General Troubleshooting

Problem: Software reports it cannot find the inter-

face circuit.

•

Is the interface circuit power LED lit?

•

Is the USB cable connected?

•

Has Windows plug-and-play detected the board?

Bring up Control Panel->System->Device

Manager, and look at what device nodes are indi-

cated for USB. If there is an Unknown device node

attached to the USB, delete it—this forces plug-

and-play to try again.

•

Are jumper JU1 and headers J1 and J2 properly

configured for USB operation? See Tables 2 and 3.

Detailed Description of Hardware

The MAX5422 EV kit is an assembled and tested PCB

that evaluates the MAX5422 256-tap, nonvolatile, linear

digital potentiometer. The MAX5422 has an end-to-end

resistance of 50kΩ and the wiper can be programmed

to one of 256 tap positions. The MAX5422 features an

internal, nonvolatile memory (EEPROM) used to store

the wiper position for initialization during power-up. The

MAX5422 EV kit provides an on-board SPI-compatible

serial interface to program the MAX5422.

The EV kit uses a MAX5422 IC in an 8-pin TDFN pack-

age on a proven two-layer PCB design. The MAX5422

EV kit provides two options to power the MAX5422 IC. It

can operate from the 3.3V supply generated from the

USB interface circuit, or from a user-supplied 2.7V to

5.25V external DC power supply. The logic level trans-

lators (U7, U8) provide proper SPI-interface operation

when using a 2.7V to 5.25V external power supply.

MAX5422 Evaluation Kit

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Figure 3. Simple Low-Level 3-Wire Interface