Datasheet

Local Interconnect Network (LIN) Bus
Transmitter Characteristics
Receiver Characteristics
Transmit Input (TXD)
TXD Dominant State Timeout
Receive Output (RXD)
RXD Wake-up Request
Supply Voltage (V
SUP
)
TPIC1021A-Q1
www.ti.com .......................................................................................................................................................... SLIS117A – AUGUST 2007 – REVISED JUNE 2009
This I/O pin is the single-wire LIN bus transmitter and receiver.
The driver is a low-side transistor with internal current limitation and thermal shutdown. There is an internal
30-k Ω pullup resistor with a serial diode structure to V
SUP
, so no external pullup components are required for LIN
slave mode applications. An external pullup resistor of 1 k Ω , plus a series diode to V
SUP
must be added when the
device is used for master node applications.
Voltage on LIN can go from – 40-V to 40-V dc without any currents other than through the pullup resistance.
There are no reverse currents from the LIN bus to supply (V
SUP
), even in the event of a ground shift or loss of
supply (V
SUP
).
The LIN thresholds and ac parameters are LIN Protocol Specification Revision 2.0 compliant.
During a thermal shut down condition the driver is disabled.
The receiver ’ s characteristic thresholds are ratio-metric with the device supply pin. Typical thresholds are 50%,
with a hysteresis between 5% and 17.5% of supply.
The receiver is capable of receiving higher data rates ( > 100 kbps) than supported by LIN or SAEJ2602
specifications. This allows the TPIC1021A to be used for high-speed downloads at end-of-line production or
other applications. The actual data rates achievable depend on system time constants (bus capacitance and
pullup resistance) and driver characteristics used in the system.
TXD is the interface to the MCU ’ s LIN protocol controller or SCI/UART used to control the state of the LIN output.
When TXD is low, the LIN output is dominant (near ground). When TXD is high, the LIN output is recessive (near
battery). The TXD input structure is compatible with microcontrollers with 3.3-V and 5-V I/O. TXD has an internal
pulldown resistor.
If TXD is inadvertently driven permanently low by a hardware or software application failure, the LIN bus is
protected by TPIC1021A ’ s dominant state timeout timer. This timer is triggered by a falling edge on TXD. If the
low signal remains on TXD for longer than t
DST
, the transmitter is disabled, thus allowing the LIN bus to return to
the recessive state and communication to resume on the bus. The timer is reset by a rising edge on TXD.
RXD is the interface to the MCU ’ s LIN protocol controller or SCI/UART, which reports the state of the LIN bus
voltage. LIN recessive (near battery) is represented by a high level on RXD and LIN dominant (near ground) is
represented by a low level on RXD. The RXD output structure is an open-drain output stage. This allows the
TPIC1021A to be used with 3.3-V and 5-V I/O microcontrollers. If the microcontroller ’ s RXD pin does not have an
integrated pullup, an external pullup resistor to the microcontroller I/O supply voltage is required.
When the TPIC1021A has been in low-power mode and encounters a wake-up event from the LIN bus or NWake
pin, RXD goes low, while the device enters and remains in standby mode (until EN is reasserted high and the
device enters normal mode).
V
SUP
is the TPIC1021A device power supply pin. V
SUP
is connected to the battery through an external reverse
battery blocking diode. The characterized operating voltage range for the TPIC1021A is from 7 V to 27 V. V
SUP
is
protected for harsh automotive conditions up to 40 V.
The device contains a reset circuit to avoid false bus messages during undervoltage conditions when V
SUP
is less
than V
SUP_UNDER
.
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