551 - Surface Mount Schottky Diode 20V 500mA SOD-323
Référence : 551 ✓ Actif| Qté | Prix unitaire | Total |
|---|---|---|
| 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 Présentation
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.
Alternatives de remplacement direct pour 551 — même boîtier, compatible broche à broche. Les références à boîtier différent nécessitant une retouche du PCB sont exclues.
Outil de comparaison rapide — sélectionnez des références alternatives pour une comparaison côte à côte :
RB551VM-30TE-17
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
MBR0520
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
B0515LS
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
SS12-E3
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
RB520S-30
✅ Remplacement direct📋 Alternative de référence (hors catalogue)
551 Valeurs maximales et caractéristiques électriques
| Manufacturer | Pan Jit International Inc. |
| Part Number | RB551V-30-AU_R1_000A1 |
| Device Type | Surface Mount Schottky Barrier Diode |
| Marking Code | 551 |
| Boîtier | SOD-323 |
| Reverse Voltage (VR) | 20 V |
| Working Peak Reverse Voltage (VRWM) | 30 V |
| Average Rectified Forward Current (IO) | 500 mA |
| Température de jonction en fonctionnement | -55C to +125C |
| Storage Temperature | -55C to +150C |
| Type de montage | Surface Mount |
| Statut RoHS | Compliant |
| Lead-Free | Yes |
Configuration des broches de 551
| Broche 1 | Anode — Positive terminal (forward-biased current enters) |
| Broche 2 | Cathode — Negative terminal marked by bar on package top (forward-biased current exits) |
Applications typiques
551 convient pour 6 applications: 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.
Recommandé
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.
Recommandé
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.
Recommandé
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.
Recommandé
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.
Recommandé
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.
Recommandé
Récapitulatif des produits recommandés
Données de référence d'ingénierie pour 551 — comparaison, recommandations de conception et informations de conformité.
Guide de sélection
Comparaison avec les alternatives
| Paramètre | Ce produit | 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 |
Principaux différenciateurs
- 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))
Notes de conception
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.
Informations de conformité
RoHS compliant per Pan Jit datasheet marking. Not AEC-Q100 qualified - this is a commercial-grade part. For automotive applications, verify with manufacturer.
