551 - Surface Mount Schottky Diode 20V 500mA SOD-323
Teilenummer: 551 ✓ Aktiv| Menge | Stückpreis | Gesamt |
|---|---|---|
| 1 | $0.18 | $0,18 |
| 10 | $0.14 | $1,40 |
| 100 | $0.09 | $9,00 |
| 500 | $0.07 | $35,00 |
| 1.000 | $0.05 | $50,00 |
551 Übersicht
A Schottky barrier diode is a semiconductor device that uses a metal-semiconductor junction instead of a PN junction to achieve switching behavior. This construction yields a lower forward voltage (typically 0.3-0.5 V compared to 0.7 V for silicon PN diodes) and essentially zero reverse recovery time, which makes Schottky diodes ideal for high-frequency switch-mode power supplies, OR-ing circuits, and low-voltage rectification. As a member of the Schottky diode family, the 551 sits within the broader taxonomy of diodes -> discrete semiconductors -> semiconductor devices.
Key features of the 551 include a 20 V reverse voltage rating (with a typical working peak reverse voltage of 30 V per the manufacturer's 551-marking datasheet), 500 mA continuous forward current, low forward voltage drop (VF approximately 0.35 V at low current), and ultra-fast switching with negligible reverse recovery charge. The SOD-323 package provides a low-profile surface-mount footprint suitable for handheld and portable equipment, while operating across a typical -55C to +125C junction temperature range.
Technically, the device uses a planar Schottky barrier construction that minimizes junction capacitance and provides stable forward characteristics. The low capacitance makes the 551 well-suited for use in switching regulators up to several hundred kHz, and the part is commonly placed across an inductive load as a freewheeling diode to protect switching transistors from back-EMF.
Typical applications include reverse-polarity protection in USB ports and lithium-ion battery packs, freewheeling diodes in buck/boost converters, signal clamping in ESD-sensitive interfaces, low-voltage rectification in handheld electronics, and OR-ing diodes in redundant power architectures. Designers select the 551 when a compact, low-VF, fast-switching rectifier is needed where a standard recovery rectifier would waste too much power.
When designing with the 551, note that the SOD-323 package has limited thermal mass; ensure that the average forward current does not exceed 500 mA and that the junction temperature stays within rated limits at worst-case ambient. Place the part close to the source of transient energy for effective freewheeling, and respect the 20 V reverse voltage ceiling to avoid catastrophic reverse breakdown.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found on the manufacturer's brief datasheet, enabling faster BOM decisions for engineers who need a small-footprint Schottky rectifier.
Drop-in-Alternativen für 551 – gleiches Gehäuse, Pin-kompatibel. Bauteile mit anderem Gehäuse, die eine PCB-Überarbeitung erfordern, sind ausgeschlossen.
Schnellvergleichstool – Wählen Sie Alternativbauteile für den Direktvergleich:
RB551VM-30TE-17
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
MBR0520
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
B0515LS
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
SS12-E3
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
RB520S-30
✅ Drop-In📋 Referenzalternative (nicht im Katalog)
551 Grenzwerte & elektrische Eigenschaften
| Manufacturer | Pan Jit International Inc. |
| Part Number | RB551V-30-AU_R1_000A1 |
| Device Type | Surface Mount Schottky Barrier Diode |
| Marking Code | 551 |
| Gehäuse | SOD-323 |
| Reverse Voltage (VR) | 20 V |
| Working Peak Reverse Voltage (VRWM) | 30 V |
| Average Rectified Forward Current (IO) | 500 mA |
| Betriebs-Sperrschichttemperatur | -55C to +125C |
| Storage Temperature | -55C to +150C |
| Montageart | Surface Mount |
| RoHS-Status | Compliant |
| Lead-Free | Yes |
551 Pin-Konfiguration
| Pin 1 | Anode — Positive terminal (forward-biased current enters) |
| Pin 2 | Cathode — Negative terminal marked by bar on package top (forward-biased current exits) |
Typische Anwendungen
551 ist geeignet für 6 Anwendungs: Reverse-Polarity Protection in USB and Battery Packs, Freewheeling Diode in Buck/Boost Converters, Low-Voltage Rectification in Portable Electronics, OR-ing Diodes in Redundant Power Architectures, Signal Clamping in ESD-Sensitive Interfaces, Switch-Mode Power Supply Output Rectification.
Reverse-Polarity Protection in USB and Battery Packs
The 551's 20 V reverse voltage and 500 mA forward current ratings make it ideal for reverse-polarity protection in USB ports and single-cell lithium-ion battery packs. Placed in series between the connector and the load, the 551 blocks reverse current flow that could damage downstream components when a battery is inserted incorrectly. According to typical application circuits, the 551's low forward voltage (approximately 0.35 V at 100 mA) introduces only a small drop in the forward path, preserving system efficiency. Compared to a P-channel MOSFET reverse-protection circuit, the 551 Schottky approach is simpler and cheaper for currents up to 500 mA. The SOD-323 footprint is small enough to fit inside a USB Type-A connector shell or a Li-ion battery protection module, making it the preferred choice for compact handheld designs.
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Freewheeling Diode in Buck/Boost Converters
The 551 functions as a freewheeling (catch) diode in buck and boost converter switching regulator topologies, conducting inductor current when the switching MOSFET turns off. According to switching converter design guidelines, the 551's near-zero reverse recovery time and low forward voltage drop minimize switching losses and improve overall converter efficiency at switching frequencies up to several hundred kHz. In a typical 5 V to 3.3 V buck converter using LM2591HVS-ADJ or similar controllers, the 551 across the inductor carries the full load current during the MOSFET off-time. The 500 mA current rating supports medium-power loads including point-of-load regulators for microcontrollers and low-power FPGAs. The SOD-323 package is preferred over larger SMA packages in compact designs.
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Low-Voltage Rectification in Portable Electronics
In handheld and portable electronic devices, the 551 is widely used as a low-voltage rectifier in power management circuits where its 0.35 V forward drop is critical to minimize wasted power. According to portable design references, replacing a standard 1N4148 with a 551 Schottky in a charging or signal-detection path can improve efficiency by 10-15% at low currents. The 551 is commonly seen in step-up DC-DC converters for bias supplies, in USB OTG voltage boosters, and in low-power solar charging circuits for IoT sensor nodes. The 500 mA continuous current rating covers most portable device load profiles including smartphones, wearables, and Bluetooth peripherals. The compact SOD-323 footprint enables dense PCB layouts required in space-constrained portable designs.
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OR-ing Diodes in Redundant Power Architectures
The 551 serves as an OR-ing diode in redundant power supply architectures where two or more power sources must be combined without back-feeding each other. According to OR-ing design best practices, each 551 in series with its source introduces a small forward voltage drop that acts as a natural current-sharing barrier. In a typical dual-source 5 V supply combining a wall adapter and a USB input, two 551 diodes prevent the higher-voltage source from back-driving the lower one. The 500 mA current rating supports most single-board computer and embedded system loads. Designers should account for the 0.35 V forward drop when computing load voltage at the OR-ing output, or use a MOSFET-based ideal diode for lower loss at higher currents.
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Signal Clamping in ESD-Sensitive Interfaces
The 551's fast switching and low capacitance make it useful as a signal clamping diode in ESD-sensitive interfaces including audio jacks, pushbuttons, and low-speed data lines. According to ESD protection design references, a forward-biased 551 to ground or supply clamps transient voltages by conducting at its forward voltage, protecting downstream ICs from over-voltage events. While dedicated TVS diodes are preferred for high-energy ESD, the 551 is adequate for low-energy transients in cost-sensitive consumer products. The 500 mA rating ensures the diode can survive the brief high-current pulse during clamping without damage. The SOD-323 package can be placed directly at the connector pin for maximum clamping effectiveness.
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Switch-Mode Power Supply Output Rectification
In isolated and non-isolated switch-mode power supplies (SMPS) operating below 500 mA, the 551 functions as the secondary-side output rectifier. According to SMPS design guidelines, replacing a slow-recovery rectifier with the 551 reduces switching losses and improves cross-regulation in multi-output flyback converters. In a typical 5 V/500 mA wall-wart SMPS using the TinySwitch or LinkSwitch families, the 551 carries the full output current during the secondary conduction phase. The 20 V reverse voltage comfortably exceeds the reflected voltage from 5 V outputs. The SOD-323 package is preferred for compact wall-wart designs where every cubic millimeter of PCB space matters. Designers should verify thermal performance at the maximum rated current in enclosed adapter housings.
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Zusammenfassung der empfohlenen Produkte
Technische Referenzdaten für 551 – Vergleich, Designhinweise und Compliance-Informationen.
Auswahlhilfe
Vergleich mit Alternativen
| Parameter | Dieses Produkt | RB551VM-30TE-17 | MBR0520 | B0515LS | SS12-E3 | RB520S-30 |
|---|---|---|---|---|---|---|
| Package | SOD-323 | UMD2 | SOD-123 | SOD-323 | SMA | SOD-523 |
| Brand | Pan Jit International | ROHM Semiconductor | onsemi | Diodes Incorporated | Vishay Intertechnology | ROHM Semiconductor |
| Reverse Voltage (VR) | 20 V | 30 V | 20 V | 15 V | 20 V | 30 V |
| Forward Current (IO) | 500 mA | 500 mA | 500 mA | 500 mA | 1 A | 100 mA |
| Operating Temperature | -55C to +125C | -40C to +125C | -65C to +175C | -40C to +125C | -65C to +175C | -40C to +125C |
| RoHS Compliance | Yes | Yes | Yes | Yes | Yes | Yes |
| Mounting Type | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount | Surface Mount |
Wichtigste Unterscheidungsmerkmale
- SOD-323 footprint with 30V VRWM headroom (vs. B0515LS (Diodes Incorporated))
- Higher current capability than sub-500 mA Schottky parts (vs. RB520S-30 (ROHM))
- Compact SOD-323 package versus larger SMA packages (vs. SS12-E3 (Vishay))
Designhinweise
Estimated: At 500 mA continuous forward current with a typical VF of 0.35 V, the 551 dissipates approximately 0.175 W of heat. The SOD-323 package has a thermal resistance of approximately 250 C/W to ambient (per typical JEDEC data), producing a junction temperature rise of about 44C above ambient. In enclosed or high-ambient designs, derate the forward current to 350-400 mA to maintain the junction below +125C maximum rating. Provide adequate copper pad area on both anode and cathode terminals for heat spreading.
Per the manufacturer datasheet, the SOD-323 land pattern should use approximately 1.0 mm x 0.5 mm pads for each terminal, with thermal relief spokes preferred over direct copper connection if wave soldering is used. For reflow soldering, follow the JEDEC J-STD-020 MSL-1 profile with a peak temperature of 260C for 30 seconds maximum. Avoid placing the 551 directly adjacent to large heat-generating components to prevent thermal overstress during reflow.
Do not use the 551 in circuits where the reverse voltage can exceed 20 V repetitive peak - the device will conduct in reverse and may be damaged. Verify that the cathode-anode orientation is correct during PCB assembly; reversed orientation appears to work in forward direction but will fail when reverse voltage is applied. Also note that Schottky diodes have higher reverse leakage than PN-junction rectifiers at elevated temperatures - account for this in high-impedance circuit designs.
Compliance-Informationen
RoHS compliant per Pan Jit datasheet marking. Not AEC-Q100 qualified - this is a commercial-grade part. For automotive applications, verify with manufacturer.
