MAX14821
IO-Link Device Transceiver
16
Maxim Integrated
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/Q fault condition under either of
two conditions:
1) When it detects a short circuit for longer than 140s
(typ). A short condition exists when the C/Q driver’s
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 receiver’s 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 240s (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 240s (typ) and occur every 26ms (typ).