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Analog Devices Inc./Maxim Integrated MAX5940DESA+T
- Part No.:
- MAX5940DESA+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Power Over Ethernet (PoE) Controllers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX5940DESA+T.pdf
- Description:
- IC POE CNTRL 1 CHANNEL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,394
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Product details
Overview
MAX5940DESA+T from Maxim Integrated is an IEEE 802.3af-compliant powered device (PD) interface controller for Power-over-Ethernet systems, integrating detection signature, programmable classification, and a 90V-rated isolation N-channel MOSFET with 1.5Ω on-resistance at +85°C. It delivers active-high and active-low PGOOD outputs, adjustable UVLO threshold (37.4V to 39.9V turn-on), and supports inrush current control via external GATE-to-OUT capacitance. Used in IP phones and security cameras requiring robust PD handshaking.
For engineers reviewing the MAX5940DESA+T datasheet, MAX5940DESA+T pinout, MAX5940DESA+T application, or MAX5940DESA+T equivalent, key selection criteria include its 90V absolute maximum rating, dual PGOOD signaling, UVLO adjustability, leakage <10µA in detection mode, and SO-8 package compatibility with PoE midspan/splitter architectures.
Technical Context
The MAX5940DESA+T operates across three IEEE 802.3af-defined modes: detection (1.4–10.1V input, <10µA offset current), classification (12.6–20V, programmable Class 0–4 via RCLASS resistor), and power mode (VIN >37.4V, with 7.4V UVLO hysteresis). Its internal MOSFET gate is driven by a 10µA constant-current source, enabling controlled inrush limiting through external CGATE capacitance.
UVLO threshold is externally programmable via a 25.5kΩ ±1% resistor divider on the UVLO pin, setting turn-on between 12V and 67V; default operation uses VEE tie-down. The device asserts both PGOOD (open-drain, referenced to OUT) and PGOOD (open-drain, referenced to VEE) when VOUT is within 1.2V of VEE and VGATE exceeds 5V above VEE.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| IEEE Compliance | Fully compliant with IEEE 802.3af PD interface requirements including detection, classification, and power-mode sequencing. |
| Max Input Voltage | 90V absolute maximum rating - supports high-drop twisted-pair cabling and transient margin in PoE applications. |
| UVLO Threshold | Adjustable 37.4V to 39.9V turn-on (default); 30V turn-off with 7.4V hysteresis - accommodates cable IR drop without false shutdown. |
| MOSFET RON | 1.5Ω max at +85°C - limits conduction loss and thermal rise under 500mA continuous load current. |
| Detection Leakage | <10µA offset current - ensures reliable PSE detection signature recognition even with diode bridge or reverse polarity. |
| Classification Accuracy | Class 0–4 support with ±1% RCL tolerance; e.g., Class 3 (255Ω) yields 26.45–29.55mA classification current - meets IEEE 802.3af Class power allocation. |
| Operating Temp | -40°C to +85°C - qualified for industrial and outdoor IP camera, wireless node, and telephony deployments. |
Pinout & Package
MAX5940DESA+T is housed in an 8-pin SOIC (SO-8) package with 150-mil body width, JEDEC MS-012AC compliant, and rated for -40°C to +85°C operation. Pin 1 is UVLO; pin 7 is PGOOD (active-low); no internal connection at pins 1 and 7 for MAX5940A/C variants, but fully functional for MAX5940B/D.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (UVLO) | Undervoltage lockout programming input | Accepts external resistor-divider to set custom power-on threshold (12V–67V); tied to VEE for default 39V turn-on. |
| 2 (RCLASS) | Classification current setting node | Connects to VEE via precision resistor (e.g., 255Ω for Class 3) to define IEEE 802.3af power class. |
| 3 (GATE) | Internal MOSFET gate driver output | Sources 10µA constant current; external CGATE capacitor controls inrush slew rate and peak current. |
| 4 (VEE) | Negative supply input / MOSFET source | Connects to -48V PoE return; serves as reference for all internal circuitry and MOSFET source terminal. |
| 5 (OUT) | MOSFET drain output | Delivers regulated PoE power to downstream DC-DC converter; withstands up to 90V relative to VEE. |
| 6 (PGOOD) | Active-high power-good indicator | Open-drain output referenced to OUT; goes high-Z when VOUT ≥ VEE + 1.2V and VGATE ≥ VEE + 5V. |
| 7 (PGOOD) | Active-low power-good indicator | Open-drain output referenced to VEE; pulled to VEE under same valid-power conditions as PGOOD. |
| 8 (GND) | Positive input power terminal | Connects to PoE +48V (or diode bridge anode); forms VIN = GND – VEE differential input. |
Key Features
| Feature | Design Value |
|---|---|
| Dual PGOOD signaling | Simultaneous active-high (PGOOD, referenced to OUT) and active-low (PGOOD, referenced to VEE) outputs enable flexible DC-DC enable logic in diverse power architectures. |
| Programmable UVLO | External resistor-divider on UVLO pin sets turn-on threshold from 12V to 67V - allows optimization for long-cable runs or nonstandard PoE sources. |
| Inrush current control | GATE pin drives external CGATE capacitor to linearly ramp MOSFET VGS, limiting dI/dt and preventing PSE overcurrent shutdown during power-up. |
| 90V absolute rating | Supports full 802.3af voltage range plus margin for transients and worst-case cable drop - eliminates need for external clamping in most designs. |
| Low detection leakage | <10µA input offset current ensures reliable PSE detection even with protection diodes or reversed polarity inputs. |
Applications
| IP Phones | Security Cameras |
|---|---|
Use Scenario: Powered via IEEE 802.3af PoE switch in enterprise VoIP deployment with optional local wall adapter fallback. IC Role / Device Role: PD interface controller managing detection, classification, and isolation switching before enabling downstream DC-DC conversion. Use Value: Dual PGOOD outputs simplify OR-ing logic with wall adapter supply; 90V rating prevents latch-up during surge events on long cable runs. |
Use Scenario: Outdoor PTZ camera powered over PoE with extended temperature operation and transient immunity. IC Role / Device Role: Provides IEEE-compliant PD handshaking and robust 500mA power path with integrated MOSFET and UVLO hysteresis. Use Value: 7.4V UVLO hysteresis compensates for 2–3V IR drop across 100m CAT5e cable; -40°C to +85°C rating ensures reliability in uncontrolled environments. |
| Wireless Access Nodes | Computer Telephony |
Use Scenario: Ceiling-mounted Wi-Fi 6 access point drawing up to 12.95W (Class 3) from PoE infrastructure. IC Role / Device Role: Enables precise Class 3 classification (26.45–29.55mA) and smooth transition to power mode with glitch-free PGOOD assertion. Use Value: Programmable RCLASS resistor ensures accurate power budgeting; wide UVLO hysteresis avoids oscillation during intermittent cable contact. |
Use Scenario: USB-powered VoIP desk phone with PoE backup and hot-swap capability. IC Role / Device Role: Manages dual-supply arbitration (PoE vs. USB), detection signature integrity, and safe power sequencing to audio codec/USB PHY. Use Value: GATE pin allows external control of MOSFET for supply switchover; <10µA detection leakage preserves signature accuracy during USB-only operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PD interface controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX5940CESA+ | Fixed 35.4V UVLO threshold; single PGOOD (active-high only); same 90V rating and SO-8 package. | Lacks PGOOD and UVLO adjustability - suitable only where fixed threshold and single power-good signal suffice. | Select MAX5940CESA+ only if design does not require dual PGOOD signaling or custom UVLO tuning. |
| LT4275IMS#PBF | IEEE 802.3at (PoE+) compliant; 100V rating; includes auxiliary power detection and I2C monitoring; 16-pin QFN package. | Supports higher power (up to 25.5W) and advanced diagnostics - overqualified for basic 802.3af Class 3/4 needs. | Choose LT4275IMS#PBF only when upgrading to PoE+ or requiring telemetry; not a drop-in replacement due to pin count, package, and feature set. |
Compared with MAX5940CESA+, MAX5940DESA+T adds critical flexibility via dual PGOOD outputs and field-programmable UVLO, while LT4275IMS#PBF introduces PoE+ capability and digital interface at the cost of increased complexity and non-compatible packaging.
Availability
MAX5940DESA+T is available at Aetrix Electronics and suitable for IP phones, security cameras, wireless access nodes, and computer telephony systems requiring stable component supply, long-term PoE interoperability, and industrial temperature resilience.
Supply support for MAX5940DESA+T 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
Maxim Integrated (now part of Analog Devices) designs precision analog, mixed-signal, and power management ICs for demanding industrial, communications, and computing applications.
The MAX5940 family delivers integrated IEEE 802.3af PD interface functionality - engineered specifically for PoE-powered endpoints needing detection, classification, isolation, and robust power sequencing in compact SO-8 form factor.
FAQ
What is the absolute maximum voltage rating for MAX5940DESA+T?
The MAX5940DESA+T has a 90V absolute maximum rating on GND and VEE pins, enabling reliable operation under IEEE 802.3af's full voltage range plus margin for cable drop and transients. This rating is confirmed in the Absolute Maximum Ratings table and distinguishes it from the 80V-rated MAX5940A/B variants. Exceeding 90V risks permanent damage per Maxim's datasheet specification.
How does MAX5940DESA+T support dual PGOOD signaling?
MAX5940DESA+T provides both PGOOD (pin 6, active-high, referenced to OUT) and PGOOD (pin 7, active-low, referenced to VEE). Both assert simultaneously when VOUT is within 1.2V of VEE and VGATE exceeds 5V above VEE. This dual-output architecture simplifies interfacing with diverse DC-DC converters that accept either polarity enable signal - a key differentiator from MAX5940A/C variants which offer only PGOOD.
Can MAX5940DESA+T be used without an external diode bridge?
Yes, MAX5940DESA+T is explicitly designed to operate with or without an external diode bridge, as stated in the General Description and Detailed Description sections. Its internal architecture handles polarity reversal and maintains detection signature integrity regardless of bridge presence - making it suitable for both alternative-A (spare-pair) and alternative-B (signal-pair) PoE implementations.
What is the purpose of the UVLO pin on MAX5940DESA+T?
The UVLO pin on MAX5940DESA+T enables external programming of the undervoltage lockout threshold using a 25.5kΩ ±1% resistor divider between GND and VEE. When left unconnected or tied to VEE, it defaults to 39V turn-on. This programmability allows system designers to compensate for voltage drop across long Ethernet cables or adapt to nonstandard PoE sources - a feature exclusive to MAX5940B/D variants like MAX5940DESA+T.
How is inrush current controlled in MAX5940DESA+T?
MAX5940DESA+T controls inrush current by charging the internal MOSFET's gate via a 10µA constant-current source applied to the GATE pin. An external capacitor (CGATE) connected between GATE and OUT creates a linear VGS ramp, slowing the MOSFET's turn-on and limiting dI/dt. This method avoids PSE overcurrent shutdown during power-up - a core function detailed in the Inrush Current Limit section of the datasheet.
MAX5940DESA+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- Controller (PD)
- Number of Channels:
- 1
- Power - Max:
- 12.95 W
- Internal Switch(s):
- Yes
- Auxiliary Sense:
- No
- Standards:
- 802.3af (PoE)
- Voltage - Supply:
- 39.9V ~ 67V
- Current - Supply:
- 400µA
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX5940DESA+T FAQ
1.How can I place an order for MAX5940DESA+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX5940DESA+T 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 MAX5940DESA+T reliable?
The price and inventory of MAX5940DESA+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX5940DESA+T is usually 5 days.
3.What payment methods are accepted for MAX5940DESA+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX5940DESA+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX5940DESA+T?
MAX5940DESA+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX5940DESA+T 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 MAX5940DESA+T?
For technical support, including MAX5940DESA+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX5940DESA+T requirements.
6.How does Aetrix verify that MAX5940DESA+T is sourced from the original manufacturer or authorized distributors?
All MAX5940DESA+T 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 MAX5940DESA+T meets industry standards.
7.What is the process for return or replacement of MAX5940DESA+T?
All MAX5940DESA+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX5940DESA+T, 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 MAX5940DESA+T part is unused and in its original packaging.
Return procedure for MAX5940DESA+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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