AS8220 datasheet(16/34 Pages) AMSCO

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AS8220A

Objective Data Sheet - Detailed Description

Fail Silent Behavior

In order to be fail silent, undervoltage detection on the two power supplies VIO and VCC is implemented

VIO: Supply voltage for I/O digital level adaptation

VCC: Supply voltage (+5V)

State transitions due to under voltage detection

In case of VIO undervoltage is detected, STANDBY mode will be entered regardless of the voltage present on pin

STBN.

In case VCC undervoltage is present, the device will enter power off mode (bus state: Idle_HZ), regardless on

supply voltage at VIO and the voltage present on STBN.

State transitions due to voltage recovery detection

Starting from the power off, the device enters STANDBY mode only in case VCC undervoltage flag is reset..

When VCC

≤ VCCTHL the device is in power off state and the bus wires are not terminated (bus state: Idle_HZ).

Mode Transitions

In case all the undervoltage flags are reset the operation mode is selected by STBN according to Table 6.

Table 6. Pin Signalling and Operating modes

Inputs

Operation Mode

OutPut

STBN

RxD

RxEN

Where: H = Digital level high

L = Digital level low

x = Do not care

Float = The analog output is not driven

HNORMAL

Bus = Data_0

Bus = Active

Bus = Idle or Data_1

Bus = Idle

STANDBY

Table 7. Transition Table

Supply Voltage Flag Event

Host Event

Intial Mode

VIO

VCC

STBN

Next Mode

Normal

→L

Standby

→HL

Standby

→LL

Normal

→H

Power Off

→L

Standby

Any

→HX

Power Off

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