AS8530_1 Datasheet, PDF (13/32 Pages) ams AG – LIN Transceiver with Integrated Voltage Regulator and MCU Interface for Automotive Applications

AS8530
Datasheet - Detailed Description
7 Detailed Description
The AS8530 chip consists of a low drop-out regulator and a LIN bus transceiver, which is a bi-directional bus interface for data transfer between
LIN bus and the LIN protocol controller. Additionally integrated is a RESET unit with a power-on-reset delay and a programmable window
watchdog. It also includes a watchdog time-out on LIN TX node to indicate if the microcontroller is stuck in a loop and to release unintentional
LIN bus dominant state.
7.1 Voltage Regulator (LDO)
The voltage regulator has three operating modes. The features of the operating modes are given below:
Normal mode: Stability to be better ±0.25V over input range and temperature for load current up to 50mA. The LDO Output provides a
voltage of 5V or 3.3V as OTP option.
Standby mode: The Standby mode is a low quiescent current mode used in car applications that are always switched on. The load current
in standby mode is 5mA. Quiescent current (no load) is less than 45mA typically at room temperature.
Sleep mode: Power down or temporary shutdown of the regulator can be set by a register bit. This bit can be written through 2-wire MCU
interface.
The LDO takes the input from bandgap and scales it up to the required voltage. The LDO starts charging only after the POR-VSUP event occurs
(RESET_VSUP_N switched from low to high). The LDO can be powered-down by a control signal (temporary shutdown register) for the
temporary shutdown mode.
7.2 Temperature Limiter
Temperature limiter produces a power down when temperature exceeds 155ºC ±10%. It powers up and generates a reset when it returns to
135ºC ±10% junction temperature. During thermal shut down, temperature sensor is supplied by VSUP. During the temperature ramp-up phase,
as soon as the temperature exceeds 135ºC ±10%, a warning signal is issued and is written into the diagnostic register, which can be read
through the SP interface.
7.3 VSUP Undervoltage Reset
VSUP undervoltage reset generates a reset RESET_VSUP_N, switched from low to high when VSUP ramps up above VSUVR_OFF. This is
used to enable proper initialization of mode control and diagnostic registers. If VSUP < VSUVR_ON, then RESET_VSUP_N switches from high
level to low level (active). This is considered to be the master reset and will have the highest priority over all other signals. As soon as VSUP <
VSUVR_ON, the LDO, LIN Transceiver is completely shut off and system comes to a complete stop. AS8530 enters into the normal operating
mode only after VSUP > VSUVR_OFF.
7.3.1 VSUP Undervoltage in Normal Mode
Supply Voltages below VSUVR_OFF and above VSUVR_ON do not influence the voltage regulator. The output voltage VCC follows VSUP.
7.3.2 VSUP Undervoltage in Standby Mode / Sleep Mode
No exit from the sleep mode or standby mode take place if the VSUP voltage drops down to VSUVR_OFF. If VSUP goes below VSUVR_ON,
RESET_VSUP_N is active and resets the mode control and diagnostic register. The voltage regulator, LIN Transceiver modules are turned off. If
VSUP rises again above VSUVR_OFF, RESET_VSUP_N is switched from low to high. The system enters normal mode where LIN Transceiver
and LDO are switched on.
7.3.3 VSUP Undervoltage in Low Slew Mode
The behavior of AS8530 at low VSUP voltages is equal to the sleep mode. The low slew mode (set by control register through serial interface as
an option) will be cancelled, if VSUP drops below VSUVR_ON in this mode. The AS8530 enters the normal mode, if VSUP rises again above
VSUVR_OFF.
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