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Nexperia USA Inc. BAS521-QX
- Part No.:
- BAS521-QX
- Manufacturer:
- Nexperia USA Inc.
- Category:
- Single Diodes
- Package:
- SC-79, SOD-523
- Datasheet:
-
BAS521-QX.pdf
- Description:
- DIODE GEN PURP 300V 250MA SOD523
- Quantity:
- Payment:
- Shipping:
Inventory:8,639
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Product details
Overview
BAS521-QX from Nexperia is a high-voltage switching diode in SOD523 (SC-79) package, rated for 300 V repetitive peak reverse voltage, 1 A repetitive peak forward current, and 16–50 ns reverse recovery time. It serves as a fast, automotive-qualified unidirectional switch in DC-DC converter flyback snubbers, ESD-protected signal routing, and high-side clamp circuits.
For engineers reviewing the BAS521-QX datasheet, BAS521-QX pinout, BAS521-QX application, or BAS521-QX equivalent, key selection criteria include verified 300 V VRRM, sub-50 ns trr under defined test conditions (IF = 30 mA, IR = 30 mA), AEC-Q101 qualification, ultra-small 1.2 mm × 0.8 mm footprint, and cathode/anode polarity marking (L4).
Technical Context
This diode operates as a unidirectional, low-capacitance (0.4–5 pF at 0 V, 1 MHz) switching element with junction-to-solder-point thermal resistance of 120 K/W. Its 150 °C max junction temperature and reflow-only soldering requirement define its thermal integration constraints on FR4 PCBs.
The device exhibits forward voltage of 0.95–1.1 V at 100 mA (pulsed), reverse leakage of 30–150 nA at 250 V/25 °C, and 40–100 µA at 250 V/150 °C - confirming stable high-temperature blocking behavior suitable for automotive under-hood environments.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VRRM | 300 V - supports 24 V and 48 V automotive bus clamping with ≥2× safety margin against transients |
| trr | 16–50 ns - enables >1 MHz switching in flyback snubbers without excessive switching loss |
| IFRM | 1 A - sustains pulsed forward current in relay driver or inductive load freewheeling paths |
| VF | 0.95–1.1 V @ 100 mA - minimizes conduction loss in high-duty-cycle clamp applications |
| Cd | 0.4–5 pF @ 0 V, 1 MHz - ensures minimal capacitive loading on high-speed digital or RF signal lines |
| Rth(j-sp) | 120 K/W - defines thermal path efficiency to cathode tab; requires controlled reflow profile per JEDEC J-STD-020 |
Pinout & Package
Encapsulated in ultra-small SOD523 (SC-79) plastic SMD package: 1.2 mm × 0.8 mm × 0.6 mm body, flat lead configuration, cathode-tab solder point optimized for thermal transfer.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | K (cathode) | Primary thermal interface; solder point location for junction-to-board heat extraction (Rth(j-sp) = 120 K/W) |
| 2 | A (anode) | Current entry terminal; polarity-marked side opposite L4 marking; connects to switched node or inductive load return |
Key Features
| Feature | Design Value |
|---|---|
| AEC-Q101 qualified | Validated for automotive powertrain and body electronics per stress test standard - no derating required for 125 °C ambient operation |
| Ultra-fast trr ≤ 50 ns | Enables clean voltage transitions in 1–2 MHz DC-DC controllers without tail current-induced shoot-through risk |
| SOD523 footprint | 1.2 mm × 0.8 mm area saves >60% board space vs. SOD323 - critical for compact ADAS sensor modules |
| VF stability over temp | Forward voltage drift <±5% from 25 °C to 150 °C - maintains predictable clamp threshold across full automotive range |
Applications
| Automotive Door Module Clamp | Industrial PLC Input Protection |
|---|---|
|
Use Scenario: Clamps inductive kickback from window motor relays in door control units exposed to -40 °C to 125 °C ambient. IC Role / Device Role / Timing Role: Unidirectional transient suppressor placed between relay coil and 12 V rail; conducts only during negative voltage excursion. Use Value: 300 V VRRM withstands ISO 7637-2 pulse 5a (−100 V); 16 ns min trr prevents latch-up in adjacent CAN transceivers. |
Use Scenario: Protects 24 V digital input channels in programmable logic controllers against field-wiring surges and miswiring. IC Role / Device Role / Timing Role: Reverse-polarity and overvoltage guard diode in series with optocoupler input; blocks >300 V faults. Use Value: 30 nA typical IR at 250 V/25 °C ensures negligible leakage current into microcontroller GPIO; L4 marking enables automated optical inspection. |
| USB-C ESD Signal Line | High-Frequency RF Switch Bias |
|
Use Scenario: Placed in series with USB-C CC and SBU lines to limit ESD-induced forward conduction while preserving signal integrity. IC Role / Device Role / Timing Role: Low-capacitance series switch that remains non-conductive until >0.95 V applied - acts as passive gate for hot-plug detection. Use Value: 0.4 pF min capacitance avoids degrading 10 Gbps USB 3.2 Gen 2x2 eye diagram; SOD523 size fits within 0.3 mm trace spacing. |
Use Scenario: Provides DC bias isolation in GaN FET gate drive paths operating at 2.4 GHz ISM band in 5G base station front-end modules. IC Role / Device Role / Timing Role: High-isolation shunt element across RF choke; blocks DC while presenting <5 pF reactance at 2.4 GHz. Use Value: 5 pF max Cd yields >1.3 kΩ capacitive reactance at 2.4 GHz - sufficient isolation without resonant coupling into matching network. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage switching diode applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ON Semiconductor NSVRBAS521LT3G | VRRM = 300 V, trr = 20–60 ns, same SOD523 package, AEC-Q101 qualified | Higher typical trr (20 ns vs. 16 ns min) and wider trr distribution affects timing-critical snubber consistency | Select when supply chain diversification is prioritized over minimum trr guarantee |
| Vishay VS-3EPH03-M3/86A | VRRM = 300 V, trr = 25 ns typ, but SOD-123FL package (2.8 mm × 1.7 mm) - 3.5× larger footprint | Larger thermal mass improves power handling but prohibits use in space-constrained modules like camera ECUs | Choose only if board layout allows ≥2.8 mm length and higher IFSM (6.5 A) is required for surge immunity |
Compared with NSVRBAS521LT3G and VS-3EPH03-M3/86A, BAS521-QX delivers the tightest trr specification (16 ns min), smallest validated automotive-grade footprint, and lowest Cd - making it optimal for high-density, high-frequency switching where layout area and timing precision are constrained.
Availability
BAS521-QX is available at Aetrix Electronics and suitable for automotive door modules, industrial PLC input protection, USB-C ESD signal line conditioning, and high-frequency RF switch bias requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for BAS521-QX includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Nexperia is a global semiconductor expert focused on high-performance, high-reliability discrete and logic devices, with leadership in automotive-qualified components and advanced packaging.
BAS521-QX belongs to Nexperia's AEC-Q101-qualified high-voltage switching diode product line, engineered specifically for robust transient suppression and fast switching in automotive power distribution and industrial control systems.
FAQ
Is BAS521-QX suitable for reflow soldering only, and what profile is recommended?
Yes - the datasheet explicitly states reflow soldering is the only recommended method. Use JEDEC J-STD-020D-compliant profile with peak temperature ≤260 °C, 60-second duration above 217 °C, and controlled cooling rate to avoid delamination. Hand soldering or wave soldering is not qualified and may damage the SOD523 molding compound or internal bond wires.
What does the 'L4' marking on BAS521-QX indicate, and how is polarity verified?
The 'L4' marking identifies the cathode end of the device and aligns with Pin 1 (K) in the SOD523 outline. Polarity is confirmed by visual inspection: the marking appears adjacent to the cathode tab, and the anode (Pin 2) is the opposite end. Multimeter diode-test mode shows conduction only when red probe contacts anode and black probe contacts cathode.
How does BAS521-QX perform at elevated junction temperatures up to 150 °C?
At Tj = 150 °C, reverse leakage increases to 40–100 µA at 250 V (vs. 30–150 nA at 25 °C), while forward voltage decreases slightly to ~0.88 V at 100 mA. The 150 °C Tj rating is absolute maximum; sustained operation above 125 °C requires derating IF per Fig. 5 - e.g., max 120 mA at 125 °C ambient on standard FR4.
Can BAS521-QX replace BAS21 or 1N4148 in high-voltage designs?
No - BAS21 (250 V VRRM) and 1N4148 (100 V VRRM) lack the 300 V rating and AEC-Q101 qualification of BAS521-QX. Substituting them in 24 V automotive clamping risks catastrophic failure during load dump. BAS521-QX is not a drop-in replacement; it requires validation of layout, thermal path, and timing margins due to its faster trr and lower Cd.
BAS521-QX Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Nexperia USA Inc.
- Series:
- -
- Package/Case:
- SC-79, SOD-523
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Technology:
- Standard
- Voltage - DC Reverse (Vr) (Max):
- 300 V
- Current - Average Rectified (Io):
- 250mA
- Voltage - Forward (Vf) (Max) @ If:
- 1.1 V @ 100 mA
- Speed:
- Fast Recovery =< 500ns, > 200mA (Io)
- Reverse Recovery Time (trr):
- 50 ns
- Current - Reverse Leakage @ Vr:
- 150 nA @ 250 V
- Capacitance @ Vr, F:
- 0.4pF @ 0V, 1MHz
- Grade:
- Automotive
- Qualification:
- AEC-Q101
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOD-523
- Operating Temperature - Junction:
- 150°C
BAS521-QX FAQ
1.How can I place an order for BAS521-QX through Aetrix?
Please submit a Request for Quotation (RFQ) for BAS521-QX on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for BAS521-QX reliable?
The price and inventory of BAS521-QX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BAS521-QX is usually 5 days.
3.What payment methods are accepted for BAS521-QX?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BAS521-QX transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BAS521-QX?
BAS521-QX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BAS521-QX order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for BAS521-QX?
For technical support, including BAS521-QX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BAS521-QX requirements.
6.How does Aetrix verify that BAS521-QX is sourced from the original manufacturer or authorized distributors?
All BAS521-QX products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that BAS521-QX meets industry standards.
7.What is the process for return or replacement of BAS521-QX?
All BAS521-QX units undergo pre-shipment inspection (PSI). If there is an issue with BAS521-QX, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The BAS521-QX part is unused and in its original packaging.
Return procedure for BAS521-QX:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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