SI3452

S i 3 4 5 2/53 Q UAD H I G H - VO L TAG E P OR T C ONTROLLER F OR P O E A ND POE+ PSES Features  Each Si3452/3 high-voltage port  controller supports four PSE power interfaces  Programmable current limits for PoE (15.4 W), PoE+ (30 W), and proprietary systems (up to 40 W) per port  I2C interface requires no external MCU for easy, low-cost management of 4 to 48 ports by the host system  Unique mixed-signal IC high-voltage component integration simplifies design, lowers power dissipation, minimizes external BOM, and  reduces PCB footprint Internal low-RON power FETs with current-sense circuitry Integrated transient voltage surge suppressors DC disconnect (Si3453) or proprietary dV/dt disconnect (Si3452) sensing methods Programmable architecture supports IEEE 802.3af (PoE) and IEEE 802.3at (PoE+) PSEs Programmable current limits for PoE (350 mA) and PoE+ (600 mA), and custom limits to 850 mA Per-port current and voltage monitoring for sophisticated power management and control Power policing mode Robust multi-point detection Supports 1-Event and 2-Event classification algorithms Comprehensive, robust, faultprotection circuitry Supply under-voltage lockout (UVLO) Output current limit and shortcircuit protection Foldback current limiting Dual-threshold thermal overload protection Fault source reporting for intelligent port management  Extended commercial (–10 to 85 °C) and industrial (–40 to 85 °C) operating temperatures  Compact, 6×6 mm2, 40-pin QFN RoHS-compliant package Ordering Information: See page 30. Pin Assignments 40-pin QFN VOUT1 VOUT2 32 GND12 39 38 37 36 35 34 40 33 31 VEE2 30 29 28 27 DET1 DET2 RST AD1 AD0 INT VEE1 VEE VREF AIN AOUT AGND RBIAS AGND NC VEE4 1 2 3 4 5 6 7 8 9 10 19 11 12 13 14 15 16 17 18 20 VDD DGND AD0 AD1 AD2 AD2 AD3 RST VEE3 AD3 Si3452 (Top View) 26 25 24 23 22 21 VDD VOUT4 GND34  Power over Ethernet Endpoint switches and Midspans for IEEE Std 802.3af and 802.3at  Supports high power PDs, such as: Pan/Tilt/Zoom security cameras 802.11n WAPs Multi-band, multi-radio WAPs  Security and RFID systems   Industrial automation systems Networked audio  IP Phone Systems and iPBXs  Metropolitan area networked WAPs, cameras, and sensors  WiMAX ASN/BTS and CPE/ODU systems See "9. Pin Descriptions" on page 27. Rev. 1.0 4/10 Copyright © 2010 by Silicon Laboratories VOUT3 SDA DET4 DET3 SCL NC NC Applications Si3452/3 S i3452/3 Description When connected directly to the host system or configured in Auto mode, each Si3452/3 high-voltage port controller provides all of the critical circuitry and sophisticated power measurement functionality for the high-voltage interfaces of four complete PSE ports. The Si3452/3 fully integrates robust, low-RON (0.3  typical) power MOSFET switches, low-power dissipation current sensing circuitry, and transient voltage surge suppression devices. The on-chip current sense circuitry and power MOSFETs provide programmable scaling of current limits to match either PoE (350 mA, 15.4 W), PoE+ (600 mA, 30 W), and extended (800 mA, 40 W) power requirements on a perport basis. Designed for use in Endpoint PSE (e.g., Ethernet switches) or Midspan PSE (e.g., inline power injectors) applications, each Si3452/3 also performs the IEEE-required powered device (PD) detection, classification, and disconnect functionality. The flexible architecture enables powered device disconnect detection using either dc disconnect (Si3453) or Silicon Laboratories' proprietary dV/dt disconnect (Si3452) sensing algorithm. dV/dt disconnect is an alternative to dc disconnect that requires no additional BOM components, does not dissipate extra device power, and fully interoperates with all powered devices. Also provided are multi-point detection algorithms and per-port current and voltage monitoring. Intelligent protection circuitry includes power supply under-voltage lockout (UVLO), port output current limiting and short-circuit protection, thermal overload sensing and port shutdown, and transient voltage surge-suppressors capable of protecting the Si3452/3 from a variety of harsh surge events seen on the RJ-45 interface. To maximize system design flexibility and minimize cost, each Si3452/3 connects directly to a system host controller through an I2C serial interface, eliminating the need for an external MCU. The Si3452/3 can be set to one of 12 unique addresses, allowing control of up to 48 ports on a single I2C bus. Functional Block Diagram GND34 GND12 RST AD2 AD3 AD1 AD0 RST AD3 AD2 AD1 AD0 MCU Core & PSE FSM LV SPI HV SPI & Port Control Channel Mode & Limit Control PER PORT ANALOG Detection & Classification DC or dV/dt Disconnect Gate Control, Current Limit & Foldback Thermal Prot. DET4 DET3 DET2 DET1 256 Byte SRAM 8 kByte EPROM PLL POR PGA Temp Sensor MEAS. MUX WDT 10b ADC AMUX VOUT4 VOUT3 VOUT2 I2C Voltage Regulator & Monitor VREF & Central Bias Current Sense VOUT1 VEE1 VEE2 VEE3 AGND RBIAS DGND VREF 2 AGND AOUT VDD Rev. 1.0 VEE4 VDD INT SDA VEE SCL AIN S i3452/3 TABLE O F C ONTENTS Section Page 1. Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2. PSE System-Level Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3. PSE Application Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4. Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1. Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.2. Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.3. Port Turn-On and Power FETs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.4. Disconnect Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.5. Transient Voltage Surge Suppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.6. Temperature Sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.7. Port Measurement and Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 4.8. SMBus/I2C Interface Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5. Register Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 5.1. Interrupt (Registers 0x00–0x01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.2. Port Event (Registers 0x02–0x05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 5.3. Port Status (Registers 0x06–0x09) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.4. Port Configuration (Registers 0x0A–0x11) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.5. Command and Return Registers (Registers 0x12–0x1C) . . . . . . . . . . . . . . . . . . . . .19 5.6. Device Status Register (0x1D) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 6. Operational Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.1. Port Turn On . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 6.2. Changing the Interrupt Mask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 6.3. Port Voltage and Current Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 7. PCB Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 8. Firmware Release Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 8.1. Initialization Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 8.2. Current Limiting in 2x Power Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 8.3. I2C Address ACK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 8.4. Reading or Writing Unused Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 9. Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 10. Package Outline: 40-Pin QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 11. Recommended PCB Footprint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 12. Ordering Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 12.1. Evaluation Kits and Reference Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 13. Device Marking Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Document Change List . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 Contact Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 Rev. 1.0 3 S i3452/3 1. Electrical Specifications Unless noted otherwise, specifications apply over the operating temperature range with VDD = +3.3 V and VEE = –48 V relative to GND. VDD pins should be electrically shorted. AGND pins, DGND, GND12, and GND34 should be electrically shorted ("GND"). VEE, VEE1, VEE2, VEE3, and VEE4 should be electrically shorted ("VEE"). VPort for any port is measured from GND to the respective VOUTn. Table 1. Absolute Maximum Ratings1 Type Supply voltages Description VEE to GND VDD to GND VDD1 to VDD2 Any VEE to any other VEE Any GND to any other GND Voltage on digital pins Voltage on analog pins SDA, SCL, ADn, RST, INT VREF, AIN, AOUT, RBIAS, OSC VOUTn, DETn DETn peak currents during surge events2 Maximum continuous power dissipation3 Maximum junction temperature Ambient storage temperature Lead temperature (soldering, 10 seconds maximum) Rating –62 to +0.3 –0.3 to +3.6 –0.3 to +0.3 –0.3 to +0.3 –0.3 to +0.3 (GND – 0.3) to (VDD + 0.3) (GND – 0.3) to (VDD + 0.3) (VEE – 0.3) to (GND + 0.3) ±5 1.2 125 –55 to 150 260 Unit V V V V V V V V A W °C °C °C Notes: 1. Functional operation should be restricted to those conditions specified in Table 2. Functional operation or specification compliance is not implied at these conditions. Stresses beyond those listed in absolute maximum ratings may cause permanent damage to the device. 2. See IEEE Std 802.3-2005, clause 33.4, for a description of surge events. 3. If all ports are on with 600 mA load, the power dissipation is 25 °C, –35 V over the full temperature range. 2. 1x mode current limit is enforced during the 60 ms TSTART time. 3. In auto mode, class policing is automatically enabled. In manual mode, ICUT must be programmed manually. See "5.4. Port Configuration (Registers 0x0A–0x11)" on page 18 for more information. 4. 600 mA is consistent with the IEEE 802.3at draft standard. ICUT is user-programmable in 3.2 mA increments to over 800 mA for non-standard applications. 5. For 2x mode and extreme overload or short-circuit events, TOVLD will dynamically decrease to prevent excessive FET heating. This is consistent with the 802.3at draft. Table 7. DC- and dV/dt Disconnect Specifications Description Load current to prevent disconnect Load current to guarantee disconnect Disconnect delay Symbol ION IOFF dc disconnect dV/dt disconnect TDCDV_DLY Time from IOFF load current to port turn off Test Conditions Min 10 — — 300 Typ — — — — Max — 5 2 400 Unit mA mA mA ms Rev. 1.0 7 S i3452/3 Table 8. Port Measurement and Monitoring Specifications Description Port current measurement offset Port current measurement tolerance Symbol IOFFSET %TOL Test Conditions 20 mA ≤ IPORT ≤ ICUT. For final IPORT reading, add offset to% of reading tolerance. Min –5 –4 Typ — — Max 5 4 Unit mA % Table 9. SMBus (I2C) Electrical Specifications VDD = 3.0 to 3.6 V Description Input low voltage Input high voltage Output low voltage Input leakage current Symbol VIL VIH VOL IL Test Conditions SCL, SDA pins Tj < –10 °C SCL, SDA pins over full temp range SCL, SDA pins SCL, SDA pins, driving ≤ 8.5 mA SCL, SDA pins Min — Typ — Max 0.85 0.8 Unit V 2.2 — — — — — — 0.6 40 V V µA Table 10. Address Pin Electrical Specifications* VDD = 3.0 to 3.6 V Description Input low voltage Input high voltage Input leakage current Symbol VIL VIH IH, IL Test Conditions AD0, AD1, AD2, AD3 pins AD0, AD1, AD2, AD3 pins AD0, AD1, AD2, AD3 pins Min — 0.7 x VDD –10 Typ — — — Max 0.8 — 10 Unit V V µA *Note: At power-up, these pins are logic inputs. A 10 k pull up or pull down resistor is used for address selection. After address recognition, the pins are used for internal communications. 8 Rev. 1.0 S i3452/3 Table 11. SMBus (I2C) Timing Specifications (see Figure 1) VDD = 3.0 to 3.6 V Description Serial bus clock frequency SCL high time SCL low time SCL, SDA rise time SCL, SDA fall time Bus free time Start hold time Start setup time Stop setup time Data hold time Data setup time Time from hardware or software reset until start of I2C traffic Delay from event to INT pin low or from clear-on-read to INT pin high Symbol fSCL tSKH tSKL tR_SCL tF_SCL tBUF tSTH tSTS tSPS tDH tDS tRESET Test Conditions Min 0 600 1.3 20 20 Typ — — — — — — — — — — — — Max 400 — — 300 150 — — — — — — 100 Unit kHz ns μs ns ns μs ns ns ns ns ns ms Between START and STOP conditions. Between START and first low SCL. Between SCL high and START condition. Between SCL high and STOP condition. 1.3 600 600 600 200 200 Reset to start condition — tINT — — 5 ms Notes: 1. Not production tested (guaranteed by design). 2. All timing references measured at VIL and VIH. 3. The Si3452/3 will stretch (pull down on) SCK during the ACK time period if required. The maximum SCL stretching is 10 µsec; so, SCL only needs to be bidirectional for I2C bus speeds over 50 kHz. fSC L t R_SCL t F_SC L t SKH tSKL S CL tBU F tST H t DS tD H tSPS SDA D7 D6 D5 D4 D3 D0 Start Bit Stop Bit Figure 1. I C Timing Diagram Rev. 1.0 9 2 S i3452/3 Table 12. Interrupt (INT) Specifications Description Output low voltage Symbol VOL Test Conditions INT pin driving ≤ 8.5 mA Min — Typ — Max 0.6 Unit V Table 13. Input Voltage Reference Specifications Description Nominal VREF input Reference tolerance VREF loading Input current Symbol Test Conditions Min — — –10 Typ 1.1 — — Max — 1 +10 Unit V % µA 10 Rev. 1.0 S i3452/3 2. PSE System-Level Diagrams SCL Host Controller I2C INT Si8405 Digital Isolator RST I2C PSE State Machines and Measurement Subsystem OTP RAM Mixed Signal Resources Si3452/3 Figure 2. 4-Port System with Direct Host Connection 3. PSE Application Diagrams +3.3 V Host / Switch 4x10 k Tie high or low to select address AD0 AD1 AD2 AD3 Si8405 Bidirectional Isolator AD0 AD1 AD2 AD3 VDD AGND DGND GND12/34 SCL SDA INT RST 1.1 V (e.g. TLV431) VREF DET4 DET3 DET2 To Magnetics DET1 Si3452/3 RBIAS 44.2 k 1% VEE VEE[4:1] VOUT4 VOUT3 VOUT2 VOUT1 –54 V PORT1 PORT2 PORT3 PORT4 Figure 3. 4-Port Application Diagram Using DC– or dV/dt Disconnect and I2C Host Interface Rev. 1.0 4 Ports of PoE+ 11 High Voltage Interface SDA S i3452/3 4. Functional Description Integrating four independent, high-voltage PSE port interfaces, the Si3452/3 high-voltage port controller enables an extremely flexible solution for virtually any PoE or PoE+ PSE application. The Si3452/3 provides all of the highvoltage Power over Ethernet PSE functions. Each port of the Si3452/3 integrates all high-voltage PSE controller functions needed for a quad-port PoE design, including the power MOSFET, efficient current-sensing circuitry, transient voltage surge suppressor, and multiple detect and disconnect circuits. When the dc disconnect or dV/dt disconnect sensing methods are selected, the external BOM is typically only a single filter capacitor on each high-voltage port. When a PD device has been properly detected and classified, the port is powered by a –54 V nominal supply with continuous monitoring of voltage and current for feedback to the host system. In addition to the required IEEE features, the Si3452/3 includes many additional features:  Per port current / voltage monitoring and measurement  Support for 1-Event and 2-Event classification algorithms  Start up in shutdown or auto mode  Alternative A (typically used for endpoint systems) or Alternative B (typically used for midspan systems) detection timing 4.1. Detection The Si3452/3 has per-port signature detection that satisfies the IEEE Std 802.3™-2005 specifications. However, by utilizing a 3-point voltage-forced detection method, the Si3452/3 yields robust recognition of valid and invalid powered device (PD) signatures, properly identifying signatures often mischaracterized by other detection techniques. 3 point detection 2 event classification Port powerup Figure 4. PSE Sequencing (3-Point Detection followed by 2-Event Classification and Powerup) Vport Relative to GND The detection circuitry performs the function of setting the output voltage on any channel to the proper value for detection or classification and then measuring the resulting line current. A typical detection cycle consists of applying 4 V, then 8 V, and back to 4 V, with the current limit set to 3 mA. The current is measured after an appropriate settling time. For a valid PD, the detection signature must be compliant with the detection voltage both increasing and decreasing. 12 Rev. 1.0 S i3452/3 4.2. Classification Following a successful PD detection, the classification phase will be automatically initiated in all operational modes. During this phase, a single measurement will be made at 18 V to determine how much power the PD device will draw under maximum loads per the IEEE 802.3af and 802.3at standards. The current limit during this test mode is 60 mA nominal. The Si3452/3 supports 1-Event and 2-Event classification. When operating in PoE (15.4 W) mode results in 2-Event classification probes. The 1-Event classification is compliant to IEEE standard 802.3-2005. 2-Event classification is compliant to draft IEEE P802.3at. 4.3. Port Turn-On and Power FETs The FET is turned on with a gate drive that results in a very low-noise turn-on waveform with a slew rate of less than 1 V/µsec (See Figure 5). The power FET switch on each port has been sized to have a typical ON resistance of approximately 0.3 . The shunt resistor for current measurement has also been set to 0.1 . Including interconnection and process variation, the total resistance to VEE for a port that is on is 0.6  (max). This limits the maximum power dissipation per channel to < 250 mW when the operating current is 600 mA, the maximum current allowed by the IEEE 802.3at PoE+ standard. The FET has a programmable operating current limit. Each channel can be set to support output currents of 400 mA or 800 mA minimum. In addition to the normal current limit, there is a short circuit current shutdown approximately 25% greater than the nominal current limit. If there is a transient current surge where the current ramps up faster than the programmed current limit can respond, the gate drive voltage is clamped immediately to VEE. The clamp is enabled for at least 10 µs, which allows the normal current circuitry to respond. Another important protection feature is foldback current limiting. When VOUT is near VEE, the current limit is at maximum. As the VDS of the driver switch increases (and VOUT is closer to ground), the current limit goes to its lowest level. The amount of the foldback current is scaled proportionally with the programmed current limit. Figure 5. Turn-On Waveform—Vport Relative to GND Rev. 1.0 13 S i3452/3 4.4. Disconnect Detection 4.4.1. dV/dt Disconnect (Si3452) The dV/dt disconnect function can be used to detect a disconnected device without using dc disconnect or ac disconnect. In dV/dt disconnect mode, the FET current limit is switched to 7.5 mA. If the voltage across the FET increases, a load is assumed to be present, and the FET current limit is automatically switched back to its pre-selected value. If, after 350 ms, the FET voltage has not increased, there is no load present, and the FET is turned off. In addition to operating in a manner functionally distinct from DC disconnect, dV/dt disconnect requires no additional external components and fully interoperates with all powered device DC Maintain Power Signatures. For more information, see "AN399: dV/dt Disconnect and the IEEE 802.3 PoE Standard". 4.4.2. DC Disconnect (Si3453) The port current is continuously monitored by the Si3452/3. The Si3452/3 can dynamically change the measurement scale to achieve accuracy over a wide range of currents. As defined in the IEEE 802.3 PoE standard, the PSE should disconnect if the port current is less than a nominal 7.5 mA for more than 350 ms. 4.5. Transient Voltage Surge Suppression The Si3452/3 features robust on-chip surge protectors on each port; this is an industry first. This unique protection circuitry acts as an active device that can withstand lightning-induced transients as well as large ESD transient events. When the port voltage exceeds its protection limit and the current reaches a triggering threshold, current is shunted from the port to the ground pins. Internal circuitry is provided to protect the line outputs from externally-coupled fault currents. These are transient currents of up to 5 A peak. The operation of the protection circuits depends on the operating mode of the channel switch and the direction of the fault current. The clamping operation is performed on the detect pin. The switch itself will also be protected by the current limit. If the transient lasts long enough to heat up the die, then the temperature sense circuit will shut off the switch, and all the fault current will flow through the clamp diode. 4.6. Temperature Sense A temperature sense signal is used in conjunction with the current limit status signals from the gate drive blocks. Any channel that is generating excess heat is assumed to be operating in current limit mode, with both high voltage drop and high current. If the port is in PoE mode, an overload will generally not result in thermal shutdown before the 60 ms ICUT period. If the port is in PoE+ mode, an overload may cause the port to shut down prior to the 60 ms ICUT period. In either case, the event is reported as ICUT. The faster shutdown in PoE+ mode is consistent with and specifically allowed by the 802.3at draft and provides much more robust overload protection than is possible with external FETs. In addition, there is a thermal shutdown if the package temperature exceeds 120 °C. If this threshold is reached, all output drivers are turned off and detection modes are disabled. This secondary threshold limit guards against the possibility that the overheating is not caused by a driver operating in current limit. 4.7. Port Measurement and Monitoring VEE monitoring in conjunction with port current monitoring allows measurement of port power. Port power monitoring, dynamic power allocation via LLDP*, and port power policing allow efficient power supply sizing. The Si3452/3 is factory-calibrated and temperature-compensated for the following measurements:  Port current measurement. These measurements are auto-ranged and scaled to a 16 bit number at 100 µA per bit. Port current accuracy is ±4% ± 2 mA.  VEE is measured with a scale of 64 V. The measurement is reported as a 16-bit number scaled at 1 mV per bit. VEE measurement accuracy is ±4% over the valid VEE range. *Note: LLDP = Link Layer Discovery Protocol. Refer to IEEE 802.3at (draft) and IEEE 802.1AB for more information. 14 Rev. 1.0 S i3452/3 4.8. SMBus/I2C Interface Description The I2C interface is a two-wire, bidirectional serial bus. The I2C is compliant with the System Management Bus Specification (SMBus), version 1.1 and compatible with the I2C serial bus. Reads and writes to the interface by the system controller are byte-oriented with the I2C interface autonomously controlling the serial transfer of the data. A method of extending the clock-low duration is available to accommodate devices with different speed capabilities on the same bus. The I2C provides control of SDA (serial data), SCL (serial clock) generation and synchronization, arbitration logic, and START/STOP control and generation. A typical I2C transaction consists of a START condition followed by an address byte (Bits7–1: 7-bit slave address; Bit0: R/W direction bit), one or more bytes of data, and a STOP condition. Each byte that is received (by a master or slave) must be acknowledged (ACK) with a low SDA during a high SCL (see Figure 6). If the receiving device does not ACK, the transmitting device will read a NACK (not acknowledge), which is a high SDA during a high SCL. The direction bit (R/W) occupies the least-significant bit position of the address byte. The direction bit is set to logic 1 to indicate a "READ" operation and cleared to logic 0 to indicate a "WRITE" operation. All transactions are initiated by a master, with one or more addressed slave devices as the target. The master generates the START condition and then transmits the slave address and direction bit. If the transaction is a WRITE operation from the master to the slave, the master transmits the data one byte at a time, waiting for an ACK from the slave at the end of each byte. For READ operations, the slave transmits the data waiting for an ACK from the master at the end of each byte. At the end of the data transfer, the master generates a STOP condition to terminate the transaction and free the bus. Figure 6 illustrates a typical SMBus/I2C transaction. Silicon Laboratories recommends the use of bidirectional digital isolators, such as the Si840x, to isolate the I2C communications interface between the Si3452/3 high-voltage port controllers and the system host controller. Slave Addr ess Register Address Write Data 0 ST ART 1 0 A3 A2 A1 A0 R/W# ACK by IC A7 A6 A5 A4 A3 A2 A1 A0 ACK by IC D7 D6 D5 D4 D3 D2 D1 D0 ACK by IC ST OP by Master F ixed IC Address Pin Set IC Address Write Sequence Setup Register Addr ess Slave Address Register Address Slave Address Transfer Data to Setup Address Register Data 0 START 1 0 A3 A2 A1 A0 R/W# ACK by IC A7 A6 A5 A4 A3 A2 A1 A0 0 1 0 A3 A2 A1 A0 R/W# ACK by IC D7 D6 D5 D4 D3 D2 D1 D0 Not ACK by Master STOP by Master ACK by IC START Fixed IC Addr ess Pin Set IC Addr ess Read Sequence F ixed IC Address Pin Set IC Addr ess Figure 6. Typical I2C Bus Transactions The Si3452 does not support the alert response address (ARA) protocol. Polling is used to determine which controller is interrupting in an interrupt-driven system. Rev. 1.0 15 S i3452/3 4.8.1. Address Pins Table 14. Address Pin Assignment Pin # Pin Name 21 24 25 26 27 28 34 36 AD3 AD3 AD2 AD2 AD1 AD0 AD0 AD1 Pins with the same name must be externally connected and then tied high or low via a weak (10 k) pull up or pull down to establish the device address at power up. The Si3452/3 powers up in either Auto mode or Shutdown mode depending on the ordering part number. For more information, see "12. Ordering Guide" on page 33. 4.8.2. Address Format The address byte of the I2C communication protocol has the following format: Table 15. I2C Address Byte Protocol Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 0 1 0 AD3 AD2 AD1 AD0 R/W AD3, AD2, AD1, and AD0 are the pin-selected address bits (pull up = 1; pull down = 0). For the R/W bit, see Figure 6. The device will also respond to the global address, 0x30. The Si3452 does not support bus arbitration; so, a global read command will generally give an invalid result. Global writes can be useful for initialization as well as for shutting down low-priority ports. Table 16 lists the valid device addresses: Table 16. Address Selection AD3 AD2 AD1 AD0 Address Valid 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0x20 0x21 — — 0x24 0x25 — — 0x28 0x29 0x2A 0x2B 0x2C 0x2D 0x2E 0x2F Y Y N N Y Y N N Y Y Y Y Y Y Y Y 16 Rev. 1.0 S i3452/3 5. Register Interface The registers types are described in the following sections. 5.1. Interrupt (Registers 0x00–0x01) An interrupt (INT pin low) is generated if any bit of the Interrupt register (register 0x00) is true. The Interrupt register contains the information about which port is generating the interrupt or if the interrupt is due to a global event. The port interrupt is generated by the port event register masked by the interrupt mask register. Port event = (tSTART Event AND tSTART mask) OR (tICUT Event AND tICUT mask) OR (Rgood_CLS_event AND Rgood_CLS_mask) OR (DET_COMPL_EVENT AND DET_COMPL_MASK) OR (PwrGood_change AND Pwrgood_change_MASK) OR (Penable_event AND Penable_mask) The device event bit of the interrupt register is set if there is a change in the VEE or temperature status in register 0x1D. Reading 0x1D clears the event. 5.2. Port Event (Registers 0x02–0x05) This register contains bits that become true if the event has occurred. The registers are Clear On Read (COR) so that reading these registers will clear the INT pin if the INT pin is being held low due to a port event. “tSTART“ is an event bit indicating an overload occurred for all but 5 ms of the initial 60 ms start up time. “tICUT“ is an event bit indicating that an overload condition has existed for greater than 60 ms after the first 60 ms. tICUT has a 16:1 up/down counter so that, if the overload is present at less than a 6.66% cycle, the port will not shut down. Overload is defined as I>ICUT or port voltage not within 2 V of VEE. The port is turned off on this event. A tICUT event is also generated if the port is shutdown due to an overload or due to the protection clamp turning on. If the port is set to auto mode, it will attempt to re-power after >750 ms if there is a good detection signature. “Rgood CLS“ indicates classification has been completed. Classification is only attempted after an Rgood; so, if this bit is set, it indicates that detection gave an Rgood and classification is complete. “DET compl“ indicates the completion of a detection cycle. Normally, this bit will be masked. The DET complete bit is used for legacy detection via modified link pulses. If the link pulse is returned indicating a PD is present, then, normally, a detection is done, and the port is powered only if the result is not a short. In some cases, it may be desirable to deny power to a port where an overload has been detected until the port is unplugged. In this case, the Ropen result will be used to indicate the port has been unplugged and detection and classification can resume. “Disconnect event“ indicates a disconnect has occurred. DC power was removed due to the dV/dt or DC disconnect. Overload conditions or loss of VEE turns off ports but does not generate a disconnect event. “Pgood“ indicates the port has been turned on and did not shut down during the Tstart time. “Penable“ indicates a port has been turned on. 5.3. Port Status (Registers 0x06–0x09) These registers specify the port status. They are read-only registers. “Pwr good“ indicates that the port has been turned on and the port voltage is within 2 V of VEE. “Pwr Enable“ indicates the port has been turned on. The three class status bits indicate the last classification result for that port. If a classification has not been done or if the port is shut down with no new classification result, the class status is reported as unknown. Rev. 1.0 17 S i3452/3 The three detect status bits indicate the last detection result for that port. If a detection has not been done or if the port is shut down with no new detection result, the detection status is reported as unknown. 5.4. Port Configuration (Registers 0x0A–0x11) These registers indicate the port configuration; they are read/write registers. The port priority bit is set if the port is not high priority. Low-priority ports are shut down when the shutdown lowpriority ports command is issued. The “PoE+“ bit specifies the dc current limit at either 425 mA or 850 mA nominal*. *Note: The PoE+ mode should be set correctly according to the electrical design of the PSE circuit (transformer and conductor current carrying capacity). The PoE+ port mode can safely be changed prior to port turn-on, but changes after port turnon do not have an immediate effect and are not recommended. “Disconnect enable“ must be set for power to be removed if there is a disconnect. The disconnect type (based on dc disconnect or Silicon Labs’ proprietary dV/dt disconnect) is determined by the ordering part number. “Port mode“ is set according to Table 17. Table 17. Port Mode Selection Port Mode Setting B1, B0 00b 01b 10b Mode Description The power is shut down with no detection pulses. A command to manually power the port is ignored. The port can be powered by the manual power command. Detection is done and classification is done for Rgood, but the port does not power. Detection classification and port powering are all automatic with no host intervention required. ICUT and ILIM are automatically set according to the PoE+ mode and classification result. Shutdown Manual Semiauto 11b Auto ICUT is the nominal current level at which the port will automatically power down if ICUT is exceeded for 60 ms. It can be set with 3.2 mA resolution. The accuracy of current measurement is approximately 5%; so, ICUT is normally set 7% higher than the supported current level. ICUT is automatically set based on the classification result and PoE+ mode. The automatically-set ICUT level is appropriate for a 45 V minimum system power supply for classes 0–3 and for a 51 V minimum power supply for PoE+ mode. This feature is classification policing. If the Si3452/3 is in the semi-auto mode, ICUT will not be updated according to the classification result. This means that if it is desired to set ICUT at port turn-on, this should be done before the port is turned on. Once a port is turned on, ICUT can be changed dynamically. It is often undesirable to use a low value of ICUT during port turn-on because inrush can trigger the ICUT event. For this reason, it is normal to allow the port to turn on with the automatic ICUT setting and then later change this value after port current has stabilized and also if the PD and PSE have negotiated for a different ICUT value based on the PoE L2 power negotiation protocol (LLDP). The Si3452/3 supports 2-Event classification as defined in the IEEE 802.3at draft. 2-event classification is an alternative to L2 power management where the PSE advertises it is capable of PoE powering by generating two classification pulses. 2-Event classification is only supported for auto mode. If the Si3452/3 is in auto mode and the first event classification result is Class 4, the mark, second event, and second mark are performed. Power is applied only if the second event is also Class 4. If the second event is not Class 4, the classification error is reported, and the port will not power. If the port is in manual mode, classification is done prior to turning on the port. 18 Rev. 1.0 S i3452/3 5.5. Command and Return Registers (Registers 0x12–0x1C) The global command register enables manual port turn-on or turn-off, chip reset, port reset, and measurement of port current and VEE. Register 0x12 is a Write only register. See Table 24 on page 23 for a list of all available commands. If the command results in a numerical return value, that value is stored in the measurement registers, which are read-only. Each of the five possible measurements results in a 2 byte return value, and that value is stored in a unique register. VEE is encoded in mV units; so, the full scale is 65.535 V. Iport is encoded in 100 µA units; so, the full scale is 6.5535 A. The output data is updated by the proper command register write operation (see Table 23). This means that the numerical value of the port current or VEE voltage in the measurement register will be the value at the time the command was issued. If the port turns off due to an overload or disconnect, the port current register contents will not be set to zero. If a command to read port current is issued and the port is off, the return value will be zero. 5.6. Device Status Register (0x1D) The device event bits are listed in Table 18. Table 18. Device Status Bits Bit B6 - OverTemp B5 - VEE UVLO Description The Si3452/3 has per-port thermal shutdown sensors as well a global thermal shutdown at a slightly higher temperature. The global thermal shutdown bit of the device event register is set if this occurs. VEE UVLO. The part is put in its reset state if VEE is not in a valid range. The Device status register is RO. The VEE, UVLO, and overtemp bits reflect the device status. They are set if VEE or temperature is out of range and reset if the VEE or temperature is in range. Bit 6 of the Interrupt register is set if there is a change in the overtemp status (bit 6 of 0x1D), and bit 5 of the Interrupt register is set if there is a change in the VEE UVLO status (bit 5 of 0x1D). Reading register 0x1D clears these bits of the Interrupt register but does not clear the device status register. In addition, bit B0 indicates whether or not detection back-off is used. For PSEs that are wired as Alternative B (power on the spare pair–typically used for midspans), the time between detection pulses is increased to slightly over two seconds to avoid interference with Alternative A (power on the data pair–typically used for endpoints). Bit B0 can be toggled using the 0x10 command code. Rev. 1.0 19 20 B7 B6 B5 B4 B3 B2 B1 B0 POWER_UP Overtemp change Port 4 event Rgood CLS mask DET compl mask Disconnect mask PwrGood mask Port 3 event Port 2 event Port 1 event PwrEn mask Device status mask tSTART mask tICUT mask VEE UVLO change 0x00 0x85 tSTART Event tICUT Event tICUT Event tICUT Event tICUT Event Rgood CLS DET compl Rgood CLS DET compl Disconnect Ev Disconnect Ev Rgood CLS DET compl Disconnect Ev Rgood CLS DET compl Disconnect Ev tSTART Event tSTART Event tSTART Event PwrGood Change PwrGood Change PwrGood Change PwrGood Change PwrEn Change PwrEn Change PwrEn Change PwrEn Change 0x00 0x00 0x00 0x00 PwrGood Status CLS Stat B2 CLS Stat B2 CLS Stat B2 CLS Stat B2 CLS Stat B1 CLS Stat B1 CLS Stat B1 CLS Stat B0 CLS Stat B0 CLS Stat B0 CLS Stat B1 CLS Stat B0 PwrGood Status PwrGood Status PwrGood Status PwrEnable Status PwrEnable Status PwrEnable Status PwrEnable Status DET Stat B2 DET Stat B2 DET Stat B2 DET Stat B2 DET Stat B1 DET Stat B1 DET Stat B1 DET Stat B1 DET Stat B0 DET Stat B0 DET Stat B0 DET Stat B0 0x00 0x00 0x00 0x00 Port priority Port priority Port priority Port priority B7 B7 B7 B7 B6 B6 B6 B6 B5 B5 B5 B5 B4 B4 B4 B4 PoE+ PoE+ PoE+ PoE+ B3 B3 B3 B3 Discon En Discon En Discon En Discon En B2 B2 B2 B2 Port Mode B1 Port Mode B1 Port Mode B1 Port Mode B1 B1 B1 B1 B1 Port Mode B0 Port Mode B0 Port Mode B0 Port Mode B0 B0 B0 B0 B0 00000100b 00000100b 00000100b 00000100b 0x75 0x75 0x75 0x75 Table 19. Si3452/3 Register Map Address Register Name Type Interrupts S i3452/3 0x00 Interrupt Reg 1 RO 0x01 Interrupt Mask 1 RW Port Events 0x02 Port 1 Events COR 0x03 Port 2 Events COR 0x04 Port 3 Events COR 0x05 Port 4 Events COR Status Rev. 1.0 0x06 Port 1 Status RO 0x07 Port 2 Status RO 0x08 Port 3 Status RO 0x09 Port 4 Status RO Configuration 0x0A Port 1 Config RW 0x0B Port 2 Config RW 0x0C Port 3 Config RW 0x0D Port 4 Config RW 0x0E Port 1 ICUT RW 0x0F Port 2 ICUT RW 0x10 Port 3 ICUT RW 0x11 Port 4 ICUT RW Table 19. Si3452/3 Register Map (Continued) B7 B6 B5 B4 B3 B2 B1 B0 POWER_UP Address Register Name Type Global Device CMD Code B5 CMD Code B4 CMD Code B3 CMD Code B2 CMD Param B1 CMD Param B0 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 OverTemp VEE UVLO Alternative B Timing 0x00 0x12 Command Register WO 0x13 VEE MSB RO 0x14 VEE LSB RO 0x15 Current P1 MSB RO 0x16 Current P1 LSB RO 0x17 Current P2 MSB RO 0x18 Current P2 LSB RO 0x19 Current P3 MSB RO 0x1A Current P3 LSB RO 0x1B Current P4 MSB RO Rev. 1.0 0x1C Current P4 LSB RO 0x1D Device Status RO Revision 0x60 Hardware Revision RO 0x61 Firmware Revision RO 0x62 Firmware Revision RO 0x63 Firmware Revision RO S i3452/3 21 S i3452/3 Table 20. Si3452/3 Detect Encoding Value 000b 001b 010b 011b 100b 101b 110b 111b Condition Unknown Short Reserved Rlow Good Rhigh Ropen Reserved Table 21. Si3452/3 Class Encoding Value 000b 001b 010b 011b 100b 101b 110b 111b Condition Unknown Class 1 Class 2 Class 3 Class 4 Probes Not Equal Class 0 Class Overload Table 22. Si3452/3 Port Mode Encoding Value 00b 01b 10b 11b Condition Shutdown Manual Semiauto Auto 22 Rev. 1.0 S i3452/3 Table 23. Si3452/3 Port Configuration PoE+ bit Class Auto Mode Setting of ICUT Register 0x1E 0x35 0x75 0x75 0xC9 ICUT Nominal Ilim Nominal* 0 or 1 don’t care 0 or 1 don’t care 0 or 1 don’t care 0 1 1 2 0/3 4 4 97 mA 170 mA 375 mA 375 mA 640 mA 425 mA 425 mA 425 mA 425 mA 850 mA *Note: During initial port turn-on (TSTART time of 60 ms), the current limit is set to 425 mA, even in PoE+ mode. Table 24. Si3452/3 Command Codes Command Power on port Power off port Reset port Toggle detection back-off timing2 Reset chip Get VEE Read port current Shut down low-priority ports CMD Register 0x04 | port no 0x08 | port no 0x0C | port no 0x10 0x14 0x18 0x1C | port no 0x20 [B5..B2] 0001b 0010b 0011b 0100b 0101b 0110b 0111b 1000b [B1..B0] Command Parameter 2 bit port number1 2 bit port number 2 bit port number NA NA NA 2 bit port number NA 2 Byte Return Value — — — — — VEE in mV units Port current in 100 µA units — Notes: 1. Port 1 has 2 bit port number 0x00; port 2 is 0x01, etc. 2. This command toggles bit 0 of Register 0x1D. When bit zero is set, the detection back-off of 2 seconds is implemented (alternative B or “midspan” mode). Rev. 1.0 23 S i3452/3 6. Operational Notes 6.1. Port Turn On If the port is turned on by putting it in auto mode, the Si3452/3 will take care of all specified timing, and it will take care of the two-event classification if the first event result is Class 4 and PoE+ mode is enabled. However, if automatic mode operation is not desired after port turn-on, the port should be set to semi-auto or manual mode once it has powered. In automatic mode, ICUT is set according to the classification result. The port turn-on command is used to turn on a port in semi-auto or manual mode. If the port is turned on in semiauto mode, turn-on is delayed until the next detection and classification. If the detection or classification result is not valid, the port will not power. If the classification is Class 4 and PoE+ mode is enabled, a 2-event classification is given. ICUT setting is not automatic for port turn-on in semi-auto or manual mode. If the port is turned on by putting it in manual mode, the normal sequence is to start with the port in semi-auto mode and interrupt on a classification complete, which indicates that there is a valid PD signature and that a classification result is available. Based on the classification result, the host can make a decision to apply power or not. The IEEE standard requires that a port be powered within 400 ms of a valid detect complete. It is also desirable to power the port prior to the start of the next detection pulse, which can occur in as little as 300 ms. Therefore, it is recommended that ports be powered in under 250 ms from the class complete interrupt when using the manual mode turn-on command. Using manual mode turn-on, detection is not done prior to port turn on, but classification is always performed just prior to port turn on. Ports are turned on in manual mode regardless of the classification result. 2-event classification is performed if the first event result is Class 4 and the port is enabled for PoE+ mode. The manual mode classification step does not generate a classification complete flag because it is assumed that the classification was already done in semi-auto mode and the host has already made the decision to grant power. During the initial 60 ms (Tstart) time of port turn-on, 1x current limit and ICUT = 375 mA (nominal) is enforced. After Tstart, if the port is not overloaded, Pgood is set to true, and ICUT and 1x or 2x current limit will follow the I2C register settings. In auto mode, the I2C registers are set according to the classification result, but, if desired, they can be overwritten after Pgood becomes true. After Tstart, 2x current limit is always allowed if PoE+ mode is enabled. 6.2. Changing the Interrupt Mask The INT register and INT pin are always synchronized. However, there can be up to a 5 ms delay between an event that causes or clears an interrupt and the update of the register and pin. Thus, if the INT mask register is changed to clear an interrupt or to block an interrupt source, there can be up to a 5 ms delay between the change of the INT mask register and the resultant change in the INT register and INT pin. Generally, use of the mask register to clear interrupts is not recommended; it is better to clear an interrupt by reading the appropriate COR register. 6.3. Port Voltage and Current Measurements Port current voltage and current are reported as of the time the measurement command is written to register 0x12. Spikes of current or other momentary current changes are not filtered. It may be desirable to add a ~1 second averaging filter to reported current when using port current information for power management decisions. 24 Rev. 1.0 S i3452/3 7. PCB Layout Guidelines Following are some PCB layout considerations. See also "12.1. Evaluation Kits and Reference Designs" on page 33 for reference design information. Please visit the Silicon Labs technical support web page at https://www.silabs.com/support/pages/contacttechnicalsupport.aspx and register to request support for your design, particularly if you are not closely following the recommended reference design. Due to the high current of up to 800 mA per port, the following board layout guidelines apply. In addition, contact Silicon Laboratories for access to complete PSE reference design databases including recommended layouts. The VEE1, VEE2, VEE3, and VEE4 pins can carry up to 800 mA and are connected to a VEE bus. The VEE bus for a 24 port PCB layout can thus carry as much as 20 A current. With 2 oz. copper on an outer layer, a bus of 0.4 inches is needed. For an inner layer, this increases to a 1 inch wide bus. Use of large or multiple vias is required for properly supporting the 800 mA per channel operating current. The VEE pin does not carry high current and can be connected directly to the bus as well. The best practice is to devote an entire inner layer for VEE power routing. Similarly, GND1/2 and GND3/4 pins can carry up to 1.6 A per pin, and the GND return bus should be at least as wide as the VEE bus described above. The best practice is to devote an entire inner layer for ground power routing. The ground power plane does not generally have a high frequency content (other than external faults); so, it is generally acceptable to use the ground power plane as a ground signal plane and tie AGND and GND12, GND34 to this plane as well. The VOUTn pins carry up to 800 mA dc and up to 5 A in faults; so, a 20 mil trace with wide or multiple vias is also recommended. The VDETn pins also carry fault current; so, this pin connection to VOUTn needs to use 20 mil traces and wide or multiple vias where needed. The VDD currents are not large; so, it is acceptable to route the VDD nodes on one of the outer layers. If care is taken to avoid disruption of the high current paths, VDD can be globally routed on one of the power planes and then locally routed on an inner or outer layer. To avoid coupling between surge events and logic signals, it is recommended that VOUTn traces be routed on the side opposite the I2C interface pins. The thermal pad of the Si3452/3 is connected to VEE. At full IEEE 802.3at current of 600 mA on each port, the dissipation of the Si3452/3 is up to 1.2 W; so, multiple vias are required to conduct the heat from the thermal pad to the VEE plane. As many as 36 small vias provide the best thermal conduction. Rev. 1.0 25 S i3452/3 8. Firmware Release Notes Devices marked with firmware revision 01 (see "13. Device Marking Diagram" on page 34) have the firmware revision registers set as 0x61 = 0x00; 0x62 = 0x02, and 0x63 = 0x4F (0.2.79). The following are known issues, all of which may be addressed with a future firmware revision: 8.1. Initialization Time Issue: The initialization time after a reset or power up is 65 ms. Impact: None - informational. Workaround: Wait 100 ms after a reset before beginning I2C transactions. 8.2. Current Limiting in 2x Power Mode Issue: In 2x current limiting mode, current is limited at the 1x value during the Tstart time as required by the 802.3at draft standard. For the last 0.4 ms of the 60 ms Tstart time, the current limit is increased to the 2x value. Impact: This would only be seen if the PD applies a continuous overload during the inrush time. The slight extra spike of current is less than 1 ms; so, it falls within the allowed current limit transient response. Workaround: None 8.3. I2C Address ACK Issue: Very rarely, the Si3452 may not ACK the I2C address byte. Impact: This is allowed in the I2C specification. Workaround: Retransmit the address byte if there is an ACK failure. 8.4. Reading or Writing Unused Registers It is recommended that unused registers not be read or written. In particular, reads from unused registers can be interpreted as clear on read and may clear unexpected memory locations. 26 Rev. 1.0 S i3452/3 9. Pin Descriptions VOUT1 VOUT2 32 GND12 DET1 DET2 39 38 37 36 35 34 40 33 31 VEE2 30 29 28 27 RST AD1 AD0 INT VEE1 VEE VREF AIN AOUT AGND RBIAS AGND NC VEE4 1 2 3 4 5 6 7 8 9 10 19 11 12 13 14 15 16 17 18 20 VDD DGND AD0 AD1 AD2 AD2 AD3 RST VEE3 AD3 Si3452 (Top View) 26 25 24 23 22 21 VDD GND34 VOUT4 Table 25. Si3452/3 Pin Descriptions Pin # Name Type Description 1 2 3 VEE1 VEE VREF Supply Supply Analog input Driver 1 VEE supply. Short to VEE, VEE2/3/4. Global PoE (–48 V nom.) or PoE+ (–54 V nom.) supply. Short to VEE1/2/3/4. 1.1 V nom. voltage reference from reference generator (for example, TLV431 or power management unit). Measurement data converter input. Short to AOUT. Measurement multiplexer subsystem output. Short to AIN. Analog ground reference. Short to AGND pin 8, GND12/34, DGND. External 44.2 kΩ (±1%) resistor to ground sets internal bias currents. Analog ground reference. Short to AGND pin 6, GND12/34, DGND. Do not connect (float). Driver 4 VEE supply. Short to VEE, VEE1/2/3. Do not connect (float). Port 4 power FET switch output. When on, provides a low impedance path to VEE4. 4 5 6 7 8 9 10 11 12 AIN AOUT AGND RBIAS AGND NC VEE4 NC VOUT4 Analog input Analog output Ground Analog input Ground No connect Supply No connect Analog I/O Rev. 1.0 VOUT3 DET4 DET3 SDA SCL NC NC 27 S i3452/3 Table 25. Si3452/3 Pin Descriptions (Continued) Pin # Name Type Description 13 DET4 Analog I/O Connection for port 4 detection, classification, and transient surge protection. This pin is tied to VOUT4. I2C data pin Ground supply for protection clamps. Short to AGND, GND12, DGND. I2C clock pin Do not connect (float). Connection for port 3 detection and classification. See DET4 for detailed description. +3.3 V (±10%) isolated supply. Short to VDD pin 30. Port 3 power FET switch output. When on, provides a low impedance path to VEE3. Chip address bit 3 pin, read after reset. Address set with defined resistor dividers. Pin also used for internal communications. Short to AD3 pin 24. Driver 3 VEE supply. Short to VEE, VEE1/2/4. Active low digital reset. Short to RST pin 38. Chip address bit 3 pin, read after reset. Address set with a 10 kpull-up or pulldown resistor. Also used for internal communications. Short to AD3 pin 21. Chip address bit 2 pin, read after reset. Address set with a 10 kpull-up or pulldown resistor. Also used for internal communications. Short to AD2 pin 26. Chip address bit 2 pin, read after reset. Address set with a 10 kpull-up or pulldown resistor. Also used for internal communications. Short to AD2 pin 25. Chip address bit 1 pin, read after reset. Address set with a 10 kpull-up or pulldown resistor. Also used for internal communications. Short to AD1 pin 36. Chip address bit 0 pin, read after reset. Address set with a 10 kpull-up or pulldown resistor. Also used for internal communications. Short to AD0 pin 34. Digital ground reference. Short to AGND, GND12/34 +3.3 V isolated supply. Short to VDD pin 19. Driver 2 VEE supply. Short to VEE, VEE1/3/4. Port 2 power FET switch output. When on, provides a low impedance path to VEE2. Connection for port 2 detection and classification. See DET4 for detailed description. Chip address bit 0 pin. See description for- and short to AD0 pin 28. Ground supply for protection clamps. Short to AGND, GND34, DGND. Chip address bit 1 pin. See description for- and short to AD1 pin 27. 14 15 16 17 18 SDA GND34 SCL NC DET3 Digital I/O Ground Digital I/O No connect Analog I/O 19 20 VDD VOUT3 Supply Analog I/O 21 AD3 Digital I/O 22 23 24 VEE3 RST AD3 Supply Digital input Digital I/O 25 AD2 Digital I/O 26 AD2 Digital I/O 27 AD1 Digital I/O 28 AD0 Digital I/O 29 30 31 32 DGND VDD VEE2 VOUT2 Ground Supply Supply Analog I/O 33 DET2 Analog I/O 34 35 36 AD0 GND12 AD1 Digital I/O Ground Digital I/O 28 Rev. 1.0 S i3452/3 Table 25. Si3452/3 Pin Descriptions (Continued) Pin # Name Type Description 37 DET1 Analog I/O Connection for port 1 detection and classification. See DET4 for detailed description. Active low digital reset. Short to RST pin 23. Port 1 power FET switch output. When on, provides a low impedance path to VEE1. Active low interrupt output pin. Connect the thermal pad to a plane which connects to Vee. For best results, use a 5 x 5 or larger via array for best thermal conductivity with 1 square inch or larger of plane area per device. 38 39 RST VOUT1 Digital input Analog I/O 40 ePAD INT Vee Digital output Supply Rev. 1.0 29 S i3452/3 10. Package Outline: 40-Pin QFN The Si3452/3 is packaged in an industry-standard, RoHS compliant 6 x 6 mm2, 40-pin QFN package. Figure 7. 40-Pin QFN Mechanical Diagram Table 26. Package Diagram Dimensions Dimension Min Nom Max A A1 b D D2 e E E2 L aaa bbb ccc ddd eee 0.80 0.00 0.18 0.85 0.02 0.25 6.00 BSC. 0.90 0.05 0.30 3.95 4.10 0.50 BSC. 6.00 BSC. 4.25 3.95 0.30 4.10 0.40 0.10 0.10 0.08 0.10 0.05 4.25 0.50 Notes: 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. Dimensioning and Tolerancing per ANSI Y14.5M-1994. 3. This drawing conforms to JEDEC outline MO-220, Variation VJJD-2 4. Recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. 30 Rev. 1.0 S i3452/3 11. Recommended PCB Footprint Figure 8. PCB Land Pattern Table 27. PCB Land Pattern Dimensions Dimension e E Min 0.50 BSC 5.42 REF Max Notes: General 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification. 3. This Land Pattern Design is based on IPC-SM-782 guidelines. 4. All dimensions shown are at Maximum Material Condition (MMC). Least Material Condition (LMC) is calculated based on a Fabrication Allowance of 0.05 mm. Solder Mask Design 5. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad is to be 60 µm minimum, all the way around the pad. Stencil Design 6. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 7. The stencil thickness should be 0.125 mm (5 mils). 8. The ratio of stencil aperture to land pad size should be 1:1 for the perimeter pads. 9. A 4x4 array of 0.80 mm square openings on 1.05 mm pitch should be used for the center Vee pad. Card Assembly 10. A No-Clean, Type-3 solder paste is recommended. 11. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. Rev. 1.0 31 S i3452/3 Table 27. PCB Land Pattern Dimensions (Continued) Dimension D E2 D2 GE GD X Y ZE ZD — — 4.00 4.00 4.53 4.53 — 0.89 REF 6.31 6.31 Min 5.42 REF 4.20 4.20 — — 0.28 Max Notes: General 1. All dimensions shown are in millimeters (mm) unless otherwise noted. 2. Dimensioning and Tolerancing is per the ANSI Y14.5M-1994 specification. 3. This Land Pattern Design is based on IPC-SM-782 guidelines. 4. All dimensions shown are at Maximum Material Condition (MMC). Least Material Condition (LMC) is calculated based on a Fabrication Allowance of 0.05 mm. Solder Mask Design 5. All metal pads are to be non-solder mask defined (NSMD). Clearance between the solder mask and the metal pad is to be 60 µm minimum, all the way around the pad. Stencil Design 6. A stainless steel, laser-cut and electro-polished stencil with trapezoidal walls should be used to assure good solder paste release. 7. The stencil thickness should be 0.125 mm (5 mils). 8. The ratio of stencil aperture to land pad size should be 1:1 for the perimeter pads. 9. A 4x4 array of 0.80 mm square openings on 1.05 mm pitch should be used for the center Vee pad. Card Assembly 10. A No-Clean, Type-3 solder paste is recommended. 11. The recommended card reflow profile is per the JEDEC/IPC J-STD-020 specification for Small Body Components. 32 Rev. 1.0 S i3452/3 12. Ordering Guide Ordering Part Number1 Detect Timing 2 Powerup Mode2,3,4 Disconnect Method Firmware Revision Package5 Temp. Range Si3452-B01-GM Si3452A-B01-GM Si3452B-B01-GM Si3452C-B01-GM Si3452D-B01-GM Si3453-B01-GM Si3453A-B01-GM Si3453B-B01-GM Si3453C-B01-GM Si3453D-B01-GM Si3452-B01-IM Si3452A-B01-IM Alt A Alt A PoE PoE (15.4 W) Shutdown Alt B Auto Alt A PoE+ (30 W) Alt B Alt A Alt A PoE (15.4 W) Alt B Auto Alt A PoE+ (30 W) Alt B Alt A Alt A PoE PoE (15.4 W) Shutdown Auto PoE Shutdown dV/dt disconnect 0.2.79 –10 to 85 °C ambient DC disconnect dV/dt disconnect dV/dt disconnect 0.2.79 –40 to 85 °C ambient Notes: 1. Add “R” to the end of the ordering part number to denote tape-and-reel option. E.g., Si3452-B01-GMR. 2. For alternative A, power is applied to wire pairs 1,2 and 3,6. For alternative B, power is applied to wire pairs 4,5 and 7,8 (the spare pairs in the case of 10/100 Ethernet). Conventionally, alternative B is used for midspan power injectors. For alternative B, detection is done with over 2 seconds between detection pulses so as to avoid interfering with end-point equipment trying to provide power using alternative A. 3. Devices powering up into shutdown mode are intended for use with a system host that provides run-time configuration or power-management. 4. The maximum PoE or PoE+ power applies to all ports on Auto mode devices. 5. All devices are packaged in RoHS-compliant, 40-pin, 6x6 mm QFN. 12.1. Evaluation Kits and Reference Designs Part Number Populated Device Description Related Ethernet Chipset Type Si3452MS8-KIT Si3452-B01-GM PoE+ 8-port Midspan PSE evaluation kit. Includes PC-control interface, PD loads, and cables. PoE/PoE+ 24-port daughtercard PoE+ 8-port Gb-Ethernet switch PoE/PoE+ 24-port daughtercard None Evaluation Kit Si3452V1-RD* Si3452V2-RD* Si3452M1-RD* Si3452-B01-GM Si3452-B01-GM Si3452-B01-GM Vitesse E-StaX (VSC7407) Vitesse SparX-G8e (VSC7398) Marvell Prestera-DX, xCAT Reference Design Reference Design Reference Design *Note: Due to unique high-voltage and high-power design considerations, Silicon Laboratories recommends that the reference designs be followed very closely for both bill of materials and layout. Please visit the Silicon Labs technical support web page at https://www.silabs.com/support/pages/contacttechnicalsupport.aspx and register to request support for your design, particularly if you are not closely following the recommended reference design. Rev. 1.0 33 S i3452/3 13. Device Marking Diagram Figure 9. Device Marking Diagram Table 28. Device Marking Table Line # 1 Text Value Si3452 Description Base part number. This is not the “Ordering Part Number” since it does not contain a specific revision. Refer to "12. Ordering Guide" on page 33. for complete ordering information. X = Device revision. YY = Firmware revision. Device type. GM = extended commercial temp range; IM = industrial temp range. All devices are RoHS-compliant. Trace code – assigned by the assembly subcontractor. Pin 1 identifier. Assembly year Assembly week. 2 2 3 4 XYY GM TTTTTT O YY WW 34 Rev. 1.0 S i3452/3 DOCUMENT CHANGE LIST Revision 0.4 to Revision 0.41                    VEE UVLO only. Due to the protection clamp, OVLO is not supported. Updated thermal information. Removed support for pin-selectable auto mode powerup. Changed device status to device event flags in Interrupt register. Si3452 is dv/dt disconnect, and Si3457 is DC disconnect. Added "6. Operational Notes" on page 24. Updated "12. Ordering Guide" on page 33. Added "12.1. Evaluation Kits and Reference Designs" on page 33. Revision 0.41 to Revision 0.42  Updated Vdd typical current.  Updated logical levels.  Clarified port turn on commands  Made reset timing “TBD”. The timing for samples is approximately 50 ms. There is an objective to improve this, but the final reset time has not yet been established. Added Table 15, “I2C Address Byte Protocol,” on page 16. Updated "5.1. Interrupt (Registers 0x00–0x01)" on page 17. Updated "5.3. Port Status (Registers 0x06–0x09)" on page 17. Updated "5.4. Port Configuration (Registers 0x0A– 0x11)" on page 18. Updated "5.5. Command and Return Registers (Registers 0x12–0x1C)" on page 19. Updated Table 18, “Device Status Bits,” on page 19. Updated Table 19, “Si3452/3 Register Map,” on page 20. Updated Table 23, “Si3452/3 Port Configuration,” on page 23. Added "6.2. Changing the Interrupt Mask" on page 24. Removed “8.4. Port Current Inaccuracies in dV/dt Mode”. Updated "12. Ordering Guide" on page 33. Revision 0.45 to Revision 0.46  Updated Table 3, “UVLO, and Reset Specifications,” on page 5.  Updated Table 6, “VOUT Drive and Power-on Specifications,” on page 7. Changed Revision 0.42 to Revision 0.43   current limit to 2x for PoE+ mode. Added “-IM” industrial temp range devices. Adjusted temp specs to accommodate -GM and -IM grades.  Updated Table 10, “Address Pin Electrical Specifications*,” on page 8. Removed 2.2 V min limit for VIL.  Revision 0.43 to Revision 0.44 Removed I2C ARA and bus arbitration support.  Added low-priority port function.  Clarified port turn-on function.  Added minimum or maximum specs for parameters that had been “TBD” or typical only.   Updated Table 11, “SMBus (I2C) Timing Specifications (see Figure 1),” on page 9. Changed data hold time to 200 nsec. Updated text in "7. PCB Layout Guidelines" on page 25.  Updated text in "12.1. Evaluation Kits and Reference Designs" on page 33. Revision 0.44 to Revision 0.45        Revision 0.46 to Revision 0.47   Updated Table 6, “VOUT Drive and Power-on Specifications,” on page 7. Updated Table 9, “SMBus (I2C) Electrical Specifications,” on page 8. Updated Figure 3 on page 11. Updated "4. Functional Description" on page 12 Updated "4.4. Disconnect Detection" on page 14. Updated "4.5. Transient Voltage Surge Suppression" on page 14. Updated "4.8. SMBus/I2C Interface Description" on page 15. Changed SDA and SCL input low to 0.85 V. Minor editorial corrections. Revision 0.47 to Revision 1.0  Added "8.4. Reading or Writing Unused Registers" on page 26.  Clarified ePAD connection in Table 25, “Si3452/3 Pin Descriptions,” on page 27.  Updated firmware revision in Ordering Guide from 2.78 to 2.79. Rev. 1.0 35 S i3452/3 CONTACT INFORMATION Silicon Laboratories Inc. 400 West Cesar Chavez Austin, TX 78701 Tel: 1+(512) 416-8500 Fax: 1+(512) 416-9669 Toll Free: 1+(877) 444-3032 Please visit the Silicon Labs Technical Support web page: https://www.silabs.com/support/pages/contacttechnicalsupport.aspx and register to submit a technical support request. The information in this document is believed to be accurate in all respects at the time of publication but is subject to change without notice. Silicon Laboratories assumes no responsibility for errors and omissions, and disclaims responsibility for any consequences resulting from the use of information included herein. Additionally, Silicon Laboratories assumes no responsibility for the functioning of undescribed features or parameters. Silicon Laboratories reserves the right to make changes without further notice. Silicon Laboratories makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Silicon Laboratories assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Silicon Laboratories products are not designed, intended, or authorized for use in applications intended to support or sustain life, or for any other application in which the failure of the Silicon Laboratories product could create a situation where personal injury or death may occur. Should Buyer purchase or use Silicon Laboratories products for any such unintended or unauthorized application, Buyer shall indemnify and hold Silicon Laboratories harmless against all claims and damages. Silicon Laboratories and Silicon Labs are trademarks of Silicon Laboratories Inc. Other products or brandnames mentioned herein are trademarks or registered trademarks of their respective holders. 36 Rev. 1.0