MAX14820 Datasheet, PDF (27/29 Pages) Maxim Integrated Products – IO-Link Device Transceiver

MAX14820
IO-Link Device Transceiver
Applications Information
UART Interfacing
The logic levels of the microcontroller interface I/Os
(TXC, TXQ, TXEN, and RX) are defined by V_L.
GPO
TXQ
TX
TXC _MAX14820
RTS
TXEN
RX
RX
Figure 12. UART Interface
1μF
1/2
SDC36C
LDOIN VP
VCC
MAX14820
DO
C/Q
DI
GND
1/2
SDC36C
0.8Ω
1μF
1/2
SDC36C
SDC36C
Figure 13. MAX14820 Operating Circuit with TVS Protection
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
transients must be limited to -55V (relative to V_CC) on DO
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.
To protect against large transients at V_CC, insert a
lowpass filter on V_CC (see Figure 13 and the Typical
Operating Circuit).
External Power
The device is powered by V_CC and the 5V regulator, V₅.
V_L is a reference voltage input to set the logic levels of
the microcontroller interface. The logic and SPI interface
are operational when V₅ and V_L are present even if V_CC
is not present.
The V_P output provides a reverse-polarity-protected volt-
age one diode drop below V_CC and can be used for sup-
plying external circuitry, like power supplies.
Connect LDOIN to V₅ to power the V₅ input with an
external supply (Figure 14). This configuration disables
operation of the internal 5V regulator and reduces power
consumption.
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