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Analog Devices Inc./Maxim Integrated MAX5945CAX+
- Part No.:
- MAX5945CAX+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Power Over Ethernet (PoE) Controllers
- Package:
- 36-BSOP (0.295", 7.50mm Width)
- Datasheet:
-
MAX5945CAX+.pdf
- Description:
- IC POE CNTRL 4 CHANNEL 36SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,137
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Product details
Overview
MAX5945CAX+ from Maxim Integrated is a quad-port IEEE 802.3af-compliant network power controller for Power-Sourcing Equipment (PSE), delivering PD discovery, classification, programmable current-limit (202–220 mV sense threshold), DC/AC load disconnect detection, and -48V port control in endpoint or midspan configurations. It operates across 0°C to +70°C and integrates I²C-compatible 3-wire serial interface with separate SDAIN/SDAOUT for optocoupler isolation.
For engineers reviewing the MAX5945CAX+ datasheet, MAX5945CAX+ pinout, MAX5945CAX+ application, or MAX5945CAX+ equivalent, this device supports real-time fault response via four independent SHD_ inputs, hardware RESET, watchdog-enabled graceful takeover, and full register-level configuration of startup timeout (50–70 ms), overcurrent timeout (50–70 ms), and AC disconnect threshold (300–350 µA).
Technical Context
The MAX5945CAX+ implements four independent state machines-one per Ethernet port-with auto/semi-auto/manual/shutdown operating modes. Each port features dual-stage detection (3.8–4.2 V and 9.0–9.6 V probe voltages), classification (16–20 V probe, 50–75 mA current thresholds), and foldback current limiting (VFLBK_ST = 30 V, VFLBK_END = 50 V).
Its analog front-end includes VEE undervoltage lockout (27–30 V), overvoltage protection (61–64 V), thermal shutdown at +150°C, and programmable gate-charging current. The I²C slave interface supports Fast Mode (400 kHz) with address selection via A0–A3 pins, enabling up to 16 devices on one bus.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| IEEE Compliance | Full IEEE 802.3af PSE compliance for PoE Class 0–4 PD detection and classification. |
| Port Count | Four independent -48V Ethernet ports with dedicated GATE_, SENSE_, OUT_, DET_, and SHD_ signals. |
| Current-Limit Threshold | 202–220 mV default VSENSE clamp voltage; programmable via I²C for precise class-based overcurrent protection. |
| DC Load Disconnect | 3–5 mV VSENSE threshold enables reliable detection of open-circuit or disconnected PDs. |
| AC Load Disconnect | 300–350 µA DET_ current threshold with OSC_IN monitoring for midspan AC disconnect functionality. |
| Operating Temperature | 0°C to +70°C commercial range; validated for stable operation in LAN switches and power injectors. |
| I²C Interface | 3-wire (SCL, SDAIN, SDAOUT), Fast Mode (400 kHz), 16-device addressing via A0–A3 pins. |
Pinout & Package
MAX5945CAX+ is housed in a 36-pin SSOP package (body size 12.8 mm × 7.5 mm, 0.635 mm pitch), rated for surface-mount assembly and compatible with standard reflow profiles.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| RESET | Hardware reset input | Pull low ≥300 µs to reset all registers and latch AUTO/MIDSPAN logic levels; internal 50 kΩ pullup to VDD. |
| MIDSPAN | Mode select input | Internal 50 kΩ pulldown defaults to endpoint PSE; drive high to enable midspan operation with cadence timing. |
| INT | Open-drain interrupt output | Active-low signal indicating fault (overcurrent, thermal, UVLO); sinks up to 15 mA at 0.4 V. |
| SCL / SDAIN / SDAOUT | I²C clock and bidirectional data lines | Separate input/output paths support optocoupler isolation; SDAOUT drives external optocoupler LED, SDAIN receives phototransistor output. |
| A0–A3 | I²C address inputs | Set lower 4 bits of 7-bit slave address (MSB = 010); internal 50 kΩ pullups to VDD. |
| DET1–DET4 | Detection/classification voltage outputs | Drive PD signature resistors during discovery (Phase 1: 3.8–4.2 V; Phase 2: 9.0–9.6 V; Class: 16–20 V). |
| SHD1–SHD4 | Independent port shutdown controls | Active-low inputs; internal 50 kΩ pullups to VDD; enable sub-millisecond hardware-initiated port disable. |
| SENSE1–SENSE4 | Current-sense negative inputs | Connect to MOSFET source; monitor VSENSE for current-limit (202–220 mV) and overcurrent (90–104 mV) thresholds. |
| GATE1–GATE4 | External FET gate drivers | Drive N-channel MOSFET gates; internal clamp limits VGATE to ≤11.4 V above VEE; supports fast pulldown (100 mA max). |
| OUT1–OUT4 | Drain voltage sense nodes | Low-leakage inputs (<2 µA) for power-good monitoring and open-circuit detection; used with 100 Ω–100 kΩ resistor to AGND. |
| VEE | Negative analog supply rail | Accepts -32 V to -60 V input; bypassed with 1 µF capacitor to AGND; referenced for all analog measurements. |
| AGND | Analog ground reference | High-side analog return; connects to +32 V to +60 V AGND rail; isolated from DGND for noise immunity. |
| DGND | Digital ground reference | Digital logic return; separate from AGND to prevent coupling between analog and digital domains. |
| VDD | +3.3 V digital supply | Supplies core logic and I²C interface; operates from 3.0 V to 5.5 V; UVLO at 1.7 V with 120 mV hysteresis. |
| AUTO | Mode enable input | Internal 50 kΩ pulldown defaults to shutdown mode; drive high to enter automatic operation post-reset. |
| OSC_IN | AC disconnect oscillator input | Accepts 100 Hz ±10%, 2 VP-P ±5%, +1.2 V offset sine wave; ports disable if peak < 1.8–2.1 V (OSC_FAIL threshold). |
Key Features
| Feature | Design Value |
|---|---|
| Pin- and function-compatible replacement | Direct drop-in alternative to LTC4259A in existing PSE designs-no PCB changes required. |
| Programmable current-limit foldback | Configurable VFLBK_ST (30 V) and VFLBK_END (50 V) enable adaptive current limiting during overvoltage events. |
| Hardware watchdog with graceful takeover | 164 ms decrement timer resets port control to safe state if firmware hangs-prevents uncontrolled power delivery. |
| Dual-path I²C interface | Isolated SDAIN/SDAOUT allows galvanic separation using optocouplers-critical for high-voltage PSE safety compliance. |
| Midspan cadence timing support | Integrated timing engine synchronizes detection/classification sequences across four ports for IEEE 802.3af midspan injector timing. |
| Class-overcurrent detection | Monitors PD current against class-specific thresholds (e.g., Class 3: 21.5–24.5 mA) to prevent system-level power budget violations. |
Applications
| LAN Switch Endpoint PSE | Midspan Power Injector |
|---|---|
Use Scenario: Integrated into 24- or 48-port enterprise Ethernet switches to deliver PoE to IP phones, wireless APs, and security cameras. IC Role / Device Role / Timing Role: Controls four ports simultaneously as part of multi-channel PSE ASIC subsystem; manages detection timing (≤320 ms), classification (≤40 ms), and startup (50–70 ms). Use Value: Enables compact, thermally efficient switch designs with per-port fault isolation and software-configurable power budgets. |
Use Scenario: Embedded in standalone PoE injectors that add power to existing data-only Ethernet links (e.g., legacy cabling infrastructure). IC Role / Device Role / Timing Role: Acts as primary PSE controller in midspan topology; uses MIDSPAN pin and cadence timing to meet IEEE 802.3af midspan detection window requirements (2.0–2.4 s delay). Use Value: Eliminates need for custom timing circuitry-hardware-enforced cadence ensures interoperability with all IEEE 802.3af-compliant PDs. |
| Industrial IoT Gateway | Smart Building Controller |
Use Scenario: Powers ruggedized sensors and edge controllers in factory automation networks where EMI and thermal stress are critical. IC Role / Device Role / Timing Role: Provides robust -48V port control with VEE UVLO (27–30 V), OV (61–64 V), and thermal shutdown (+150°C) for field reliability. Use Value: Ensures continuous operation under brownout conditions and prevents damage during power surges or ambient overheating. |
Use Scenario: Manages power to PoE-enabled lighting ballasts, HVAC actuators, and access control readers in centralized building management systems. IC Role / Device Role / Timing Role: Delivers coordinated, software-managed power sequencing across multiple zones using I²C register control and INT-driven event handling. Use Value: Supports dynamic power allocation and remote fault diagnostics via host microcontroller without additional supervisory ICs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar quad-port PSE controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LTC4259A | Pin- and function-compatible; identical 36-pin SSOP footprint and register map; same IEEE 802.3af feature set and timing behavior. | No midspan cadence timing support; requires external timing components for midspan mode. | Select LTC4259A only when replacing legacy designs without midspan requirements or when sourcing constraints favor Linear Technology inventory. |
| MAX5980ATJ+ | IEEE 802.3at (PoE+) compliant; supports up to 30 W per port; higher VEE range (-57 V to -50 V); 40-pin TQFN package. | Enables Class 4 and 5 PD support; not backward-compatible with MAX5945CAX+ layout or firmware due to different pinout and register structure. | Choose MAX5980ATJ+ when upgrading to PoE+ power levels or requiring enhanced thermal performance in space-constrained applications. |
Compared with LTC4259A, MAX5945CAX+ adds integrated midspan cadence timing and watchdog-controlled fail-safe operation; compared with MAX5980ATJ+, it offers cost-optimized 802.3af compliance in a smaller SSOP package but lacks PoE+ power capability and requires external current-sense resistors.
Availability
MAX5945CAX+ is available at Aetrix Electronics and suitable for LAN switches, midspan power injectors, and industrial IoT gateways requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.
Supply support for MAX5945CAX+ 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) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for communications, computing, and industrial applications.
The MAX5945 belongs to Maxim's Power-over-Ethernet (PoE) PSE controller product line, designed specifically for IEEE 802.3af-compliant power-sourcing equipment in both endpoint and midspan topologies.
FAQ
What is the operating temperature range for the MAX5945CAX+?
The MAX5945CAX+ is specified for the commercial temperature range of 0°C to +70°C. This rating applies to the C-grade version explicitly denoted by the 'C' in the part number and is validated across all electrical parameters including VEE UVLO (27–30 V), thermal shutdown (+150°C junction), and I²C timing (400 kHz Fast Mode). It is intended for use in controlled-environment networking equipment such as office LAN switches and indoor power injectors.
Does the MAX5945CAX+ support both endpoint and midspan PSE configurations?
Yes, the MAX5945CAX+ supports both configurations. Endpoint mode is the default (MIDSPAN pin internally pulled low); driving MIDSPAN high enables midspan operation with built-in cadence timing that meets IEEE 802.3af midspan detection window requirements (2.0–2.4 s delay). The device performs full PD detection, classification, and power delivery in either mode without external timing components.
How does the MAX5945CAX+ handle overcurrent faults across its four ports?
The MAX5945CAX+ uses per-port VSENSE monitoring with a default current-limit clamp voltage of 202–220 mV. Upon overcurrent, it initiates foldback limiting (VFLBK_ST = 30 V, VFLBK_END = 50 V), disables the affected port's GATE_, asserts INT, and logs the fault in status registers. Recovery is configurable via RSTR bits-options include immediate restart, 16×tFAULT, 32×tFAULT, or 64×tFAULT delays-enabling system-level power management decisions.
Can the MAX5945CAX+ be used with optocoupler-isolated I²C communication?
Yes, the MAX5945CAX+ is explicitly designed for optocoupler isolation with separate SDAIN and SDAOUT pins. SDAOUT drives the optocoupler LED side, while SDAIN receives the phototransistor output-eliminating ground-loop risks in high-voltage PSE systems. This architecture maintains full I²C Fast Mode (400 kHz) timing compliance and supports up to 16 devices via A0–A3 address inputs.
What is the purpose of the OSC_IN pin on the MAX5945CAX+?
The OSC_IN pin enables AC load disconnect detection in midspan applications. It accepts a 100 Hz ±10%, 2 VP-P ±5%, +1.2 V offset sine wave. If the positive peak falls below the OSC_FAIL threshold (1.8–2.1 V), ports with ACD_EN_ enabled shut down and remain disabled until OSC_IN is restored. When unused, OSC_IN must be left unconnected-no pullup/pulldown is required.
MAX5945CAX+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 36-BSOP (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Controller (PSE)
- Number of Channels:
- 4
- Power - Max:
- 15.4 W
- Internal Switch(s):
- No
- Auxiliary Sense:
- No
- Standards:
- 802.3af (PoE)
- Voltage - Supply:
- 32V ~ 60V
- Current - Supply:
- 4.2mA
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-SSOP
MAX5945CAX+ FAQ
1.How can I place an order for MAX5945CAX+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX5945CAX+ 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 MAX5945CAX+ reliable?
The price and inventory of MAX5945CAX+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX5945CAX+ is usually 5 days.
3.What payment methods are accepted for MAX5945CAX+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX5945CAX+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX5945CAX+?
MAX5945CAX+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX5945CAX+ 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 MAX5945CAX+?
For technical support, including MAX5945CAX+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX5945CAX+ requirements.
6.How does Aetrix verify that MAX5945CAX+ is sourced from the original manufacturer or authorized distributors?
All MAX5945CAX+ 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 MAX5945CAX+ meets industry standards.
7.What is the process for return or replacement of MAX5945CAX+?
All MAX5945CAX+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX5945CAX+, 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 MAX5945CAX+ part is unused and in its original packaging.
Return procedure for MAX5945CAX+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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