8.3.2 Transmit Input Pin (TXD)

This pin 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, LIN output is dominant (near ground). When TXD is high, LIN output is recessive (near

battery). TXD input structure is compatible with microcontrollers with 3.3 V and 5.0 V I/O. This pin has an internal

pull-down resistor.

8.3.2.1 TXD Dominant State Timeout

If the TXD pin is inadvertently driven permanently low by a hardware or software application failure, the LIN bus

is protected by TPIC1021’s Dominant State Timeout Timer. This timer is triggered by a falling edge on the TXD

pin. If the low signal remains on the TXD pin for longer than tDST, 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 pin.

8.3.3 Receive Output Pin (RXD)

This pin is the interface to the LIN protocol controller or SCI/UART of the MCU, 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

TPIC1021 to be used with 3.3 V and 5 V I/O microcontrollers. If the microcontroller’s RXD pin does not have an

integrated pull-up, an external pull-up resistor to the microcontroller I/O supply voltage is required.

8.3.3.1 RXD Wake-up Request

When the TPIC1021 has been in low power mode and encounters a wake-up event from the LIN bus or NWake

pin the RXD pin will go LOW while the device enters and remains in Standby Mode (until EN is re-asserted high

and the device enters Normal Mode).

8.3.4 Ground (GND)

This is the TPIC1021 device ground connection. The TPIC1021 operates with a ground shift as long as the

ground shift does not reduce VSUP below the minimum operating voltage. If there is a loss of ground at the ECU

level, the TPIC1021 does not have a significant current consumption on the LIN pin while in the recessive state

(<100 µA sourced via the LIN pin) and for the dominant state the pull-up resistor should be active.

8.3.5 Enable Input Pin (EN)

The enable input pin controls the operation mode of the TPIC1021 (Normal or Low Power Mode). When enable

is high, the TPIC1021 is in normal mode allowing a transmission path from TXD to LIN and from LIN to RXD.

When the enable input is low, the device is put into low power (sleep) mode and there are no transmission

paths. The device can enter normal operating mode only after being woken up. The enable pin has an internal

pull-down resistor to ensure the device remains in low power mode even if the enable pin floats.

8.3.6 NWake Input Pin (NWake)

The NWake input pin is a high-voltage input used to wake up the TPIC1021 from low power mode. NWake is

usually connected to an external switch in the application. A falling edge on NWake with a low that is asserted

longer than the filter time (tNWAKE) results in a local wake-up. The NWake pin provides an internal pull-up current

source to VSUP.

8.3.7 Inhibit Output Pin (INH)

The inhibit output pin is used to control an external voltage regulator that has an inhibit input. When the

TPIC1021 is in normal operating mode, the inhibit high-side switch is enabled and the external voltage regulator

is activated. When TPIC1021 is in low power mode, the inhibit switch is turned off, which disables the voltage

regulator. A wake-up event on for the TPIC1021 will return the INH pin to VSUP level. The INH pin output current

is limited to 2 mA. The INH pin can also drive an external transistor connected to an MCU interrupt input.

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TPIC1021

SLIS113E – OCTOBER 2004 – REVISED MAY 2022

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