general description the max13487e evaluation kit (ev kit) is a fully assem- bled and tested pcb that contains a half-duplex rs- 485/rs-422 autodirection-controlled transceiver with esd protection. the ev kit circuit features a differential driver and receiver. the circuit? receiver is a 1/4-unit load for the rs-485 bus and can communicate up to 500kbps. the max13487e autodirection and reduced- driver slew-rate features are demonstrated on the ev kit circuit. the ev kit can also be used to evaluate the max13488e ic, which can communicate up to 16mbps. power for the transceiver circuit is provided by a max256 h-bridge dc/dc converter, which powers the isolated section of the max13487e rs-485/rs-422 circuit. input- ripple current and radiated noise are minimized by using an h-bridge design. the isolated h-bridge dc-dc con- verter operates at 420khz. 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 max13487e. a max1659 linear low dropout (ldo) reg- ulator provides the regulated output and up to 300ma of current. the output current limit and thermal shut- down provide for a robust isolated rs-485/rs-422 transceiver circuit and power supply. the transceiver and power circuits and pcb are designed for 2500v rms isolation. features demonstrates max13487e autodirection feature designed for 2500v rms isolation 1/4 rs-485 unit loading 500kbps half-duplex rs-485/rs-422 communication +5v dc input range isolated +5v output center-tapped full-wave rectifier output 420khz switching frequency output current limit and thermal shutdown low-cost integrated-fet h-bridge design also evaluates max13488e (after ic replacement) fully assembled and tested evaluates: max13487e/max13488e max13487e evaluation kit ________________________________________________________________ maxim integrated products 1 19-3204; rev 1; 11/08 component list for pricing, delivery, and ordering information, please contact maxim direct 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. ordering information # denotes rohs compliant. part type MAX13487EEVKIT# ev kit designation qty description c1 1 10? ?0%, 10v x7r ceramic capacitor (1206) murata grm31cr71a106k c2 1 0.47? ?0%, 16v x7r ceramic capacitor (0805) murata grm219r71c474k c3, c5, c6, c7 4 0.1? ?0%, 16v x7r ceramic capacitors (0603) murata grm188r71c104k c4 1 1? ?0%, 16v x7r ceramic capacitor (0805) murata grm21br71c105k d1, d2 2 30v, 1a schottky diodes (sod123) diodes inc. b130law d3 1 15v, 350mw ?% zener diode (sot-23) c entr al s em i cond uctor c m p z 5245b+ designation qty description ju1, ju3, ju4, ju5, ju6 5 2-pin headers ju2 1 3-pin header r1 1 39.2k ?% resistor (0603) r2, r9 2 100k ?% resistors (0603) r4, r5 2 270 ?% resistors (0805) r6, r8 2 220 ?% resistors (0805) r7 1 120 ?% resistor (0805) t1 1 500?, 1.5w, 3:8-turn, 400khz transformer (6-pin gull wing) halo electronics tgm-380narl u1 1 half-duplex, high-speed transceiver (8 so) maxim max13487eesa+
evaluates: max13487e/max13488e 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 max13487e 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. 1) connect a voltmeter to the vout and gnd pc pads. 2) verify that a shunt is not installed across the pins of jumper ju1 (u2 enabled). 3) verify that a shunt is installed across pins 1-2 of jumper ju2 (u1 enabled). 4) verify that a shunt is installed across the pins of jumpers ju3 (autodirection enabled), ju4 (pull- down), ju6 (pullup), and ju5 (bus terminated). 5) connect the +5v power supply to the vin pad. connect the power supply? ground to the pgnd pad. 6) turn on the power supply and verify that the volt- meter at vout reads +5v. 7) using the logic signal generator, apply a +5v logic signal to the txd pcb pad and pgnd. 8) using the oscilloscope and differential probes, verify the signal at the a-b pads (isolated side). note: the +5v supply powering the max13487e ev kit must be current-limited at 550ma and the output load current for the output should be limited to less than 300ma. detailed description of hardware the ev kit features a max13487e ic in an 8-pin so sur- face-mount package and demonstrates the esd- protected max13487e rs-485/rs-422 autodirection transceiver. the differential driver and receiver are con- figured for half-duplex operation and communicate up to 500kbps. the transceiver circuit is a 1/4-unit load on the receiver? 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 pgnd pads, respectively. the max13487e ic is powered from the isolated vout supply. photocoupler u4 provides isolation for the receiver? ro signal (rxd pad) and u5 provides isola- tion for the data-in di signal (txd pad). the ev kit demonstrates the max13487e slew-rate limited driver, which minimizes emi radiation. photocouplers u4 and u5 are rated for up to 15mbps. the max13487e receiver signal is provided at the ro pin. the ro pin will give a logic-high if a-b > +200mv. a logic-low is given if a-b < -200mv. refer to the transmitting and receiving sections in the function tables in the max13487e/max13488e ic data sheet for additional information on the autodirection circuitry operation. also see the autodirection and receiver enable selection section in this document for configur- ing the autodirection and receiver operation. max13487e evaluation kit 2 _______________________________________________________________________________________ component suppliers note: indicate that you are using the max13487e or max13488e when contacting these component suppliers. * ep = exposed pad. component list (continued) designation qty description u2 1 integrated primary-side controller and h-bridge driver (8 so-ep*) maxim max256asa+ u3 1 linear regulator (8 so) maxim max1659esa+ u4, u5 2 15mbps cmos photocouplers (5 so) cel/nec ps9151-a 6 shunts (ju1?u6) 4 rubber bumpers 1 pcb: max13487e evaluation kit# supplier phone website cel/nec ( c al i for ni a e aster n lab or ator i es/n e c ) 408-588-2247 www.cel.com central semiconductor corp. 631-435-1110 www.centralsemi.com diodes, inc. 805-446-4800 www.diodes.com halo electronics, inc. 650-903-3800 www.haloelectronics.com murata electronics north america, inc. 770-436-1300 www.murata- northamerica.com
the ev kit input power is typically a +5v dc source that provides at least 450ma of current to the max256 inte- grated primary-side controller and h-bridge driver cir- cuit. the max256 contains an on-board oscillator, pro- tection circuitry, and internal h-bridge fets to provide power to the primary of the transformer t1. the max256 prevents cross conduction of the h-bridge mosfets by implementing break-before-make switching. the max256 programmable oscillator is programmed to 420khz by resistor r1. the switching-frequency duty cycle is fixed at 50% to control energy transfer to trans- former t1 isolated output. the max256 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 1.9v (typ), the max256 ic will shut down. surface-mount transformer t1 provides galvanic isola- tion and the vout output is powered from a center- tapped full-wave rectifier circuit (d1 or d2) to reduce output-voltage ripple. it feeds a max1659 ldo regula- tor configured for +5v output. the ldo output is current limited and features thermal shutdown to pro- vide for a robust isolated supply at vout, which can provide up to 300ma of current. the two-layer pcb is designed for 2500v rms isolation, with 300 mils spacing between the pgnd and gnd planes. the bottom pcb pgnd plane under u2 is uti- lized as a thermal heat sink for power dissipation of the max256 thermally enhanced so package. test points tp1 (pgnd) and tp2 (gnd) are provided on the pcb for probing the respective ground plane or to connect the pgnd to gnd planes for nonisolated evaluation of the circuit. jumper selection the max13487e ev kit features several jumpers to reconfigure the receiver/driver enable circuits, and shut- down for the max256 and max13487e ics. additionally, pcb pads are provided for connecting an external load to the isolated +5v output at vout and gnd. shutdown control the max13487e ev kit features two jumpers that con- figure the shutdown mode of the circuit. jumper ju1 configures the max256 dc-dc converter and ju2 con- figures the max13487e ic for shutdown mode. see table 1 for placing the ev kit circuit or the desired ic in shutdown mode. autodirection and receiver enable selection the max13487e ev kit features a 2-pin jumper (ju3) to set the max13487e receiver mode of operation, autodirection, or receiver output enabled. refer to the autodirection circuitry section in the max13487e/ max13488e ic data sheet for more information on the max13487e re pin modes of operation. see table 2 for configuring the receiver mode of operation using jumper ju3. evaluates: max13487e/max13488e max13487e evaluation kit _______________________________________________________________________________________ 3 table 1. ju1 and ju2 shutdown mode control * to avoid bus contention, ensure that only one driver has control of the bus at a time. ju1 shunt position max256 mode pin ju2 shunt position max13487e shdn pin ev kit operation mode not installed connected to vin through r2 1-2 connected to vout all ics operational installed connected to pgnd 2-3 connected to gnd shutdown not installed connected to vin through r2 2-3 connected to gnd max13487e shutdown, all other ics operational table 2. driver and receiver ju3 functions shunt position re pin max13487e autodirection or receiver mode installed connected to vout autodirection enabled* not installed connected to gnd through r9 receiver ro output enabled
evaluates: max13487e/max13488e rs-485 bus pullup/pulldown and termination resistors configuration jumpers ju6 and ju4 are provided for connecting the mandatory pullup and pulldown resistors onto the rs-485 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 3 for configuring the pullup and pulldown resistors. r6 and r8 can be higher valued if the differential terminal resistor (r7) is not used. jumper ju5 is provided for terminating the a and b bus lines when the max13487e ev kit is connected at the end of an rs-485 bus. resistor r7 provides 120 of ter- mination when jumper ju5 is used. see table 4 for con- figuring the termination mode. max13487e evaluation kit 4 _______________________________________________________________________________________ table 3. ju6, ju4 functions, pullup, pulldown resistors shunt position a and b line signal none not pulled up or down installed a signal pulled up, connected to vout b signal pulled down to gnd table 4. ju5 functions, bus termination shunt position a-b pins and rs-485 bus termination ev kit bus connection none not terminated mid point installed terminated end of bus line evaluating the max13488e ic and other transformer configurations/designs max13488e evaluation the max13487e ev kit can also evaluate the max13488e ic. to evaluate the max13488e, replace ic u1 with the max13488e. note that the max13488e driver slew rate is not limited and allows transmission speeds of up to 16mbps. refer to the max13487e/ max13488e ic data sheet for additional information. smaller transformer and 2000v rms isolation design the ev kit? two-layer pcb is designed for 2500v rms isolation, with 300 mils spacing between the pgnd and gnd planes. additionally, transformer t1 is rated for 3000v rms and is an integral part of the dielectric with- stand voltage of the ev kit circuit. photocouplers u4 and u5 are guaranteed to withstand 3750v 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 u4 and u5, so the pcb must be considered when designing and testing the ev kit cir- cuit. for example, if less than 2500v rms isolation is needed, a smaller 2000v rms transformer may be used to save board area, but then the entire circuit will have only 2000v rms of isolation.
evaluates: max13487e/max13488e max13487e evaluation kit _______________________________________________________________________________________ 5 max13487e u1 vin ck_rs st1 st2 gnd gnd t1 tp1 pgnd 1 2 3 6 5 4 d1 d2 vcc vcc mode 1 8 7 6 5 2 3 r1 39.2k 1% r2 100k c2 0.47 f 16v c1 10 f 10v vout vout vdd gnd anode vin vin 4 shdn pgnd ju1 c6 0.1 f r4 270 r8 220 ju6 1 2 51 max256 u2 u4 c3 0.1 f 16v d3 3 1 c4 1 f 16v tp2 gnd v0 cathode 44 2 2 ro re ju3 ju2 vout 3 rxd pgnd gnd a vout vout shdn out out in in in gnd 3 6 7 81 2 4 5 max1659 u3 vout vin vdd cathode gnd anode c7 0.1 f r5 270 5 1 u5 v0 4 5 4 di gnd 6 a 2 3 txd 3 3 2 1 shdn r6 220 ju4 vout r7 120 c5 0.1 f ju5 b gnd 7 8 b v cc set 2 1 r9 100k figure 1. max13487e ev kit schematic
evaluates: max13487e/max13488e max13487e evaluation kit 6 _______________________________________________________________________________________ figure 2. max13487e ev kit component placement guide component side figure 3. max13487e ev kit pcb layout?omponent side
evaluates: max13487e/max13488e max13487e evaluation kit _______________________________________________________________________________________ 7 figure 4. max13487e ev kit pcb layout?older side
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 8 _____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. evaluates: max13487e/max13488e max13487e evaluation kit revision number revision date description pages changed 0 1/08 initial release 1 11/08 revised data sheet in several places with changes to resistors r6 and r8. 1, 2, 4, 5 revision history
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