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MAX14821

IO-Link Device Transceiver

Applications Information

UART Interfacing

The logic levels of the microcontroller interface I/Os

The device can be interfaced to microcontrollers where

the on-board UART TX output cannot be programmed as

a logic output (GPO). In this case, connect the TX output

of the UART to the TXC input for IO-Link communication

and connect a separate GPO output on the microcon-

troller to TXQ for standard IO (SIO) mode operation

(Figure 12). As the TXQ and TXC inputs are internally

logically ANDed, the unused input (TXC or TXQ) must be

held high while the other is in operation.

Transient Protection

Inductive load switching, surges, and bursts create high

transient voltages. C/Q, DO, and DI should be protected

against high overvoltage and undervoltage transients.

Positive voltage transients on C/Q, DO, and DI must be

limited to +55V relative to GND and negative voltage

and C/Q and to -55V (relative to GND) on DI. Figure 12

shows suitable protection using TVS diodes to meet both

the IEC 61000-4-2 ESD and IEC 61000-4-5 surge testing.

Other protection schemes may also be suitable.

Operating Circuit).

External Power

the microcontroller interface. The logic and SPI interface

is not present.

plying external circuitry, like power supplies.

external supply (Figure 14). This configuration disables

operation of the internal 5V regulator and reduces power

consumption.

Figure 12. UART Interface

Figure 13. MAX14821 Operating Circuit with TVS Protection

TXQ

GPO

TXC

TX

TXEN

RTS

RX

RX

MAX14821

MAX14821

0.8Ω

1F

1F

LDOIN

DO

1/2

SDC36C

1/2

SDC36C

GND

C/Q

1/2

SDC36C

SDC36C

DI