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AS8650

Datasheet - Detailed Descr i p ti on

7 Detailed Description

The AS8650 consists of the following components on chip:

DCDC converter with 5V outputs that supplies the three LDO voltage regulators and the CAN Transceiver

One voltage regulator for 3.3V output voltage and two programmable voltage regulators in the range of 3.3V to 1.8V

CAN bus Transceiver according to ISO 11898

Integrated RESET unit with a power-on-reset delay and a programmable watchdog time

7.1 Operating Modes and States

The AS8650 provides four main operating modes normal, receive only, standby, and sleep. In normal mode, the CAN Transceiver can be

disabled in case of over-temperature condition. The detailed transition table for each mode is shown in the subsequent pages.

7.1.1 Normal Mode

In normal mode DCDC converter, the three voltage regulators, BUS Transceiver, and Window Watchdog are turned on with full functionality. All

the LDO regulators are capable of delivering maximum load current possible as per their respective ratings. The BUS Transceiver is capable of

sending the TxD data from the microcontroller to the CANH at the maximum rate.

7.1.2 Receive-only Mode

In this mode, the CAN transmitter is disabled. The CAN receiver, the three voltage regulators, and over-temperature monitor circuit are enabled.

7.1.3 Standby Mode

This is the mode after power up. The Standby mode is a functional low-power mode where the CAN Transceiver is disabled. The bus wake-up

(low power receiver) circuit, LDO1, and over-temperature monitor circuit are enabled. Both LDO2 and LDO3 can be enabled or disabled (default

state) using the host command. The AS8650 can enter normal mode, sleep mode or receive only mode through host command.

7.1.4 Sleep Mode

Sleep mode is the current saving mode that is entered by host command or by over-temperature condition. The DCDC converter, the three

voltage regulators, CAN Transceiver, the reset, and window watchdog unit are all switched off. The bus wake-up (low power receiver) circuit,

oscillator, and over-temperature monitor circuit are active. The bus is in recessive state (high). The only wake-up possible is through remote

wake-up (through the bus lines) or local wake up (through the WAKE pin) as described in the WAKE specification. In the case of entering sleep

7.2 Power Management Strategy

The detailed block diagram and the power management strategy are shown in Figure 4.

supply. Some of the important modules among them are Over-temperature monitor, Local Wake block, Internal Power-on Reset module, Internal

Oscillator, complete mode-control unit, Undervoltage comparators of three external LDOs.

output from VSUP. This 5V output is then used to generate all the three LDOs. This high-efficiency step-down DCDC converter contains the

following features:

Current limited operation

Thermal shutdown

up the external micro-controller. All the I/Os that interface with the micro-controller work on this supply.

I2C or SPI settings in the range from 3.3V to 1.8V.