ultrafast