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Skyworks Solutions Inc. SI3500-A-GMR
- Part No.:
- SI3500-A-GMR
- Manufacturer:
- Skyworks Solutions Inc.
- Package:
- 20-VQFN Exposed Pad
- Datasheet:
-
SI3500-A-GMR.pdf
- Description:
- IC REG BUCK ADJ 400MA 20QFN
- Quantity:
- Payment:
- Shipping:
Inventory:2,253
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Product details
Overview
SI3500-A-GMR from Silicon Laboratories is a high-voltage (42–57 V) integrated DC-DC converter with on-chip PWM controller and power N-FET, delivering up to 10 W output power. It supports non-isolated (buck) and isolated (flyback) topologies, features dual-level hot-swap current limiting (140 mA inrush / 400 mA operating), and provides adjustable output voltage from 1.8 V to 12 V. It is used in Power over Ethernet (PoE) power sourcing equipment such as Si3452-based systems.
For engineers reviewing the SI3500-A-GMR datasheet, SI3500-A-GMR pinout, SI3500-A-GMR application, or SI3500-A-GMR equivalent, key selection considerations include input surge immunity (80 V transient), integrated 65 V Zener clamp, thermal shutdown at 160 °C, soft-start control via external capacitor, and compatibility with both isolated and non-isolated 3.3 V/5 V PoE supply designs.
Technical Context
The SI3500-A-GMR integrates a constant-frequency (350 kHz) PWM controller with monolithic N-channel switching FET (RDS(on) = 0.3–0.86 Ω) and dual-mode soft-start-SSFT pin for non-isolated applications and ISOSSFT pin for isolated configurations. Its error amplifier supports internal feedback (via FB pin) or external opto-coupled feedback (via EROUT).
It implements a two-stage hot-swap switch: initial 140 mA inrush limit for safe input capacitor charging, then automatic transition to 400 mA operating limit once VHSO drops near VNEG. Input protection includes undervoltage lockout (UVLO turn-on at ≤42 V, turn-off at ≥30 V), overvoltage clamp (65 V Zener), and ±80 V transient rating per IEC 61000-4-2.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 42–57 V DC - supports standard 48 V PoE PSE rails with margin for ripple and transients. |
| Output Voltage Range | 1.8–12 V DC - programmable via external resistor divider on FB pin for flexible system supply generation. |
| Max Output Power | 10 W - enables single-chip 3.3 V/2 A or 5 V/2 A PoE-powered subsystems without external FETs. |
| Switching Frequency | 350 kHz - balances efficiency, EMI, and inductor size; fixed-frequency PWM avoids subharmonic instability. |
| Hot-Swap Current Limits | 140 mA (inrush) / 400 mA (operating) - prevents input rail collapse during startup and protects against sustained overloads. |
| Thermal Shutdown | 160 °C junction temperature - latches off until cooldown; 25 °C hysteresis prevents cycling near trip point. |
| Feedback Reference | 1.23 V at FB pin - precision internal reference enables ±5% output regulation tolerance across line/load/temperature. |
Pinout & Package
SI3500-A-GMR uses a RoHS-compliant 5 × 5 mm, 20-pin QFN package with exposed thermal pad (VNEG) requiring ≥9 thermal vias to a 2 in² copper plane tied to VNEG.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 EROUT | Error amplifier output / PWM input | Drives opto-coupler LED in isolated topologies; connects directly to PWM comparator input. |
| 2 SSFT | Soft-start output | Sinks 25 µA to charge external capacitor, controlling output voltage ramp rate in non-isolated mode. |
| 3 VDD | Internal 5 V bias rail | Supplies internal logic and opto-coupler drive; regulated from VPOS, accurate ±10% over input range. |
| 4 ISOSSFT | Isolated-mode soft-start enable | When tied to VDD, disables isolated soft-start; when decoupled via 0.1 µF to VSSA, ramps duty cycle clamp. |
| 7 HSO | Hot-swap switch output | Source of integrated N-FET; connects to VNEG through internal switch; senses current for dual-limit control. |
| 9 VNEG (Pad) | Negative input rail / thermal pad | Primary return path for all currents; must be soldered to PCB ground plane for thermal and electrical integrity. |
| 12 VPOS1 | High-voltage input force node | Direct connection to input source; carries full input current; referenced to VNEG for UVLO/OVLO sensing. |
| 16 VPOS2 | High-voltage input sense node | Provides feedback to internal bias and protection circuits; decoupled from VPOS1 to reduce noise coupling. |
| 17 VSS1 / 19 VSS2 | Switcher negative supply rails | Externally tied to HSO; provide local return paths for switching regulator circuitry and gate drive. |
| 18 SWO | Switching transistor output | Drain of integrated N-FET; connects to inductor (non-isolated) or transformer primary (isolated); rated 3 A avg. |
| 20 FB | Feedback input | Connects to resistor divider from output; compares to 1.23 V reference to regulate non-isolated outputs. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated hot-swap switch with dual current limits | Enables controlled inrush (140 mA) and robust fault protection (400 mA), eliminating need for external hot-swap controllers. |
| On-chip 350 kHz PWM controller + N-FET | Reduces BOM count by integrating gate driver, oscillator, error amp, and 0.3–0.86 Ω RDS(on) FET in one die. |
| Configurable isolated/non-isolated topology support | Single IC supports buck (3.3 V/5 V PoE PSUs) and flyback (isolated auxiliary supplies) via pin-strapping and external component selection. |
| 65 V integrated Zener clamp + 80 V transient rating | Withstands hot-plug surges and EMC transients without external TVS, simplifying front-end protection design. |
| Two-mode soft-start (SSFT/ISOSSFT) | Prevents output overshoot and FET stress: SSFT controls FB reference ramp (non-isolated); ISOSSFT clamps PWM duty (isolated). |
Applications
| Power over Ethernet (PoE) PSE | Industrial Network Switches |
|---|---|
|
Use Scenario: Generating 3.3 V or 5 V auxiliary power from 48 V PoE input in Si3452-based PSE controllers. IC Role / Device Role / Timing Role: Primary DC-DC converter providing regulated, current-limited, and surge-protected output for downstream PHY and controller ICs. Use Value: Eliminates need for discrete FET, controller, and hot-swap IC-reducing solution size by >40% and enabling compact 2-layer PoE board layouts. |
Use Scenario: Supplying isolated 5 V/12 V bias rails for Ethernet PHYs and management microcontrollers in DIN-rail mounted switches. IC Role / Device Role / Timing Role: Flyback-mode isolated DC-DC controller with opto-coupled feedback (EROUT → TLV431 + PS2911) for reinforced insulation. Use Value: Achieves 3.75 kVRMS isolation compliance using standard transformers-no external gate drivers or error amplifiers required. |
| Internet Appliances | Telecom Line Cards |
|
Use Scenario: Providing 12 V/0.8 A main supply and 3.3 V/1.5 A logic rail from centralized 48 V backplane in VoIP phones and IP cameras. IC Role / Device Role / Timing Role: Dual-output capable converter (using cascaded stages) with independent soft-start sequencing for clean power-up. Use Value: Meets EN 61000-4-5 surge immunity (±1 kV) and maintains regulation during 48 V input dips to 42 V (UVLO hysteresis). |
Use Scenario: Generating -48 V derived bias supplies (e.g., -12 V, -5 V) for analog front-end circuits in carrier-grade line cards. IC Role / Device Role / Timing Role: Inverting buck-boost topology enabled by connecting SWO to VPOS and FB to negative output rail. Use Value: Supports negative output configurations without polarity-reversal diodes or extra regulators-reducing component count and leakage paths. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage DC-DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT3748IMSE#PBF | Requires external MOSFET; no integrated hot-swap switch or Zener clamp; 55 V max input; 100 kHz–1 MHz adjustable frequency. | Used in isolated flyback designs where higher frequency or custom FET selection is needed; lacks inrush current control. | Choose when designing for >10 W or needing >1 MHz operation; adds complexity but improves efficiency at light loads. |
| TPS54260DGQR | 60 V max input; no integrated hot-swap; no Zener clamp; requires external current-sense resistor; 2.5–600 kHz frequency. | Targeted at non-isolated buck converters only; lacks dual-current-limit hot-swap and isolated topology support. | Choose for cost-sensitive, lower-power (<5 W) industrial supplies where PoE surge immunity is not required. |
Compared with LT3748IMSE#PBF and TPS54260DGQR, the SI3500-A-GMR uniquely integrates hot-swap control, 65 V Zener clamp, and dual-mode soft-start in a single 5×5 mm QFN-enabling complete 48 V PoE PSU designs with minimal external components and no layout compromises for surge handling.
Availability
SI3500-A-GMR is available at Aetrix Electronics and suitable for Power over Ethernet (PoE) power sourcing equipment, industrial network switches, and telecom line card power supplies requiring stable component supply and long-term lifecycle continuity.
Supply support for SI3500-A-GMR 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 mixed-signal ICs for timing, connectivity, and power management, with core expertise in high-voltage analog integration and energy-efficient design.
The SI3500 product line was developed specifically for high-reliability, compact DC-DC conversion in Power over Ethernet infrastructure-addressing the need for integrated surge protection, hot-swap control, and topology flexibility in space-constrained PSE modules.
FAQ
What is the maximum continuous input voltage the SI3500-A-GMR can withstand without damage?
The SI3500-A-GMR has an absolute maximum DC input rating of 60 V between VPOS and VNEG, and a transient rating of 80 V for ≤50 µs pulses. Its integrated 65 V Zener clamp actively limits input voltage during hot-plug events, making it suitable for 48 V PoE systems with typical 10–20% ripple and surge margins. Operation above 57 V violates recommended conditions and risks reliability degradation.
Can the SI3500-A-GMR generate a negative output voltage relative to the input positive rail?
Yes, the SI3500-A-GMR supports negative output configurations by connecting SWO to VPOS and referencing FB to the negative output rail-enabling inverting buck-boost topologies. This capability is documented in Section 3.4 of the datasheet and used in telecom line card designs requiring -12 V or -5 V bias supplies from a +48 V input.
Does the SI3500-A-GMR require external components to implement undervoltage lockout (UVLO)?
No, UVLO is fully integrated: the SI3500-A-GMR turns on at ≤42 V (max) and turns off at ≥30 V (min), with built-in hysteresis. No external resistors or comparators are needed-the function is implemented internally using precision bandgap references and threshold detection circuitry tied to VPOS1/VPOS2.
How does the dual current limit in the hot-swap switch operate during startup of the SI3500-A-GMR?
At power-up, the SI3500-A-GMR enforces a 140 mA inrush limit while charging the switcher supply capacitor. Once VHSO drops within ~1.25 V of VNEG-indicating near-full capacitor charge-it transitions to the 400 mA operating limit and enables the switching regulator. This staged approach prevents input rail collapse and ensures reliable startup under capacitive loads.
Is the SI3500-A-GMR still recommended for new designs?
No-the official datasheet (Rev. 1.2) explicitly states "Not Recommended for New Designs." While fully functional and supported for existing production, designers should evaluate Silicon Labs' newer alternatives (e.g., Si3462/Si347x family) for PoE PSE applications requiring extended lifetime, enhanced efficiency, or updated feature sets.
SI3500-A-GMR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Skyworks Solutions Inc.
- Series:
- -
- Package/Case:
- 20-VQFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 42V
- Voltage - Input (Max):
- 57V
- Voltage - Output (Min/Fixed):
- 1.8V
- Voltage - Output (Max):
- 12V
- Current - Output:
- 400mA
- Frequency - Switching:
- 350kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 20-QFN (5x5)
SI3500-A-GMR FAQ
1.How can I place an order for SI3500-A-GMR through Aetrix?
Please submit a Request for Quotation (RFQ) for SI3500-A-GMR 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 SI3500-A-GMR reliable?
The price and inventory of SI3500-A-GMR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SI3500-A-GMR is usually 5 days.
3.What payment methods are accepted for SI3500-A-GMR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SI3500-A-GMR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for SI3500-A-GMR?
SI3500-A-GMR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your SI3500-A-GMR 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 SI3500-A-GMR?
For technical support, including SI3500-A-GMR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SI3500-A-GMR requirements.
6.How does Aetrix verify that SI3500-A-GMR is sourced from the original manufacturer or authorized distributors?
All SI3500-A-GMR 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 SI3500-A-GMR meets industry standards.
7.What is the process for return or replacement of SI3500-A-GMR?
All SI3500-A-GMR units undergo pre-shipment inspection (PSI). If there is an issue with SI3500-A-GMR, 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 SI3500-A-GMR part is unused and in its original packaging.
Return procedure for SI3500-A-GMR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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