MAX149X1EVKIT# Analog Devices

Evaluates: MAX14938/MAX14939/ MAX149X1 Evaluation Kit MAX14941/MAX14942/ MAX14945/MAX14948 Startup Procedure General Description The EV kit is fully assembled and tested. Follow the steps The MAX149X1 evaluation kit (EV kit) is a fully assembled below to verify board operation. and tested PCB that demonstrates the functionality of the MAX14938 isolated RS-485/Profibus transceiver. The 1) Set the DC power supply to 3.3V and connect the EV kit operates from a single 3.3V supply and features an DC power supply between the EV kits V and DDA on-board isolated power supply to power the secondary- GNDA connectors. side of the circuit. 2) Ensure that all jumpers are in their default positions (see Table 1). The MAX149X1 EV kit can also be used to evaluate the 3) Turn on the power supply. MAX14939, MAX14941, MAX14942, MAX14945, and 4) Set the signal/function generator to output a 100kHz MAX14948. 0-to-3V square wave. NOTE: Set the signal/function generator to operate with a high-impedance load. If Features needed, the R1 pad is available to add a 50 impedance Operates From a Single 3.3V Supply to ground. Terminal Block Connectors for Easy RS-485/Profibus 5) Connect the signal/function generator to the TXD Evaluation test point. 2750V Isolation for 60s 6) Using the oscilloscope, verify that the A and B outputs RMS Fully Assembled and Tested switch as the signal toggles. Quick Start Required Equipment MAX149X1 EV kit 3.3V, 1A DC power supply Signal/function generator Oscilloscope Ordering Information appears at end of data sheet. The PROFIBUS-DP logo is a registered trademark of PROFIBUS and PROFINET International (PI). 19-8391 Rev 1 7/16Evaluates: MAX14938/MAX14939/ MAX149X1 Evaluation Kit MAX14941/MAX14942/ MAX14945/MAX14948 Evaluating the Isolated RS-485 Interface Detailed Description of Hardware The EV kit is a fully assembled and tested circuit board Driver and Receiver Enable Selection for evaluating the MAX14938 isolated RS-485/Profibus The EV kit features three jumpers (J2, J3, and J4) to transceiver (U2). The EV kit has been designed to allow enable/disable the driver and receiver outputs. Set J2 for evaluating the MAX14938 alone or in a standard to 2-3 to enable the receiver. Set J3 to 1-2 to enable the RS-485 configuration. The EV kit is powered from a single driver. To actively control both enables, open J2 and J3 3.3V power supply. and close J4, which connects DE and RE together. Powering the Board Resistors R2R4 Configuration The power on the EV kit is derived from a single 3.3V For end-of-the-line transceivers, close J6 to connect a source. Connect an external supply from GNDA to either 120 resistor (R3) between the A and B RS-485 I/Os on the V test point or P1 connector to supply the 3.3V to DDA the MAX14938. the logic-side (A) of the circuit. Pullup and pulldown resistors are generally used on the An on-board MAX258 transformer driver (U1) and external receiver inputs to guarantee a known state in the event transformer (TX1) generate an isolated supply for powering that all nodes on the bus are in receive mode, or the the (B) isolated-side of the board. To disable the MAX258 cable becomes disconnected. The exact value for these circuit, connect jumper J1 to 2-3. To disconnect the output resistors will vary with the application. Pads are of the transformer circuit from the MAX14938 LDO input, provided for pullup (R2) and pulldown (R4) resistors for remove the shunt on J5. the A-B lines, although the use of these resistors is purely optional. Note that the MAX14938 features true fail-safe receiver inputs, which ensures that RXD is high when the receiver inputs are shorted, open, or connected to an idle bus. Table 1. Jumper Table (J1-J6) JUMPER SHUNT POSITION DESCRIPTION 1-2 MAX258 transformer driver is disabled. J1 2-3* MAX258 transformer driver is enabled. 1-2* RE is high. The RS-485 receiver is disabled. J2 2-3 RE is low. The RS-485 receiver is enabled. 1-2* DE is high. The RS-485 driver outputs are enabled. J3 2-3 DE is low. The RS-485 driver outputs are disabled. Open* DE and RE are not connected together. J4 Closed DE and RE are connected together. Open Output of the transformer circuit is not connected to VLDO. J5 Output of the transformer circuit is connected to VLDO and powers the B-side of Closed* the MAX14938. *Default position. Maxim Integrated 2 www.maximintegrated.com