MIC2196 Power Over Ethernet

Transcription

1 IEEE 802.3af PD Evaluation Board (Non-Isolated) General Description The MIC2196 Power Over Ethernet (POE) Powered Device (PD) Evaluation Board is designed to offer a complete IEEE802.3af compliant power solution. The evaluation board includes a low cost POE signature and classification circuit, an EMI filter, and an non-isolated flyback dc/dc converter using the MIC2196 control IC. The MIC2196 is a 400KHz current mode PWM dc/dc controller that is housed in the small and low pin count SO8 package. When a powered Ethernet cable is plugged into the evaluation board, the front end handshaking circuit will apply the correct signature and classification impedances to accept power from the Power Sourcing Equipment (PSE). At the application of power from the PSE, with input voltages between 36V and 57V, the dc/dc flyback converter will engage and generate a 3.3V output with up to 2.5A of output current. Features 36V to 57V input voltage 3.3V output voltage RJ45 input and output connectors IEEE 802.3af signature circuit IEEE 802.3af classification circuit* EMI filter Low cost single winding transformer MIC2196DC/DC flyback converter Non-isolated configuration 400KHz fixed frequency PWM control Related Documentation MIC2196 Datasheet This evaluation board is for use with IEEE802.3af enabled Switch/Routers which provide power to the Ethernet cable as defined in IEEE802.3af PSE requirements. * Patent Pending Evaluation Board Evaluation Board Picture Top View: Layout and Dimensions July 2004

2 Evaluation Board Description When the RJ45 connector is plugged into a PSE, the Front end handshaking circuit will apply the correct signature and classification impedances to gain power from the PSE. At the application of power, the Flyback primary circuit is applied with between 36V and 57V. This then converts power to the secondary circuit at 3.3V up to 2.5A. Schematic * NF: Optional components Not Fitted on the evaluation board Evaluation Board Setup with PSE The follow steps describe the procedure for setting up the evaluation board with available 802.3af compliant Power Sourcing Equipment. 1. Plug in IEEE 802.3af compliant powered Ethernet cable into RJ45_1 input connector 2. After automatic hand-shaking sequence, 3.3V power will be applied to post PL1 3. Data from input is available at output connector RJ45_2 2

3 Evaluation Board Discrete Setup The follow steps describe the procedure for setting up the evaluation board discretely to emulate 802.3af power sourcing equipment. 1. Plug in one end of CAT5 Ethernet cable into RJ45_1 input connector, with the wires of the other end exposed 2. Connect banana plug termination to brown, blue, orange, and green pairs. 3. Prepare test gear: a. 1 Power Supply Unit PSU capable of supplying 60V with a 1A current limit b. 2 Digital Volt Meters (DVMs) with 60V measuring capability c. 2 amps meters: 300µA to 400mA range (input side), and 2.5A rated for output side d. Electronic Load. 3.3V capable set to 2.5A load. 5. Turn on all apparatuses 6. Check Signature a. Set PSU to 9V b. Ammeter 1 should read between 280µA to 368µA 7. Check Classification a. Set PSU to: 15V to 20V range b. Ammeter 1 should read between 26mA to 30mA (Class 3) 8. DC/DC Power Supply Turn On & Startup a. Set PSU to: 36V to 57V range b. DMV2 at the PL1 post should read 3.3V 4. Apply test setup Test Setup 3

4 PD Controller Circuit Signature To comply with IEEE 802.3af, it mandatory to provide a 25K resistance (R11) and 100nF capacitance (C13) across the power line to receive power from the PSE (signature). MOSFET Q5 is used to hold off the input capacitance of the dc/dc converter during the signature detection phase. Classification The MIC2196 POE eval board is set to Class 3. Power classification is optional, and can be removed to reduce cost. The default classification is Class 0. To remove the Classification option, the following components can be removed from the MIC2196 POE eval board: Q4, Q6, R13. To set a Classification Level, the MIC2196 POE eval board s classification circuit can be configured as follows: Class Input Current V IN =14.5V to 20.5V PD Power Class Component Modification Class 0 0mA 4mA 0.5W to 12.95W remove Q4, Q6, R13 Class 1 9mA 12mA 0.5W to 3.8W R13 = 953Ω Class 2 7mA 20mA 3.8W to 6.5W R13 = 536Ω Class 3 26mA 30mA 6.5W to 12.95W R13 = 340Ω Class 4 36mA 44mA Not defined R13 = 270Ω Front End Analog Handshaking Limits: The following are the limits that the evaluation board has been designed to: DESCRIPTION TEST CONDITION MIN MAX Signature Test (Resistance) Classification Test, Class 3 (Line Current) DC/DC Full Power (Line Current) V IN = 2.7V to 10.1V 19KΩ 26.5 KΩ V IN = 14.5V to 20.5V 26mA 30mA V IN = 36V; I OUT =2.5A 229mA 310mA 4

5 Flyback Converter Performance V IN = 36V to 60V Efficiency ~ 80% at full load V OUT ripple < 100mV Load Regulation = 1.7% at V IN = 48V Transient Response V OUT Ripple 2.5A 0.5A 200mV/DIV 100mV/DIV Switching Edges Efficiency 85 CH1 = Primary V DS (20V/DIV) CH2 = Gate drive (5V/DIV) Note: Gate rise/fall time is increased by 10Ω resistor to help reduce the frequency of RF emissions. Efficiency (%) VIN = 37V VIN = 48V VIN = 59V I OUT (Amps) 5

6 EMI Reduction Conducted and radiated high frequency emissions can be reduced by adding damping to the switching sources (Primary MOSFET switch and Secondary diode). The method for this is based on the empirical approach of measuring the ringing frequency, adding a critical capacitance and then calculating a series damping resistor. The effects of this approach can be seen in the following scope traces. Primary MOSFET Switch Secondary Schottky Diode After damping After damping Before damping Before damping R5=60Ω, C10=150pF R6 = 100Ω, C11 = 1500pF 6

7 Bill of Materials Ref Qty Part Description Vendor P/N Vendor U1 1 Low Voltage Boost PWM MIC2196BM Micrel.Inc Q2 1 N channel 100V DS MOSFET SI3430DV Vishay Siliconix Q3 1 NPN med-power transistor 80V/1A CXT3019 Central Semi Q4 1 Small Signal NPN Transistors BC846B Central Semi BC846B Vishay Semiconductor Q5 1 N channel 60V DS MOSFET Si2308DS Vishay Siliconix 2N7002E Vishay Telefunken Q6 1 N channel 60V DS SOT-23 MOSFET CMPDM7002A Central Semi 2N7002E Diodes. Inc BR1, MB2S Vishay 2 100V, BRIDGE BR2 HD02 Diodes. Inc D1 1 Fast Switching diodes. MELF Glass S0D-80 LS4148 Vishay Telefunken D2 1 5A, 40V Schottky diode SBM540 Diodes. Inc OR Power Mite package B540 D3 1 Zener Diode, 9.1V, SOT-23 BZX84C9V1 Central Semi BZX84C9V1 Diodes. Inc D4 1 Voltage Regulator Diodes 24V MMSZ5252B Diodes.Inc ZMM5252B L1 1 12uH 1812LS-123XJBC Coilcraft NL453232T-120J TDK GRM185R61A105KE36D murata C1608X5R1A105KT TDK C1 1 1uF/10V,X5R, ZD105KAT AVX LMK107BJ105ML-T TAIYO YUDEN JV0603G105KXQCW1BC Vishay BC C2 1 33uF/ 100V, Radial. 517D336M100CC6A Vishay C6 0 NF ( open location) 517D336M100CC6A Vishay C3 1 1nF/50V, 0603 C1608COG1H102J. TDK VJ0603Y102KXAAT Vishay Vitramon C4, C5 2 47uF/ 6.3V, X5R,1210 GRM32ER60J476ME20L murata C3225X5R0J476KT TDK JMK316BJ476KN-T TAIYO YUDEN VJ1206G476JXYTW1BC Vishay BC GRM32ER72A105KA01L murata GRM31CR72A105K***L C7 1 1uF/100V,X7R,1210 HMK325BJ105ML-T TAIYO YUDEN 12101C105KAZ1A AVX C nF/ 50V, 0603 VJ1206Y105KXBTW1BC Vishay BC C1608X7R1H104KT. TDK VJ0603Y104KXAAT. Vishay Vitramon C nF/100V C2012X7R2A104KT. TDK VJ0805Y104KXBAT. Vishay Vitramon 7

8 594D127X06R3C2T. Vishay Sprague C uF / 6.3V TPSD107M006R0150 AVX C3225X5R0J107M TDK C10, C11, R5, R6 0 NF( open location ) Z2 1 Voltage Regulator Diodes 39V MMSZ5259B Diodes.Inc ZMM5259B R1 1 1M ( 0603 size), 1% CRCW FRT1 Vishay Dale R2 1 15K (0805 size), 1% CRCW FRT1 Vishay Dale R K ( 0603 size), 1% CRCW FRT1 Vishay Dale R ohms (1206 size), 1% WSL-1206-R15-F Vishay Dale R ( 0805 size), 1% CRCW080520R0FRT1 Vishay Dale R8 1 1K (0603 size), 1% CRCW FRT1 Vishay Dale R K (0805 size), 1% CRCW FRT1 Vishay Dale R K ( 0603 size), 1% CRCW FRT1 Vishay Dale R K ( 0603 size), 1% CRCW FRT1 Vishay Dale R K (0805 size), 5% CRCW JRT1 Vishay Dale R (0805 size), 1% CRCW FRT1 Vishay Dale R K (0603 size),5% CRCW JRT1 Vishay Dale R K ( 0603 size), 5% CRCW JRT1 Vishay Dale PL1 1 2 way 0.1" pitch header T1 1 PoE Magnetic H2019 Pulse TLA-6T127LF TDK T2 1 Flyback transformer VP20066 Coiltronics PCA14.5/6ER-U10S002 TDK RJ45_1, SS S-A-NF RJ45 socket RJ45_2 A111 Belfuse/Stewart Vendor Phone Numbers Micrel.Inc Vishay corp Diodes.inc murata Sumida Micro Commercial Components AVX NEC ( CEL ) Coilcraft Pulse Central Semi TAIYO YUDEN Belfuse/Stewart TDK

9 PCB Layout Top Silkscreen Top Layer Bottom Silkscreen Bottom Layer MICREL, INC FORTUNE DRIVE SAN JOSE, CA USA TEL +1 (408) FAX +1 (408) WEB The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser s own risk and Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale Micrel, Incorporated.