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AS8515

Datasheet - AS8515 To p Die Overview

7 AS8515 Top Die Overview

The AS8515

Top die consists of a resistive divider, a low dropout regulator, and a LIN bus transceiver. Additionally integrated are a RESET unit

with a power-on-reset delay, programmable window watchdog and timeout watchdog timers as a factory programming option. It also includes a

watchdog timeout on LIN Tx node to indicate if the Microcontroller is stuck in a loop and the LIN bus remains in dominant time for more than the

necessary time.

7.1 Voltage Attenuator

A resistive divider is used as a battery voltage attenuator. Like the amplifier, the attenuator can be enabled or disabled through SPI, and in the

device standby mode, we additionally need logic high on MEN pin for enabling. Internal reverse polarity protection is provided for VSENSE pin.

Figure 3. Attenuator Implementation

7.2 Voltage Regulators (LDO)

The device has a low-dropout voltage regulator named LDO, 3.3V voltage outputs. The output of the LDO is VCC. The regulator is always ON

except when the device enters the over-temperature shutdown.

The regulator has in-built short-circuit current limitation feature. The regulator can be temporarily shut down for hard reset of the external circuitry

by configuring the device to temporary shutdown mode through SPI.

The LDO power-up happens when the POR-VSUP event occurs (RESET_VSUP_N switching from low to high). The LDO will be switched off if

there is an under voltage on VCC, that is, when RESET_VCC_N switches back to low.

7.3 LIN Transceiver

The device has a LIN transceiver with slew-controlled bus driver for controlling the electromagnetic emissions from the LIN bus. Further, the slew

rate is independent of the bus load. The transmitter relays the data from the LIN controller (Tx pin) to the bus (LIN pin), and the receiver provides

the data on the bus to the controller (Rx pin). The transceiver conforms to the LIN 2.1 standard.

The LIN transceiver has a timeout watchdog for Tx. After the timeout, the LIN bus will be released to the recessive state from the dominant state.

The bus driver has an in-built short-circuit current limitation facility to protect the device from damage when there is a short between the bus and

the supply. In addition to the data receiver, there is a low-power receiver active in the device standby mode which received a wake-up event from

the LIN bus to bring the device to normal mode.

7.4 Temperature Monitor/Limiter

The temperature limiter circuit powers down the device when the junction temperature exceeds 170°C (nominal). It also issues an over-

temperature warning at 160°C (nominal). The device is powered up again when the junction temperature falls below 140°C (nominal). The over-

temperature warning flag is also cleared at this temperature.

The temperature limiter circuit can be optionally disabled through SPI.

VSENSE

VSENSE_IN

VSENSE_GND

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