Evaluates: MAX14853/MAX14855/ MAX148X2 Evaluation Kit MAX14857/MAX14859 Startup Procedure General Description The EV kit is fully assembled and tested. Follow the steps The MAX148X2 evaluation kit (EV kit) is a fully assembled below to verify board operation. and tested PCB that demonstrates the functionality of the MAX14855 isolated RS-485/RS-422 transceiver. The EV 1) Set the DC power supply to 3.3V and connect the 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 J2 and J3 are in their default positions (see Table 1). The MAX148X2EVKIT may also be used to evaluate the 3) Turn on the power supply. MAX14853, MAX14857, and MAX14859. 4) Set the signal/function generator to output a 1MHz 0-to-3V square wave. NOTE: Set the signal/function Features generator to operate with a high-impedance load. If the Operates from a Single 3.3V Supply function generator does not have that option, the R1 pad is available to add a 50 impedance to ground. Terminal Block Connectors for Easy RS-485/RS-422 5) Connect the signal/function generator to the TXD Evaluation test point. 2750V Isolation for 60s RMS 6) Verify that the Y and Z outputs switch as the signal toggles. Fully Assembled and Tested Quick Start Ordering Information appears at end of data sheet. Required Equipment MAX148X2EVKIT 3.3V, 1A DC power supply Signal/function generator Oscilloscope 19-7567 Rev 2 7/16Evaluates: MAX14853/MAX14855/ MAX148X2 Evaluation Kit MAX14857/MAX14859 Resistors R2R4 Configuration Detailed Description of Hardware For end-of-the-line transceivers, close J4 and/or J7 to The MAX148X2 EV kit is a fully assembled and tested connect a 120 termination resistor (R3) between the Y circuit board for evaluating the MAX14855 isolated and Z driver outputs and/or (R6) the A and B inputs on RS-485/RS-422 transceiver (U1). The EV kit has been the MAX14855. designed to allow for evaluating the MAX14855 alone or in a standard RS-485 configuration. The EV kit is powered Pullup and pulldown resistors are generally used on the from a single 3.3V power supply. receiver inputs to guarantee a known state in the event that all nodes on the bus are in receive mode, or the cable External Power Supply becomes disconnected. The exact value for these resistors The power on the EV kit is derived from a single 3.3V will vary with the application. Pads are provided for pullup source. Connect an external supply to the V test DDA (R2, R5) and pulldown (R4, R7) resistors, although the point or the P1 connector to supply the 3.3V to the logic- use of these resistors is purely optional. Note that the side (A) of the circuit. The integrated push-pull transformer MAX14855 features true fail-safe receiver inputs, which driver and external transformer, TX1, generate an isolated ensures that RXD is high when the receiver inputs are supply for powering the isolated side (B) of the board. shorted, open, or connected to an idle bus. Evaluating the Isolated RS-485/RS-422 Interface Selecting a Transformer Driver and Receiver Enable Selection Table 2 is a list of transformers designed to operate with the MAX14855 family. Select the transformer that The MAX148X2 EV kit features three jumpers (J1, J2, and best meets the performance requirements of the end J3) to enable/disable the driver and receiver outputs. Set application. All transformers in Table 2 can be used on the J1 to 2-3 to enable the receiver. Set J2 to 1-2 to enable MAX148X2 EV kit. the driver. To actively control both enables, remove J1 and J2 and close J3, which connects DE and RE together. Table 1. Jumper Table (J1-J7) 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. J2 2-3 Driver is disabled. Open* DE and RE are not connected together. J3 Closed DE and RE are connected together. Open* Y and Z are not connected through the on-board 120 resistor. J4 Closed Connects the on-board 120 resistor between Y and Z. Open* Z is not connected to B. J5 Closed Z is connected to B (loopback mode). Open* Y is not connected to A. J6 Closed Y is connected to A (loopback mode). Open* A and B are not connected through the on-board 120 resistor. J7 Closed Connects the on-board 120 resistor between A and B. *Default position. Maxim Integrated 2 www.maximintegrated.com