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Analog Devices Inc./Maxim Integrated MAX5940CESA+T
- Part No.:
- MAX5940CESA+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Power Over Ethernet (PoE) Controllers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX5940CESA+T.pdf
- Description:
- IC POE CNTRL 1 CHANNEL 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,164
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Product details
Overview
The MAX5940CESA+T from Maxim Integrated is an IEEE 802.3af-compliant powered device (PD) interface controller for Power-over-Ethernet systems. It provides detection signature, classification signature, and integrated isolation MOSFET with programmable inrush current control. It features fixed UVLO threshold (35.4V turn-on), 90V absolute maximum rating, <10µA detection leakage, and operates from –40°C to +85°C in 8-pin SO package. It enables reliable PD handshaking in IP phones and security cameras.
For engineers reviewing the MAX5940CESA+T datasheet, MAX5940CESA+T pinout, MAX5940CESA+T application, or MAX5940CESA+T equivalent, this page delivers verified technical context, exact pin functions, real-world timing behavior under twisted-pair voltage drop, confirmed classification current ranges per IEEE Class 0–3, and validated alternatives for PoE front-end design.
Technical Context
The MAX5940CESA+T implements a three-phase PD state machine: detection (1.4V–10.1V input), classification (12.6V–20V), and power mode (VIN > 35.4V). Detection uses a 25.5kΩ signature resistor with <10µA offset current; classification sets current via RCLASS-to-VEE resistor (e.g., 255Ω for Class 3 = 26.45–29.55mA).
In power mode, it drives an internal N-channel MOSFET (RON = 0.8–1.5Ω at +85°C) using constant-current GATE charging (10µA typ), enabling controlled inrush via external CGATE. Its fixed UVLO has 4.2V hysteresis and 0.32ms deglitch time to tolerate cable IR drop and prevent false toggling during PSE transitions.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Detection Offset Current | <10µA - ensures PSE slope measurement (ΔV/ΔI) remains accurate during discovery phase |
| Classification Current Range | 0–41.4mA - supports IEEE 802.3af Classes 0–4 via external RCLASS resistor selection |
| UVLO Turn-On Threshold | 35.4V (fixed) - guarantees stable entry into power mode after PSE completes classification |
| MOSFET On-Resistance | 0.8–1.5Ω at +85°C - limits conduction loss and thermal rise under 500mA continuous load |
| PGOOD Assertion Threshold | VOUT within 1.2V of VEE & VGATE ≥5V above VEE - enables safe downstream DC-DC converter enable sequencing |
| Absolute Max Rating | 90V - accommodates worst-case PoE transients and long-cable voltage overshoots |
| Operating Temp Range | –40°C to +85°C - qualified for industrial and outdoor IP camera and wireless node deployments |
Pinout & Package
MAX5940CESA+T is housed in an 8-pin SOIC (SO) package with 150-mil body width, JEDEC MS-012AC compliant, and moisture sensitivity level (MSL) 1.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 7 | No Connection | Not internally bonded - must remain unconnected on PCB; no pull-up/down required |
| 2 | UVLO | Fixed-threshold undervoltage lockout input - tied to VEE for default 35.4V turn-on; not adjustable |
| 3 | RCLASS | Classification current setting node - connects to VEE via precision resistor (e.g., 255Ω for Class 3) |
| 4 | VEE | Negative supply rail - connects directly to -48V PoE return; source terminal of internal MOSFET |
| 5 | OUT | Power output - drain of internal N-MOSFET; supplies regulated load after detection/classification |
| 6 | PGOOD | Active-high open-drain power-good flag - referenced to OUT; signals valid VOUT for DC-DC enable |
| 8 | GND | Positive input reference - connects to PoE +48V side; forms VIN = GND − VEE differential input |
Key Features
| Feature | Design Value |
|---|---|
| Fully integrated 802.3af PD interface | Eliminates need for discrete detection resistors, classification circuitry, and external MOSFET drivers |
| Programmable classification signature | Supports all five IEEE classes via single external resistor - enables precise power budgeting by PSE |
| Integrated isolation MOSFET with inrush control | Reduces BOM count and layout area while limiting peak inrush to safe levels via CGATE capacitor |
| Wide UVLO hysteresis (4.2V) | Prevents oscillation during cable voltage sag - critical for stable operation over 100m Cat5e runs |
| PGOOD referenced to OUT | Enables direct interfacing with DC-DC converters requiring input-referenced enable signals |
Applications
| IP Phones | Security Cameras |
|---|---|
Use Scenario: Powered via PoE switch in enterprise VoIP deployment with centralized UPS backup. IC Role / Device Role / Timing Role: PD interface controller managing detection, classification, and power ramp-up before codec and DSP initialization. Use Value: Ensures IEEE-compliant handshake within 75ms classification window and sustains 500mA load without thermal derating. | Use Scenario: Outdoor PTZ camera with PoE+ fallback, operating in –20°C to +60°C ambient. IC Role / Device Role / Timing Role: Front-end PD controller providing robust detection under EMI-rich environments and glitch-free transition to power mode. Use Value: 90V abs max rating and 0.32ms UVLO deglitch time prevent false shutdown during lightning-induced transients on Ethernet cables. |
| Wireless Access Nodes | Computer Telephony |
Use Scenario: Dual-band 802.11ac AP mounted on ceiling, drawing up to 12.95W (Class 3). IC Role / Device Role / Timing Role: Classification engine setting precise 26.45–29.55mA signature to match PSE power allocation. Use Value: RCLASS resistor tolerance (±1%) and internal bias stability ensure PSE assigns correct Class 3 power budget every time. | Use Scenario: USB phone adapter with PoE input and local wall adapter fallback. IC Role / Device Role / Timing Role: Isolation controller enabling seamless switchover between PoE and wall supply without disrupting call audio path. Use Value: GATE terminal allows external logic to force MOSFET off - enabling priority-based power source arbitration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PD interface controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX5940BESA+T | Adjustable UVLO (external resistor-divider), dual PGOOD/PGOOD outputs | Required when system needs programmable turn-on threshold or active-low enable for DC-DC | Select MAX5940BESA+T only if UVLO adjustment or complementary PGOOD signaling is mandatory |
| LT4275IMS#PBF | IEEE 802.3at (PoE+) compliant, 30W support, integrated hot-swap FET, higher accuracy classification | Suitable for next-gen devices needing >12.95W or tighter Class 0–4 current tolerance | Choose LT4275IMS#PBF when upgrading to PoE+ or requiring ±1% classification current accuracy |
Compared with MAX5940CESA+T, MAX5940BESA+T adds design flexibility via UVLO programming but increases component count; LT4275IMS#PBF enables higher power and tighter compliance at cost of larger footprint and higher BOM cost - MAX5940CESA+T remains optimal for cost-sensitive, fixed-threshold 802.3af Class 0–3 designs.
Availability
MAX5940CESA+T is available at Aetrix Electronics and suitable for IP phones, security cameras, wireless access nodes, and computer telephony systems requiring stable component supply across extended temperature and PoE transient conditions.
Supply support for MAX5940CESA+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 high-performance analog and mixed-signal ICs for power, interface, and sensing applications.
The MAX5940 family targets IEEE 802.3af Power-over-Ethernet powered devices, delivering integrated detection, classification, and power-switching functionality in minimal footprint for space-constrained endpoints.
FAQ
What is the UVLO threshold of the MAX5940CESA+T and is it adjustable?
The MAX5940CESA+T has a fixed undervoltage lockout turn-on threshold of 35.4V and turn-off threshold of 30V, yielding 4.2V hysteresis. It is not adjustable - unlike MAX5940B/MAX5940D variants, the UVLO pin must be tied to VEE to activate the internal reference. This simplifies design for applications where standard 802.3af compliance without customization is sufficient. The MAX5940CESA+T maintains this fixed behavior across its full –40°C to +85°C operating range.
Does the MAX5940CESA+T support IEEE 802.3af Class 4 power classification?
Yes, the MAX5940CESA+T supports Class 4 classification with a nominal current of 36.6–41.4mA when a 178Ω resistor is connected from RCLASS to VEE. However, Class 4 is reserved for future use per IEEE 802.3af and not implemented in deployed PSEs. For production designs, MAX5940CESA+T is typically configured for Class 0–3 using 10kΩ, 732Ω, 392Ω, or 255Ω RCLASS resistors. The MAX5940CESA+T datasheet confirms Class 4 current range but notes it is not enabled in fielded infrastructure.
How does the MAX5940CESA+T limit inrush current during power-up?
The MAX5940CESA+T limits inrush current by charging the gate of its internal N-channel MOSFET with a 10µA constant-current source. The resulting dV/dt at the OUT pin is controlled by the MOSFET's intrinsic drain-to-gate capacitance and any external CGATE capacitor (recommended 100V ceramic) placed between GATE and OUT. This soft-start mechanism prevents peak currents exceeding 500mA and avoids tripping upstream PSE current limits. No external gate driver or timing components are required - the MAX5940CESA+T implements full inrush control autonomously.
What is the function of the PGOOD pin on the MAX5940CESA+T?
The PGOOD pin on the MAX5940CESA+T is an active-high, open-drain output referenced to OUT. It goes high-impedance only when both conditions are met: VOUT is within 1.2V of VEE (i.e., MOSFET fully enhanced), and VGATE is ≥5V above VEE. Otherwise, it pulls OUT low - enabling direct connection to the ON pin of downstream DC-DC converters like the MAX5014. A 100kΩ pullup to GND is recommended if the load requires active-high logic. This precise sequencing ensures power rails stabilize before enabling downstream regulation.
Can the MAX5940CESA+T operate without an external diode bridge?
Yes, the MAX5940CESA+T is explicitly designed to operate with or without an external diode bridge, as stated in its datasheet. Its differential input architecture (GND–VEE) and internal detection/classification circuitry function correctly regardless of bridge presence. When used without a bridge, polarity protection must be ensured externally - e.g., via TVS diodes or series MOSFETs - since reverse input voltage can damage the IC. The MAX5940CESA+T's specification of "works with or without external diode bridge" refers to functional compatibility, not inherent reverse-voltage tolerance.
MAX5940CESA+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:
- 36.6V ~ 67V
- Current - Supply:
- 400µA
- Operating Temperature:
- -40°C ~ 85°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX5940CESA+T FAQ
1.How can I place an order for MAX5940CESA+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX5940CESA+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 MAX5940CESA+T reliable?
The price and inventory of MAX5940CESA+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX5940CESA+T is usually 5 days.
3.What payment methods are accepted for MAX5940CESA+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX5940CESA+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX5940CESA+T?
MAX5940CESA+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX5940CESA+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 MAX5940CESA+T?
For technical support, including MAX5940CESA+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX5940CESA+T requirements.
6.How does Aetrix verify that MAX5940CESA+T is sourced from the original manufacturer or authorized distributors?
All MAX5940CESA+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 MAX5940CESA+T meets industry standards.
7.What is the process for return or replacement of MAX5940CESA+T?
All MAX5940CESA+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX5940CESA+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 MAX5940CESA+T part is unused and in its original packaging.
Return procedure for MAX5940CESA+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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