Evaluates: MAX14940/MAX14943/ MAX149X2 Evaluation Kit MAX14946/MAX14949 General Description Quick Start The MAX149X2 evaluation kit (EV kit) is a fully assembled Required Equipment and tested PCB that demonstrates the functionality of the MAX149X2 EV kit MAX14943 isolated RS-485/PROFIBUS transceiver. The 3.3V, 1A DC power supply EV kit operates from a single 3.3V supply and features an Signal/function generator on-board isolated power supply to power the secondary- Oscilloscope side of the circuit. Startup Procedure The MAX149X2 EV kit comes with the MAX14943GWE+ The EV kit is fully assembled and tested. Follow the steps installed, but can also be used to evaluate the pin-compatible below to verify board operation: MAX14940, MAX14946, and MAX14949 ICs. 1) Set the DC power supply to 3.3V and connect the Features DC power supply between the EV kits VDDA and GNDA connectors of the EV kit. Operates from a Single 3.3V Supply 2) Ensure that J2 and J3 are in their default positions Terminal Block Connectors for Easy RS-485/ (see Table 1). PROFIBUS Evaluation 3) Turn on the power supply. 5000V Isolation for 60s RMS 4) Set the signal/function generator to output a 100kHz 0 to 3V square wave. Note: Set the signal/function Fully Assembled and Tested generator to operate with a high-impedance load. If Proven PCB Layout needed, the R1 pad is available to add a 50 impedance to ground. Ordering Information appears at end of data sheet. 5) Connect the signal/function generator to the TXD test point. 6) Verify that the A and B outputs switch as the signal toggles. Table 1. Jumper Settings (J1J6) JUMPER SHUNT POSITION DESCRIPTION 1-2 Receiver is disabled. RXD is high impedance. J1 2-3* Receiver is enabled. RXD is active. 1-2* Driver is enabled. DEM is high. J2 2-3 Driver is disabled. DEM is low. Open* DE and RE are not connected together. J3 Closed DE and RE are connected together. Open* A and B are not connected through the on-board 120 resistor. J4 Closed Connects the on-board 120 resistor between A and B. *Default position. 19-7646 Rev 0 6/15Evaluates: MAX14940/MAX14943/ MAX149X2 Evaluation Kit MAX14946/MAX14949 Resistors R2 R4 Configuration Detailed Description of Hardware For end-of-the-line transceivers, close J4 to connect a The MAX149X2 EV kit is a fully assembled and tested circuit 120 resistor (R3) between the A and B RS-485 I/Os on board for evaluating the MAX14943 isolated RS-485/ the IC. Profibus transceiver (U1). The EV kit has been designed to allow for evaluating the IC alone or in a standard Pullup and pulldown resistors are generally used on the RS-485 configuration. The EV kit is powered from a single receiver inputs to guarantee a known state in the event 3.3V power supply. that all nodes on the bus are in receive mode, or the cable becomes disconnected. The exact value for these External Power Supply resistors varies with the application. Pads are provided for The power on the EV kit is derived from a single 3.3V pullup (R2) and pulldown (R4) resistors for the A-B lines, source. Connect an external supply from GNDA to either although the use of these resistors is purely optional. Note the VDDA test point or P1 connector to supply the 3.3V to that the MAX14943 features true fail-safe receiver inputs the logic side (A) of the circuit. The integrated push-pull that ensure RXD is high when the receiver inputs are transformer driver and external transformer (TX1) generate shorted, open, or connected to an idle bus. an isolated supply for powering the (B) isolated side of Selecting a Transformer the board. Table 2 is a list of transformers designed to operate with Evaluating the Isolated RS-485 Interface the device family. Select the transformer that best meets Driver and Receiver Enable Selection the performance requirements of the end application. All transformers in Table 2 can be used on the EV kit. The EV kit features three jumpers (J1, J2, and J3) to enable/disable the driver and receiver outputs. Set J1 to 2-3 to enable the receiver. Set J2 to 1-2 to enable the driver. To actively control both enables, remove J1 and J2 and close J3, which connects DE and RE together. Table 2. Transformer Selection ISOLATION A-SIDE CAN BE USED WITH MAXIM MANUFACTURER/PART NUMBER TURNS RATIO VOLTAGE (V ) SUPPLY (V) PART NUMBERS RMS HALO TGMS-1440V6LF 1CT: 1.33CT 2750 5V MAX14940, MAX14946 HALO TGMS-1464V6LF 1CT:2.4CT 2750 3.3V MAX14940, MAX14946 HALO TGMR-1440V6LF 1CT:1.33CT 5000 5V MAX14943, MAX14949 HALO TGMR-1464V6LF 1CT:2.4CT 5000 3.3V MAX14943, MAX14949 WURTH 750315226 1CT:1.3CT 2750 5V MAX14940, MAX14946 WURTH 750315228 1CT: 2CT 2750 3.3V MAX14940, MAX14946 WURTH 750315230 1CT:1.3CT 5000 5V MAX14943, MAX14949 WURTH 750315232 1CT: 2CT 5000 3.3V MAX14943, MAX14949 Maxim Integrated 2 www.maximintegrated.com