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Silicon Labs SI3400-BZ-GM
- Part No.:
- SI3400-BZ-GM
- Manufacturer:
- Silicon Labs
- Category:
- Power Over Ethernet (PoE) Controllers
- Package:
- 20-VQFN Exposed Pad
- Datasheet:
-
SI3400-BZ-GM.pdf
- Description:
- IC POE CNTRL 1 CHANNEL 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:1,885
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Product details
Overview
SI3400-BZ-GM from Silicon Laboratories is a fully integrated IEEE 802.3-compliant Power over Ethernet (PoE) Powered Device (PD) interface IC with integrated switching regulator, hotswap controller, dual diode bridges, and transient surge suppressor. It delivers up to 10 W regulated output power in non-isolated (buck) or isolated (flyback) topologies, supports Class 0–4 detection/classification, and operates across –40°C to +85°C ambient temperature.
For engineers reviewing the SI3400-BZ-GM datasheet, SI3400-BZ-GM pinout, SI3400-BZ-GM application, or SI3400-BZ-GM equivalent, this page provides verified technical context, confirmed pin functions, real-world application mappings, and validated alternative options for PoE PD design - all grounded in Silicon Labs' Rev. 0.9 specification and functional documentation.
Technical Context
The SI3400-BZ-GM implements a dual-mode hotswap interface with programmable classification (Class 0–4), dual-level current limiting (130 mA inrush / 350 mA operating), and true early power-loss detection via PLOSS pin referenced to input-side diode bridge voltage. Its integrated 0.3 Ω switching FET and constant-frequency 350 kHz PWM controller support both buck and flyback topologies with 1.23 V feedback reference and ±5% output voltage tolerance.
It integrates two full diode bridges (CT1/CT2 and SP1/SP2 paths), IEC60060-compliant transient surge protection (±82 V), undervoltage lockout (30–36 V turn-on hysteresis), thermal shutdown at 160°C, and foldback current limiting - enabling direct RJ-45 connection with only four external components for full 802.3 compliance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Power Class Support | IEEE 802.3 Class 0–4 (0–12.95 W); SI3400-BZ-GM rated for ≤10 W output |
| Input Voltage Range | 2.8 V to 57 V DC; supports legacy and standard-compliant PSEs |
| Switching Frequency | 350 kHz fixed-frequency PWM; enables compact magnetics and predictable EMI behavior |
| Hotswap FET RDS(on) | 0.5–1.4 Ω typical; minimizes conduction loss during high-current startup and steady-state operation |
| Regulated Feedback Voltage | 1.23 V ±0.03 V; precision reference enables accurate output regulation in buck/flyback designs |
| Thermal Shutdown Threshold | 160°C junction temperature with 25°C hysteresis; prevents permanent damage during sustained overload |
| Early Power-Loss Detection | PLOSS pin asserts high-impedance when input falls below 27 V; gives microcontroller ≥100 µs to save state |
Pinout & Package
SI3400-BZ-GM is housed in a Pb-free, RoHS-compliant 5 × 5 mm, 20-pin QFN package with exposed thermal pad (VNEG). Pin assignments are validated per Rev. 0.9 functional block diagram and pin description table.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VPOSF / VPOSS | Positive input rail (front/rear bridge outputs) | Connects to diode bridge outputs; supplies hotswap switch and internal bias rails |
| VNEG | Negative input rail / thermal pad | Common return for CT1/CT2/SP1/SP2 bridges; must be connected to PCB ground plane via ≥9 thermal vias |
| HSO | Hotswap switch output | Drives switching regulator input capacitor; transitions from high-Z to VNEG after soft-start completion |
| SWO | Switching FET output | Drives external inductor (buck) or transformer primary (flyback); integrates 0.3–0.86 Ω power MOSFET |
| FB | Feedback input | Monitors regulated output via resistor divider; 1.23 V reference sets output voltage (e.g., 5 V = R1/R2 = 2.87k/7.32k) |
| PLOSS | Early power-loss indicator | Open-drain output pulled up to VPOS; goes high-Z at <27 V input - enables graceful shutdown before VOUT collapse |
| RDET / RCL | Detection & classification resistors | RDET = 25.5 kΩ sets 25.5 kΩ signature; RCL sets Class 0–4 current (e.g., 127 Ω = Class 1, 10.5 mA) |
Key Features
| Feature | Design Value |
|---|---|
| Integrated dual diode bridges | Eliminates 4 external Schottky diodes; enables true early power-loss detection by monitoring pre-bridge voltage |
| IEC60060 transient protection | Withstands ±82 V, 300 ns/50 µs surges on CT1–CT2 and SP1–SP2 - no external TVS required for basic compliance |
| Dual-level hotswap current limit | 130 mA inrush limit prevents PSE tripping; auto-switches to 350 mA operating limit after capacitor charge - supports legacy + standard PSEs |
| Programmable classification | Single RCL resistor selects Class 0–4; guaranteed currents (e.g., Class 3 = 26–30 mA) with 1% resistor tolerance |
| Isolated/non-isolated topology support | Same IC supports buck (non-isolated) and flyback (isolated) via FB loop configuration - reduces BOM variants |
Applications
| Voice over IP Telephones | Wireless Access Points |
|---|---|
Use Scenario: Desktop VoIP phone powered via single Ethernet cable, requiring low-noise 3.3 V/5 V rails and fast power-loss response. IC Role / Device Role / Timing Role: SI3400-BZ-GM serves as primary PD interface and DC-DC converter, managing detection, classification, and regulated output generation. Use Value: Integrated diode bridges and PLOSS enable sub-100 µs power-fail warning, allowing DSP to save call state before brownout. |
Use Scenario: Indoor/outdoor Wi-Fi AP with PoE input, needing compact 5 V/2 A supply and robust surge immunity in uncontrolled environments. IC Role / Device Role / Timing Role: SI3400-BZ-GM acts as complete front-end PD controller and buck regulator, eliminating discrete hotswap FET and bridge diodes. Use Value: 0.5–1.4 Ω hotswap RDS(on) and integrated surge suppression reduce board area by >30% vs. discrete solutions while meeting IEC61000-4-5 Level 3. |
| Security Cameras | Point-of-Sale Terminals |
Use Scenario: Outdoor IP camera with IR illumination, requiring stable 12 V output and thermal resilience in wide-temperature enclosures. IC Role / Device Role / Timing Role: SI3400-BZ-GM provides regulated 12 V via flyback topology and monitors input voltage for early shutdown during cable disconnect. Use Value: 160°C thermal shutdown with 25°C hysteresis prevents latch-up in sealed housings; foldback current limiting protects during motor-driven PTZ faults. |
Use Scenario: Retail POS terminal with Ethernet backhaul, needing reliable 5 V/1.5 A supply and Class 2 power negotiation for USB peripherals. IC Role / Device Role / Timing Role: SI3400-BZ-GM executes IEEE 802.3 Class 2 detection (17–20 mA) and delivers regulated 5 V to main logic and peripheral ports. Use Value: Guaranteed Class 2 current with 127 Ω RCL resistor ensures PSE allocates 3.84–6.49 W - sufficient for display, scanner, and printer interfaces. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PoE PD interface applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT4275AIMSE#PBF | Higher max power (up to 25.5 W), supports IEEE 802.3at, requires external MOSFET and diode bridges | Suitable for higher-power devices (e.g., PTZ cameras); lacks integrated switching FET and diode bridges | Choose LT4275AIMSE#PBF when >10 W output or 802.3at compliance is required; SI3400-BZ-GM preferred for cost-sensitive ≤10 W designs with minimal external parts. |
| TPS23753APWPR | Integrated DC-DC controller (no power FET), supports flyback only, 100 kHz switching, requires external diode bridges | Targets isolated PoE systems; lacks buck topology support and early power-loss detection | Choose TPS23753APWPR for flyback-only designs needing TI ecosystem support; SI3400-BZ-GM offers broader topology flexibility and faster fault response. |
Compared with LT4275AIMSE#PBF and TPS23753APWPR, SI3400-BZ-GM uniquely integrates diode bridges, surge suppression, switching FET, and early power-loss detection in a single 5×5 mm QFN - reducing component count by ≥7 parts and enabling sub-100 µs fail-safe shutdown not available in either alternative.
Availability
SI3400-BZ-GM is available at Aetrix Electronics and suitable for voice over IP telephones, wireless access points, security cameras, and point-of-sale terminals requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.
Supply support for SI3400-BZ-GM 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
Silicon Laboratories is a fabless semiconductor company specializing in timing, IoT, and connectivity solutions, with deep expertise in mixed-signal IC design and system-level integration.
The SI3400-BZ-GM belongs to Silicon Labs' PoE PD controller product line, engineered specifically to simplify IEEE 802.3-compliant powered device implementation by integrating front-end interface, protection, and DC-DC conversion into one compact IC.
FAQ
What is the maximum continuous output power supported by the SI3400-BZ-GM?
The SI3400-BZ-GM is specified for up to 10 W of continuous regulated output power, as stated in the official Silicon Labs documentation. This rating applies to both buck and flyback topologies under recommended operating conditions (–40°C to +85°C, 36–57 V input). Higher power operation requires the Si3401 variant or external diode bridge bypassing per AN313.
Does the SI3400-BZ-GM support IEEE 802.3af and 802.3at standards?
The SI3400-BZ-GM supports IEEE 802.3af (PoE) Class 0–4 detection and classification, including pre-standard legacy PSE compatibility. It does not support 802.3at (PoE+) or 802.3bt, as those require higher power handling (≥30 W) and different classification protocols beyond the SI3400-BZ-GM's design scope.
How does the PLOSS pin function in the SI3400-BZ-GM?
The PLOSS pin on the SI3400-BZ-GM is an open-drain output that transitions to high-impedance when the input voltage (|CT1–CT2| or |SP1–SP2|) falls below 27 V. Because it monitors voltage *before* the integrated diode bridges, SI3400-BZ-GM detects power loss earlier than conventional solutions - providing ≥100 µs warning for microcontroller state save before VOUT collapse.
Can the SI3400-BZ-GM be used in both isolated and non-isolated PoE designs?
Yes, the SI3400-BZ-GM supports both isolated (flyback) and non-isolated (buck) switching topologies. Its integrated error amplifier, 1.23 V reference, and flexible FB pin configuration allow either architecture. Non-isolated designs use direct FB feedback; isolated designs employ optocoupler-based secondary-side regulation referenced to the SI3400-BZ-GM's FB input.
What is the purpose of the ISOSSFT pin on the SI3400-BZ-GM?
The ISOSSFT pin on the SI3400-BZ-GM enables isolated-mode soft-start control. When connected to VDD, it configures the internal soft-start circuit for flyback operation, preventing transformer saturation during startup. In non-isolated (buck) designs, ISOSSFT is tied to VDD or left unconnected per Rev. 0.9 recommendations - its function is specific to isolated topologies.
SI3400-BZ-GM Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Silicon Labs
- Series:
- -
- Package/Case:
- 20-VQFN Exposed Pad
- Packaging:
- Tray
- Product Status:
- Obsolete
- Type:
- Controller (PD), DC/DC
- Number of Channels:
- 1
- Power - Max:
- 15 W
- Internal Switch(s):
- Yes
- Auxiliary Sense:
- No
- Standards:
- 802.3af (PoE)
- Voltage - Supply:
- 2.8V ~ 57V
- Current - Supply:
- 2mA
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (5x5)
SI3400-BZ-GM FAQ
1.How can I place an order for SI3400-BZ-GM through Aetrix?
Please submit a Request for Quotation (RFQ) for SI3400-BZ-GM 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 SI3400-BZ-GM reliable?
The price and inventory of SI3400-BZ-GM are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SI3400-BZ-GM is usually 5 days.
3.What payment methods are accepted for SI3400-BZ-GM?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SI3400-BZ-GM transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SI3400-BZ-GM?
SI3400-BZ-GM orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SI3400-BZ-GM 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 SI3400-BZ-GM?
For technical support, including SI3400-BZ-GM datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SI3400-BZ-GM requirements.
6.How does Aetrix verify that SI3400-BZ-GM is sourced from the original manufacturer or authorized distributors?
All SI3400-BZ-GM 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 SI3400-BZ-GM meets industry standards.
7.What is the process for return or replacement of SI3400-BZ-GM?
All SI3400-BZ-GM units undergo pre-shipment inspection (PSI). If there is an issue with SI3400-BZ-GM, 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 SI3400-BZ-GM part is unused and in its original packaging.
Return procedure for SI3400-BZ-GM:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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