MAX14821 Datasheet, PDF(16/31 Page) Maxim Integrated Products

◁

MAX14821

IO-Link Device Transceiver

Detailed Description

The MAX14821 is a sensor/actuator transceiver designed

for IO-Link device applications supporting all the speci-

fied IO-Link data rates. In IO-Link applications, the

device acts as the physical layer interface to a microcon-

troller running the data-link layer protocol. The device

contains an additional 24V digital input and an additional

24V digital output. Two internal linear regulators gener-

ate common sensor and actuator power requirements:

5V and 3.3V.

The device detects IO-Link wake-up conditions on the C/Q

line and generates a wake-up signal on the WU output.

The C/Q and DO drivers are independently configurable to

any one of three driver output types: push-pull, high-side

(PNP), or low-side (NPN).

The C/Q and DI inputs have selectable current sinks that

can be enabled for use in actuators where the master

requires a Type 2 load. The device is configured and

monitored through an SPI interface. Extensive alarms are

available through SPI.

24V Interface

The device features an IO-transceiver interface capable

of operating with voltages up to 36V. This is the 24V inter-

face and includes the C/Q input/output, the logic-level

digital output (DO), and the logic-level digital input (DI).

Configurable Drivers

The device features selectable push-pull, high-side (PNP),

or low-side (NPN) switching drivers at C/Q and DO.

Set the C/Q_N/P and C/Q_PP bits in the CQConfig reg-

ister to select the driver mode for the C/Q driver. When

configured as a push-pull output, C/Q switches between

VP and ground. Set the C/Q_PP bit to 1 to select push-

pull operation at C/Q. Set the C/Q_PP bit to 0 to configure

the C/Q output for open-drain operation. The C/Q_N/P bit

selects NPN or PNP operation when C/Q is configured as

an open-drain output.

Set the DoN/P and DoPP bits in the DIOConfig register

to select the driver mode for the DO output. When con-

figured as a push-pull output, DO switches between VCC

and ground. Set the DoPP bit to 1 for push-pull operation.

The DoN/P bit selects NPN or PNP operation when DO is

configured as an open-drain output. Set the DoPP bit to 0

to select high-side or low-side operation at DO.

C/Q Driver and Receiver

The TXEN input enables the C/Q driver. Drive TXEN high

to enable the C/Q driver. Drive TXEN low to disable the

driver.

The C/Q driver is specified to supply up to 100mA DC

load current.

The HiSlew bit increases the slew rate of the C/Q and DO

driver outputs. Set HiSlew to 1 for data rates of 230kbps

or higher. Set HiSlew to 0 to reduce both the C/Q and DO

driver slew rates to reduce EMI emission and reflections.

The C/Q receiver is always on. Disable the RX output

through the RxDis bit in the CQConfig register. Set the

RxDis bit to 1 to set the RX output high. Set the RxDis bit

to 0 for normal receive operation.

The C/Q receiver has an analog lowpass filter to reduce

high-frequency noise present on the line. Set the RxFilter

bit in the CQConfig register to 0 to set the filter corner

frequency to 500kHz (typ). Set the RxFilter bit to 1 to set

the corner frequency of the filter to 1MHz (typ). Noise

filters are present on both the C/Q and DI receivers and

are controlled simultaneously by the RxFilter bit.

C/Q Fault Detection

The device registers a C/QFault condition under either of

two conditions:

1) When it detects a short circuit for longer than 160Âµs

(typ). A short condition exists when the C/Q driverâs

load current exceeds the 140mA (typ) current limit.

2) When it detects a voltage level error at the C/Q out-

put. A voltage level error occurs when the C/Q driver

is configured for open-drain operation (NPN or PNP),

the driver is turned off, and the C/Q voltage is not

pulled to exceed the C/Q receiverâs threshold levels

(< 8V or > 13V) by the external supply.

When a C/QFault error occurs, the C/QFault and

C/QFaultInt bits are set, IRQ asserts, and the driver is

turned off 240Âµs (typ) after the start of the fault condition.

When a short-circuit event occurs on C/Q, the driver

enters autoretry mode. In autoretry mode the device

periodically checks whether the short is still present and

attempts to correct the driver output. Autoretry attempts

last for 350Âµs (typ) and occur every 26ms (typ).

▷