MAX13487E Evaluation Kit. Evaluates: MAX13487E/MAX13488E. Features

Transcription

1 9-0; Rev ; /08 General Description The MAX87E evaluation kit (EV kit) is a fully assembled and tested PCB that contains a half-duplex RS- 85/RS- AutoDirection-controlled transceiver with ESD protection. The EV kit circuit features a differential driver and receiver. The circuit s receiver is a /-unit load for the RS-85 bus and can communicate up to 500kbps. The MAX87E AutoDirection and reduceddriver slew-rate features are demonstrated on the EV kit circuit. The EV kit can also be used to evaluate the MAX88E IC, which can communicate up to 6Mbps. Power for the transceiver circuit is provided by a MAX56 H-bridge DC/DC converter, which powers the isolated section of the MAX87E RS-85/RS- circuit. Inputripple current and radiated noise are minimized by using an H-bridge design. The isolated H-bridge DC-DC converter operates at 0kHz. Input power to the EV kit circuit can be supplied by a +5V DC source. The DC-DC converter circuit uses a surface-mount transformer to provide galvanic isolation and a full-wave rectifier, and provides a regulated +5V to the MAX87E. A MAX659 linear low dropout (LDO) regulator provides the regulated output and up to 00mA of current. The output current limit and thermal shutdown provide for a robust isolated RS-85/RS- transceiver circuit and power supply. The transceiver and power circuits and PCB are designed for 500V RMS isolation. DESIGNATION QTY DESCRIPTION C C C, C5, C6, C7 C D, D D 0µF ±0%, 0V X7R ceramic capacitor (06) Murata GRMCR7A06K 0.7µF ±0%, 6V X7R ceramic capacitor (0805) Murata GRM9R7C7K 0.µF ±0%, 6V X7R ceramic capacitors (060) Murata GRM88R7C0K µf ±0%, 6V X7R ceramic capacitor (0805) Murata GRMBR7C05K 0V, A Schottky diodes (SOD) Diodes Inc. B0LAW 5V, 50mW ±5% zener diode (SOT-) C entr al S em i cond uctor C M P Z 55B+ Features Demonstrates MAX87E AutoDirection Feature Designed for 500V RMS Isolation / RS-85 Unit Loading 500kbps Half-Duplex RS-85/RS- Communication +5V DC Input Range Isolated +5V Output Center-Tapped Full-Wave Rectifier Output 0kHz Switching Frequency Output Current Limit and Thermal Shutdown Low-Cost Integrated-FET H-Bridge Design Also Evaluates MAX88E (After IC Replacement) Fully Assembled and Tested PART MAX87EEVKIT# #Denotes RoHS compliant. Ordering Information TYPE EV Kit Component List DESIGNATION QTY DESCRIPTION JU, JU, JU, JU5, JU6 5 -pin headers JU -pin header R 9.kΩ ±% resistor (060) R, R9 00kΩ ±5% resistors (060) R, R5 70Ω ±5% resistors (0805) R6, R8 0Ω ±5% resistors (0805) R7 0Ω ±5% resistor (0805) T U 500µH,.5W, :8-turn, 00kHz transformer (6-pin Gull Wing) HALO Electronics TGM-80NARL Half-duplex, high-speed transceiver (8 SO) Maxim MAX87EESA+ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct , or visit Maxim s website at

2 *EP = Exposed pad. Component List (continued) DESIGNATION QTY DESCRIPTION U U U, U5 Integrated primary-side controller and H-bridge driver (8 SO-EP*) Maxim MAX56ASA+ Linear regulator (8 SO) Maxim MAX659ESA+ 5Mbps CMOS photocouplers (5 SO) CEL/NEC PS95-A 6 Shunts (JU JU6) Rubber bumpers PCB: # Quick Start Required Equipment Before beginning, the following equipment is needed: One +5V 550mA current-limited power supply with a built-in current meter One voltmeter One logic signal generator One oscilloscope with a differential probe Procedure The MAX87E EV kit is fully assembled and tested. Follow the steps below to verify board operation. Caution: Do not turn on the power supply until all connections are completed. ) Connect a voltmeter to the and PC pads. ) Verify that a shunt is not installed across the pins of jumper JU (U enabled). ) Verify that a shunt is installed across pins - of jumper JU (U enabled). ) Verify that a shunt is installed across the pins of jumpers JU (AutoDirection enabled), JU (pulldown), JU6 (pullup), and JU5 (bus terminated). 5) Connect the +5V power supply to the VIN pad. Connect the power supply s ground to the P pad. 6) Turn on the power supply and verify that the voltmeter at reads +5V. 7) Using the logic signal generator, apply a +5V logic signal to the TXD PCB pad and P. 8) Using the oscilloscope and differential probes, verify the signal at the A-B pads (isolated side). Component Suppliers SUPPLIER PHONE WEBSITE CEL/NEC ( C al i for ni a E aster n Lab or ator i es/n E C ) Central Semiconductor Corp Diodes, Inc HALO Electronics, Inc. Murata Electronics North America, Inc Note: Indicate that you are using the MAX87E or MAX88E when contacting these component suppliers. Note: The +5V supply powering the MAX87E EV kit must be current-limited at 550mA and the output load current for the output should be limited to less than 00mA. Detailed Description of Hardware The EV kit features a MAX87E IC in an 8-pin SO surface-mount package and demonstrates the ESDprotected MAX87E RS-85/RS- AutoDirection transceiver. The differential driver and receiver are configured for half-duplex operation and communicate up to 500kbps. The transceiver circuit is a /-unit load on the receiver s bus. The EV kit features PCB pads to ease interfacing with the driver/receiver logic signals on the non-isolated side using the TXD, RXD, and P pads, respectively. The MAX87E IC is powered from the isolated supply. Photocoupler U provides isolation for the receiver s RO signal (RXD pad) and U5 provides isolation for the data-in DI signal (TXD pad). The EV kit demonstrates the MAX87E slew-rate limited driver, which minimizes EMI radiation. Photocouplers U and U5 are rated for up to 5Mbps. The MAX87E receiver signal is provided at the RO pin. The RO pin will give a logic-high if A-B > +00mV. A logic-low is given if A-B < -00mV. Refer to the Transmitting and Receiving sections in the Function Tables in the MAX87E/MAX88E IC data sheet for additional information on the AutoDirection circuitry operation. Also see the AutoDirection and Receiver Enable Selection section in this document for configuring the AutoDirection and receiver operation.

3 The EV kit input power is typically a +5V DC source that provides at least 50mA of current to the MAX56 integrated primary-side controller and H-bridge driver circuit. The MAX56 contains an on-board oscillator, protection circuitry, and internal H-bridge FETs to provide power to the primary of the transformer T. The MAX56 prevents cross conduction of the H-bridge MOSFETs by implementing break-before-make switching. The MAX56 programmable oscillator is programmed to 0kHz by resistor R. The switching-frequency duty cycle is fixed at 50% to control energy transfer to transformer T isolated output. The MAX56 IC includes UVLO for controlled startup and provides controlled turn-on during power-up and during brownouts. If the input voltage at VIN falls below.9v (typ), the MAX56 IC will shut down. Surface-mount transformer T provides galvanic isolation and the output is powered from a centertapped full-wave rectifier circuit (D or D) to reduce output-voltage ripple. It feeds a MAX659 LDO regulator configured for +5V output. The LDO output is current limited and features thermal shutdown to provide for a robust isolated supply at, which can provide up to 00mA of current. The two-layer PCB is designed for 500V RMS isolation, with 00 mils spacing between the P and planes. The bottom PCB P plane under U is utilized as a thermal heat sink for power dissipation of the Table. JU and JU Shutdown Mode Control JU SHUNT POSITION MAX56 MODE PIN JU SHUNT POSITION MAX56 thermally enhanced SO package. Test points TP (P) and TP () are provided on the PCB for probing the respective ground plane or to connect the P to planes for nonisolated evaluation of the circuit. Jumper Selection The MAX87E EV kit features several jumpers to reconfigure the receiver/driver enable circuits, and shutdown for the MAX56 and MAX87E ICs. Additionally, PCB pads are provided for connecting an external load to the isolated +5V output at and. Shutdown Control The MAX87E EV kit features two jumpers that configure the shutdown mode of the circuit. Jumper JU configures the MAX56 DC-DC converter and JU configures the MAX87E IC for shutdown mode. See Table for placing the EV kit circuit or the desired IC in shutdown mode. AutoDirection and Receiver Enable Selection The MAX87E EV kit features a -pin jumper (JU) to set the MAX87E receiver mode of operation, AutoDirection, or receiver output enabled. Refer to the AutoDirection Circuitry section in the MAX87E/ MAX88E IC data sheet for more information on the MAX87E RE pin modes of operation. See Table for configuring the receiver mode of operation using jumper JU. MAX87E SHDN PIN EV KIT OPERATION MODE Not installed Connected to VIN through R - Connected to All ICs operational Installed Connected to P - Connected to Shutdown Not installed Connected to VIN through R - Connected to MAX87E shutdown, all other ICs operational Table. Driver and Receiver JU Functions SHUNT POSITION RE PIN MAX87E AUTODIRECTION OR RECEIVER MODE Installed Connected to AutoDirection enabled* Not installed Connected to through R9 Receiver RO output enabled *To avoid bus contention, ensure that only one driver has control of the bus at a time.

4 RS-85 Bus Pullup/Pulldown and Termination Resistors Configuration Jumpers JU6 and JU are provided for connecting the mandatory pullup and pulldown resistors onto the RS-85 bus A and B lines, respectively. Pullup resistor R8 and pulldown resistor R6 define the voltage on the A and B lines in conjunction with R7 when the driver input (DI) is high. See Table for configuring the pullup and pulldown resistors. R6 and R8 can be higher valued if the differential terminal resistor (R7) is not used. Table. JU6, JU Functions, Pullup, Pulldown Resistors SHUNT POSITION None Installed Table. JU5 Functions, Bus Termination Jumper JU5 is provided for terminating the A and B bus lines when the MAX87E EV kit is connected at the end of an RS-85 bus. Resistor R7 provides 0Ω of termination when jumper JU5 is used. See Table for configuring the termination mode. A AND B LINE SIGNAL Not pulled up or down A signal pulled up, connected to B signal pulled down to SHUNT POSITION A-B PINS AND RS-85 BUS TERMINATION EV KIT BUS CONNECTION None Not terminated Mid point Installed Terminated End of bus line Evaluating the MAX88E IC and Other Transformer Configurations/Designs MAX88E Evaluation The MAX87E EV kit can also evaluate the MAX88E IC. To evaluate the MAX88E, replace IC U with the MAX88E. Note that the MAX88E driver slew rate is not limited and allows transmission speeds of up to 6Mbps. Refer to the MAX87E/ MAX88E IC data sheet for additional information. Smaller Transformer and 000VRMS Isolation Design The EV kit s two-layer PCB is designed for 500V RMS isolation, with 00 mils spacing between the P and planes. Additionally, transformer T is rated for 000V RMS and is an integral part of the dielectric withstand voltage of the EV kit circuit. Photocouplers U and U5 are guaranteed to withstand 750V RMS. However, the circuit uses the isolated transformer to transfer power from the primary side to the secondary side and the withstand voltage of the transformer, as well as photocouplers U and U5, so the PCB must be considered when designing and testing the EV kit circuit. For example, if less than 500V RMS isolation is needed, a smaller 000V RMS transformer may be used to save board area, but then the entire circuit will have only 000V RMS of isolation.

5 R 9.kΩ % R 00kΩ 8 CK_RS ST VCC VCC MODE ST TP T 6 5 D D P VIN U MAX87E VIN P SHDN VIN RXD P TXD C 0μF 0V JU C 0.7μF 6V U MAX56 TP C 0.μF 6V D 6 7 SHDN OUT IN OUT IN IN U MAX659 8 SET 5 C μf 6V C6 0.μF 5 VDD ANODE V0 U CATHODE R5 70Ω VIN ANODE 5 VDD R 70Ω U5 V0 C7 0.μF R9 00kΩ JU JU RO RE SHDN VCC B A 5 DI C5 0.μF R7 0Ω R8 0Ω R6 0Ω JU6 JU JU5 B A CATHODE Figure. MAX87E EV Kit Schematic 5

6 Figure. MAX87E EV Kit Component Placement Guide Component Side Figure. MAX87E EV Kit PCB Layout Component Side 6

7 Figure. MAX87E EV Kit PCB Layout Solder Side 7

8 REVISION NUMBER REVISION DATE DESCRIPTION Revision History PAGES CHANGED 0 /08 Initial release /08 Revised data sheet in several places with changes to resistors R6 and R8.,,, 5 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 8 Maxim Integrated Products, 0 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.